OCCUPATIONAL EXPOSURES OF VETERINARY STAFF DURING PREGNANCY

Samar Shubaiber

A b i s submitted in conformity wiîh the requirements for the degree of Master of Science

Graduate Department of Pharmaceutid Sciences, University of Toronto

O Copyright by Samar Shuhaiber 2001

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ABSTRACT

OCCUPATIONAL EXfOSURFS OF VETERINARY STAFF DURING PREGNANCY

Master of Science, November 2001 Samar Shuhaiber

Department of Pbarmaceutid Sciences University of Toronto

In this study the reproductive effects associated with occupationai exposure to inhaled

anaesthetics and x-radiation were investigated. Ninety women contacted the Mothensk Program

requesting counseiiing on their occupational exposures in vetennary medicine, of these 54

pregnant women were enrolled in the study, followed-up and matched to controis. The rates of

major malformations (p=û.71), spontaneous abortion (p=0.98), pre-terni delivery (p=l.Oûû) and

low binh weight infants (p=0.09) were similar between the study and control groups.

Since the study patients were unable to provide the radiation levels to which they had

been exposed, records of annual radiation doses of vetennary staff were obtained from the

National Dose Registry and analyzed. Al1 the vetennary practices had annual mean radiation

doses below the whole-body annual permissible dose quivalent of 20 mSv.

These findings suggest that veterinary staff exposed to inhaled anaesthetics and/ or x-

radiation are not at an increased nsk for major malformation above the 3% baseline risk.

ACKNOWLEDGEMENTS

As author of this thesis, 1 believe it is imperative to acknowledge those individuals who

have conulbuted their time and effort to this project. First, I would like to thank my supervisor

Dr. Gideon Koren for providing me with the opportunity to work on this project, and for his

guidance and encouragement. Next 1 would like to thank Adnenne Einmon for providing the

liaison wi th the Ontario Veterinary Medical Association, and her moral support. My heartfelt

gratitude goes out to Dr. Ingeborg Radde who taught me the value of hard work, and instilled in

me the ability to think critically.

1 would also like to thank Dr. Willem Sont at the Radiation Protection Bureau of Health

and Welfare Canada for providing data on the radiation doses of veterinary staff practising in

Ontario. 1 would like to acknowledge the Ontario Veterinary Medical Association, the Ontario

Association of Vetennary Technicians, Potruff Smith Insurance Broken, and Govemment of

Canada Human Resources Development Canada for financiall y supporting this project.

1 would like to thank my parents and siblings for their constant support and

encouragement. Finally, 1 would like to express my deepest gratitude to my fiancé Monir Ayyad

for his patience and understanding, his assistance in cornputer programs, and support throughout

the duration of this project.

TABLE OF CONTENTS

. . .................................................................................................................................. ABSTRACT 11

... ........................................................................................................... ACKNOWLEDGMENTS iii

... ..................................................................................................................... LIST OF TABLES viii

.................................................................................................................... LIST OF FIGURES ix

........................................................................................................... LIST OF APPENDICES x

.................................................................................................. LIST OF ABBREWTIONS ...xi

1 . . . ............................................................................................................ INTRODUCTION 1

............................................................................................ 1.2 Statement of The Problem 1

.................................................................................................... 1.3 Purpose of The Study 2

..................................................................................................................... 1.4 Objectives 2

............................................................................... 1.5 Hypothesis S tatement of Researc h 3

................................................................................ 1 .5 . 1 Rationale for Hypothesis 3

.............................................................................................. 1.6 Review of The Literature 4

.................................... 1.6.1 Mechanism of Action of Inhaled Anaesthetics 4

................................................................... 1.6.2 Toxicity of ïnhaled Anaesthetics 4

................................................................................ 1 6.2.1 Acute Toxicity 5

. . ............................................................................. 1 .6.2.2 Chronic Toxicity 5

........................................................................... Halothane -6

............................................................................ Enflurane 6

1.6.2.3 Reproductive Studies on Inhaled Anaesthetics In Animais.. ........... 7

1.6.2.4 Fetal Effects of Occupational Exposure To Inhaieâ Anaesthetics ... 8

iv

........................................................................ 1.6.3 Sources of Ionizing Radiation 9

...................................................... 1.6.4 Biological Effects of Ionizing Radiation 10

..................... 1 A.4.1 Effmts of Ionizing Radiation on The Human Fetus 10

................................................................................... Fetal Stage 11

.... 1.6.4.2 Fetal Effects of Occupational Exposure To Ionizing Radiation 12

................................................................................................ 1.7 Rules and Regulations -13

........................................................................................................................ METEOD 15

....................................................................................................................... 2.1 Subjects 15

2.1.1 Occupational Exposures of Veterinary Staff During Pregnancy

.............................................................................. (project 1) 15

2.1.2 Analysis of Radiation Dosages (project 2) ................................................... 16 .......................................................................................................... 2.2 Data Collection 16

.................. 2.2.1 Occupational Exposures of Veterinary Staff During Regnanc y 16

............................................ ................. 2.2.2 Analysis of Radiation Dosages .... 18

.............................................................................................................. 2.3 Data Analysis 18

2.3.1 Occupational Exposures of Veterinary Staff During Pregnancy .................. 18

2.3.1.1 Analysis of Demographics and Pregnancy Outcome ..................... 18

2.3.1.2 Analysis of Occupational Exposure Data ...................................... 19

.................................................................... 2.3.2 Analysis of Radiation Dosages 19 C

........................................................................................................................ 3 . RESULTS 20

3.1 Occupational Exposures of Veterinary Staff During Pregnancy

.................................................................................................. (project 1) -20

v

3.1 . 1 Enrollment and Follow-up ........................................................................... 20

3.1.2 Demographics and Obstetrical History ........................................................ 20

3.1.3 Pregnancy Outcome and Neonatal Characteristics ....................................... 22 .

3.1.4 Major Malformations ................................................................................... 23

3.1.4.1 Maternal Details of Malformed Babies ............................. .., ........... 24

A) Control Subjects ........................... ., ........................................ -24

B) Study Subjects ............... ... ................................................... 25

3.1.5 Occupational Charactenstics and Exposure Details ..................................... 27

3.1 .5 . 1 Analysis of Occupationai Characteristics and Exposures By Type

..................................................................................... of Practice 30

3.1.5.2 Analysis of Occupational Characteristics and Exposures By Years

in Practice ............................................................................... 35

3.1 5 . 3 Anal ysis of Occupational Characteristics and Exposures B y Job

................................................................................ Classification 140

3.2 Anaiysis of Radiation Dosages (project 2) ................................................................. 46

....... 3.2.1 Anaiysis of Annual Mean Radiation Dosages for Veterinary Ractices 46

............ 3.2.2 Anaiysis of Cumulative Mean Radiation Dose B y Type of Practice 46

3.2.3 Cornparison of Cumulative Mean Radiation Doses With The Nurnber of

..................................................................................................... Workers 3 3

3.2.4 Analysis of Number of Workers In Vetennary Practices ............................. 54

............................................................................................................... DISCUSSION 3 6

4.1 Occupationai Exposures of Vetennary Staff During Pregnancy *

........................................................................................... (project 1) 56

4.1.1 Matemal Demographics and Obstetrical History ......................................... 57

.......... 4.1.2 Pregnanc y Outcorne, Delivery Parameters and Neonataî Parameters 58

v i

4.1.3 Major Malformations ................................................................................ 59

..................................... 4.1 -4 Occupational Characteristics and Exposure Details 60

4.1.4.1 Occupational Characteristics and Exposure Details B y Type of

................................................................................................... Prac tice 62

4.1.4.2 Occupational Characteristics and Exposure Details By Years In

Prac tice ....................................................................................... 63

4.1.4.3 Occupational Characteristics and Exposure Details By Job

Classification ................................................................................. 64

4.2 Analysis of Radiation Dosages (project 2) ................................................................. 66

........................................................ 5 . CONCLUSIONS AND RECOMMENDATIONS 70

............................................................................................................................ REFERENCES 72

............................................................................................................................. APPENDICES 80

vii

Table 1 .

Table 2 .

Table 3 .

Table 4 .

Table 5 .

Table 6 .

Table 7 .

Table 8 .

Tabie 9 .

LIST OF TABLE!3

Demographics and Obstetrical History of Study Subjects and Controls ..................... -22

Pregnancy Outcome and Neonatal Parameters of Study Subjects and Control ............. 23

........................................................ Major Malformations Reported Among Subjects -24

................... Job Classification of Vetennary Subjects Who Participated In The Study 27

Anaesthetics Used By Veterinary Subjects and Comparison of ExPosure To Inhaled

Anaesthetics Before and After Diagnosis of Pregnancy ................................................ 29

Comparison of Exposure To X-radiation Before And After Diagnosis

...................................................................................... of Regnancy 30

Comparison of Occupational Characteristics of Small-Animal and Mixed-Animal

................................................................................................................. Workers 30

Comparison of Exposure To Inhaled Anaesthetics Between Small-Animai Workers

......................................................................................... and Mixed-Anirnal Workers 32

Details of Exposure To X-radiation By Type of Ehctice ............................................. 34

Table 10 . Occupational Characteristics B y Number of Years In Ractice ................................... 36

Table 1 1 . Details of Exposure To Inhaled Anaesthetics B y Nurnber of Years In Ractice ......... 37

Table 12 . Details of Exposure To X-radiation By Numeber of Years In Practice ...................... 39

Table 13 . Occupational Characteristics By Job Classification .................................................... 41

Table 14 . Details of Exposure To Inhaled Anaesthetics By Job Classification ........................... 42

Table 15 . Details of Exposure To X-radiation B y Job Classification ......................................... -44

viii

LIST OF FIGURES

Figure 1.1 Chernical Structures of Inhaled Anaesthetics ........................................... .5

Figure 1.2 Proportion of Vetennary Staff Who Contacteci The Motherisk Rogram In Various

Trimestem.. ................................................................................ -20

Figure 2.1 Distribution of Annual Mean Radiation Doses Among Vetennary hct i ces For

The Past 1 1 Years.. ............................................................................................. -47

Figure 2.2 Distribution of Cumulative Mean Radiation Doses Among Veterinary Clinics

and Hospi tals ........................................................................................................ -52

Figure 2.3 Comparison of Cumulative Mean Radiation Doses of Equinel Large-Animal

............................................... Ractices To Those of Pet/ Cat Practices 53

....................... Figure 3.1 Average Number of Workets In Veterinary Clinics and Hospitals 55

Figure 3.2 Comparison of The Average Number of Workers In Pet1 Cat Practices To The

........................................... Average Number In Equind Large-Animal Practices 55

LIST OF APPENDICES

................................ Appendix A . Advertisement In OVMA Magazine and OAVT Magazine 80

................ Appendix B . Flyer Sent To Vetennary Clinics and Vetennary Hospitals In Ontario 82

........................................... Appendix C . Flyer Sent To Subscribers To The OVMA Magazine 85

Appendix D . List of Exposures Known To Be Safe To The Human Fetus. That Was Used To

.......... ................*........ Select Patients For The Control Group ................. ..... : 88

......................................................................... Appendix E . Mothensk Telephone Intake F o m 91

.......................... Appendix F . Prospective Occupational Vetennary Exposures Questionnaire 94

Appendix G . Mohensk Follow-up Form ................................................................................. 101

Appendix H . Retrospective Occupational Vetennary Exposures Questionnaire .................... -106

Appendix 1 . Data Rovided By The National Dose Registry At The Radiation Protection

Bureau: Annual Mean Radiation Doses For 100 Randomly Selected Veterinary

Practices For The Past 1 1 Years ........................................................ 1 12

WAG

NTOSH

RR

CI

OR

PPm

rnrem

mSv

ICRP

OVMA

OAVT

EDC

MSc

SES

ASD

VSD

Pb/g

MSDs

LIST OF ABBREVIATIONS

"waste" anaesthetic gases

United States National Xnstitute for Occupational Safety and Health

relative risk

confidence interva1

odds ratio

parts per million

milliroentgen-equivalent man

millisievert

International Commmission on Radiological Protection

Ontario Veterinary Medical Association

Ontario Association of Veterinary Technicians

expected date of confinement

Masters of Science

socioeconomic status

atrial septal defect

ventricular septal defect

blood-gas partition coefficient

material safety data sheets

1. INTRODUCTION

Dunng the last generation women have entered occupational fields in which they are

exposed to potential reproductive hazards, such as heavy metals, organic solvents, and radiation.

Typically occupationai regulations and exposure thRsholds established by the regdatory bodies

take into consideration only the average, healthy employee. In the case where there are

occupational regulations and exposure thresholds for pregnant employees, kere is generally a

lack of experimental data to verify whether they are sufficient to protect the fetus.

Vetennarians and vetennary technicians an a group of professionals faced with a

multitude of health hazards in their daily work, including exposure to "waste" anaesthetic gases

(WAG), pesticides, animal-induced trauma, needle-stick injuries and x-radiation. In particular,

exposure to WAG and x-radiation scem to represent the major concems. Although the health

hazards of occupational exposure to WAG and x-radiation have been addressed in the medical

literature'", there seems to be a lack of information on adverse reproductive effects associated

with health hazards. The purpose of the pïesent sîudy is to close this gap through research of the

effects of veterinary exposure to WAG and x-radiation on the fetus.

1.2 Statement of The Problem

Vetennary staff are exposed to various health hazards in their daily work. of which

exposure to WAG and x-radiation represent the most common concern. According to the

College of Veterinarians of 0ntario4, there are 2745 veterinarians currently practising in ontarios

4 5 % of whom are womens. To date, there are 1100 veterinary technicians practising in Ontario,

of whom 98% are women6. Reproductive effects associated with exposure to these health m

hazards have not been adequately addressed in the medical literature. Therefore, a need exists to

determine the reproductive effects associated with occupational exposure to WAG and x-

radiation in the veterinary field and, ultimately determine whether exposure recommendations of

1

the United States National Institute for Occupational Safety and Health (NIOSH) and those of

the Ontario Ministry of Labour provide adequate protection for pregnant veterinary staff and

their unborn babies.

1.3 Purpose of The Studv

In this study potential adverse effects associateci with in utero exposk to WAG and x-

radiation in the veterinary field wiil be described. Exposure of female vetennary staff to these

health hazards and the extent to which they practise precautionary measures recommended by

the Ontario Ministry of Labour, will be describeci.

1.4 Objectives

This research has two main objectives, both of which concentrate on exposure to WAG

and x-radiation. The first objective is to compare the rate of major malformations between a

group of practising Ontario vetennary staff and a contml group exposed to non-teratogenic

agents, matched for maternal age (f 2 years) and gestational age ( i l .5 weeks) at time of cal1 to

the Motherisk Program. The second objective is to compare the rates of other adverse

reproductive outcornes (i.e. spontaneous abortion, prematurity, and low birth weight) between

the group of practising vetennary staff and the matched control group. In addition, the

occupational exposure of femaie vetennary staff to WAG and diagnostic radiation will be

described, and the extent of implementation of precautionary measures recommended by the

Ontario Ministry of Labour will be determined.

1 J Hvwthesis Statement of Research

Hypothesis 1

The rate of major malformations among veterinary staff is not different from the rate among non-

teratogen controls.

Hypothesis II

The rate of spontaneous abortion among veterinary staff is greater than the rate among non-

teratogen controls.

Hypothesis III

The rate of pre-term delivenes among vetennary staff is not different from the rates among non-

teratogen controls.

Hypothesis IV

The rate of low birth weight babies delivered among veterinary staff is not different from the

rates among non-teratogen controls.

1.5.1 Rationale for H y p theses

1 hypothesize that the level of occupational exposure to WAG and x-radiation in Ontario

is below the teratogenic level. Therefore, occupational exposure to WAG is probably not

associated with adverse reproductive effects. Both Johnston et al' (1987) and Schenker et al8

(1990) showed that veterinary staff who are exposed excessively to diagnostic radiation are at an m

increased nsk for spontaneous abortion. Hence, exposure to diagnostic radiation may be

associated with an increased nsk for spontaneous abortion, depending on the balance between

the amount of exposure and precautions used by staff.

1.6 Review of The Literature

1.6.1 Mechanism of Action of Inhaied Anaesthetics

Although the mechanism by which inhaled anaesthetics exert their phannacologic effects

is not known for certain, many theories exist. These theories are classified into two categones

(1) metabolic theones, which attribute the phenomenon of anaesthesia to interference with nerve

ce11 function through depression of neuronal respiration or neuronal metaboiism, and (2)

membrane theories, which attribute the phenomenon of anaesthesia to the agent interfering with

changes that noxmally occur in the ce11 membrane during neuronal excitation, impulse

conduction and newtransmitter releaseg.

1.6.2 Toxicity of Inhaled Anaesthetics

Almost al1 inhaled anaesthetics consist of simple halogen-substituted hydrocarbons, al1 of

which are ethers except for halothane2 (figure 1.1). The most commonly used inhaled

anaesthetics today are nitrous oxide, halothane, isoflurane, methoxyflurane, and enflurane2.

However, the medical field determines the choice of the agent useci, i. e. surgery, obstetrics,

dentistry or vetennary medicine. Studies addressing the toxicity of inhaied anaesthetics in

humans do not use concentrations of inhaled anaetshetics to define acute exposure versus cluonic

exposure. The magnitude of exposure is merely base on whether the exposure is occupational,

hence personal would be constantly exposed to trace levels of inhaled anaethetics, or the

exposure is of patients to whom inhaled anasthetics were administered once or several times.

Figure 1.1 Chernical Stmctures of Inhaled Anaesthetics

halothane enflurane

meîhoxyflurane isoflurane

l.6.2.l Acute Toxicity

Acute exposm to inhaled anaesthetics is associated with drowsiness, headache. fatigue.

nausea, itch. depression (low mood) and inïtabilitylO. These short-terrn adverse effects are

madiated by direct action on brain neurons. These adverse effects resolve u p n the affectcd

person leaving the area in which the anaesthetic is king usedo.

1.6.2.2 Chronic Toxicity

Long-term, continuous exposun to trace concentrations of inhaled anaesthetics is

associated with reproductive disorders, liver &mage1'-", kidney damage'* ", and neurologie

disordersI0. This toxicity is mediated through reactive metabolites, which result from

biotransformation of the parent compoundsl* 3. There are three proposed mechanisms by which

inhaled anaesthetics cause toxicity; (1 jaccurnulation of toxic metabolites (which are othecwise

readi 1 y excreted), (2) production of reactive intermediates that bind covalentl y wi th proteins, and

(3) foxmation of haptens that elicit hypersensitive or immune responsesl. However the exact

mechanism by which toxicity occurs has not been determined for any of the agent&

Halothane

Approximately 20% of halothane undergoes biotransfomation3 by cytochrome P450

system mixed function oxidase or to fluonde, bromide and trïfluoroacetic acidl* 2. Liver damage,

due to cytotoxic metabolites. can occur in one of two ways: (1) mild hepatic damage resulting in

a transient increase in semm transaminase levels, which resoIves uneventfulty and (2) "halothaner -

hepatitis" which is a rare immune-mdiated injury that occurs in patients who have had many

exposures to halothane3.

En f l urane

Eighty percent of enflurane is exhaled unchanged2, of the remainder, 2-4% undergoes

hepatic metabolism2 to produce difluoromethoxy-dichloroacetic acid and inorganic fiuoride.

However, the inorganic fluonde is not typically associateci with renal damage, since its peak

concentration is below the threshold for nephrotoxicit 9.

Methoxvflurane

Methox yflurane i s ex tensi vel y me tabolized (50-70%) in the liver, to inorganic fluoride,

acetic acid, oxalic acid and di fluoromethox y-dic hloroacetic acid. The free fluoride and oxalic

acid may cause renal damage2. possibly by direct inhibition of the urine concentrating ability of

the kidney and by interference with the action of vasopressin3. The mechanism of fluride- D

induced nephrotoxicity is not fully elucidated3.

Isoflwane

A minute amount, 0.2% of isoflurane is metabolized to produce a small quantity of

fluoride and trifluoroacetic acid. The amounts of metabolites are not sufficient to cause rend or

hepatic toxicity2. The rest of the body load is exhaied unchanged.

Nitrous Oxide

Nitrous oxide is pnxiominantly exhaled unchanged. There is a nsk hypoxia occumng

with the use of this agent since has been administered at inspired concentrations of 80% or more

to induce anasthesia2. Although this agent is not associated with hepatotoxicity or rend toxici~?

in humans, in animals nitrous oxi& has been shown to oxidize the cobalt atom in vitamin Blz

resulting in megaloblastic changes in the bone rnarrow and a neuropathy. A sirnilar neuropathy

has also been observed in dentists2.

1.6.2.3 Reproductive Studies on Inhaled Anaesthetics In Animals

Most reproductive studies in Sprague-Dawley rats exposed to trace, subanaesthetic and

13-18 anaesthetic concentrations of halothane have not demonstrateci teratogenicity . Similarly

studies of Sprague-Dawley rats and Swisd ICR mice exposed to enflurane did not show

18.19 teratogenic effects . In contrast, exposure to a high enflurane concentration of 10,000ppm

(1.0%) was associated with fetotoxic cffocts, including cleft plate in Swisd ICR rnicezO. Studies

in Sprague-Dawley rats and Swisd ICR Mce exposed to trace and subanaesthetic concentrations

of methoxyflurane did not show an increased risk for ~nalformations'~~ 2'. Exposure to high

concentrations of isoflurane has not b a n associated with t e r a t ~ ~ e n i c i t ~ ' ~ ~ *. Studies in Sprague- *

Dawley rats exposed to high concentrations of nitrous oxide did not reveal any teratogenic

effectsl'* 19* " However, at 500,000 ppm (50%) concentration, nitrous oxide caused major

rnalf~rmations'~* 19* which included a decrease in ossification centres in the vertebral

column, limbs and ribs.

1.6.2.4 Fetal Effkcts of Ckcupational Exposure To Inhaled Anaesthetics

Most of the existing evidence in humans does not associate occupational exposure to

WAG with an increased nsk of congenital birth defec t~"~ " Numerous s t ~ d i e s ~ ~ ~ 31-36 have

s h o w an increased nsk for spontaneous abortions arnong female personnel, including

anaesthetists, operating-room nurses, and dental assistants exposed to inhalation anaesthetics. A

recent meta-analYsis3' showed that occupational exposure to "waste" anaesthetic gases is

associateci with an increased nsk for spontaneous abortions (RR=l.48,95% CI 1 A to 1 S8). The

meta-analysis included nineteen studies of various designs, with anaesthetists, operating-room

physiciand nurses, dental assistants, operating-room workers, hospital workers, health workers,

vetennarians and veterinary assistants as subjects. However. most of the studies included in the

meta-analysis were conducted before scavenging had becorne a legal requirement. Another

Limitation was that none of the included studies attempted to establish a relationship between the

amount of exposure and the magnitude of nsk for spontaneous abortion. The final, most

important limitation is that al1 the studies were retrospective.

In the veterinary field, Johnson et al7 (1987) have s h o w that even though the odds ratio

for spontaneous abortion with exposure to WAG in female veterinarians and female vetennary

assistants was greater than 1.0 when adjusted for use of diagnostic x-rays, it did not mach

statistical significance (95% CI 0.86-9.53 and 0.92-5.52, respectively). The study also indicated

that female vetennarians exposed to WAG were not at an increased risk of giving birth to

children with congenital abnomalities~(0~=0.33, 95% CI 0.12-0.90). An important Limitation

of this study was the use of a subjective measure to report the amount exposure to WAG, which

consisted of a scale of one (no odour present) to four (imtating odour present). Schenker et al8

8

(1990) demonstrated that the rates of spontaneous abortions were similar among female

vetennhans and female lawyers. There is a misperception that the concentrations of "waste"

anaesthetic gases are much greater in vetennary facilities than in operating-rooms for humans.

Ward and l land^' (1982) measured WAG levels of 2 parts per million (ppm) in veterinary

facilities compared to lûppm in hospitals for humans'? Even though the average room volume

in veterinary practice is smaller, operating time is shorter and doors of veterinary surgery rooms

are normally left open to allow technicians concumnt assistance in other rooms thus resulting in

"waste" anaesthetic gas concentrations being lower than in operating rooms for humans. In

addition, veterinary staff spend only a small portion of their working time pedonning ~ u r ~ e $ ~ .

Despite al1 these factors, the level of "waste" anaesthetic gases in vetennary facilities pimarily

depends on the presence of gas scavenging systems, good anaesthetic practices, periodic

examination and maintenance of anaesthetic machines.

1.6.3 Sources of Ionizing Radiation

Individuals are constantly exposeci to different sources of ionizing radiation, both natural

and man-made. According to the Canadian Nuclear ~ssocia t ion~~ the average person is exposed

to an annual dose of 2mSv from naniral background radiation, which includes cosrnic and

terrestrial radiation. Medical applications of radiation contribute the most to man-made sources

of radiation, with the average individual recciving a dose of 0.92mSv each yea?9. The medical

applications of ionizing radiation include diagnostic x-ray examinations, use of

radiopharmaceuticals in nuclear medicine, and therapeutic uses such as irradiation of tumours or

physiotherapy. Other sources of ionizing radiation corne from nuclear weapon testing, brick and *

masonry buildings, air travel, television, and nuclear po wer reactors". Taking into consideration

ail the sources of ionizing radiation, the annual dose of radiation to which the average person is

exposed to is 3. lmsg9.

1.6.4 Biologieal Effects of lonizing Radiation

Exposure to ionizing radiation is an established health hazard. Ionizing radiation may

lead to various degrees of organ damage. This tissue damage is mediated by ions and free

radicals, which may in turn induce mutati~ns, cancer or birih defects".

1.6.4.1 Effects of Ionizing Radiation On The Fetus

Data on the effects of ionizing radiation on the fetus are largely based on experimental

studies in animals and data derived from the Hiroshima and Nagasaki disasters. The radiation

doses used in animai studies ranged from 25rads to doorads, adrninistered at various stages of

The radiation doses reported in the Hiroshima and Nagasaki disasters ranged fmm 1

to 1300rads, dcpending on the distance from the hypocentre of the explosion42'. In utero

exposure to high-dose ionizing radiation may lead to death of the embryo. intrauterine growth

rrtardation, or congenital malformations4'. The cardinal manifestations of ionizing radiation on

the human embryo include growth retardation and central nervous system effects, including

microcephaly and eye malformations4'. A wide range of abnomalities have been reported

following irradiation of animals using different doses at various stages of gestation including,

growth retardation, neural tube defects. central nervous system abnormalities, ocular anomalies,

limb, heart and facial defects, and genital malformations4'. The spectrum of teratogenic effects

of ionizing radiation differs among animal and human studies4'"* 48"2. Several reasons have

been proposed to explain this phenomenon; ~ i c k s ' ~ (1958) found that the human fetus is

radiosensitive to the central nervous system effects of radiation until the late fetal stage. The m

other reason is that the early organogenesis period of humans is substantially shorter than this

period in rats4'. The direct effccts of ionizing radiation on the fetus depend on the stage of

pregnancy at which exposure occurs (Le. temporal relationship) and dose of radiations4.

10

The pre-implantation stage occurs at 0-2 weeks post-conception4'. During this period the

embryo is most sensitive to the lethai effects of radaiation4. There is no evidence of growth

retardation in this period4'.

Im~lantation

The implantation period occurs 10-14 days after conception. Irradiation of the fetus in

this period may result in transient intrauterine growth retar&tion4'.

Orprano~enesis

Organogenesis is tk pend of cellular differentiation that Wes place at 2-7 weeks afker

conception. The fetus is susceptible to the lethal, teratogenic and p w t h mtarding effccts of

ionizing radiation4'. Studies have show that exposure to radiation doses 2360rads is associated

55 56 with an increased risk for spontaneous abortion : . Most of the evidence indicates that diagnostic exposure of the human fetus to doses

c5rads has not been assaciated with congenital malformations or growth retardation 51, S1.58

IIekabad9 (1 978) and Goldstein and ~ u r ~ h ~ ~ ~ * " (1929) have demonstrated that therapeutic

irradiation during pregnancy with doses in excess of lOOrads is not only associated with mental

retardation, but also with rnicrophthalmia, cataracts, strabismus, retinal degeneration and optic

atrophy .

Fetal S t a~e - The fetal period occurs 8 4 weeks post-conception. The effects of in utero exposure to

radiation in the Hiroshima and Nagasaki disasters have been investigated b y several

researcherS44. 57.58. 6267 . Otake and schullU (1984) showed that the greatest nsk for mental

11

retaïLdation and micmcephaly o c c d when exposure took place at 8-15 weeks of gestation.

~ lu rnmer~~ (1952) has shown that Hiroshima children exposed in utero to the atomic bomb

between 16 and 20 weeks of gestation had milder degrees of microcephal y, mental retardation,

and stunted growth.

1.6.4.2 Fetai Effeets of Occupationai Exposure To 10-g Radiation

Several researchers have studied the reproductive effects of occupational exposure of

female workers to ionizing radiation in vanous fields. Larsen6' (199 1) showed that female

physiotherapists exposed to high-frcquency electmmagnetic radiation were not at an increased

risk of major birth defects (OR=1.7,95% CI 0.64.3). The study took into account maximum

level of exposure, duration and frequency of exposure to ionizing radiation. This finding was

confirmeci by Roman et ai" (1996) who showeci chat the offspring of female medical

radiographers were not at an increased nsk for major malformations (RR=1 .O, 95% CI 0.8-1 -2).

The author had intensled to establish a dose-response relationship by linking dosimetry records

with pregnancy outcorne, but this proved to be impossible since dosimetry data are not retained,

as radiographers are not designated as cl assi fkd radiation workers.

When compared to radiologists, veterinarians and veterinary technicians are probabl y

exposed to a higher level of radiation because they usually need to restrain animals manually

during the procedure. A case-control study7 showed that exposure of female veterinarians and

female veterinary assistants to diagnostic x-rays was not associated with an increased nsk for

major birth defects (ORd.7 1,95% CI 0.27-1 90). However, the study found that veterinary

assistants, who were exposed to x-rays, were ai an increased risk for spontaneous abortion *

(OR=2.45,95% CI 1.10-5.46). Although Schenkar et al8 (11990) did not show an increased nsk

for spontaneous abortion among female veterinarians compared to lawyers (RR=0.9), they

reported a slightly increased risk for spontaneous abortion arnong female veterinarians exposed

to 5 or more x-ray films per week (RR=1.8 1.95% CI 1.01-3.24) compared to those exposed to O-

4 x-ray films per week (RR=1.8.95% CI 0.7-4.9). Neither study took i n t ~ account the use of

precautionary measures.

1.7 Rules and Remilations

The United States National Institute for Occupational Safety and Heath (NIOSH)

recommends that the maximum advisable concentration (8 hour time-weighted average) should

be 25 parts per million (ppm) for nitmus oxide and 2ppm for halothane. methoxyfiurane and

isoflwane in room air. When these anaesthetics are used with nitrous oxide, MOSH

rtcommends that the manimurn advisable concentration does not exceed OSppm for halothane,

methoxyfiurane or isoflunuie in room air7'. These exposure limits have been adopted for

regulatory purposes by the province of Ontario.

According to the National Council on Radiation Protection and ~ e a s u r e m e d , the

maximum permissible dose squivalent to the fetus h m occupational exposure of the mother

during the entire gestational period should not exceed 5-m (which is equivalent to SmSv;

the biologic damage that can occur from O.Srad). Canadian regulations are based on those of the

International Commission on Radiological Protection (ICRP) Publication 60". This publication

specifies that annual permissible dose equivalent limit to the whole body of occupationall y

exposed personnel should not exceed 20milisieverts (mSv) (which is equivalent to the biologic

damage that can occur h m 2rads). However, the annual dose limit for radiation personnel in

Ontario is 50rn~v'*. According to Health and Welfare Canada Safety Code 28" lead aprons,

lead gloves and thyroid collars used for veterinary x-ray procedures must provide attenuation m

equivalent to at les t 0.5mm of lead at peak x-ray tube voltages of up to 150 kilovolts. The

safety code also recommends that protective clothing should be radiographed annually or when

damage is suspected. Personnel who are likely to receive a radiation dose in excess of 1/20 the

13

pennissible dose equivaient limit, must Wear personai dosimeters underneath the lead apron. For

pregnant personnel the dose equivalent Iirnit to the abdomen should not exceed 2mSv for the

remainder of the pregnancy (which is equivalent to the biologic damage that can occw from

0.2rads). In Ontario the dose equivalent limit for pregnant personnel is 4rnsvT4. Al1 personnel

who restrain animais for x-ray procedures are required to Wear a lead apron and lead gloves.

Veterinary x-ray equipment and its accessories must conform to the Radiation Emitting Devices

Act and the Food and Dmg AC^".

2. METKODS

This thesis is comprised of two projects, first to evaluate pregnancy outcome of

vetennary staff following occupational exposure to inhaled anaesthetics and x-radiation and to

describe the relevant exposures, and secondly to analyze radiation dosages of veterinary staff

obtained from the National Dose Registry. Hence, the description of methodology is separate for

each of the projects.

2.1 Subiects

2.1.1 Oceupationd Exposures of Veterinary Staff hving Pregnancy (pmject 1)

Advertisements were placed in the Ontario Vetennary Medical Association (OVMA)

Magazine and the Ontario Association of Veterinary Technicians (OAVT) Magazine inviting

veterinary staff who were pregnant or who were planning pregnancy to contact the Motherisk

Program to participate in a study on occupational exposures in vetennary medicine (Appendix

A). In addition, flyers advertising the study were sent to al1 the vetennary clinics and vetennary

hospitals in Ontario (Appendix B), and to subscnbers to the OVMA Magazine (Appendix C).

Women who contacted the Mothensk Program were counselled on various occupational

exposures including; inhalation anaesthetics, x-radiation and toxoplasmosis infstion (depending

on their concerns). The women were then informecl about the study and were invited to

participate.

Eligible callers were selected for the study based on the following criteria:

Inclusion Criteria

1. Currentl y pregnant - 2. Veterinary staff: veterinarian, registered vetennary technician, animal health technologistl

technician or veterinary assistant

3. Occupational exposure to inhaled anaesthetics and or x-radiation

4. Verbal informed consent to participate

5. Ability to cornrnunicate in English

There were no other exclusion criteria for the study. The study subjects were matched by

matemal age t 2 years and gestational age k1.5 weeks of gestation, to subjects of a contml group

which consisted of women who contacted the Mothensk Program requesting counselling on

exposures known to be safe to the human fetus, such as: acetarninophen, erythromycin,

penicillins, ibuprofen, naproxen, hair dye etc.. . . (Appendix D). The shidy was approved by the

Research Ethics Board of the Hospital for Sick Children.

2.1.2 Analysis of Radiation Dosages (project 2)

The National Dose Registry in Ottawa was approached and some general radiation levels

for veterinary staff were obtained

2.2 Data Collection

2.2.1 Occupational Exposures of Veterinary Staff D u ~ g Pregnancy (project 1)

The Motherisk Telephone Intake Fom (Appendix E) was used to collect details

including: matemal date of birth, obstetrical history, last menstmd period, medical history,

cigarette and alcohol use and illicit dnig use for each patient. Veterinary staff (study subjects)

were further asked about their occupational exposures.

Veterinary staff were contacted later during pregnancy and asked details of their

occupational exposures using the Occupational Veterinary Exposures Prospective Questionnaire

(Appendix F). These details included years of practice. type of practice, duation of work-shift,

exposure to inhaled anaesthetics, x-radiation, and pesticides, techniques used, monitoring of

WAG and radiation levels, use of protective equipment and sideeffects. The questionnaire was

validated by k i n g administered to the first twenty patients enrolled in the study. The necessary

changes were then ma& and the final version of the questionnaire was adopted, and

administered to the rest of the patients.

Subjects in both groups were contacted after at least four months of their Expected Date

of Confinement (EDC) in ordtr to complete the Mothensk Follow-up Form i ~ ~ p e n d i x 0).

Participants were asked details about the outcome of the pngnancy, birth weight. presence or

absence of birth defects, and perinatal and postnatal complications. The data from the follow-up

of both groups of patients were confmed by requesting the patients' verbal consent to obtain

written documentation from the child's physician. At the time of follow-up study patients were

asked further details about their occupational exposure to inhalation anesthetics, x-radiation prior

and during prepancy. as well as any animal- induced trauma and the status of their

toxoplasmosis titres. These data were recorded using the Occupational Veterinary Exposures

Retrospective Questionnaire (Appendix H).

Major malformations were defined as k i n g life-threatening, requiring major surgery or

having serious cosmetic effe~ts'~. Although Heinonen et alT6 (1977) have reported a 14%

baseline risk for major malformations among children followed-up until six y e m of age, the

population baseline risk used for this study was 3%. since the children in this study were

followed-up at a younger age i.e. when they were less than 2 years old.

To ensure consistency of the data collection and to minimize variability among interview

styles the MSc candidate completed al1 the required forms for the study patients and for most of

the control patients. C

2.2.2 A d y s i s of Radiation h g e s (pmject 2)

The National Dose Registry at the Radiation Protection Bureau of Health Canada was

contacted, to request the annual radiation doses of veterinarians, veterinary technicians, and

animal healthcare technicians working for the past 11 years in 100 randody selected veterinary

practices in Ontario. These data included the annual mean, range, standard deviation, and median

radiation doses, as well as the number of workers in each practice. To ensuk anonymity of the

various practices their names were withheld, although the bureau indicated whether the practice

is a clinic or a hospital and the type of animai practice (i.e. small animal, large animal, mixed

(small and large) equal. mixed mostly small. mixed mostly large).

23 Data Analvsis

Ml the data were entered into Excel4.0 and statistically analyzed using SigmaStat 2.03.

2.3.1 Occupational Exposures of Veterinary Staff During Pregnancy (project 1)

2.3.1.1 Analysis of Demographics and Pregnancy Outcome

Continuous &ta were compared using the Student's t-test when it followed a normal

distribution; data not normally distributed were compared using the Mann-Whitney Rank Sum

Test. These data included: matemal age, the infant's birth weight and gestational age at birih.

Roportions, including: gravidity, parity, and number of spontaneous abortions and therapeutic

abortions, were compared using the Chi Square Test. Fisher's Exact Test was used to c o m p a

the rate of major malformations between the two groups.

2.3.1.2 Anal ysis of Occupational Exposure Data

Data describing occupational exposures were analyzed using descriptive statistics.

Proportions were used to analyze the type of animal practice, type of vetennary service, and

inhalation anaesthetics used. The mean and standard deviation, median and mode were used to

describe the work-shift duration and years of practice. Frequencies were used to analyze

duration or arnount of exposure, protective equipment use, anaesthetic system used, anaesthetic

technique used method of animal restraint, and use of techniques to monitor exposure. Sub-

analyses were perfomed taking into consideration type of practice, years in practice (i.e.

experience of veterinary personnel) and job classification (veterinmians versus technicians).

Even though it did not seem useful to compare techniques used and use of precautionary

measwes between veterinarians and technicians, since this is probabl y detennined by the

veterinarians present, the sub-analysis was still conducted in order to enable one to compare the

data to the results of previous studies. Although other information was collected including:

other occupational exposures, marital status, socioeconomic status (SES), patemal

demographics. these data were not anal yzed since they do not pertain to the objectives of this

study .

23.2 Analysis of Radiation Dosages (project 2)

The Mann -Whitney Rank Sum Test was used to compare the cumulative mean radiation

doses and number of workers among the veterinary practices, since these data were not normally

distributed. To ensure appropriate statistical representation of veterinary practices for which less

than 6 years of data were available, a sub-analysis that excluded these practices was conducted.

A sub-analysis excluding practices that employed a single worker was also perfomed.

3. RESULTS

3.1 OccunationaI Exwsures of Veterinaw Staff dur in^ Preennncv (pmject 1)

3.1.1 Enrollment and Follow-up

From January 1999 until Febmary 2001,90 women contacted the Motherisk Program,

requesting counselling on their occupational exposures in vetennary medicine. From this group

of women. 60 were enrolled in the study and 5 women were excluded since ihey resided in

provinces other than Ontario and, thus. were difficult to reach. At the time of completion of the

study 30 patients were sti1l planning pregnancy, 54 patients were followed-up, and 4 patients

could not be reached (or were lost to follow-up). Al1 the patients that were followed-up were

matched to controls.

Figure 1.2 shows that the majority of veterinary subjects contacted the Motherisk

Program in the first trimester (68.5%). a quarter w e n in the second trimester (25.9%) and a few

subjects contacted the program in the last trimester (5.6%).

Figure 1.2 Proportion of Veterinary Subjects Who Contacted The Mothensk Program In Various Tri mesters

third trimester second trimester (14)

3.1.2 Demographics and Obstetricai Ristory

Matemal demographics and obstetricai history are shown in table 1. Mean materna1 age

was 30.6 and 30.9 years for the study group and the control group, respectively. Rc-pregnancy

weight was similar between the study patients and the controls. Parity was the only obstetrical

parameter thai was statisticall y significantly different between the two groups. About t h -

quarters of the patients in the study group had no children (live bitths), wheréas approximately

half of those in the control group did not have any children (live births).

There were very few women who smoked cigarettes in either group. There was one

heavy smoker (>IO cigaretteslday) in the study group. On the other han& there were 2 smokers

in the conml p u p , one of whom smokeâ heavily (A0 cigarettedday). but ceased doing so

during the first nirnesteq the other woman continued smoking 5-10 cigatettedday throughout

pregnancy. Alcohol use among the two groups was similar (p=0.64), with most women

consuming no more than 5 drinks in total throughout the pregnancy.

Tabie 1. Demographics and Obstetrical History of Study Subjects and Contmls

Study N=54 (%)

Control N=54 (%)

' Re-pregnancy Weight (kg) Gravidiîy

G1 G2 G>2

Parity m P l -1

Spontaneous Abortion SA0 SA1 S b 1

Thefapeutic Abortion TAO TA1 TA>1

Cigarette Use YeS

3.1.3 Pregaancy Outcome and Neonatai Characteristics

no Alcohol Use

Rcgnancy outcome and neonatal characteristics are shown in table 2. There were no

statistical differences in matemal weight gain or pregnancy outcome. Neonates in the study

group were older than neonates in the conaol group by 0.75 weeks of gestation. The neonates in

the study group were heavier than neonates in the control group (pa.03). The cornparison was

repeated excluding the trisomy-18 baby in the control group, which resulted in borderline

statistical significance (p4.05). Upon excluding the trisomy- 18 baby and the premature babies

in both groups. dong wiîh k i r matched pairs, the difference in birth weight did not reach

2 (3.7)

1 (1.9)

1 (1.9)

2 (3.7) 53 (98.1) 52 (96.3)

statistical significance (p=0.09). ïhe rates of delivety complications and feal distress were

similar between the two groups.

Age at follow-up was statistically significantly different (p<0.001) between the groups.

Children in the study goup were followed-up at 6-3 months, whereas those in the mntrol group

were followed-up at 1 1.7 momhs.

Table 2. Pregnancy Outcome and Neonatal Characteristics of Study Patients and Controis

Weight Gain (kg)

Pregnancy Outcorne

-

cesarian section Gestational Age at Birth ( w k GA)

* one study patient was lost to foliow-up

15.5 k 5.8

N=53 (?40)*

term (237 wks GA) pre-term (<37 wks GA)

Age at Foilow-up (mths)

only partial data are available for 3 patients

11 (23.4) 39.8 + 1.6

3.1.4 Major M.Horeaiions

15.3 k 7-1

46 (95.8) 2 (4.2)

6.3 + 2.1

Major malformations are detaiied in table 3. The rate of major maEomiuions h e m

0.46

6 (12.0) 39.2 f 1.5

the study and control groups was not statistically sigiuficantîy diffkrent ( p 4 . 7 1 ). Major

N=54 (%) 1 0.98

0.03

47 (94.0) 3 (6.0)

11.7 k 3 . 4

malformations in the study group consisted of: pyioric stenosis, diaphragmatic hemia, atrial

<0.001

septal defect (ASD) and microvill~s inclusion disease. The ASD comcted spontaneously

between 3.5 months and 4.75 months. On the other hand, different malformations were reporteci

in the control group; trisomy-18, bladder extrophy, and ventricular septal defect (VSD). The rate

of major malfornations was identical between the groups when the andysis was repeated

excluding the infant with the VSD.

Table 3. Major Malformations Reported Among Subjects

Birth Defects** none

1 Aaial Septal Defcct (ASD) 1 Ventricular Septal Defect (VSD)

major Description of Defect

1 Microvillus Inclusion Disease I B ladder Extroph y

Study* N=47 (%)

43 (91.5)

Diaphragmatic Heniia

* 3 study patients could not be reached ** Fisher's Exact Test used

Control N=SO (96)

47 (94.0) 4 (8.5)

Py loric S tenosis

3.1.4.1 Materna1 Details of Malfomed Babies

3 (6.0) Trisomy 18

A) Control Subjects

Trisomv-18 (control no. 1)

This was a control subject, 28.5 years of age, who had used several courses of

pivampicillin to ma t recurrent winary tract infections in the iast trimester, acetaminophen for

headaches, calcium carbonate for heartburn, and dimenhydrinate for nausea and vorniting during

pregnancy. This woman had toxemia for which she was treated with labetalol from 37 weeks of

gestation until the end of the pregnancyr She d e ü v e d a female trisomy-18 baby at 39 weeks of

gestation, weighing 1989g (i.e. with severe intrautenne growth retardation) who died at 5 days of

age.

24

Venüicular Septal Defect (control no. 53)

This was a control patient, 26.5 years of age, who had used acetaminophen for heaàaches,

diphenhydrarnine for allergies, t h a t lozenges for a common cold, and salbutamol to control

asthma duxing the pregnancy. She delivered a 30%g male baby at 35.7 weeks of gestation with

a ventricular septal defcct. The infant was seen by a cardiologist who claimed that the heart

defect may regress spontaneously by two years of age (muscular-type VSD):

Urinarv Bladder Extro~hv (control no. 63)

This was a control subject, 35.5 years of age, who had used acetaminophen for

headaches, one tablet of Menadine on one occasion for hay-fever, topical clotrimazole for

ringworm, and.blue and blsck cohosh in the last 3 weeks of pregnancy to induce labour. She

delivered a 3381g male baby at 39.6 weeks of gestation with urinary bladder extrophy and one

undescended testicle. The baby underwent same &y surgery to correct the bladder extrophy .

Surgery was also performed ai 10 months to correct the undescended testicle.

B) Study Subjects

Pvloric Stenosis (study no. 30)

The patient was an animal health technician, 3 1 .O years of age, who had used salbutarnol

throughout pregnancy for asthma. She had been occupationally exposed to isofiurane for no

more than 2 houn per week, which she discontinued using at 8 weeks of gestation. She was also

taking 6-9 filmdwk, which she also stopped doing at 4-5 weeks of gestation. The woman

delivered a 2778g male baby at 40.0 weeks of gestation with pyloric stenosis. The baby

underwent corrective swgery 3 weeks after birth.

Aûial S e ~ t a i Defect (study no. 36)

The subject was a registered veterinary technician, 33.0 years of age, who had two

courses of amoxicillin for recurrent urinary tract infections, cephalexin for bronchitis and a

unnary tract infection. She delivered a 4û91g apparentiy healthy female baby at 39.0 weeks of

gestation. The baby had an electrocardiograrn at 3.5 months for a suspected atrial septal defect.

Another electrocardiogram done, at 4.75 months, showed that the defect had comcted

spontaneously at 6 months. The patient was occupationally exposed to at least 9 hours per week

of halothane and isoflurane, which she reduced to no more than 2 houn per week upon diagnosis

of pregnancy. She was W n g no more than 5 x-ray films per week, which she discontinued at 4

weeks of gestation. This patient completely stopped working at 24 weeks of gestation due to

hemorrhaging .

Microvillus Inclusion Disease (sîudy no. 38)

The subject was a veterinarian, 29.0 years of age, who did not use any medications during

the pregnancy. She was occupationally exposed to at least 9 houts per week of isoflurane, which

was reduced to 3-6 hours per week upon pregnancy diagnosis. She was also taking 6-9 x-ray

films per week, which she reduced to no more than 5 films per week and discontinued at 8 weeks

of gestation. The woman delivered a female baby at 39.0 weeks of gestation weighing 43 18g,

who was diagnosed with microvillus inclusion disease at 6 weeks. The baby was hospitalized at

7 days for acidosis as a result of diarrhea leading to dehydration and was placed on total

parenteral nutrition. However, the baby developed more complications and died at 4.5 months.

Dia~hramnatic Hemia (study no. 45)

The subject was a registered vetennary technician, 3 1 .O years of age, who had been

diagnosed with lupus erythematosus, for which she did not receive any treatment. The woman

had used acetaminophen for migraines and Diclectin (doxylamine succinate and pyridoxine

hyrochloride) for nausea and vorniting during the pregnancy. She was occupationally exposed to

at least 9 hours per week of isoflurane. which continued throughout pregnancy. She was also

taking at lest 10 films per week, which she reduced to no more than 5 films per week for the

remaining duration of the pregnancy. She delivered a 3608g male baby at 40.0 weeks of

gestation with diaphragmatic hemia. The baby underwent surgery at 5 days:

3.1.5 Occupational Characteristics and Exposure Details

Table 4 shows the breakdown of veterinary staff who participateci in the study. Arnong

veterinary staff enrolled in the study, more than 50% were veterinarians, about 37% were

veterinary technicians and animal techniciand technologists, and only 10% were assisting staff.

The majority of the patients (79.6%) worked in small-animai practices; the rest of the patients

(20.4%) worked in mixed-animai practices. One patient worked in an animal reseacch facility at

a phannaceutical Company. This patient only perfomed surgical procedures.

Table 4. Job Classification of Veterinary Subjects Who Participated In The Study

Table 5 specifies the difierent i-aled anaesthetics used and the duration of exposure to

inhaled anaesthetics before and after the diagnosis of pregnancy. Halothane and isoflurane were

the only inhaled anaesthetics to which patients were exposed. More than half (55.6%) used

Job Classification

veterinarians

registered veterinary technicians

animal health techniciand technologists

vetennary assistants

animai care aides

N=54 (96)

29 (53.7)

17 (31.5)

3 (5.6)

4 (7.4)

i (1.9)

isoflurane only in surgical procedures, 38.9% used both isdurane and halothane. Very few

patients used only halothane (5.6%). The majority (68.6%) of vetennary staff were exposed to

either 3-6 h d w k or 2 9hrdwk of inhaled anaesthetics. The number of patients exposed to

1 9 W w k substantially dropped from 17 to 9 patients &ter the diagnosis of pregnancy. with most

patients reducing their exposure to 5 2hrdwk. Two women discontinued the use of inhaled

anaesthetics after pregnancy was diagnosed. Scavenging was the most comhon precautionary

measure to reduce exposure to inhaied anaesthetics used by patients. Only 3 women used

cartridge-masks. The anaesthetic techniques applied (in order of most popular to least popular)

were endotracheal tube, mask, and anaesthetic chamber. Two women reported that the level of

inhaled anaesthetics ("waste anaesthetic gas") was measured only once, using dosimeter badges

at their practice.

The number of x-ray films taken per week before and after the diagnosis of pregnancy is

shown in table 6. The majority of vetennary staff were taking either SS fi W w k or 6-9

filmdwk. After the diagnosis of prcgnancy, 34 women completely discontinued taking x-ray

films, and the number of women taking 210 filmdwk drastically reduced from 8 patients to

none. Manual restraint was the most frequently utilized method of restraint, usually involving

the patient herself and another employee. Tranquilizers were also used to facilitate restraining

the animal for x-ray procedures. Ali veterinary staff wore lead aprons when taking x-ray films.

However, not al1 patients used lead gloves and thyroid collars as precautionary measures. Most

patients (84.6%) monitored their radiation exposure using dosimeters (film badges). However,

very few participants were aware of the 1 s t reading on their dosimeters.

Table S. Anaesthetics Used By Vetennary Patients and Comparison of Exposure To Inhaled Anaesthetics Before and After Diagnosis of Pregnancy

Occupational Characteristics

1 Anaesthetics Used

I isoflurane and halothane isoflurane on1 y halothane only

Duration of Exposure to Isoflurane

, variable Dwation of Exposure to Halothane

12 h/wk 3-6 h/wk 7-8 h/wk 29 hrdwk 4-6 hrdwk* 6-9 hrdwk*

Exposure Before Diagnosis of Pregnancy**

19 hrdwk Exposure After Diagnosis of Regnancy**

12 h d w k 3-6 h d w k 7-8 h d w k

* sale used in the prospective questionnaire 4

used to validate the questionnaire ** 3 patients were lost to follow-up

ffered slightly for rst 20 patients, which were

Table 6. Comparison of Exposure To X-radiation Before and After Diagnosis of Regnancy

Exposure To X-radiation

Before Diagnosis of Pregnancy

O f i l d w k 15 filmdwk 6-9 filmsfwk 1 10 filmdwk 15 or 6-9 filmdwk*

After Diagnosis of Pregnancy

1 10 filmdwk * One patient's expasme was variable

3.1.5.1 Anaïysis O€ Oceupationa1 Characteristics and Exposures By Type O€ Practice

Occupational characteristics by type of practice are shown in table 7. There were 43

women who worked in small animal practices and 11 women who worked in mixed animal

practices (either mixed qua1 or mixed mostIy small animal practices). There were no statistical

ciifferences in materna1 age, years in practice or weekly work-shift among the two groups.

Table 7. Comparison of Occupational Characteristics of Small-Animal and Mixed-Animal Workers

* median value reported p

Matemal Age (years)

No. Years In Practice

Weekly Workshift (lm)*

Details of occupational exposure to inhaled anaesthetics are shown in table 8. The

frequency of use of scavenging systems was the only precautionary measure that statistically

30

S mall- Animal Workers N=43 (96)

30.9 f 3.7

6.3 + 3.3 40

Mixed- Animal Workers N=l 1 (%)

29.5 f 2.8

5.8 f 4.2

45

P-value

0.22

0.7

0.29

differed between the small animal practice group and the mixed animal practice group (p4.02).

There were no statistical differences in the anaesthetic techniques used or the type of anaesthesia

circuit used (rebreathing; p=û.58 and non-rebreathing Bain Circuit p=0.29. Small animal

workers were exposed to a similar amount of inhaled anaesthetics (waste anaesthetic gas)

compared to mixed animal workers both before (pE0.30) and after the diagnosis of pregnancy

(pS.23). A comparison of the level of inhaled anaesthetics to which small animal workers were

exposed before and after the diagnosis of pregnancy showed a statistical difference (m.01). A

sirnilar comparison among the mixed animal workers did not reach statistical significance

(@.OS). The number of workers who discontinued use of inhaled anaesthetics did not differ .

between the groups (p=û.30').

Details of occupational exposure to x-radiation are show in table 9. The method of

animal restra.int did not differ between the two groups. There were no statistical differences in

the use of precautionary mesures such as lead aprons and lead gloves. The frequency of use of

thyroid collars was greater arnong the small-animal workers than among the rnixed-animal

workers (p=0.0 1). Small-animal workers were exposed to a similar amount of x-radiation

compared to mixed-animai workers both before (p=0.84) and after pregnancy diagnosis

(p=0.23). When one compared the amount of x-radiation to which small-animai workers were

exposed before and after pregnancy diagnosis, no statistical difference was seen (p=0.12). A

similar comparison arnong the mixed-animal workers did not reveal a statistical significance

(pd.15). The number of workers who discontinued taking x-ray films after the diagnosis of

pregnancy did not differ between the two groups (p*. 17).

The rate of major birth defects did not differ statistically between the small-animal

workers and the mixed-animal workers @=Cl. 168), with two defects in each group.

Table 8. Comparison of Exposure To Inhakd Anaesthetics Beiween Small-Animal Workers And Mi xed- Animal Workers

1 Exposure Before Diagnosis of Pregnancy

29 W w k Exposures After Diagnosis of Pregnancy*

2 3 M w k Exposure Stopped**

only in first trimester Use of Cartridge-Ma&

1 aiways 1 sometimes

1 Use of Scavenge System

1 aiways 1 sometimes

Small- Animal Workers N=43 (%)

Mixed-Animal Workers N=11(%)

* 3 patients were lost to follow-up ** 4 patients were lost to follow-up

Table 8. (continued) Details of Exposure To Inhaled Anaesthetics

Use of Endotracheai Tube

always sometimes r a d y

Use of Mask

always sometimes rare1 y

Use of Anaesthetic Chamber/ Cage

aiways sometimes rarely

Smail- Animal Workers N=43 (96)

Mixed- Animai Workers

N=ll (%)

Table 9. Details of Exposure To X-radiation By Type of Practice

S mail-Animal Workers*

Mixed-Animal Workers

Exposure Before Diagnosis of Regnancy**

O filmdwk S5 filmdwk 6-9 filmdwk

variable Exposures After Diagnosis of Pregnancy**

N=41(%) N=10 (96)

1 (2.5) N=41(%)

110 filmslwk Exposure Stopped

always sometimes

N=10 (96)

Y= no

Restraint By Patient

always sometimes

2 (4.9) N=41(%)

O (0.0) N=9 (%)**

31 (75.6) 10 (24.4) N=42 (96)

9 (100.0) O (0.0)

N=ll (96)

rarely Restrain t B y Tanquilizers

always sometimes lare1 y

O (0.0) N=42 (96)

O (0.0) N=ll (a)

*one patient performed surgical procedures in a ~search facility thus was not expoa radiation ** 2 patients were lost to follow-up 5 Fisher's Exact Test used

4 (9.5) 30 (7 1.4) 8 (19.0)

2 (18.2) 5 (45.5) 4 (36.4)

Table 9. (continued) Details of Exposure To X-radiation

3.13.2 Analysis of Occupational Characteristics and Exposures by Years In Practice

Restraint B y Mechanicd Means always sometimes arely

Use of Lead Apron

aiways sometimes rare1 y

Use of Lead Gloves

dways some times rarely

Use of Thyroid Colhr

always sometimes rare1 y

Use of Dosimeter (film-badge)

always sometimes rare1 y

* one patient performed surgical procedures

There were 28 patients who had been in practice for no more than 5 years ("recent"), and

26 patients in practice for more than 5 years ('old"). Table 10 shows occupational characteristics

radiation

Small-Animal Workers*

N=42 (%)

1 (2.4) 9 (2 1.4) 32 (76.2) N=42 (%)

42 (100.0) O (0.0) O (0.0) N=42 (%)

35 (83.3) 6 (14.3) 1 (2.4) N=42 (%)

39 (92.9) 3 (7.1) O (0.0) N=42 (%)

36 (87.8) 3 (7.3) 2 (4.9)

in a research facility

by number of years in practice. The patients who had been practising for more than 5 years were

olâer (~4 .001 ) and had shorter work-shifts (p=0.01). Table 11 shows details of exposure to

Mixed-Animal Workers

N=11(%)

O (0.0) 2 (18.2) 9 (81.8) N=11(%)

il (100.0) O (0.0) O (0.0)

N=11 (Sb)

7 (63.6) 3 (27.3) 1 (9.1)

N=l 1 (%)

9 (81.8) O (0.0) 2 (18.2)

N=ll (%)

8 (72.7) 1 (9.1)

2 (18.2) thus was not

inhaled anaesthetics. There were no statistical differences in the frequency of use of cartridge-

P-value

0.84

1 .O0

0.3 1

0.0 1

0.32

exposed to x-

rnask (pO.62) or use of scavenging (pa.37). Workers who had been &actising for more than 5

years used anaesthetic chambers more fiequently than those who had been practising for 15

years (p=0.002). The amount of inhaled anaesthetics (waste anaesthetic gas) to which recent

workers compared to the amount to which "old" workers were exposed to was similar before

(W. 14) and after pregnancy diagnosis (pc0.08). Upon comparing the amount of inhaled

anaesthetics to which ment workers were expowd before and after pregnancy diagnosis, the

result was statistically different (pc0.03). A similar cornparison arnong the long-standing ("olb')

workers did not reveal a statistical difference (p=0.07). The number of workers who

discontinued the use of inhaled anaesthetics was similar among the two grOups (pd.60).

Table 12 shows details of exposure to x-radiation. Most of the methods of animal

restraint did not differ between the two groups. A greater number of "016' workers relied on

tranquilizers as a fonn of animal restraint when taking x-ray films, compared to the "recent"

workers (pd.01). The frequency of use of protective equipment against x-radiation did not

differ between the groups. "Recent" workers were exposed to a similar arnount of x-radiation

compared to the old workea, both before (w.56) and after the diagnosis of pregnancy

(w.34). When comparing the amount of x-radiation to which 'Lecent" workers were exposeci

to before and after pregnancy diagnosis, the difference was statistically significant (pc0.03). A

similar cornparison among the old workers did not reveal a statisticai significance (M. 18). The

number of workers who discontinued taking x-ray films in each group was not statistically

di fferen t (p=0.59).

Table 10. Occupational Characteristics B y Number of Years in Practice

4

Matemal Age (years)

Weekly Workshift (hrs)

P-value

4.001

0.0 1

S Years in Practice N-28

28.9 +, 2.7

- 42.4 i 6.4

>5 Years In Practice N=26

32.5 f 3.5

36.6 f 8.9

Table 11. Details of Exposure To Inhaled Anaesthetics By Nurnber of Years in Practice

1 Exposure Before Diagnosis of Pregnancy*

O M w k 12 hrdwk 3-6 hrs/wk 7-8 hrdwk 29 hrs/wk

Exposures After Diagnosis of Pregnancy*

sometimes I always

( Use of Scavenge System

sometimes I always 1 rarely * 3 patients were lost to follow-up

<c Years In Practice

N=27 (%)

O (0.0) O (0.0) 12 (44.4) 5 (18.5) 10 (37.0)

>5 Years In Prac tice

Table 1 1. (continued) Details of Exposwe to Inhaled Anaesthetics By Nwnber of Years In Practice

Use of Endotracheal Tube

aiways sometimes rarely

Use of Mask

aiways sometimes rarelv

Use of Anaesthetic Chamberl Cage

al ways sometimes rarely

27 (96.4) 25 (96.2) 1 (3.6) 1 (3.8) 1 O (0.0) - O (O..)

15 Years In Pmctice N=28 (%)

>5 Years In Practice N=26 (96)

Table 12. Details of Exposure to X-radiation B y Number of Years In Practice

P-value

, 0.56

0.34

0.73

0.56

0.94

0.0 1

exposed to X-

radiation ** 3 patients were lost to follow-up

>5 Years In Practice

N=24 (96)

O (0.0) 8 (34.8) 11 (4.7.8) 4 (17.4) 1 (4.2)

N=24 (%)

1 (4.2) 14 (58.3) 8 (33.3) 1 (4.2)

N=24 (96)

20 (83.3) 4 (16.7)

N=26 (%)

16 (61.5) 9 (34.6) 1 (3.8) N=26 (%)

20 (76.9) 6 (23.1) O (0.0) N=26 (96)

6 (23.1) 17 (65.4) 3 (1 1.5)

thus, was not

Exposure Before Diagosis of Pregnancy**

O filmdwk 15 filmdwk 6-9 filmslwk 210 filmdwk variable Exposures After Diagnosis of Pregnancy**

O filmdwk <c f i l d w k 6-9 films/wk 110 filmdwk Exposure Stopped**

Y= no Restraint By Patient

dways sometimes rare1 y Restraint By Staff

always sometimes rare1 y Restraint B y Tanqui lizers

al ways sometimes rare1 y * one patient performed surgical procedures in

<5 Years In Practice*

N=27 (96)

1 (3.7) 13 (48.1) 9 (33.3) 4 (14.8) O (0.0)

N=27 (%)

5 (18.7) 16 (59.3) 5 (18.5) 1 (3.7) N=26 (%)

19 (73.1) 7 (26.9)

N=27 (96)

19 (70.4) 6 (22.2) 2 (7.4) N=27 (%)

20 (74.1) 7 (25.9) O (0.0)

N=27 (%)

O (0.0) 18 (66.7) 9 (33.3)

a research facility,

Table 12. (continued) Details of Exposure To X-radiation Practice

Restra.int B y Mechanical Means

always 1 sometims

dways sometimes

. rarelv Use of Lead Apron

<C Years In Prac tice*

N=27 (96)

l alwavs someti mes

1 (3.7) 7 (25.9) 19 (70.4) N=27 (96)

rarelv Use of Lead GIoves

>5 Years In Practice

N=26 (96)

P-value

0.36

0 (0.0) 1 4 (15.4)

O (0.0) N=27 (%)

rarelv Use of Thyroid Collar

I always sometimes

22 (84.6) N=26 (%)

always sometimes rarelv

Use of Dosimeter (film-badge)

1 rarely 1 3 (1 1.5) 1 1 (3.8) 1 * one patient performed surgical procedures in a rcsearch facility thus was not exposed to x- radiation

1 .O0

O (0.0) N=26 (96)

1 (3.7) N=27 (96)

3-15 J Analysis of Occupational Characteristics and Exposures By Job Classification

0.58

25 (92.6) O (0.0) 2 (7.4) N=26

Occupational characteristics by job classification are shown in table 13. There were 29

veterinarians. 20 technicians (including: registered veterinary technicians, animal health

technicians. and animal health technologists) and 5 assistants (including: veterinary assistants

and animal care aides). The assistants were excluded from the analysis because their work duties

are not well defined and. hence. may Vary from one practice to another. Matemal age differed

between the veterinarians and the technicians (p=0.004). The technicians were younger than the

veterinarians (29.1 and 32.0 years, resp&tively). The duration of the weekly work-shifi did not

differ between the two groups. The technicians had been in practice for a longer period

compared to the veterinarians (5.0 and 6.5 years, respectively).

1 (3.8) N=26 (%) 0.08

23 (88.5) 3 (11.5) O (0.0) N=26 (96) 0.58

Table 13. Occupational Characteristics By Job Classification

1 Matemal Age (years) 1 32.0 1: 3.5 1 29.1I 3.1 1 04

Veterinarians N=29

1 I

Weekl y Workshi ft (hrs) 1 41.6 f 8.0 1 37.6 f 8.6 I 0.10

1 Years In Practice* t 1 1

1 5.0 1 6.5 1 0.02

Technicians N=20

* median value reporteci

P-value

Details of occupational exposure to inhaled anaesthetics by job classification are shown

in table 14. There were no staiistical differences in the frequency of use of precautionary

measures or the anaesthesia techniques used between the veterinarians and the technicians.

Compared to the technicians, veterinarians were exposed to inhaled anaesthetics for a shorter

duration both before (p=0.02) and after the pregnancy diagnosis (@.Ml 1). A compbson of the -

amount of inhaled anaesthetics io which veterinarians were exposed to before and after

pregnancy diagnosis did not reveal statistical signi ficance (@. 10). A sirnilar cornparison

arnong the technicians also did not reach statistical significance (p=O. 14).

Table 14. Details of Exposure To I n h W Anaesthetics By Job Classification

( Veterinarians 1 Technicians 1 P-value

Exposure Before Diagnosis of Regnancy

29 h d w k Exposures After Diagnosis of Pregnancy

N=29 (96)

29 h d w k Exposure S topped

always some times

I

N=18 (%)* I 0.02

5 (17.2) N=29 (%)

only in first trimester Use of Cartridge-Mask

2 (6.9) N=28 (96)

always sometimes

9 (50.0) N=L8 (%)*

1 (3.6) N=29 (96)

rarley üse of Scavenge System

0.001

7 (38.9) N=18 (%)*

aiways sometimes

0.26

O (0.0) N=20 (%)

27 (93.1) N=29 (Sb)

d e y Use of Endotracheal Tube

0.24

dways sometimes

19 (95.0) N=20 (96)

O (0.0) N=29 (96)

rarley Use of Mask

0.4 1

O (0.0) N=20 (%)

O (0.0) N=29 (96)

0.4 1

rarley >se of Anaesthetic Chambed Cage

always sometimes rarley -

O (0.0) N=20 (%)

10 (50.0) N=20 (96)

19 (65.5) N=29 (96)

0.18

0.70

3 patients were lost to follow-up

O (0.0) 4 (13.8)

25 (86.2)

0 (0.0)l 4 (20.0) 16 (80.0)

Details of exposure to x-radiation by job classification are show in table 15. There were

no statisticai differences in the methods of animal restraint or in the use of precautionary

measwes used between the vetennarians and the technicians. The vetennarians were exposed to

a sirnilar amount of x-radiation before (p=0.39) and after pnqpncy diagnosis (p=û.O8),

compared to the technicians. When the arnount of x-radiation to which the veterinarians were

exposed before and after the diagnosis of the pregnancy was compared, the difference was

statistically significant (pS.01). A sirnilar cornparison among the technicians did not reveal a

statisticaily significant difference (p=0.70).

The rates of spontaneous abortion and major malformations did not differ between the

veterinarians and the technicians (p=l .O0 and pd.3 1, respectively).

Table 15. Details of Exposure To X-radiation B y Job Classification

Exposure Before Diagnosis of Pregnancy P Technici ans * N=18 (96)-

O filmdwk <5 filmdwk 6-9 filmdwk 210 filmdwk variable

Exposures After Diagnosis of Pregnancy

O filmdwk S5 filmdwk 6-9 filmdwk 210 fiimdwk

Exposure Stopped

no Restraint B y Patient

sometimes l always

rarely Restraint By Staff

sometimes l rarely

Restrain t B y Tanquilizers

always I

rare1 y I * one patient perfonned surgical procedures in a research facil radiation ** 2 patients were lost to follow-up

y thus was not

Table 15. (continued) Details of Exposure To X-radiation

1 Restra.int By Mechanicd Means

1 Use of Lead Apron 1 N=29(%)

rare1 y Use of Lead Gloves

O (0.0) N=29 (%)

rarely Use of Thyroid Collar

1 3 (10.7) * one patient performed surgical procedures in a research faci

O (0.0) N=29 (%)

always sometimes rarely Use of Dosimeter (film-badge)

radiation

24 (82.8) 3 (10.3) 2 (6.9)

N=28 (%)**

Technicians*

y thus was not

** one patient had not been providcd with a dosimeter at the time of the interview

3.2 Analvsis of Radiation Dosapes (pmject 2)

3.2.1 Analysis of Annual Mean Radiation Doses For Veterinary Practices

The annual mean radiation doses were substantially below the 20mSv ümit specified by

the ICRP for al1 the vetennary practices for the p e n d requested (figure 2.1). In only one

veterinary practice the dose equivalent limit of 4mSv, indicated for pregnant personnel in

Ontario, was exceeded. wiîb its annual mean radiation dose being 4.45mSv in 1986. The annual

mean radiation doses did not follow a particuiar pattem over the pend of 1988 to 1998. The

cumulative mean radiation dose, which refers to the mean of the annual radiation dose over 11

years, varied widely among veterinary practices ranging from 0.00 to 0.77mSv (figure 2.2).

3.2.2 Anaiysis of Cumuiative Mean Radiation Dose By Type of Practice

Theie were 60 vetennary hospitals, 36 vetennary clinics. and four vetennary services.

The vetennary services were excluded from the analysis becausc only a few were represented.

The pattern of distribution of cumulative mean radiation doses among the clinics and hospitals

was similar (@.54), with a mean of 0.07f 0.02mSv and 0.lM 0.OZmSv. cespectively (figure

2.2). The median cumulative mean radiation dose was the same for clinics and hospitals, at

0.û4mSv.

The registry does not usually~ecord the type of animal practice to which the radiation

doses belong i.e. large-animal, small-animal or mixed-animal. Therefore, the Bureau attempted

to determine this from the narne of the practice. Consequently, this information could only be

elucidated for 24 practices: seven quine/ large animal practices and 17 pet/ cat practices. nie L

equinel large animal practices had similar cumulative mean radiation doses when compared to

pet/ cat practices (p4.43) (figure 2.3). The radiation doses varied substantially among the pet/

cat practices ranging from 0.00 to 0.36mSv.

Figure 2.1 Distribution of Annual Mean Radiation Doses Among 100 Randomly Selecteà Veterinary Practices For The Past 1 1 Years -- -.

- - - - - - - - -,

- - a -

Y@- -

h i c H: hospital S: service The radiation doses for 4 practices are repnsented in each graph

Figure 2.1 (continueci) Distribution of Annual Mean Radiation Doses Among 100 Randomiy Selected Veterinary Practices For The Past 1 1 Years

I I C: chic H: hospital S: service The radiation doses for 4 practices are kpresented in each graph

Figure 2.1 (continued) Distribution of Annual Mean Radiation Doses Among 100 Randomly Seïected Veterinary Practices For The Past 1 1 Years

ig ;:: - 1.30

4 ;: % am 0.50

3 o., P

0.10 a ,IO

C: c h i c H: hospital S: service The radiation doses for 4 practices are represented in each graph

Figure 2.1 (continued) Distribution of Annual Mean Radiation Doses Among 100 Randornly SeIected Veterinarv Practices For The Past 11 Yez

1 1 f - C: chic H: hospital S: service

The radiation doses for 4 practices are represented in each graph

Figure 2.1 (continued) Distribution of Annual Mean Radiation Doses Arnong 100 Randomly Selected Veterinary Practices For The Past 11 Years

I I I 1 f C: chic H: hospital S: service The radiation doses for 4 practices arr represented in the graph

Figure 2.2 Distribution of The Mean Cumulative Radiation Doses Among Vetennary Clinics and Hospitais -A.---- -- .- ----- --r - ----y------- --

Figure 2.3 Comparison of Cumulative Mean Radiation Doses of Equine/ Large-Animal Ractices To - - - Those - - - -- of Pet/ Cat k t i c e s - - - - -- - - - -- - -- ---

3.23 Comparison of Cumulative Mem Radiation Doses With The Number of Workers

The number of workers in veterinary practices correlated significantly with cumulative

mean radiation doses in the practices (r =0.21, peû.00 1). A cornparison of the number of

workers with the cumulative mean radiation dose, while taking into consideration the type of

vetennary prac tice. reveaied a weak but statisticall y significant relationship for both clinics

53

(r = 0.35, ~=û.04) or hospitals (r a . 3 1. pc0.02). A similar correlation between the cumulative

mean radiation dose and the number of workers for both clinics (r=0.39, p=0.02) and hospitals

(r=0.28. pc0.04) when practices with less than 6 years of data were excluded from the analysis.

There was no signifiant comlation between the cumulative mean radiation doses and the

number of workers in either clinics (r=0.33, w . 0 7 ) or hospitals (d.21. pc0.15) when practices

with an average of one worker were excluded from the analysis.

3.2.4 Anaiysis of Number of Workers In Veterinary Practices

The average number of workers in veterinary clinics did nat differ signincantly from that

in veterinary hospitals (p=û.96) (figure 3.1). Similady. the average number of workers in pet/

cat practices was similar to that of equinel large animai practices (p=0.98) with a range of one to

seven worken for both types of practices (figure 3.2).

Figure 3.1 Comparison of Average Number of Workers In Veterinary Clinics and Hospitals

I veterlnuy cîlnics (count)

vaterlnuy hospit8îs (count) J F i p 3.2 Cornparison of Average Number of Workers In Pet/ Cat Practices To The Number In Equine/ Large-Animal Pmctices

Y .

1 2 3 4 5 6 7 squlnd krge animal frcilitks (count)

4. DISCUSSION

4.1 Occuiiational Exwsuiies of Veterinaw Staff D u ~ e Preenancv (project 1)

The purpose of this study was to describe potential adverse effects associated with in

utero exposure to inhaled anaesathetics and x-radiation among veterinary staff. Even though

veterinary stafî are exposed to many health hazards in their daily work, the data suggested that

staff have a sirnilar rate of adverse reproductive effects, including birth defects, spontaneous

abortion, pre-tenn delivenes and low birth weight babies, compared to women in the general

population. These findings are in agreement with the hypotheses proposed at the beginning of

the study.

The study group consisted of a random sample of veterinary staff, most of whom were

practising in Ontario, who voluntady contacted the Motherisk Program and requestcd to be

enrolled in the study. As initially intended the sample was heterogeneous, encompassing

different types of veterinary staff, including : veterinarians, registend veterinary technicians,

animal health technicians/ technologists, veterinary assistants, and animal care aides. The

sample also included workers in small-animal and mixed-animai practices from xural and d a n

regions. The fact that there were no female veterinary staff working in large-animal practices is

not surprising because previous studies have shown that female veterinary staff mostly tend to

work in small-animal practices75. The heterogeneity of the sample permitted the detection of

differences in the rates of reproductive adverse effects among different groups of veterinary staff,

i.e. veterinarians versus veterinary technicians, or small-animal workers versus rnixed-animal

workers. C

The ideal control group for this study would have consisted of pregnant veterinary staff

who were neither exposed to inhaled anaesthetics nor x-radiation; however, this was not feasible

since performing surgenes and taking x-rays represent a major part of their job. Another

approach to control for occupational exposure to inhaled anaesthetics and x-radiation, would

have been to use two control groups; one group consisting of pregnant anaesthetisisl surgeonsl

operating-room personnel, and the other group consisting of pregnant radiologistd x-ray

technicians. However, such subjects do not provide valid control groups: previous studies 25.30-36

have shown that personnel working with inhaled anaesthetics are at an increased risk for

spontaneous abortion. Radiologistd x-ray technicians cannot be compared to vetennary staff

since they do not need to restrain patients and usually stand behind a protective lead or concrete

partition, hence are probabl y exposed to substantially lower levels of radiation, if not negiigible

levels.

The study attempted to overcome some of the limitations of previous studies by

specifying the amount of WAG and x-radiation to which veterinary staff were expose4 and by

reporting on the frequcncy of use of precautionary measures and persona1 protective equipment

by the staff. Since the &ta were collected prospectively, the likelihood of recall bias to occur is

very low.

4.1.1 Matemal Demograpbies and Obstetrical History

Matemal age was matched for and thus was similar between the study and control groups

(p=0.72). The majority of the veterinary staff (study group) were nulliparous. Veterinarians

may be postponing starting a family because of the long course of pst-secondary education ( six %

years of university). Even though veterinary technicians and animal health techniciand

technologists require a shorter period of training (only two or three years of college education),

many of the participants in the study tended to have an education in several fields. There were

no other differences in obstetrical history between the two groups.

4.1.2 Pregnancy Outcorne, Delivery Parameters and Neonatal Parameters

The pregnancy outcome did not differ between the two groups, with an equal number of

live-births in both groups. This finding is in agreement with those of Schenkar et al8 (1990), and

Steele and Wilkins III7' (1996), who demonstrated that female veterinary staff were not at an

increased risk for spontaneous abortion. There were no statistical di fferences in the delivery

parameten, including method of delivery, prevalence of hemontiage or preterm delivery among

the groups.

Although gestational age at birth was significantly different, the rate of pretem birth was

similar among the study and contml groups. Hence, the difference in gestational age at bkth

was not scientifically plausible, and therefore, probably was not clinically significant. The

difference in birth weight between the groups remained statistically significant even after

excluding the trïsomy-18 baby from the analysis. The possible reasons for the difference in birth

weight between study group and the contml group were considered; 1) presence of more smokers

in the control p u p , however almost al1 of the control subjects were non-smokers, 2) rate of pre-

term delivery was similar bctween the two groups (as mentioned previously), 3) male newboms

are heavier than female newboms, but the number of male n e w b m s was similar between the

groups, 4) matemal diabetes is associated with macrosomia, however none of the study subjects

- were diabetic. 5 ) matemal weight gain did not differ between the two groups and, 5) pre;

pregnancy weight was similar between the groups. The difference in birth weight may be due to

other unknown factors. A previous ntrospective controlled cohort study8 showed that female

veterinarians were not at a greater risk of having low birth-weight infants. The rate of fetal L

distress was similar between the study and control groups.

4.13 Major � or mations

n i e similar rates of major malfomations between study and control groups confirmed

the findings of Johnson et al' (1987). Other researchers8 found an increased risk for major

malformations among female veterinarians, but their findings on1 y serve as h ypothesis-

generating since the study was not designed to detect an increased risk for birth defects. There

were four major malfomations in the study group and three in the control group; no particula.

pattern of malfonnations or syndrome existed. Although the rate of major malformations

among veterinary staff excoedcd the 3% baseline risk, it still lay in the 95% confidence interval

(0.6 to 8.5). There was a substantial difference in age of the off-spnng at foliow-up, such that

the off-spnng of the study subjects were followed-up at a younger age compared to off-spring of

the control subjects. The difference in the age of the off-spring presents a potential problem in

that the older the childrm are, the more visits to the physician they would have had including

routine examinations, vaccinations, and ilinesses, hence, there would be a p a t e r chance of

detecting defects that were rnissed at birth or shortly after. However, this was not the case since

the number of major malformations was almost equal between the groups. This study had 80%

power to detect an eight-fold increase in the rate of major malfomations above the 3% baseline

risk, with an alpha of 0.05. In order to detect a two-fold increase, 8 14 subjects are required for

each of the groups. Another way of expressing the power of this snidy, is that a sample size of

54 subjects in each of the groups only provides 6% power to detect an increased risk of major

malformations. This study was not designed or powered to look for mental retardation or

microcephaly in the off-spring of vetennary staff.

4.1.4 Occupational Charocteristics and Exposure Detaiis

Inhalation anaesthesia practices in the veterinary field are similar to the practices in the

medical field7'. In each case anaesthesia in the patient is first induced using an injectable

anaesthetic (such as thiopental sodium, methohexi tal, althesin or ketamine in the case of

humans'', and in the case of animals, using thiopentanone sodium or methohexitone sodiumgo),

anaesthesia in the patient is then maintained by an inhaled anaesthetic (such as halothane,

methoxyflurane, enflurane or isoflurane in the case of h~mans'~, and isoflurane or halothane in

the case of animals). There are two types of anaesthetic systems used for both humans and

animals; a low-flow system (Circle ~ ~ s t e r n ) ~ or rebreathing circuit7' and a high-flow system2 or

non-rebreathing circuit7'* m(also known as the Bain Circuit in vetennary practice). The latter

system allows a unidinctional flow of gas from the vapourizer to the patient upon inhalation, and

upon exhalation gases are passed through a carbon dioxide absorber, thus permitting rebreathing

of the erthaled gases. This system needs only a small amount of fresh gas to replace that inhaled

by the patientz78. ui the high-flow systed non-rebreathing circuit the gas flows back and forth

from the vapourizer as the patient inhales and exhales. Excess anaesthetic dong with exhaled

carbon dioxide are expelled from the system, hence a greater amount of gas must be added to

compensate for the lac k of rebreathing2* 78. Inhaled anaesthetics are delivered to the patient

(human or animal) through a face-mask or an endomicheal tubeZ 78.

Isoflurane appeared to be morr popular than halothane for surgical procedures in the

vetennary field. The reason for this is probably because isofiurane is not associateci with hepatic

or renal toxicity2. In contras<, halothane is 20% biotransformed resulting in organic fluorine, C

which can lead to hepatotoxicit$ In addition, isoflurane has a faster onset of action compared

to halothane since its Pwg (blood-gas partition coefficient) is 1.4~.

Cartridge-masks were not readil y used precautions by veterinary staff. Despite the

availability of means to monitor "waste" anaesthetic gas levels, such as air-sampling, dosimeter

badges and portable infra-red anal yzen, the majority of the practices did not routine1 y monitor

WAG. The reason behind this could be the high cost of monitoring. A different approach was

taken in order to quantify the levels of WAG in veterinary clinics and veterinary hospitals. An

attempt was made to compare the odour thresholds of inhaled anaesthetics to the pemiissible

exposure limits (since some participants pointed out the presence of an odour in their facilities).

However, this attempt proved to be unsuccessful ôecause none of the material safety data sheets

reviewed reported these values.

In veterinary practice exposure to x-radiation may occur in one of two ways, first by

direct contact with the pnmary x-ray beam, which may occur while personnel are restraining

animals, and secondly by exposure to scatter radiation as a result of the x-ray beam bouncing off

the animai and the x-ray table afier it has made contact with the animal? The amount of

exposure from both the pnmary beam and the scatter radiation could be reduced by collimation

(narrowing down) of x-ray beams, use of fast films and screens and by ensuring staff an not in

the vicinity of the beam9.

In order to determine the level of x-radiation to which veterinary staff are exposed,

participants were asked to provide the 1 s t reading on their dosimeter badges. However, the

majority of the women were unable to provide the& data, and therefore, a diffemnt path was

sought to obtain similar data. General radiation doses for veterinary staff were obtained h m the

National Dose ~ e ~ i s t r y ' ~ and analyzed.

A possible reason behind the substantially large number of women who discontinued

their exposwe to x-radiation compared to the small number who discontinued their exposure to

inhaled anaesthetics could be that veterinary staff may not be as concemed about their exposure

to inhaled anaesthetics as they are about their exposure to x-radiation. This may be because

there is ample evidence, including the findings of the present study, for occupational exposure to

inhaled anaesthetics not k i n g associated with an incmased risk of major birth defects7* ** 23-29 and

that exposure to inhaled anaesthetics, specifically in the vetennary field, is not associated with

any adverse reproductive effects7* '. Another reason couid be, given that manual restraint is the

more commonly utilized method to restrain animals for taking x-rays in small-animal practices8',

which in tum does not require special training, thus an y rnember of staff can carry out this task;

therefore, pregnant vetennuïans and technicians could be easily excused from taking x-rays. On

the other hand administration of inhaled anaesthetics does rcquire special training, and hence

must always be performed b y appropriatel y trained staff such as veterinarians, vetennary

technicians or animal heal th techniciand technologists.

4.1.4.1 Occupationai Characteristics and Expqsure Detaiis By Type of Practice

The finding that the frequency of use of scavenging systems was greater among the

small-animal workers than among the mixed-animal practice group could not be satisfactonl y

explained. Upon further examining the two subjects who rarely used scavenging in their

practice, it was revealed that one woman was an animai care aide who was working in a practice

in which a ceiling fan was always uscd to reduce the level of WAG around the operating table.

The other woman was a veterinarian who worked in a practice in which a scavenging system

was available but she mainly used a ceiling fan located above the preparation table to reduce the

level of WAG. A very weak explanation for this finding is that the level of WAG could be lower - in mixed animal practices because the re-breathing anaesthesia system is normally used to

anaesthesize large animals. This anaesthetic system is not suitable for small animals due to the

excessive dead space in their lungs and the breathing resistance, the non-rebreathing system

(Bain Circuit) is utilized instead. However, to compensate for the lack of re-breathing higher

oxygen and anaesthetic flow rates are required, which probably results in a greater level of

WAG'~. Thereforc, scavenging may not be routine1 y used in rnixed animal practices.

Nevertheless, given that the use of scavenging is a legal requirement in Ontario, this explanation

could not justify this finding. In addition, the finding of srnail-animai and mixed-animal workers

king exposed to a sirnilar amount of inhaled anaesthetics fwther undermines this explanation. It

is expezted that with a larger sarnple size the frequency of use of scavenging between the two

groups would not differ statistically. Exposure to inhaled anaesthetics among the small-animal

workers substantially d e c d after the diagnosis of pregnancy. Given that smali-animal

workers and mixed-animal workers were exposed to a similar amount of inhaled anaesthetics and

had a sirnilar work-shift dwation, one is unable to explain this finding.

There are no plausible reasons for the statistical difference in the frequency of use of

thymid collars among the small-animal workers and the mixed animal workers. The= were no

remarkable findings among the subjects who rarely used thyroid collars. Both subjects were

veterinarians; one patient did not use a thyroid collar because it did not provide a good fit, and

the other patient did not offer a reason for not using a thyroid collar. Besides. use of a thyroid

collar is not a legal requirement7*.

4.1.4.2 Omipational Characteristics and Exposure D e W By Years In Practice

The finding that the less expaienced ("recent") vetennary workers were younger and

worked longer shifts was not swprising. Veterinary staff who have been practising for more than

five years appared to be more cautious about their exposure to inhaled anaesthetics and x-

radiation, and therefore more diligent in using techniques that rninimized their exposure. This is

proven by the fact that none of the older workers used anaesthetic chambers, and most of them

used tranquilizers to restrain animals for x-ray pmcedures. Taking into consideration that the

amount of exposure to inhaled anaesthetics was sirnilar between the "recent" and the "'old"

workers, the substantial decrease in exposure to inhaled anaesthetics among "recent" workers

&ter the diagnosis of pregnancy cannot be enplained.

4.1.4.3 Oeeupationd Chsracteristics and Exposure Details By Job C18ssification

The technicians were younger than the veterinarians and yet ovcrall had been in practice

for longer p e n d than the vetennarians. This finding could be explained by the fact that

technicians require a shorter course of education and training to become qualified, cornpared to

veterinarians. The choiccs of anaesthesia techniques used and the methods of animal restraint

applied may also be detennined rnainly by the veterinarians present during the procedure, not by

the technicians. Therefore, the finding that anaesthesia techniques and methods of animal

restraint were similar between the veterinarians and the technicians was not surprising. This

study did not show a àifference in the frequency of use of precautions between the veterinarians

and the technicians. A possible reason for this finding is that the friequency of use of pmtective

equipment partly depends on the availability of such equipment at the practice.

This study indicated that veterinarians only usecl isoflurane and halothane in their surgical

procedures. These findings sharply contrast with findings of Langley et al76 (1995) findings that

the rnost utilized inhaled anaesthetic was methoxyflurane (5 1.4%), followed by halothane

(43.6%) and isoflurane (39.1%). A larger proportion of vetennarians (72.4%) opted to use both

types of anaesthesia circuits; re-breathing and non-rebreathing systems, compared to the

proportion reported by Wiggins et al8' (1989).

This study showed some variations in the proportions of veterinarians who used

precautions against x-radiation compared to previous studies. In their study of patterns of

ionizing radiation exposure among female veterinarians, Morwia et ala2 (1989) reported that

95.9% of veterinarians wore lead aprons. 87.9% used lead gloves and 1.2% used thyroid collan.

However, that study did not assess the frequency of use of these protective equipment by the

veterinarians. A substantial proportion of veterinarians rcported using thyroid collan, with more

than three-quariers using a thyroid collar always and on1 y 10% using it sometimes. Langley and

col leag~es '~ (1995) reporteci that 63% of veterinarians (male and female) always wore film

badges and 10% reported using film badges rarely or never.

Even though the study had limited power due to the small sarnple size. an attempt was

made to improve the quality of the study by collecting details on occupational exposures. On the

Prospective Occupational Exposures Questionnaire, subjects were asked about their exposure to

inhaled anaesthetics and x-radiation oidy dunng that point in pregnancy at which they wexe

contacted. This affects the validity of the results since their exposures could be different before

the diagnosis of the pregnancy and for the remainder of the pregnancy. in order to solve this

problem subjccts were asked about their exposures before and after the pregnancy was

diagnosed on the Retrospective Occupational Exposures Questionnaire. Nonetheless. this did

not pexmit a cornparison of the prospective reporting to the retrospective reporting.

The amount of inhaled anaesthetics and the arnount of x-radiation to which veterinarians

were exposed could not be compared to the amounts reported in previous studies because the

sales that were used to quantify exposure were different. The fkequency of use of various

techniques and precautions reporteci by the subjects does not distinguish between whether that

frequency is bas& on subjects attitudes or availability of such equipment at the practice. In

other words, some of the practices of veterinary staff are probably dictated by the availability of

the appropriate equipment at the practice.

4.2 Analvsis of Radiation Dosa- (projecî 2) _ In Canada, the radiation readings of al1 dosimeters, including dosimeters that belong to

radiologists, x-ray technicians, laboratory technicians, vetennary staff and graduate students,

must be reported to the National Dose Registry at the Radiation Protection Bureau of Health

Canada. The Bureau also offers dosimetty services (i.e. a s e ~ c e to measure radiation madings

on dosimeters) for various time intervals. Dosimeter badges of vetennary staff are measunxi

every three rnonths (quarterly)73. After the radiation dose on the dosimeter is recorde& the

dosimeter is erased, prepared for the next dose reading, and retwned to the employer dong with

the exposure resdts. In situations where regulatory dose limits are exceeded, the Bureau sen&

notices to the employer and the regdatory authority involved (the provinces xepresent the

regulatory authorities in the case of medical or veterinary x-radiation). The employer is also

asked to investigate the incident and report back to the appropriate regulatory a~thority'~.

Women of reproductive age working in vetennary practices ofien have great concems

regarding their radiation exposure. The data indicated that the overall exposure is substantially

below the minimum safety levels. This agreed with the findings of Huda et als3 (1991). who

showed that the mean annual whole-body radiation doses of radiation technologists working in

diagnostic radiology for the period of 1978 to 1988 were below the annual permissible dose

equivalent of 20 rnsv4. in addition, the annual radiation doses do not reflect the type of - veterinary practice (i.e. clinic or hospital) . Al1 but one surveyed veterinary practice adhered to

the permissible dose equivalent limit of 2mSv established by the ICRP. This practice also

exceeded the annual dose limit of 4mSv which is specified for pregnant radiation personnel in

Ontario. Since no further &ta were available, one can only speculate about the reason behind

this practice exceeding the dose limit in 1988. This practice may have upgraded its x-ray

equipment in 1989, adopting beam collimators, faster films and intensifying screens thus

significantly reducing its annual mean radiation dose. Furthemore, the annual mean radiation

dose for this practice continued to decrease over the subsequent years . probably because the

staff was becoming more familiar and experienced at using the equipment.

The findings indicated that equind large-animal practices seem to have similar

cumulative mean radiation doses compared to pet/ cat practices, radiation doses are expected to

be lower in equinel large-animal practices. Vetennary staff rarely need to restrain large animais

because of the threat of personal injury, and because the inefficiency of the task; instead,

mechanical restraint is usually used, thus allowing staff to leave the x-ray room. On the other

hand, manual restraint is the more comrnonly utilized method in pet/ cat practices". probably

resdting in a p a t e r radiation exposure to the staff. This difference was not detected perhaps

due to the small sample size. It could be theorized that the reason behind the significant

variation in the cumulative radiation doses among the pet/ cat practices is that some practices

may have more stringent requirements for use of precautionary measures (i .e. lead apron, lead

gloves, and thyroid collar) than others, thus resulting in lower levels of radiation exposure. A

more subtle reason behind the disproporîionaie number of large-animal practices represented is

the fact that only radiation workers who are likeiy to receive a radiation dose in excess of 1/20 of

the annual permissible dose equivalent limit must Wear personal dosimeters, according to the

Heaïth and Welfare Canada (Recommended Safety Procedures For Installation and Use of

Vetennary X-ray Equipment, Safety Code 281'~. This is supporteci by the findings of Wiggins et

al8' (1989) that large-animal practitioners are the least likely to Wear dosimeters (p<0.05) and of

Langley et af6 (1995) that mixed-animal and small-animal practitioners are more likely to

always Wear dosimeters compared to large-animal practitioners (p4.001).

The study indicated that a significant difference exists between the number of workers

employed in veterinary clinics and that employed in veterinary hospitals. Further analysis

revealed a weak, but statistically significant, positive correlation between the cumulative mean

radiation doses of the veterinary practices and the number of workers. However, this

nlationship was not reflected in the comlation coefficient, probably because of the smail sample

size. This finding could be explained by the fact that larger practices are capable of handling a

greater number of animals, consequentl y the staff is exposed to higher Levels of radiation.

Examination of veterinary practices for which fewer than 6 years of data were available

did not reveal panicular years for which the information was missing. However, almost al1 these

practices had only 1 or 2 workers for some years. Taking this into account one could speculate

that the mason for the missing &ta is a result of common veterinary practice; where more than

two people are requinxi to take x-rays since the animal must be fully restrained. Since workers

were probably exposed to minimal levels of radiation during those years, they may not have

found it necessary to report their exposure. In contrast to the findings of a study of diagnostic

radiology technologistss3, these data did not indicate a decrease in the annual mean radiation

doses over the period of 1988 to 1998.

The use of the mean as a mesure of distribution of annual radiation doses in veterinary

practices does not provide a robust parameter to detect outliers; the median and range are more -

appropriate measures. This is supported by the findings of Hu& et al" (1991) that the ranges for

whole-body radiation doses among radiation technologists were very different from the mean

annual radiation doses4. Another limitation is that the actual number of workers in each

veterinary practice is unknown, since the number provided by these data only represented the

workefs who Wear dosimeters. It is not uncornmon for receptionists and kennel staff to assist in

restraining animals and in surgical procedures. The assumption that the annual mean radiation

dose provided by the registry represented the dose to the surface of the abdomen was made:

however, there is some variation in the location where dosimeters are worn. Health Canada

'Xecomrnended Safcty Procedures for Installation and Use of Vetennary X-ray Equipment"

(Safety Code 281'~ specifies that a personal dosimeter must be worn undemeath the lead apron.

In contrast, the Ontario Ministry of Labour suggests that personai dosimeters used for veterinary

radiography be wom outside of the lead apron or thyroid coiiar at neck level. The location in

which the dosimeter is wom most probably has a significant impact on the dose reportecl, Since

this information was not provided this study did not takc dosimeter location into consideration.

S. CONCLUSIONS AND RECCOMENDATIONS

The study indicated that occupational exposure of vetennary staff to inhaled anaesthetics

and x-radiation during pregnancy was not associated with increased risks for major

malformations, spontaneous abortion, pre-term delivery or low birth weight infants. These

prcliminary findings provide some massurance to female veterinary staff af cchild-bearing age.

This study also uncovered some trends in the techniques and precautions used by veterinary staff.

Studies with larger sample sizes are required to verify those trends. Con- to the existing

belief that vetennary staff are exposeà to excessive levels of x-radiation, this study showed that

radiation doses of veterinary staff are considerably below the annual pennissible dose equivalent

limits. To ensure more complete anaiysis of the radiation data, M e r infornation is required,

including range, median annual radiation doses, dosimeter location, and total nurnber of workers

in each practice. The findings of this preliminary study and future stuclies would eventually

allow one to establish more specific occupational guidelines for pregnant vetennary staff.

In the meantime, pregnant vetennary staff should aim to minimize their exposm to

"waste" anaesthetic gas by always using scavenging, periodically testing anaesthetic machins for

gas le& and not emptying or filling vaporizers. The use of good anaesthetic techniques is also

advised including use of cuffed endotracheal tubes whenever feasible, avoiding use of

anaesthetic chambers or face-masks, main taining the connection between the animal and the

anaesthetic machine such that the animal breathes pure oxygen for a few minutes once vaporizers

are switched off. Similarly. pregnant staff should aim to reduce their exposure to x-radiation by

refraining from manually restraining animals p and to use sedatived tranquilizers or sand bags

instead. In situations where the animal must be restrained rnanually, and no other staff are

available for this task. pregnant staff are advised to Wear lead-aprons, lead-gloves and thyroid

collars to ensure adequate protection from radiation. Veterinary staff should ensure that

protective equipment used against radiation is in good condition by periodically radiographing

the equipment, in order to test it for damage or leaks. Finaîly, x-ray duties should be rotated

between staff members, such that no one worker receives the entire radiation exposure.

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82. Morwitz SA. Hueston WD, Wilkins III JR. Patterns of ionizing radiation exposure

among women veterinarians. JAVMA 1989; 195(6):737-739.

83. Huda W, Bews J, Gordon K, Sutherland JB, Sont WN, Ashmore JP. Doses of population

Uradiation factors for Canadian radiation technologists (1978- 1988).

Can Assoc Radio1 J 199 1 ;42(4):247-252.

APPENDM A - Advertisement for Veterinary Expowres Shidy In The OVMA Magazine and The OAVT Magazine

W A N T E D

Supporthg Research for safety inthe workplaœ.

APPENDIX B - Flyer Sent To Veterinary Ciinics and Veterinary Hospitais In Ontario

555 UNlVERSrrYAVENUE

oh^ CANADA MX; 1x8 THE HOSPIIAL FOR SICKcHIIDREN

PHONE (416) 813-1 MO

Dirm LYU. (4 1 . 8 13-6780 d - n . a W C ~ W C - ~ O ~

RE: OCCUPATIONAL EXPOSURE OF ONTARIO VETERINARY G i n Karen. MD. F R C K N3MT

STAFF DURING PREGNANCY D-r oCMoùurisk

MD. ABU'

The Motherisk Program at 'LBe Hospital for Sick Chiidrcn in Toronto strives to pmvide evidcnce-bassd informafion to womn and Wh carc profcssionrls on mcdications, infections, IBdjation and occupational exposmes during prtgnaacy and lactation. We a h mndud chical research in the field of pctnaîai/ toximIogy and arc nmentiy conducting an obsavationd prospective ccmtroiied cohort study co~xming occupational expurcs in veterinary msdicim Qiring pngnancy 'Ibis is in collaboration with the Ontario Vct t~ary Medical Association (OVMA) and the Ontario Association of Vettrinary Technicians (OAVT).

Cwrtntly the= are 2745 veterinarians and 1 100 registercd veterinary tachnicians practising in Ontario. Expomrit to inhaiational anacsthetics, diagnostic d a t i o n and pesticides appar U> rrpesent the major conccms of veterinariaas a d v c t u i ~ ~ ~ technicians. Aîtbough ocupîiond exposurr <a aiese hdth hPzrrds in veraiiuy d c i n e h a s b e t n ~ i L I t h t r r i r A i r a l l i ~ , ~ ~ ~ ~ ~ i l l ~ t O b t a ~ o f information ngading adverse rcproâuctive eff- pssoCaîcd witb these c x p ü f t ~ .

In addition to d g che repoductive effkcts ssfociated with occupati0081 exposure to inhalationai -CS, diagnostic radiation and pesticides m vctcrinary medicine, this stuày wiii descnbe the occupational expo~mc of fernale veteriaarysUnuidthee~111ttowhichpr#.lautio1181ymeanursFcccmnneadedbytht Ontario Ministry of Lahm .n implellltnted Thc uitimate goal of tb.is study Win be to attempt to écl#miac whema exposuile ~it~~)rnmendations of the Ontario Mmistry of Labour or the United States National Institute for ocCupatio1181 Safety and Health (NIOSH) provide adquate protection for pregnant veterinary staff. -.

Pccg -5 MBBS. CCFP ~ R n a r c ù F o u m d a t i o n The study which was initiateci in January of this year. appears u> have capaind the M H- siœar. MD. FR- . attention of f t d c veterinarians and vetcrinary technicians thtoughout Ontario with Sunnybiook ~cd ic i l wcf, Centre 38 cases having becn sucœ~~fully re~xuited so fa,. The sbidy will t a k pl- O V ~ Jmy Shimc. MD. FRCPC wommi ~al)qgc ~ a r p i J the next 3 y-. This sîudy is supportcd by a grant h m PomUn Smith I n s u r a ~ ~ ~ h shuhibcr. SSC Brokers and Governmtnt of Canada Human Resources Development Canada Cwnvllor

Cbayi Shuuun. MSc CkpmmnrrofGmria.

W e would apprcciate it if you wuld p s t the attachai flyer in your clinic I hospital. Joanaœ Smith. B k Phm

Should you have any questions pleasc do not hesitatc to contact the study Dcpuimcnt or^^ coordinator Samar Shuhaiber at (4 16) 8 13-6780.

Yours sinccrel

APPENDM C - Flyer Sent To Subscribers of The OVMA Magazine

555 U N l V E R S I f Y AVENUE TORONTO.ONTARI0 CANADA M5G 1x8 PHONE (416) 813-1500

June 14,

HOSPIIAL FOR SICK CHILDREN

Dear Subscriber, =

RE: OCCWPATIONAL EXPOSURE OF ONTARIO VETE-~RUARY STAFF DURING PREGNANCY

'@g@m$7j$RISK The Motherisk Program at The Hospital for Sick Children in Toronto stnves to provide evidence-based information to women and heaith care professionals on

A n t a u d Clinic for ONE/ medications, infstions, radiation and occupational exposures during pregnancy and UKmicil&kCounrclling The Division of

lactation. We also conduct c i i n i d research in the field of prenatall pesinatal Uiniai Phannicoiogy toxicology and are cumntly conducting an observational prospective contdled mrm iim: (4 16) 8 1~6780 cohon study conceming &cupational exposwes in veterinary medicine during Emaii: momrirk@sickkidr.on.a prcgnancy This is in collaboration with the Ontario veterinary Medical Association Dimror of Moribrrri& C h n L-. MD. F A ~ I T . F R O C (OVMA) and the Ontario Association of Veterinary Technicians (OAVT).

Monia Bolop. MD. ABCP Teniogcn Information Spcciaiist

k Dupuis. hiSc Phrm Dtiig Inforrmrion G n t m

A d t h n e Einanon. R N Assurant Direaor

Thomas R Eirumn. P h 0 hculty of Phrnucy

Dan hnne. MD. FRCPC Mount Sanai Iiorpicd

Mkhd Gallo. BSc Caordinaror

Dinrtar Shinya ho. MD. ABCP Diviriun of Ci inai Phmurdagy

Shcila Jacobson. MDDCh. FRCPC Divtimn of a i n i a i Phrnucdogy

M y h Momri, MSc Acrisrurr Direaor

Arroc~Üc Di-r lrcna Nulman. MD Alcohol & D r u e in Prcgrtancy

Jornne Rom. Ph0 Depanment o f Rychoiogy

krcr Selby. hlBBS. CCFP Addiction b r c h Foundation

Ncil H. Shcar. MD. FRCI'C Surmybrook h4edid H d c h Gnrnr

Jcrr). ~liiilic. .Cl 1% FKCinC U.unwA CAlege kloipirai

Samar Sl~uhril>er. 8Sc Cou~iscllor

Cllcryl Shiinian. AfSc Dcparcn~nii of C;çncricr

Jornnc Holnizr. BScPhni Drparrnicni of Pl>arniacy

Currently there are 2745 veterinarians and 1100 registered veterinary tcchnicians practising in Ontario. Exposurc to inhalational anaesthetics. diagnostic radiation and pesticides appcar to npresent the major concems of veterindans and veterinary technicians. Although occupational exposure to these health hazards in veterinary medicine has k e n addressecl in the medical literature, there seems to be a dearth of information rcgarding adverse reproductive effects associated with these exposures.

In addition to assessing the reproductive effects associated with occupational exposurc to inhalational anacsthetics, diagnostic radiation and pesticides in vcterinary medicine, this study will descnbe the occupational exposure of female vetennary staff and the extmt to which prccautionary measures mommended by the Ontario Ministry of Labour are implemented The ultimate goal of this study wiU be to atternpt to &termine whether exposm recommendations of the Ontario M i n i s ~ y of Labour or the United States National Institute for Occupationai Safety and Health (NIOSH) provide adequate protection for pngnant vetennary staff. . The study, which was initiateci in January of this year, appears to have caphued the attention of female veterinarians and vetennary technicians throughout Ontario with 38 cases having been successfully recruited so far. The study will iake place over the next 3 y-. This study is suppoited by a g a n t from Pottruff Smith Insurance Broken and Govemment of Canada Human Resources Developrnent Canada.

Should you have any questions or wish to enroll in the study please do not hesitate to contact the study coordinator Samar Shuhaiber at (416) 8 13-6780.

Yours sincerely, .

&.F-&ZtLL Motherisk Counsellor

A h-lth a r c , ttxcliing and remrch centre dcdicated cxclusivcly to cliildrrn; affilhted with (lie tlnivcrsity ofT~ronto

APPENDM D - List of Exposures Known To Be Safe To The Human Fetus Used To &ka Patients For The Control Group

EXPOSURES OF NON-TERATOGEN CONTROLS

ALLERGYI DERMATISTIS

Topid: corticos teroids sodium cromoglycate Aveeno moisturizers

S ystemic: diphenhyramine c hlorpheniramine brompheniramine pheniramine tnprolidine loratadine cetirizine astemizole h ydrox yzine

COLDS/ CONGESTION/ COUGH

throat lozenges dcxtromethorphan hydrocodone m e n e s i n dimenhydrinate frarnyce tin neomycin

psyllium docusate sodium/ calcium mineral oil lactulose activated attapulgite

ANALGESICS

acetaxninophen ASA ibuprofen meperidine naproxen cadeine indomethacin ketorolac

Non-sys temic: oxymetazoline x y lometazoline naphazoline ailergy shots sodium cromoglycate

COLD Som/ HERPES SIMPLEX

Topical: ac yclovir heparin + zinc sufalte

DEPRESSION

tricyclic antidepressants f luoxetine

OTCs rani tidine cimetidine

INFECTIONS

S ystemic: penicillins clindam ycin Topid: P ~ ~ P Y J C ~ ~ B cephalsponns erythromycin gramiciclin clavulinic acid metronidazole miconazole nitrofurantoin ciprofloxacin ketoconazole sulfarnethoxazole norfioxacin econazole trimethoprim gentarnicin c lotrimazole

nystatin

erythromycin clindarnycin benzoyl peroxide tretinoin

Systemk: tetracycline ) minocycline } before l 6 w W A doxycyciine )

Non-systemic: salbutamol theoph y lline salmeterol corticosteroids ipratropium nedocromil sodium

permethrins pyrethrins piperonyl butoxide

INFECTIOUS DISEASES

roseola herpes zoster (shingles) scarlet fever coxsackivirus

OTHER EXPOSURES

Cosmetic: hair dyel pend highlights Low electromagnetic radiation: cornputer body hair removers fax waxing pinter body hair bleach photocopier make-up Qerfumes Vaccines: tetanusl dipthena hair spray influenza deodorants C hepatitis B antiperspiran t

Miscellaneous : Tuberculin skin test fl ying caffeine (1-3 cupd &y) paints (nonsccupational) aspartamel artificial sweeteners - .

APPENDIX E - Motherisk Telephone In(nLe Forni

WCOMING: datc: timc:

fxnmchc

camp-O p s c d 10 ftUow 0 OUTGOENG:

date: timc:

compltted by:

Kidney N o 0 Y a

H a r t N o 0 Yes

Hypcriclisim N o 0 Yes

Dirktts N o 0 Ycs

Respintory N o 0 Yes

TbyrMd N o 0 Yes

PsychiiPic N o 0 Yts

EPiikpry N o 0 Yes

Viumintupp~trtioo? No0 Yu:

Oiba

0 Chlamydia ochicken pox OCMV ~Genital h e m OGonorrka O Group 8 stmp 0 Coxsackie O Hcpatitis B 0 Hcpatitis C 0 HIV O Parvovinw B 19 0 Shingles 0 Syphilis O Varialla

Othtr:

Date of contacl with infccicd pcrson: Date of lesions on contact pcrson:

Type of contact: O blood Odaycuic of- O househoid Ohospical Owiibksioas O r n u c d 0 4

o s c x d oothu

.-. Patient had diseasc in the p s t 0 -. Disease clinicaUy diagnosed? N o 0 Yeso by

Refercnced adviœ +box on pg. 1

Infant Data

Daic of birth: Gestational age at bUth: wk Birth weight: kg lb

Chcmicol: Occupation:

,EXPOSURE type: dircct rcooisbry

where: fpcmry officc home schd luha

rouk skin oral inhalation aha

duration: minutes hours days aher

bar* gloves masic respintor fumehood dut

sideeffcds: nausta vomiting diarrhca rash hcadachc trcmors blurrcd vision

ahcr

Refcnnced advice + box on pg. 1

Numbcr of times brcastfed daily: .- how oftcn?

Formuîa supplementation? Yes No Solids? Yes No name tYPt

Arc you taking medication as prcscribed? age staried pge started Yes No # t i d d a y Y t i d d a y

Referenced advice

APPENDM F - Prospective Ornipationa1 Veterimry Exposures Questionnaire

Date Patient ID

PROSPECTIVE OCCUPATIONAL VETERINARY EXPOSURES QUESTIONNAIRE

G P SA-TA Cornments

Patient's name

Home phone Work phone

Position O vetennanan O veterinary technician O other vetennary staff

Practice O private ch ic O hospiial O educationaVteaching O other

Type of practiceo small animal O large animal O mixed equal

O mixed mostly large O mixed mostly small

Work the (hdwk)

TELEPHONE LOG

Years in practice

Date Comments

ûut of losurgeries done, how fresuently do you... k L y / never. .O- 1 sght$hes 2-5 alwayd most o f t k ~ : - 0 - 1 0

Inhalational anaest hetics

B halothane O2hrdwk 0 3 - 6 W w k 07-8hrdwk 0 9 h r d w k D. cyclopropane O2hrdwk 0 3 - 6 h r d w k 0 7 - 8 M w k 0 9 h r d w k D nitrous oxide O 2 M w k O 3-6 hrslwk O 7-8hrslwk O 9 W w k f. methoxyfluorane 0 2hrsfwk 0 3-6 hrdwk O 7-Shrdwk O 9hrdwk D. isofluorane 02hrdwk 03-6hrdwk 07-Shrdwk O 9 W w k D trichloroethylene O 2hrdwks O 3-6 hrdwk O 7-8hrdwk O 9hrdwk O other 0 2hrdwks 0 3-6 hrdwk O 7-8Wwk O 9 W w k

Protective equipment (use above %de)

b cartridge-type mas k O rarely O sometimes O always O respirator O rarely O sometimes O always P fumehood O rarely O sometimes O always b scavenging O rarely O sometimes O always b other O rarely O sometimes O always

Mostly used anaesthetic system O rebreathing system O non-rebreathing sy stem (Bain ~ircuk)

Anaesthetic technique (use above d e )

O cuffed/ uncuffed endotracheal tube O b anaesthetic cages O b mask O b open &op (dxipping liquid on gauze sponge) O

Sideef fats short-term O drowsiness O fatigue

O headache O nausea O other

m g O reproductive disorders O neurologie disorders - (muscle wealaiessl tingling/ nurnbness)

rarely O sometimes O most of the time rarely O sometimes O most of the time rarely O sometimes O most of the time rarely O sometimes O most of the time

O itchiness O irritability O depression O none

O kidney damage/ problems O liver damage/ problems O other O none

Monitoring of WAG O air-sampling O dosimeter badges O portable infra-red analyzers O other O none TWAEV (ppm)

DlAGNOSTIC RADIATION

Out of 10 animals x-rayed, how fkquently do you ... ,mreLy/ nevet: 0-1 sometimes: 2-5 alwayd most of the~3&&:..6-i0

No. of films taken per week O<c O 6-9 O 110

Method of animal restraint (use above scale)

P you P another employee P anaestheticd tranquilizers P mechanical

O rarely O rarely O rarely O rarely

P other O rarely

Distance away €mm animal (m) O SO.5

Personai protective equipment (use abovc d e )

O sometimes O always O sometimes O always O sometimes O always O sometimes O always

O sometimes O always

P Iead-lined gloves O never O sometimes P lead apron O never O sometimes P thyroid collar O never O sometimes P lead glasses O never O sometimes P lead screen O never O sometimes P concrete wall O never O sometimes

b other O never ' O sometimes

O most of the time O most of the time O most of the time O most of the time O most of the cime O most of the time

O most of the time

Monitoring exposure (use above scale)

b film badge O rarely O sometimes O always

location of badge reading

INSECTICIDES

ANIlMAL USE

Insecticides used most frequentiy

O cou&aPhos O cythioate

O crotoxyhypos O crufornate O phosmet O diazinon O fenthion O malathion O ronnel O triclorfon O tetrachlorovinphos

Carbarnates P- O carbaryl O cyfluthrin O propoxur O fenvalerate (meth y lcarbamate) O pennethrin

O alletbrin O pyrethrin O tetramethrin O decamethrin

M O methoprene O lufenuron

O heptachlor O kelthane O methoxychlor O toxaphene

O other

Exposures per week Typicai length of exposure

Form most commody useà O fled tick sprays O collars O shampoos O dips O foams O baths O o r d injectable O ointmentd lotions

Protective equipment (use above scale) ? rubber gloves (Neoprene or Butyl) ? laboratory coat ? apron ? coverails ? goggles/ face shield ? other

S ide-effecîs: short-terrn O salivation O lacrimation O sweating O muscie weakness O headache O dizziness

O behavioural changes: [ ] imtability

O rarely O rarely O rarely O rarely O rarely O rarely

C

O nausea O twitching O confusion

[ 1 delusions

O sornetimes O always O sometimes O aiways O sometimes O always O sometimes O always O sometimes O always O sometimes O always

O crarnps O diarrhea O bf urred vision O restlessness O slurred speech O t~emors

[ ] paranoia [ ] aggression O none

INSECTICIDES

PREMISE USE

O not required

Insecticide used most frequently - Carbarnates O chlorpyrifos O carbaryl O malathion

Pyethroids 1 1 O pyrethroids O methoprene O pennethrin

Frequency of application comments:

Timing of application durhg the àay commentd reason:

Appkation done by

O you O other veterinary staff- O other

Proîective equipment used

Side-effects

Additionai Information

APPENDIX G - Motherisk FoUow-up Form

Pregnancy Follow Up Form MOTHERISK PROGRAM

Clinic Number Date of Interview lntenriewer

MorhaBs FIRST NAME SPcaMdms Motha's LAST NAME GcylPIWincc Tekphone (H) 0 P d Codc

BI PREGNANCY OUTCOME

How? by O uluuound Ounniocuitcsis

donc at wceks

CI DISEASES COMPUCATlNG PREGNANCY

Amniotic fluid .Irerations b No cancer O No Grdiovucular b No C a r d ~ ~ ~ i ~ w s y s t e m O NO Dcrmatology 0 NO &~%qm~w#c,thror~ O NO Endocrine 0 No Gastrointtrrinal O No Genito-urinary 0 No Hcmatology O No Infdous Disase b No IUGRlgrow~h problcmt b No Muscdo-skelccal 0 No Psychiatsic 0 No Rapiratory O No

Dct ails: dikgnosis

V& bid: Child's FIRST NAME Chi& LAST NAME Child's DATE OF BIRTH Child's docror

rrrrcr.ddrrrs ci rylprovincc tdcphone

E. TESTS OURING PREGNANCY

1. Chorionic villus rimpling O n o 0- 2. M a c d Scrum dpha-fcto protdn 0 no d ycr

3. Triple racening Cfno ayez 4. üiuuound Ono O p

5. Amnioœntcsis O n o bys 6. Fcd cchocudiography dno dys 7. Doppler d n o OF 8. Otha o n 0 b>tr:

Weight prc-pregnancy 1 b b gin Ib

Totd lcngth of labour houn k

PROM? Ono O y a : hours bdow onsa of k u r

(Prematun Rupcurc of Mcrncbnna)

Method 0 vaginal, vertex 0 iow forceps b vaginal, bncch a medium hrccps b clS cmagcny O high breeps O C/S schcdulcd O vrcuum 0 us rcpat

Hemorrhagc? Urro TruufGrion? O n o

9rtr ovcr

Pain tclief? .nrerthaia On0 bycs cpidurd d m byes anatgesic O n o dye

Apgu uom

A mude .ct i

Fcul Monitoring b n o b)ra

aplain Fcul duutss On0 0.yrr

aplain Meconium b n o dyc~

You originaliy called the Motheikk Program to find out whetner ywr exposure increased ywr baby's risk for being bom with a major Mrth defect. At that tirne, we expîained to you that every

pmgnancy has aSS% basenne risk for malfomiations.

For out own documentation, which MI help other women e%posd to the sarne drug that you were eitposed to, would you Mate with us whether your chUd was bom wiîh any birth defects?

DEFECTS O no O p Rrfirrcdtornrii~a O

O. EXPOSURES DURING PREGNANCY

I 0 Did you use m y hem1 ~rspanîions? Md you use m y vltrmlns (prarraW or oümr ~ ~ ) ?

0 Did you use mything for 8lktgle8, inxlety, colds, constlpaîlon, d8pnsrlon, dlrrrh8a, homdathe, herrtburn, pdn, w8lghtlosr?

Socid Drurir/Others Ethrnol wine(J Ono

iiquor [ ] d no batt [] 0 0 0

Tobacco d no Couine 0 no Hcroin 0 no Marijuana d no HcatjicrPri[] Uno

L L e m t W [ ] Ono Radiation 0 no Exescise 0 no

Ovrr-the-Couater/Pre~cfiption nidications and Radiation

- -

Occuparion duzing pqnmcy (whr does thc do?) Soncd SwPPcd RQlOn fbr Sypping EXPOSURES? chetnicd b n o b~

cornputer O n o OF - %

d i r t i o n 0llo Oro; noisc/vibrrtion O no b m.

Drug Nunc or Radiation Type

1

2

3

4

Seur Dacc Stop Dacc

ongoing O

onping d

ongoing b

ongoing O

~o~c~mg,g,m~) ~ r q u a y , - (od,qht,bid,tid)

G. NEONATAL HEALTH Hcnlth in hospitai intensive are? 0 no 0 YU

Home at byr B r u n fccding O no O p su~d -~pcd monrhs Mediarion during laccation ? 0 no b yes (@fi d& in sedon D)

Namc:

Infint s i k r #cmiO no O p: Formula fécdirrg 0 no O p nvrd mon& &op@ mon&

Sdids b not yct 0 ya m c d months rype:

Problans wich fecding? b no b ya crplain:

dose boqitaIizution?

G n c u Grdiovvcular Ccriml nuvousryzrcm Dermacology Eus. ya, nosc. throat Endocrine Giscrointcstinal

Gcnito-urinary Hcrnatology

Infccciow Diseue Mwculo-skclctal Respiratory

O Y s Cl V a O Ycf O Ycs d Ycs b Ycs O Yer 0 Ycs O Y a d Ycs a Yes O Yes

At wbat age ddid tbr iafintf;rr~=

Smilc (rccognicion)

Lifi h a d on own Sic waidcd

Crawl Sund on own

S p d fint wotd

Wdk unridcd

N u d range

[2 months]

[3 monthr] (68 months]

[&IO rnonthrl (8-10 months]

[8-12 months] [124S m o n h l

1 nfànt's age at followup months

Infint's wcight kg (Ib 02)

as of: b follow up 0 lu t MD visit

Infànt's haghclicrrgth , an ( inches) as oE b fotlow up 0 I r n MD visit

kn MD visit : (date or babyk agd

1. CONSENT -

OBWNED CONSENT? 0 No d Y a

Date letter sent: - Date letter CCCUvtd:

APPENDLX H - Retmspective Ckcupational Veterinary Exposures Questionnaire

MOST SEVERE IN JURY DURING ONE'S CAREER (using above categories) (Major injury is defined as one in which medical treatment is sought or self-administered)

Animal Type of injury Anatomic structure

Treatment (Rx/vaccinedsutures) Hosp (#days)

Description of situation

More pregnancy Dx:

DIAGNOSTIC RADIATION

1 No. of filrnslwk: 0 S 5 0 6.9 O t 10 I before pregnancy Px:

after pregnancy Dx:

O etoppd @ wks:

after pregnancy Dx:

O stoppai @ wks:

Appendix I - Data Provided By The National Dose Registry At The Radiation Protection Bureau: Annual Mean Radiation Doses For 100 Randomly Selected

Veterinary Practices For The Past 11 Yeam