Dr.SadeghniiatAssistant Professor of Tehran University of Medical Sciences

Member of Iranian Occupational Medicine AssociationMember of ATS & ACOEM

OCCUPATIONAL ASTHMA

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Work-Related Asthma (WRA):How big is the problem?

• An estimated 15% of adult asthma is attributable to occupational factors

ATS, 2003

WHAT IS OCCUPATIONAL ASTHMA?

• Variable air flow obstruction& Or• Airway hyperresponviness due to courses and

condition :• Working Env ,not outside the workplace

• One of the most common occupational respiratory diseases

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Work-Related Asthma includes:

• ‘New-onset asthma’ from sensitizers and irritants

• ‘Work-aggravated asthma’ : pre-existent asthma made worse by workplace exposures (Wagner & Wegman, 1998)

Types of Occupational Asthma

• New Onset - Sensitizer-induced - Irritant induced• Aggravation of underlying asthma• WORK-RELATED ASTHMA = OA + AA

More than 300 known etiologic agents Sensitization to a specific antigen

low molecular-weight, “hapten” DI,WRC high molecular weight

IgE mediated Non-IgE mediated (DI,WRC?)

Sensitizer-Induced Asthma

Sensitizer-Induced Asthma

• Sensitization may occur at <TLV• Sensitizers may also be irritants (e.g. TDI,TMA)• Prior history of atopy does not predict risk of

asthma!

Common Sensitizers(Incomplete List!)

Low MW • Isocyanates• Anhydrides• Metal salts• Epoxy resins• Fluxes• Persulfate• Aldehydes • Plicatic acid(WRC)

High MW• Animal proteins• Latex• Cereals• Seafood• Proteolytic enzymes• Wood constituents

Wood Dust And

Occupational Asthma

Occupational Health Branch California Department of Health

Services

“Draft”

Reactive airways dysfunction syndrome (RADS)

• Single• High level irritants

– Gases – Fume– Smoke

Aggravational Asthma• Very common• Initial condition not

occupational• irritant exposure

Occupational Asthma: Contributing Factors

OccupationalAsthma

HostFactors

ExposureFactors

Climate/Geography

Factors

IndustryFactors

Adapted from Brooks, 1992

KOH 2006

exposure

risk

Dose response relationship

Investigation of a case of suspected Occupational Asthma

History • Symptoms • Duration • Work history • Is patient zof exposure to any respiratory sensitisers at work?• Timing of symptoms (immediate /delayed)• Improvement away from work

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Patterns of Association between Asthma Symptoms and Work

• Asthma symptoms develop or worsen with a new job or introduction of new materials.

• Asthma symptoms develop within minutes of specific activities or exposures at work.

• Symptoms improve away from work or on vacation.

• Symptoms worsen on return to work after being away.

History Exam Lung Functions Skin tests Therapeutic

trial

Obstructive pattern On spirometry

Bronchodilatadors Provocation tests

Minimum Three – fold

Investigation of a case of suspected Occupational Asthma

Clinical investigations • PEFR • Bronchial challenge • Spirometry

• Skin prick test • RAST / ELISA

HOME-------------WORK-----HOME—WORK--HOMEWORK

Rx

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Confirming the diagnosis of occupational asthma

• Specific challenge tests= international golden standard for diagnosis

of occupational asthma

• to prove the cause-effect relationship between the agent from the workplace and the asthmatic reaction in individual level

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Occupational asthma, diagnostics

• Work related asthmatic symptoms

• Exposure to a sensitizing agent at work

• Cause-effect relationship between the exposure material and asthma– Sensitization (skin prick tests/specific IgE antibodies)– Positive provocation test– Typical long-term PEF surveillance

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Diagnostics of occupational asthma

• PEF-surveillance at home and at the workplace always, if possible

– Positive finding supports the diagnosis

– Negative finding does not exclude the diagnosis

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Prerequirements for challenge tests

1. Clinical picture fits with occupational asthma,

but the diagnosis has not yet been verified2. Asthma is stable. Inhaled steroid may be

used, stable dose every evening.3. Differential diagnostics done.4. No contraindications to challenge tests.

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Contraindications to challenge tests

• Acute infections• Unstable asthma or some other disease • Poor lung function• Facts, that prevent proper interpretation of

the challenge tests (e.g. non co-operating patient)

• Anaphylactic or otherwise very strong reaction to the challenge material in history

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Requirements, when performing challenge tests

• 24-hour follow up and facilities to treat acute and late asthmatic ( and other) reactions

• Aduquate challenge chamber and well trained staff

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Criteria for a positive provocation test reaction

• minimum 20% FEV1/PEF decrease compared to baseline before exposure and to control test

• tests with allergen extracts– minimum 15% decrease in immediate reaction (during one hour after challenge)

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WRA Surveillance Case ClassificationCase of WRA

New-Onset Asthma

(NOA)

Work-Aggravated Asthma

(WAA)

Occupational Asthma

(OA)

Reactive Airways Dysfunction Syndrome

(RADS)

Known Asthma Inducer

Unknown Asthma Inducer

With or without Objective Evidence

With or without Objective Evidence

therapy• Same as other asthma• Most important=avoidance of exposure

Management

1. Drug treatment • as for non-occupational asthma

2. Non-drug treatment • Remove from exposure • Review work place

– Is prevention possible?– Are control measures adequate?

3. Health surveillance

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CAN YOU PREVENT OCCUPATIONAL ASTHMA?

• To reduce the likelihood of damaging your lungs you can do the following:

Avoid long exposure Follow safety rules Practice good personal habits ie washing up Keep your workplace clean Ensure good ventilation Use respiratory protection - e.g. masks Don't smoke Report symptoms and signs of danger

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What preventative measures can be taken in the workplace?

• Substitution of a sensitizing agent in the workplace is a measure that should always be considered, although it is often not possible.

• Engineering and ventilation control measures are the next option, but depending on the work process these measures cannot always eliminate the hazard.

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Treatment and follow up of occupational asthma

• Usually regular asthma medication needed

• In the follow up the need of asthma medication depends on the disease severity, which varies substantially individually

• After discontinuing exposure– Some patients recover totally – In some patients mild asthma symptoms continue to exist– In some patients asthma gets worse

• Follow up by both occupational health care and pulmonologist needed

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the Sentinel Event Notification Systems for Occupational Risks (SENSOR) Program?

• Focus on prevention-oriented workplace intervention

• Sentinel Health Event– An occupational sentinel health event indicates co-workers may be

at risk (Baker, 1989

Etiology Mechanism InducersImmunologic • IgE mediated

– High molecular wght

– Low molecular haptens

• ? Cell mediated– Low molecular

Nonimmunologic– Irritant-toxic

• Grain, crab, castor beans

• Woods, gum acacia

• Animal dander, urine

• Epoxy resins

• Chloramine T

• Platinum salts

• di-isocyanates

• Red Cedar

• Cobalt

• Ammonia, chlorine

Methacholine Challenge

• + Test confirms airways reactivity only • A functional test not specific for asthma - atopy - transient reactivity • Bronchoprovocation with with specific antigen

preferable to diagnose sensitizer-induced asthma• -Tests can occur with quiescent occ asthma

Ancillary Tests

• Clinical immunology - skin prick tests - RAST - ELISA• PEF or FEV1, symptom and medication diary

• Pre/post shift and/or holiday PFTs• Work place HHE

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Related Diseases

• Industrial bronchitis• Airway irritation without

asthma• Hypersensitivity pneumonitis• Bronchiolitis obliterans• Metal or polymer fume fever

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Characteristics of Work Related Asthma

• Improvement away from work early in course

• Recurrence of symptoms on re-exposure

• Delayed asthmatic responses

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Other Occupational Lung Diseases

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Related Diseases

• Industrial bronchitis• Airway irritation without

asthma• Hypersensitivity pneumonitis• Bronchiolitis obliterans• Metal or polymer fume fever

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Prevention of occupational asthma

• Is dependent on co-operation between workplace and occupational health care– Actual knowledge of the sensitizing agents used in the

workplace– Work hygienic tasks to minimize exposure and

exposure assessments, when needed– Guidance of the right kind of working methods– In occasional exposures possibility to use respiratory

protective device– Occupational health care services: check out of

workers, when symptoms exist and follow up of lung function measurements

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Procedures after diagnosing occupational asthma

How to discontinue/minimize exposure?

• Changing agents used in the workplace• Changing work tasks/working area/environment

(replacement in another kind of work task or working environment)

• Changing the work tasks• Restrictions to the worker• Use of respiratory protective device• Re-education to another occupation ( in Finland legally set

that the insurance company of the employer is responsible for re-education)

• Retirement

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Performing challenge tests1. Confirm, that the asthma is stable

– symptoms, FEV1/PEF 24-hour follow-up, spirometry (histamine/metacholine challenge)

2. Challenge with control material– To confirm, that asthma does not react to nonspecific

agents– Challenge material and method individually chosen, in order

to mimic the challenge method and material of the active agent challenge

– Control challenge must be negative– Challenge with active agent is compared with the control

challenge

3. Challenge with active agent

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Challenge test with active agent

• Commercial allergen extracts

• Tests simulating work tasks (patient handles the material from workplace)– Individual planning: challenge materia,

concentration, duration of test e.g.– Occupational hygienist/chemist consultations

when needed– Controlled concentrations

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Challenge chamber

• Adequate ventilation• Safety of the patient• Safety of the personnel

– exhaust ventilation– easy to clean

• Facilities for generation of dusts, vapors and aerosols in controlled concentrations

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Criteria for a positive provocation test reaction

• Findings supporting positive challenge test:– symptoms– wheezing rales– dose-response– increase in hyperreactivity– recovery of the reaction on the following day– increase in exhaled nitric oxide?– increase in peripheral resistance (impulse

oscillometry)