ihe680_051211

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Occupational Safety & Health for Technologists, Engineers, and Managers By David L. Goetsch

© 2011, 2008, 2005, 2002, 1999 Pearson Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458

Chapter 21 - Radiation Hazards

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Radiation Hazards •  Radiation hazards in the workplace fall into one of

two categories: –  Ionizing –  Nonionizing

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IONIZING RADIATION: TERMS AND CONCEPTS

TYPES OF IONIZING RADIATION

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IONIZING RADIATION: TERMS AND CONCEPTS •  OSHA CFR 1910.1096 - Basic terms and concepts:

–  A dose is the amount of ionizing radiation absorbed per unit of mass by part of the body or the whole body.

–  Rad - measure of the dose of ionizing radiation absorbed by body tissues stated in terms of the amount of energy absorbed per unit of mass of tissue.

•  One rad equals the absorption of 100 ergs per gram of tissue. –  Rem - measure of the dose of ionizing radiation to body

tissue stated in terms of its estimated biological effect relative to a dose of 1 roentgen (r) of X-rays.

–  Air dose - means that an instrument measures the air at or near the surface of the body where the highest dosage occurs to determine the level of the dose.

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PRECAUTIONS AND PERSONAL MONITORING •  OSHA requires personal monitoring precautions

for employees of companies that produce, use, release, dispose of, or store sources of ionizing radiation. –  Employers must conduct comprehensive surveys to

identify/evaluate radiation hazards in the workplace. –  Employers must provide personal monitoring devices

such as film badges, pocket chambers/dosimeters & film rings.

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IONIZING RADIATION: TERMS AND CONCEPTS •  OSHA CFR 1910.1096 - Basic terms and concepts:

–  Personal monitoring devices are devices worn or carried by an individual to measure radiation doses received.

•  Widely used devices include film badges, pocket chambers, pocket dosimeters, and film rings.

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EXPOSURE OF EMPLOYEES TO RADIATION Maximum doses for individuals

in one calendar quarter.

Employers are responsible for ensuring that these dosages are not exceeded.

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EXPOSURE OF EMPLOYEES TO RADIATION •  Nuclear Regulatory Commission (NRC)

regulations specify total internal & external dose for employees may not exceed 5 rems per year. –  This same revision established a total exposure limit of

0.6 rem over the entire course of a pregnancy for female employees.

•  According to the NRC, the average radiation exposure of nuclear plant workers is less than 400 millirems annually.

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CAUTION SIGNS AND LABELS

The universal color scheme for caution signs/labels warning of radiation hazards is purple or magenta superimposed on a yellow background.

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EVACUATION WARNING SIGNAL •  Companies that produce, use, store, or transport

radioactive materials are required to have a signal-system that can warn of the need for evacuation.

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EVACUATION WARNING SIGNAL •  OSHA describes the signal system as:

– …a mid-frequency complex sound wave amplitude modulated at a subsonic frequency.”

– …not be less than 75 decibels at every location where an individual may be present whose immediate, rapid, and complete evacuation is essential.

– …a sufficient number of signal generators must be installed to cover all personnel…

– …unique, unduplicated, and instantly recognizable… – …long enough in duration to ensure that all potentially

affected employees are able to hear it. – …the signal generator must respond automatically without

the need for human activation ….fitted with backup power.

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INSTRUCTING AND INFORMING PERSONNEL •  OSHA has established specific requirements for

companies to keep employees informed concerning radiation hazards & precautions for minimizing them. –  All employees must be informed of existing radiation

hazards and where they exist. •  Extent of the hazards •  How to protect themselves.

–  All employees must be advised of any reports of radiation exposure requested by other employees.

–  All employees must have ready access to 29 CFR 1910.1096 and related company operating procedures.

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STORAGE/DISPOSAL OF RADIOACTIVE MATERIAL

•  Radioactive materials stored in unrestricted areas… –  “…shall be secured against unauthorized removal

from the place of storage.” •  A danger inherent in storing radioactive materials is

that an employee, may unwittingly attempt to move the container and damage it in the process. –  This could release doses that exceed prescribed

acceptable limits.

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STORAGE/DISPOSAL OF RADIOACTIVE MATERIAL

•  There are only three acceptable ways to dispose of radioactive waste: –  Transfer to an authorized recipient –  Transfer in a manner approved by the Atomic Energy

Commission. –  Transfer in a manner approved by any state that has an

agreement with the Atomic Energy Commission pursuant to Section 27(b) 42 U.S.C.

NRC

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NONIONIZING RADIATION •  Nonionizing radiation has a wavelength in meters

of 3 Hz 10-7 or more. –  Visible, ultraviolet, infrared, microwave, radio & AC power.

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NONIONIZING RADIATION •  Nonionizing radiation has a wavelength in meters

of 3 Hz 10-7 or more. –  Visible, ultraviolet, infrared, microwave, radio & AC power.

•  Radiation at these wavelengths does not have sufficient energy to shatter atoms and ionize them. –  However, such radiation can cause blisters and

blindness. •  There is mounting evidence of

a link between nonionizing radiation and cancer.

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NONIONIZING RADIATION The warning symbol for radio frequency radiation.

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NONIONIZING RADIATION •  The most common source of ultraviolet radiation is

the sun — potential problems include sunburn, skin cancer, and cataracts. –  Precautionary measures include special sunglasses

treated to block ultraviolet rays, and protective clothing. •  Other sources of ultraviolet radiation include:

– Lasers – welding arcs – ultraviolet lamps

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NONIONIZING RADIATION •  Radio frequency (RF) & microwave (MW)

radiation are electromagnetic radiation in the frequency range of 3 kilohertz (kHz) to 300 gigahertz (GHz) –  Microwaves occupy the spectral region between 300 GHz

and 300 MHz & RF or radio waves are 300 MHz to 3 kHz. •  RF and MW radiation are nonionizing in that there is

insufficient energy to ionize biologically important atoms. –  Primary health effects of RF and MW energy are

considered to be thermal.

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NONIONIZING RADIATION •  Use of RF and MW radiation includes:

–  Aeronautical/citizen’s (CB) radios, cellular phones, radar. –  Processing/cooking of foods, heat sealers. –  Vinyl welders, high-frequency welders, induction heaters,

flow solder machines. –  Microwave drying equipment, sputtering equipment, glue

curing, and power amplifiers.

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NONIONIZING RADIATION •  Extremely low frequency (ELF) radiation includes

alternating current (AC) fields & nonionizing radiation from 1 Hz to 300 Hz. –  As ELF frequencies are low (on the order of 1,000 km

wavelengths), static electromagnetic fields are created. •  ELF fields are considered as separate, independent,

nonradiating electric and magnetic fields. –  Electric and magnetic fields (EMFs) at 60 Hz are produced

by power lines, electrical wiring, and electrical equipment. •  Electric fields are produced by voltage and

increase in strength as the voltage increases. –  Measured in units of volts per meter (V/m).

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NONIONIZING RADIATION •  Magnetic fields are from the flow of current

through wires or electrical devices and increase in strength as the current increases. –  Magnetic fields are measured in gauss (G) or tesla (T).

•  Electrical equipment usually must be turned on for a magnetic field to be produced. –  Electric fields are present even when equipment is

turned off, as long as it is plugged in.

•  Exposure to EMFs depends on the strength of the magnetic field sources, the distance from those sources, and the time spent in the magnetic field.

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NONIONIZING RADIATION •  Hazards of lasers consist of a thermal threat to

the eyes and of electrocution from power sources. –  Smoke created by lasers in some processes can be toxic.

•  Video display terminals (VDTs) emit various kinds of nonionizing radiation—typically, levels are well below established standards. –  Concerns persist about the long-term effects of prolonged

and continual exposure to VDT-based radiation.

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ELECTROMAGNETIC FIELDS IN THE WORKPLACE

•  Studies of potential effects on worker health of occupational exposure to electric & magnetic fields reported a variety of subjective complaints, including problems with their cardiovascular, digestive, and central nervous systems. –  While much of the research has been inconclusive, the

case for a clear link between EMFs and a variety of health problems is strong.

•  The health problems most frequently associated with EMF exposure are brain cancer, acute myeloid leukemia, leukemia, and lymphatic leukemia

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ELECTROMAGNETIC FIELDS IN THE WORKPLACE

•  Occupations with a higher-than-normal incidence of leukemia and brain cancer: –  Telephone operators –  Electrical manufacturing workers –  Power plant workers –  Electrical engineers & line workers –  Power station operators –  Electricians & cable splicers

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Cancellation Approach •  Cancellation is an attenuation technique in which

the magnetic fields produced by sources of electricity are, in effect, canceled out. –  Phase currents flowing through a given conductor are

canceled out or drastically reduced by phase currents flowing in the opposite conductors.

•  In many cases, a principal source of magnetic fields is found to be the conductor systems leading to tools or power apparatus. –  These fields could be canceled via compaction of the

conductor systems.

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Shielding Approach •  Shielding, another approach to decrease exposure

to EMFs, requires the magnetic fields to be diverted around the volume considered to be sensitive to the magnetic fields, or to be contained within the device that produces the fields. –  Effectively accomplishing shielding at either the source

or the subject requires extreme care in choosing the shielding material.

•  Both cancellation and shielding are highly technical approaches requiring specialized knowledge. –  It may be necessary to consult with EMF experts before

attempting to implement either approach.

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Noise and Vibration •  Noise in the modern workplace poses two safety-

and health-related problems. –  Noise can distract workers and disrupt concentration,

which can lead to accidents. –  Exposure to noise that exceeds prescribed levels can

result in permanent hearing loss.

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HEARING LOSS PREVENTION TERMS •  Terms common to hearing loss prevention:

–  Decibel (dB) - unit used to express the intensity of sound, named after Alexander Graham Bell.

•  A logarithmic scale in which 0 Db approximates the threshold of hearing in the midfrequencies for young adults.

•  The threshold of discomfort is between 85 and 95 dB. •  The threshold of pain is between120 and 140 dB.

–  Dosimeter - the instrument that measures sound levels over a specified interval, stores the measures, and calculates the sound as a function of sound level and sound duration.

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HEARING LOSS PREVENTION TERMS •  Terms common to hearing loss prevention:

–  Noise - any unwanted sound. –  Noise dose - the noise exposure expressed as a

percentage of the allowable daily exposure. •  OSHA considers a 100% dose equals an eight-hour exposure

to a continuous90-dBA noise. –  Time-weighted average (TWA) - a value, expressed in

dBA, computed so that the resulting average is equivalent to an exposure resulting from a constant noise level over an eight-hour period.

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CHARACTERISTICS OF SOUND

Sound occurs as elastic waves that cross over (above & below)

a line representing normal atmospheric pressure.

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CHARACTERISTICS OF SOUND One decibel represents the smallest

difference in the level of sound that can be perceived by the human ear.

The weakest sound that can be heard by a healthy human ear in a quiet setting is known as the threshold of hearing (1 dBA). The maximum level that can be perceived without experiencing pain is the threshold of pain (140 dBA).

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STANDARDS AND REGULATIONS •  OSHA regulations require implementation of hearing

conservation programs under certain conditions. –  OSHA regulations should be considered minimum

standards.

•  ANSI standards provide a way to determine the effectiveness of hearing conservation programs such as those required by OSHA.

•  NIOSH bases most of its materials on OSHA regulations, although it makes recommendations that exceed OSHA regulations in some cases.

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OSHA Regulations •  OSHA 29 CFR 1910.95 requirements for hearing

conservation programs are as follows: –  Hearing hazards monitoring. –  Engineering and administrative controls. –  Audiometric evaluation. –  Personal hearing-protection devices. –  Education and motivation. –  Record keeping Program evaluation.

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Hazards Monitoring •  The most common measurements are area surveys

and dosimetry –  Area survey results are often plotted in the form of a

“noise map,” showing noise level measurements for the different areas of the workplace.

–  Dosimetry involves the use of body-worn instruments (dosimeters) to monitor exposure over the work shift.

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Engineering and Administrative Controls •  Engineering and administrative controls represent

the first two levels in the hierarchy of controls: –  Remove the hazard and remove the worker.

•  These controls should reduce hazardous exposure to the point where the risk to hearing is eliminated, or at least more manageable.

•  Engineering controls are technologically feasible for most noise sources, but their economic feasibility must be determined on a case-by-case basis.

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Audiometric Evaluation •  Audiometric evaluation is the only way to

determine whether hearing loss is being prevented. –  Occupational hearing loss occurs gradually & is not

accompanied by pain, so an affected employee may not notice the change until a large threshold shift accumulates.

–  OSHA uses the term standard threshold shift to describe an average change in hearing from the baseline levels of 10 dB or more for the frequencies of 2,000, 3,000, and 4,000 Hz.

–  NIOSH uses the term significant threshold shift to describe a change of 15 dB or more at any frequency of 500 - 6,000 Hz from baseline levels, present on an immediate retest in the same ear and at the same frequency.

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Personal Hearing Protection Devices •  A personal hearing protection device (or “hearing

protector”) is anything that can be worn to reduce the level of sound entering the ear. –  Earmuffs, ear canal caps & earplugs are the 3 main types.

•  Regardless of the kind of ear protection device used, it is important to remember the four Cs: –  Comfort, Convenience. –  Communication (the device should not interfere with the

worker’s ability to communicate). –  Caring (workers must care enough about protecting their

hearing to wear the devices).

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Education and Motivation •  To obtain sincere, energetic management support

and active employee participation, it is necessary to educate and motivate both groups.

•  Employees & managers who appreciate the sense of hearing and understand the reasons for, and the mechanics of, the hearing loss prevention program will be more likely to participate.

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VIBRATION HAZARDS •  Vibration hazards are closely associated with

noise hazards because tools that produce vibration typically also produce excessive levels of noise.

•  Vibration-related problems are serious & widespread. –  Up to 8 million workers are exposed to some type of

vibration hazard, and of these, it is estimated that more than half will show some signs of injury.

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VIBRATION HAZARDS •  The most common vibration-related problem is

known as hand-arm vibration syndrome (HAV). –  HAV is a form of Reynaud’s Syndrome, striking workers

who use vibrating power tools daily as part of their jobs.

•  Environmental conditions and worker habits can exacerbate the problems associated with vibration. –  Working with vibrating tools in a cold environment is

more dangerous than the same work in a warm environment.

–  Gripping a vibrating tool tightly will lead to problems sooner than using a loose grip.

–  Smoking and excessive noise also increase potential for HAV and other vibration-related injuries.

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VIBRATION HAZARDS •  Prevention is especially important with HAV

because the disease is thought to be irreversible. –  Treatments developed to date only reduce the symptoms.

•  Prevention strategies that can be used in any company regardless of its size: –  Purchase low-vibration tools. –  Limit employee exposure. –  Change employee work habits.

–  Loose Grip –  Smoking

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Questions? •  Radiation •  Noise •  Vibration

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