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Chapter 20
Industrial Hygiene: Toxic
Substances and Confined Spaces
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Major Topics
Hazards in the workplace
OSH Act and industrial hygiene
Airborne contaminants Asbestos hazards
Sick building syndrome
NIOSH and industrial hygiene OSHA confined spaces standard
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Industrial Hygiene
Industrial hygiene is a safety and health
profession that is concerned with
predicting, recognizing, assessing,
controlling, and preventing environmental
stressors in the workplace that can cause
sickness or serious discomfort to workers.
Common stressors include gases, fumes,vapors, dusts, mists, noise, and radiation.
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Responsibilities of the modern
industrial hygienist Code of ethics of the American Academy of Industrial
Hygiene:
To ensure the health of employees
To maintain an objective approach in recognizing,
assessing, controlling and preventing health hazardsregardless of outside pressure and influence.
To help employees understand the precautions that theyshould take to avoid health problems.
To respect employees honesty in matters relating toindustrial hygiene
To make the health of employees a higher priority thanobligations to the employer
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Role of the safety and health
professional
In companies that employ specialists, theirrecommendations are used by safety and healthprofessionals to develop, implement, monitor,and evaluate the overall safety and healthprogram.
If specialists are not employed, safety and healthprofessionals are responsible for seeking theadvice and assistance necessary to predict,recognize, assess, control, and overcomeenvironmental stressors that may causesickness or serious discomfort to employees.
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OSHA requirements relating to
industrial hygiene Use of warning labels and other means to make employees aware of
potential hazards, symptoms of exposure, precautions, andemergency treatment
Prescription of appropriate personal protective equipment and othertechnological preventive measures [29CFR 1910.133 and 1910.134subpart I]
Provision of medical tests to determine the effect on employees ofexposure to environmental stressors
Maintenance of accurate records of employee exposures toenvironmental stressors that are required to be measured ormonitored
Accessibility of monitoring tests and measurement activities toemployees
Availability of monitoring tests and measurement activity records toemployees on request
Notification of employees who have been exposed to environmentalstressors at a level beyond the recommended threshold and correctiveaction being taken
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Typical categories of hazard in the
workplace Categories: chemical, physical, biological and
ergonomic.
Chemical hazards: include mists, vapors, gases, dusts,and fumes.
Physical hazards: include noise, vibration, extremes oftemperature, and excessive radiation.
Biological hazards: come from molds, fungi, bacteria,and insects. Bacteria may be introduced in theworkplace through sewage, food waste, water or insectdroppings.
Ergonomic hazards: poorly designed workstations andtools, conditions that put workers in awkward positions orimpair their visibility.
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Routes of entry for toxic agents
The most common routes of entry for toxic
agents are inhalation, absorption,
injection, and ingestion.
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Airborne contaminants: dust,
fumes, smoke, mists, and gases Dusts are various types of solid particles that are produced when a given type
of organic or inorganic material is scrapped, sawed, ground, drilled, handled,heated, crushed or otherwise deformed. The degree of the hazard depends onthe toxicity of the parent material and the size and level of concentration of theparticles.
Fumes: Welding, heat treating, and metalizing all involve the interaction ofintense heat with the parent material, which results in tiny particles of the
parent material which can be inhaled. Smoke: Smoke is the result of incomplete combustion of carbon material. Tiny
soot or carbon particles remain that can be inhaled.
Aerosols: are liquid or solid particles that are so small that they can remainsuspended in air long enough to be transported over a distance. They can beinhaled.
Mists: are tiny liquid droplets suspended in the air. Mists are formed whenvapors return to a liquid state through condensation and when the application
of a sudden force or pressure turns a liquid into particles. Gases: become hazardous when they fill a confined unventilated space. The
mist common forms of gases in industrial settings are from welding and theexhaust from internal combustion engines.
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Remove or contain asbestos
Following factors should be considered:
Is there evidence that the ACM (asbestos containingmaterial) is deteriorating? What is the potential for furtherdeterioration?
Is there evidence of physical damage to the ACM? Whatis the potential for future damage?
Is there evidence of water damage to the ACM orspoilage? What is the potential for future damage orspoilage?
The most widely used methods for dealing with asbestosare removal, enclosure and encapsulation.
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ANSI Z9.8 (indoor air
quality/HVAC) General Coverage: ANSI Z9.8 is very specifically written to apply
primarily to office space. It applies specifically to employeeoccupancies in non industrial spaces including general officespaces, commercial operations, and office spaces with industrialfacilities.
Application flexibility: When the provisions of ANSI Z9.8 conflict with
other standards the more stringent standard is to take precedence. Acceptable air quality: Employers may establish ceiling limits (e.g. if
more than 2% of the employees complain about air quality problemsthe ceiling limit has been reached).
Tobacco smoke: The standard requires that employers evaluatesmoking in the workplace and apply whatever management controls
are appropriate.
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Asbestos: removal, enclosure and
encapsulation Removal: known as asbestos abatement. The area in question must
be completely enclosed in walls of tough plastic. The enclosed areamust be ventilated by High efficiency particle absolute (HEPA)filtered negative air machines. The ACM (asbestos containingmaterial) must be covered with a special liquid solution to cut downon the release of asbestos fibers. The ACM must be placed in leak
proof containers for disposal. Enclosure: use HEPA filtered negative air machines in conjunction
with drills or any other tools that may penetrate or otherwise disturbACMs. Construct the enclosing walls of impact resistant air tightmaterial. Post signs indicating the presence of ACMs within theenclosed area. Note the enclosed area on the plans of the building.
Encapsulation: of asbestos involves spraying the ACMs with aspecial sealant that binds them together thereby preventing therelease of fibers. The sealant should harden into a tough impactresistant skin. This approach is generally used on acoustical plasterand similar materials.
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Medical examinations for
employees who handle ACMs Medical examinations conducted at least annually should
be required for employees who handle ACMs. Theseexaminations should include front and back chest X-raysthat are at least 7 by 14. The examination should also
test pulmonary function, including forced vital capacityand forced expiratory volume at one second.
Medical records on such employees should be kept forat least 20 years. They should contain the completemedical history of the employee. These records must be
made available on request to employees, pastemployees, health care professionals, employeerepresentatives, and OSHA personnel.
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Exposure thresholds: time weighted average, short
term exposure limit, and exposure ceiling
Threshold Limit Value-Time weighted average (TLV-TWA): The timeweighted average for a conventional 8 hour work day and 40 hourwork week for a given substance to which it is believed that nearlyall workers may be repeatedly exposed on a daily basis withoutsuffering ill effects. For example the TLV-TWA for liquefiedpetroleum gas is 1000 parts per million (ppm).
Threshold Limit Value-Short term exposure limit (TLV-STEL): ASTEL is defined as a 15 minute TWA exposure that should not beexceeded at any time during the work day period. It should notoccur more than 4 times in the day (with at least 60 minutesbetween exposures). For example the TVL-STEL for isopropyl etheris 310 ppm.
Threshold Limit Value-Ceiling (TLV-C): The concentration of a givensubstance that should not be exceeded at any point during anexposure period.
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Evaluating hazards in the
workplace For hazard evaluation the following
considerations are important:
The nature of the material or substanceinvolved, the intensity of the exposure, and the
duration of the exposure. Key factors to consider are how much exposure
is required to produce injury or illness; thelikelihood that enough exposure to produce
injury or illness will take place; the rate ofgeneration of airborne contaminants; the totalduration of the exposure; and the prevention andcontrol measures used.
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Generic prevention and control
strategies
Most prevention and control strategies can
be placed in one of the following 4
categories:
Engineering controls
Ventilation
Personal protective equipment Administrative controls
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Prevention/control strategy: engineering controls,
ventilation, personal protective equipment
Engineering Controls: replacing toxic material with one that is lesshazardous or redesigning a process to make it less stressful or toreduce exposure to hazardous material or conditions, isolatinghazardous process to reduce the number of people exposed to itand introducing moisture to reduce dust.
Ventilation: exhaust ventilation involves trapping and removing
contaminated air. Used with such processes as abrasive blasting,grinding, polishing, buffing, and spray painting or finishing. Dilutionventilation involves simultaneously removing and adding air to dilutea contaminant to acceptable levels.
Personal protection: Personal protective equipment (PPE) imposesa barrier between the worker and the hazard. Typical equipment
include safety goggles, face shields, gloves, boots, earmuffs, earplugs, full body clothing, and respirators.
Specially designed eyewash and emergency wash stations (fig 20-8,9, 10) should be readily available and accessible in any work settingwhere contaminants may be present.
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Worker self protection strategies
Know the hazards in your workplace: take time to identify allhazardous material and conditions in your workplace and know thesafe exposure levels of each.
Know the possible effects of hazards in your workplace: Typicaleffects of workplace hazards include respiratory damage, skindisease and irritation, injury to the reproductive system, and damage
to the blood, lungs, central nervous system, eyesight and hearing. Use PPE properly: Choosing the right equipment, getting a proper
fit, correctly cleaning and storing equipment, and inspectingequipment regularly for wear and damage.
Understand and obey safety rules: Read warning labels beforeusing any contained substance, handle materials properly, read and
obey signs, and do only authorized work. Practice good personal hygiene: Wash thoroughly after exposure to
a hazardous substance, shower after work, wash before eating, andseparate potentially contaminated work clothes from others beforewashing them.
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NIOSH and Industrial Hygiene
The National Institute of Safety and Health [NIOSH] ispart of the Department of Health and Human Services[HHS].
The main focus of the agency is on toxicity levels and
human tolerance levels of hazardous substances. NIOSH prepares recommendations for OSHA standards
dealing with hazardous substances and NIOSH studiesare made available to employers.
Their continually updated list of toxic materials andrecommended tolerance levels are extremely helpful toindustrial hygienists concerned with keeping theworkplace safe.
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Toxic Substance
A toxic substance is one that has a
negative effect on the health of a person
or animal.
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Effect of a toxic substance
Toxic effects are functions of several
different factors including the following:
Properties of the substance
Amount of the dose
Level of exposure
Route of entry Resistance of the individual to the
substance
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Common routes of entry of toxic
substances
The most common routes of entry of toxic
substances are inhalation, absorption,
injection and ingestion.
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Dose-response relationship
A dose of toxic substance can be expressed in anumber of different ways depending on thecharacteristic of the substance: amount per unitof body weight, amount per body surface area,
or amount per unit of volume of air breathed. Olishifski expressed the dose response
relationship mathematically as : C * T = K
where:
C = concentration T = duration (time) of exposure
K = constant
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Dose threshold, lethal dose, and
lethal concentration
Dose threshold: is the minimum dose required to
produce a measurable effect.
Lethal dose: is the dose that is highly likely to
cause death. Lethal concentration: of an inhaled substance is
the concentration that is highly likely to result in
death. With inhaled substances the duration of
exposure is critical because the amount inhaled
increases with every unprotected breath.
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Acute and chronic effects and
exposures
Acute effects and exposures involves a suddendose of a highly concentrated substance. Theyare usually the result of an accident that result inan immediate health problem ranging fromirritation to death.
Chronic effects and exposures involve limitedcontinual exposure over time. Consequently theassociated health problem develops slowly.
Fig 20-3 page 439: selected toxic substancesand the organs they affect most.
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Classification of airborne toxics
Airborne toxic substances are classified according to thetype of effect they have on the body.
The primary classifications are:
irritants - cause irritation to skin, eyes, nose, mouth,
throat, and upper respiratory tract. asphyxiants - disrupt breathing so severely that
suffocation results.
narcotics/anesthetics - can inhibit normal operation of
central nervous system. With all airborne contaminants concentration and
duration of exposure are critical concerns.
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Carcinogen
A carcinogen is any substance that can
cause a malignant tumor or a tissue that
may become cancerous.
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OSHA chemical process standard,
EPA clean air act, and SARA OSHA chemical process standard: The standard requires chemical
producers to analyze their processes to identify potentially hazardoussituations and to assess the extent of the hazard. Having done so theymust accommodate this knowledge in their emergency response plansand take action to minimize the hazards. Specific additionalrequirements include: compiling process safety information,maintaining safe operating procedures, training and educating
employees, maintaining equipment, conducting incidentinvestigations, developing emergency response plans, andconducting safety compliance audits.
EPA clean air act (1990): The law is designed to reduce air pollution in the form of hazardous air pollutants, acid rain, and smog by 56billion pounds per year. This includes a 75% reduction in air toxics, a50% cut in acid rain, and a 40% decrease in smog.
Superfund Amendments and Reauthorization Act (SARA): This law isdesigned to allow individuals to obtain information about hazardouschemicals in their communities so that they can protect themselves incase of emergency. It applies to all companies that use, make,transport, or store chemicals.
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Threshold limit value (TLV)
Threshold limit values: refer to airborne
concentrations of substances and represent
conditions under which it is believed that nearly
all workers may be repeatedly exposed day afterday without adverse effect.
Threshold limits are based on the best available
information from industrial experience, from
experimental human and animal studies, andwhen possible a combination of the three.
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Time weighted average and ceiling
The time weighted average for aconventional 8 hour work day and 40 hourwork week for a given substance to which
it is believed that nearly all workers maybe repeatedly exposed on a daily basiswithout suffering ill effects.
Ceiling: the concentration of a givensubstance that should not be exceeded atany point during an exposure period.
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NIOSH categories of respirators
Class N (not oil resistant): respirators may be used only inenvironments that contain no oil based particulates. They may beused in atmospheres that contain solids or non oil contaminants.
Class R (Oil resistant): respirators may be used in atmospherescontaining any contaminant. However the filters in Class Rrespirators must be changed after each shift if oil based
contaminants are present. Class P (oil proof): respirators may be used in any atmosphere
containing any particulate contaminant.
If there is any question about the viability of an air filtering respiratorin a given setting, employees should use air supplying respirators.
Air from the air is completely blocked out, and fresh air is provided
via a self contained breathing apparatus.
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Sick building syndrome
A sick building is one that makes people sick because ithas become infested with mold, mildew, spores, andother airborne micro organisms.
Poor indoor air quality (IAQ) can cause a variety of
health problems ranging from the temporary to the longterm.
One of the keys in preventing sick building syndrome isair exchange.
Important factors in a buildings ability to eliminatecontaminated air and bring in fresh air are: ventilation, airinfiltration rates, airflow rates in ducts, airflow patterns,and fume exhaust.
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OSHA confined space standard
The OSHA confined space standard (29 CFR 1910.146)mandates that entry permits be required beforeemployees are allowed to enter a potentially hazardousconfined space.
Before the permit is issued a supervisor, safety or healthprofessional, should do the following: shut downequipment/power (locked/tagged), test the atmosphere(19.5 to 23.5% oxygen), ventilate the space, have rescuepersonnel stand by, maintain communication, and use a
lifeline (can pull an unconscious employee out of aconfined space).
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OSHA hazard communication
standard (29 CFR 1910.1200)
Any organization that uses hazardous
material in the workplace is required to
fully inform employees and on-site
contractors of the hazards and to providetraining concerning the safe handling,
storage, and use of the materials.
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Home work
Answer questions 4, 9, 11, 16, 17, 26, 29, 30, 31, and 33 on page 477. 4. List 5 OSHA requirements relating to industrial hygiene.
9. Summarize the various elements of ANSI Z9.8 (indoor air quality/HVAC).
11. What type of medical examinations should be required of employeeswho handle ACMs (Asbestos Containing Materials).
16. Explain 5 self protection strategies that employees can use in the
workplace. 17. How does NIOSH relate to industrial hygiene?
26. Describe the basic provisions of the following standards: OSHAChemical Process Standard, EPA Clean Air Act, and SARA.
29. Explain the 3 NIOSH categories of respirators.
30. What is sick building syndrome?
31. Explain the major tenets of the OSHA Confined Space Standard. 33. Summarize the requirements of OSHAs Hazard Communication
Standard.