history of occupational exposure limits

History of Occupational ExposureLevels

Jim Kapin, MPH, CIHAdvanced Chemical [email protected]

History of OELs2 Jim Kapin, MPH, CIHAdvanced Chemical [email protected]

Scenario

λ Worker X is exposed to TMNS (4,4,4,4-tetramethyl nastystuff) at a concentration of0.5 ppm as an 8 hr TWA

– Is this a problem?– How do I know?– What information do I make a determination?

History of OELs3

Relevant Factors


What is an OEL?

λ A level that will protect (all / nearly all) workers?λ Zero Exposure?λ “Typical Worker”

– “Threshold limit values (TLVs) refer to airborneconcentrations of substances and represent conditionsunder which it is believed that nearly all workers may berepeatedly exposed day after day”

λ Duration, time span– 8 hrs, 40 yrs

λ Route of exposure


Historical Figures

λ Herodotus, Pliny the Elder, Agricola all identified occupationalillnesses

λ Ramazzini, De Morbis Artificum Diatriba (1723)– Specific protective measures, “Father of Occupational Medicine”

λ McCready, Benjamin W– On the Influence of Trades, Professions, and Occupations in the

United States in the Production of Disease (1837) - First US textλ Charles Thackrah

– The Effects of the Principal Arts, Trades, and Professions and ofCivic States and Habits of Living on Health and Longevity (1831)

λ Alice Hamilton– “a pioneer into a new, unexplored field of American medicine, the

field of industrial disease”, beginning in 1910


Early attempts at OEL development

λ Max Gruber, Hygienic Institute at Munich (1883)– two hens, twelve rabbits exposed to carbon monoxide for up to 47 hours

over three days– “the boundary of injurious action of carbon monoxide lies at a

concentration in all probability of 500 parts per million, but certainly (notless than) 200 parts per million”

λ K.B. Lehmann (et al) 1880s – 1930s– Studies on ammonia and hydrogen chloride gas, chlorinated hydrocarbons

and a large number of other chemical substancesλ Kobert (1912) published a table of acute exposure limits.

– 20 substances, listed under the headings: (1) rapidly fatal to man andanimals, (2) dangerous in 0.5 to one hour, (3) 0.5 to one hour withoutserious disturbances and (4) only minimal symptoms observed.

λ US Bureau of Mines (1921).– Values for 33 workplace substances listed are those encountered in

workplaces.


Dusts

λ South Africa, 1916, exposure limit of 8.5million particles per cubic foot of air (mppcf)for the dust in gold mines (80 to 90%quartz). Later, lowered to 5 mppcf.

λ In the U.S. (1917) initial level for high quartzdusts was 10 mppcf,– Based on work by Higgins, south-western

Missouri zinc and lead mines.– Later lowered by USPHS


More Early OELs

λ Most exposure limits through the 1930s, (except fordusts) were based on acute animal exposures

λ Sayers and Dalle Valle (1935)– physiological responses to five concentrations of 37

substances, the fifth being the maximum allowableconcentration for prolonged exposure.

– Lehmann and Flury (1938) and Bowditch et al. (1940)published papers that presented tables with a single valuefor repeated exposures to each substance.

λ Volume II of Patty's Industrial Hygiene andToxicology (1949)


Beginning The Modern Era

λ ACGIH– Formed in 1938, Maximum allowable concentrations (MACs), prepared in

1939 and 1940– MAC committee (Committee on Threshold Limits) - Warren Cook, Manfred

Boditch, William Fredrick, Philip Drinker, Lawrence Fairhall and Alan Dooley– The first set of values were released in 1941– 1942 - Threshold Limits Committee presented a table of 63 toxic substances

with the “maximum allowable concentrations of atmospheric contaminants”– 1946 presented second report with the values of 131 gases, vapours, dusts,

fumes and mists, and 13 mineral dusts.λ American Standards Association (later ANSI) 1941 formed Z-37

committee– developed first standard of 100 ppm for carbon monoxide.– By 1974 had issued bulletins for 33 exposure standards for toxic dusts and

gases.


OEL Timeline


Legislative Background

λ British Factories Act of 1864– required dilution ventilation. The 1878 version specified exhaust

ventilation by fans.– The British Factories Act of 1901 created specific regulations to

control “dangerous trades”λ Massachusetts Health Department appointed health inspectors

in 1905 the to evaluate dangers of occupations,λ USPHS recommends upper limits for exposure to quartz-

bearing industrial dusts (1929)λ ACGIH prepared first maximum allowable concentrations for

chemical exposures (1939)


More Legislation

λ Walsh-Healey Public Contracts Act (1936)– Safe and healthful workplace for federal contractors

λ OSH Act (1970)– Created OSHA and NIOSH– Incorporated the 1968 ACGIH TLVs (minus 21 chemicals for

which there were ANSI standards) as PELs– Subsequent OSHA health standards asbestos, benzene, coke

oven emissions, and leadλ PELs not significantly updated

– “Benzene case” (1978), PELs Updates (1989)– PEL update requires quantitiative risk assessment, based on

1/1000 risk of fatal injury/illness, economic and technical feasibility


YesEPA (community-based standard, not an OELReference concentration (RFC)

NoAIHA (community-based standard, not an OEL)Emergency Response PlanningGuide Planning Guide (ERPG)

Yes/NoHealth and Safety Commission & Health and SafetyExecutive (Britain

Occupational exposure limit(OEL)

Yes(Commission for the Investigation of Health Hazardsof Chemical Compounds in the Work Area)

Maximum Allowableconcentration (Germany) (MAK)

YesEnvironmental Protection Agency (EPA)New chemical Exposure Limit(NCEL)

NoAmerican Industrial Hygiene Association (AIHAWorkplace EnvironmentalExposure Level (WEEL)

NoAmerican Conference of Governmental IndustrialHygienistsThreshold limit value (TLV)

NoNational Institute for Occupational Safety and HealthRecommended exposure limit(REL)

YesOccupational Safety and Health AdministrationPermissible exposure limit (PEL)

BindingRecommending BodyType of Limit

Comparison of OELs


Conceptual Issues

λ Zero Exposure? “Safe Limit”?– Dose Makes the Poison (all chemicals are toxic)

λ Duration, time span– 8 hrs, 40 yrs

λ Route of Exposureλ Protect all or some

– “TLVs refer to airborne concentrations of substances andrepresent conditions under which it is believed that nearly allworkers may be repeatedly exposed day after day”

– Acceptable risk? (1/1000, 1/10,000, 1/1000,000)?λ Regulatory or Technical?λ Technical or Economic Feasibility?


Current Efforts

λ EU, UK– Data Collection (REACH)– Criteria documents – establish dose/response

λ Threshold, non-threshold issues– Occupational Exposure standard (OES)

λ concentration at which there is no significant risk to health.– Maximum Exposure Limit (MEL).

λ substances which have serious health implications and for which anOES cannot be set

λ Carcinogens, sensitizer, etc.λ Replaced with COSHH Essentials

– Control Bands– Used by employers, not safety professionals


QUESTIONS?

history of occupational exposure limits

Health & Medicine