History of Occupational Exposure Limits

History of Occupational Exposure
Levels

Jim Kapin, MPH, CIH
Advanced Chemical Safety
858-874-5577
jim@chemical-safety.com

Scenario

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

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

2 History of OELs Jim Kapin, MPH, CIH

Relevant Factors

3 History of OELs

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 airborne
concentrations of substances and represent conditions
under which it is believed that nearly all workers may be
repeatedly 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 occupational
illnesses
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 text
λ Charles Thackrah
– The Effects of the Principal Arts, Trades, and Professions and of
Civic 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 (not
less 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 substances
λ Kobert (1912) published a table of acute exposure limits.
– 20 substances, listed under the headings: (1) rapidly fatal to man and
animals, (2) dangerous in 0.5 to one hour, (3) 0.5 to one hour without
serious 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 8.5
million 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 quartz
dusts 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 for
dusts) 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 allowable
concentration for prolonged exposure.
– Lehmann and Flury (1938) and Bowditch et al. (1940)
published papers that presented tables with a single value
for repeated exposures to each substance.
λ Volume II of Patty's Industrial Hygiene and
Toxicology (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 lead
λ 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


Comparison of OELs
Type of Limit Recommending Body Binding
Permissible exposure limit (PEL) Occupational Safety and Health Administration Yes
Recommended exposure limit
(REL) National Institute for Occupational Safety and Health No
American Conference of Governmental Industrial
Threshold limit value (TLV) Hygienists No
Workplace Environmental
Exposure Level (WEEL) American Industrial Hygiene Association (AIHA No
New chemical Exposure Limit
(NCEL) Environmental Protection Agency (EPA) Yes
Maximum Allowable (Commission for the Investigation of Health Hazards Yes
concentration (Germany) (MAK) of Chemical Compounds in the Work Area)

Occupational exposure limit Health and Safety Commission & Health and Safety
(OEL) Executive (Britain Yes/No
Emergency Response Planning
Guide Planning Guide (ERPG) AIHA (community-based standard, not an OEL) No
Reference concentration (RFC) EPA (community-based standard, not an OEL Yes


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 Exposure
λ Protect all or some
– “TLVs refer to airborne concentrations of substances and
represent conditions under which it is believed that nearly all
workers 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 an
OES 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

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