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#415 - The Scientific Basis Of Chemical Safety -- Part I: Limits On Workplace Chemical Exposures, 08-Nov-1994

In 1990, the American Public Health Association (APHA) estimated that
each year 50,000 to 70,000 Americans die of diseases developed from
toxic exposures on the job. Furthermore, APHA estimated that 350,000
new cases of occupational disease develop each year from toxic

The federal government established standards for chemicals in workplace
air for the first time in 1971, as required by the Occupational Safety
and Health Act [OSH Act] of 1970. Prior to 1971, the U.S. had no
enforceable federal standards for workplace air; instead, guidelines
(which could be voluntarily adopted, or not) were set by a private
organization called the American Conference of Governmental Industrial
Hygienists (ACGIH). The ACGIH is a private group composed of industrial
hygienists from state and local governments, plus academics and
industry consultants.

In 1946 the ACGIH established a Committee on Threshold Limits, charged
with developing "threshold limit values" (TLVs) for chemical exposures
in the workplace. A threshold is an amount below which no damage is
evident. The ACGIH says TLVs are average concentrations in air for an
8-hour workday, 40 hours per week, to which "nearly all workers may be
repeatedly exposed, day after day, without adverse effect."[2]

In 1971 the U.S. government adopted all the ACGIH's TLVs as official
government standards for workplace air. Since 1950, the ACGIH's TLVs
have also been used to set government standards in Belgium, West
Germany, Austria, Italy, the Netherlands, Portugal, Denmark, Sweden,
Finland, Norway, Spain, Switzerland, England, Japan, and probably

Furthermore, during the 15 years after 1971, at least 37 of 50 states
in the U.S. used the TLVs as the basis for setting ambient air
pollution standards --not workplace standards, but standards for the
general outdoor air. ("Ambient" means "surrounding" or "enveloping.")
Often states have taken the TLVs, reduced them by some arbitrary
"safety factor" like 100, and declared them "safe" for ambient air.
Reasons for reducing TLVs by a "safety factor" are: (a) TLVs are
established for only 40 hours of exposure each week, not continuous
exposure 168 hours per week; (b) workers are assumed to be young,
healthy, male, and employed (therefore, probably eating well, with
access to health care) whereas the general population includes pregnant
women, infants, the elderly, people with chronic ailments, people with
special sensitivity to particular chemicals, and poor people who can't
afford to eat well and rarely, if ever, see a doctor; (c) TLVs are set
based on exposure to a single chemical, but in the real world everyone
is exposed to numerous chemicals simultaneously. Since the "safety
factor" is an arbitrary number, any "safety" in TLV-based ambient air
standards must rely upon the safety of the underlying TLV itself. There
is evidence that the role of TLVs is now being extended in the U.S., to
setting standards for indoor air, standards for groundwater
contamination, and standards for cleanup at Superfund [contaminated
dump] sites.

For nearly 5 decades, no one critically examined the scientific data
underlying the TLVs. Even the TLV Committee itself seems to have relied
solely on the advice of individual Committee members who took
responsibility for setting a TLV for a particular chemical. Those
individual Committee members, it was revealed in 1988, were often
employed by the same corporations that were the major producers of the
chemicals having their TLVs set. For example, a Dow Chemical Company
representative took responsibility for setting TLVs for at least 30 of
Dow's halogenated hydrocarbons, pesticides, and other industrial
chemical products. Furthermore, in 1988 it was learned that at least
104 TLVs had been set based, in whole or in part, on data that appeared
in unpublished corporate communications. Those corporate communications
were not available from the ACGIH, from the corporations themselves, or
from individual members of the TLV committee.[3] Thus the basis of
those TLVs was secret and not available for scientific peer review.
(The Reagan administration's Occupational Safety and Health
Administration [OSHA] responded to this information in 1989 by once
again formally adopting all 600 of the TLVs, wholesale, as federal
regulations. The OSH Act of 1970 had required the federal government to
conduct its own research and set its own workplace air standards, but
between 1971 and 1989 OSHA was able to set only 12 such standards of
its own. Since there are roughly 60,000 chemicals now in commercial
use, at this rate, OSHA would take 90,000 years to set standards for
all chemicals.)

Despite the absence of open scientific process underlying many TLVs,
many other TLVs had been set based on published literature, and in
those cases, the TLVs were still assumed to be valid. However, in 1990,
independent researchers compared many TLVs to the scientific reports
upon which these TLVs are supposedly based.[4] They found that, in
numerous cases, the TLVs had been set at levels higher than the levels
shown to cause effects in humans, ranging from eye and nose irritation
to permanent changes in bodily structure and outright disease. (They
also found TLVs based on data that was 50 years old; TLVs based on
examination of as few as 3 individuals; and TLVs set to protect against
hearing loss, based on studies of eyes, noses and throats but not

The 1990 report on the scientific underpinnings of the TLVs is worth
reading. Using a uniform format, it contrasts the effects that the TLV
is supposed to prevent, against the actual scientific study of those
effects in humans which the TLV Committee says it relied upon. Here we
reprint excerpts from that 1990 report readers can see for themselves
the way scientific information has been used in setting many TLVs. We
are quoting the 1990 report verbatim, including material both inside
and outside quotation marks, and including the original use of ... to
indicate omissions; our only editing has been to remove italics from
some words. (In what follows, the notation m**3 means "cubic meter of

Acetaldehyde: EFFECT. "The TLV, 100 ppm, is recommended to prevent
excessive eye irritation and potential injury to the respiratory
tract." [ACGIH, 1976]

VALIDATION? "Several of 12 volunteers objected... strenuously even at
25 ppm... A majority... experienced... eye irritation at 50
ppm." [Silverman and others, 1946]

Benzene: EFFECT. "A TLV of 25 ppm is believed low enough to prevent
serious blood changes." [ACGIH, 1976]

VALIDATION? In "a study... of the benzene exposure of workers in the
rubber coating industry... the measured benzene vapor concentrations
averaged 18 ppm and 6 of 47 employees showed a lowered hemoglobin of
below 13.5 grams." [Pagnotto and others, 1961]

Butyl Alcohol: EFFECT. "In view of the apparent potential of n-butyl
alcohol to increase hearing loss in the younger age group of workers
and to impair vestibular [ear] function at levels somewhat below 110
ppm, a TLV of 50 ppm as a ceiling value is recommended." [ACGIH, 1976]

VALIDATION? "Butyl alcohol, at 25 ppm irritated the eyes, nose, and
throat of the majority of 10 volunteers... At 50 ppm there was a
unanimous feeling of pronounced throat irritation, in 10
volunteers." [Nelson and others, 1943]

Chlorine dioxide: EFFECT. "The recommended limit of 0.1 ppm is... to
prevent irritation and possible bronchitis." [ACGIH, 1976]

VALIDATION? "At a factory for the production of sulfite-cellulose...
extensive investigations... showed the occurrence of slight bronchitis
in 7 of 12 workers exposed to chlorine dioxide... at concentrations
lower than 0.1 ppm." [Gloemme and Lundgren, 1957]

Chlorodiphenyl--42% chlorine: EFFECT. "It is believed that this limit,
1 mg/m**3, will offer reasonably good protection against systemic
intoxication but may not guarantee complete freedom from chloracne [a
disfiguring skin disease]." [ACGIH, 1976]

VALIDATION? "In a chemical plant concerned with organic chemical
production where the chlorinated diphenyls in the actual breathing zone
of the workers were 0.1 mg/m**3 of air... seven cases of mild to
moderate chloracne of the face and head occurred among 14 chemical
operators exposed..." [Meigs and others, 1954]

Ethyl Ether: EFFECT. "Regular exposure at this concentration (400 ppm,
the TLV) should cause no demonstrable injury to health nor produce
irritation or signs of narcosis among workers." [ACGIH, 1976]

VALIDATION? "Complaints of nasal irritation began at 200 ppm in the
majority of 10 volunteers." [Nelson and others, 1943]

Fluoride as F [Fluorine]: EFFECT. "The limit, 2.5 mg/m**3, is
sufficiently low to prevent irritative effects and to protect against
disabling bone changes." [ACGIH, 1976]

VALIDATION? At a factory where the concentration of fluorides ranged
from 0.14 to 3.13 mg/m**3, "radiological [x-ray] examination revealed
signs of osteosclerosis [abnormal hardening of bone] in 48 of 189
workers." [Largent, 1961]

Isopropyl acetate: EFFECT. "The limit, 250 ppm,... is considered
adequate to prevent significant irritation of the eyes and respiratory
passages." [ACGIH, 1976]

VALIDATION? "We found that at 200 ppm, the majority of... twelve
subjects of both sexes... experienced some degree of eye
irritation." [Silverman and others, 1946]

Magnesium oxide fume: EFFECT. "The limit, 10 mg/m**3, is recommended on
the basis that this value represents a maximal desirable limit for
dusts of relatively minor hazard." [ACGIH, 1976]

VALIDATION? In 1 of 4 subjects exposed to an average concentration of
magnesium oxide at 5.8 mg/m**3 and in 2 of 4 subjects exposed to an
average concentration of magnesium oxide of 4.1 mg/m**3 "was found... a
leukocytosis [an abnormally large number of white blood cells] and a
fever resembling those caused by the heavy metals." [Drinker and
others, 1927]

Mercury: EFFECT. "Following a study of the chlorine industry it was
concluded in general that exposure at 0.1 mg/m**3 [100 micrograms/m**3]
produced no significant incidence of mercury poisoning but contained
little or no margin of safety." [ACGIH, 1976]

VALIDATION? "Symptoms or signs of chronic mercury poisoning were found
in 1 of 9 and in none of 3 men... engaged in repairing D.C. meters...
where the concentration of mercury in the atmosphere averaged 19 and 40
micrograms/m**3, respectively." [Bidstrup and others, 1951]

Mica: EFFECT. "The limit of 20 mppcf [million particles per cubic foot
of air]... should prevent disabling pneumoconiosis, but may not be
sufficiently low to eliminate positive chest x-ray findings in workers
with many years' exposure." [ACGIH, 1976]

VALIDATION? "In mica factories... the exposure to dust is limited to
muscovite mica only... which contains less than 1% free silica. When
the dust concentrations to which most workers were exposed ranged from
2 to 21 mppcf, with an average of 10 mppcf,... 27 of 61 workers
examined had ground-glass 2 readings of their chest x-rays." [Heimann
and others, 1953]

Selenium: EFFECT. "The limit of 0.2 mg/m**3 for elementary selenium and
its common inorganic compounds is believed low enough to prevent
systemic toxicity and to minimize irritation of eyes and respiratory
passages." [ACGIH 1976]

VALIDATION? In the "manufacture of rectifiers... conjunctivitis and
slight tracheo-bronchitis were present in 9 of 62 workers... The
atmospheric concentrations at different stages of the process varied
from 0.007 to 0.05 mg/m**3, nowhere reaching the recommended MAC
[maximum allowable concentration] of 0.1 mg/m**3." [Note: 0.007 to 0.5
is 4 to 28 times smaller than 0.2, the TLV.] [Kinningkeit, 1962]

Turpentine: EFFECT. "A TLV of 100 ppm is... recommended to prevent
chiefly irritative effects." [ACGIH, 1976]

VALIDATION? "Turpentine at 75 ppm caused nose and throat irritation in
several of 10 volunteers." [Nelson and others, 1943]

[To be continued.]

--Peter Montague


[1] Philip J. Landrigan, "Commentary: Environmental Disease--A
Preventable Epidemic," AMERICAN JOURNAL OF PUBLIC HEALTH Vol. 82 (July
1992), pgs. 941-943.

[2] Barry I. Castleman and Grace E. Ziem, "Editorial: Toxic Pollutants,
Science, and Corporate Influence," ARCHIVES OF ENVIRONMENTAL HEALTH
Vol. 44, No. 2 (March/April, 1989), pgs. 68, 127.

[3] Barry I. Castleman and Grace E. Ziem, "Corporate Influence on
13, No. 5 (1988), pgs. 531-559.

[4] S.A. Roach and S.M. Rappaport, "But They Are Not Thresholds: A
Critical Analysis of the Documentation of Threshold Limit Values,"

Descriptor terms: american public health association; osha; american
conference of governmental industrial hygienists; committee on
threshold limits; tlvs; belgium; west germany; austria; italy;
netherlands; portugal; denmark; sweden; finland; norway; spain;
switzerland; japan; great britain; air quality standards; clean air
act; indoor air pollution; superfund remediation; groundwater;
standards; ronald reagan; acetaldehyde; benzene; butyl alcohol;
chlorine dioxide; chlorodiphenyl; ethyl ether; fluoride; fluorine;
isopropyl acetate; magnesium oxide fume; mercury; mica; selenium;