PRINCIPLES OF TOXICOLOGY

302 CHEMICAL CARCINOGENESIS
with exposure to chemicals, many of which, before these new data were developed, were believed to
be very safe and industrially useful chemicals.
Since the mid-1970s, several organizations—both private and public—have attempted to identify
occupational carcinogens, or possible carcinogens, in an effort to reduce workplace exposure since
logically, occupational exposures to carcinogenic chemicals would potentially be their gravest threat
to human health because of their duration (a working lifetime) and the magnitude of occupational
exposures. For example, the ACGIH ranks the known carcinogenic hazard of the compounds for which
it provides TLVs in their annual listing (Table 13.11). Similarly, OSHA has identified its own list of
chemical carcinogens that it regulates (Table 13.12), and the National Institute for Occupational Safety
and Health (NIOSH), which is often referred to as the “research arm” of OSHA, provides a separate
listing of what it considers to be the known or probable carcinogens that might be encountered in the
workplace. Additional lists of known human carcinogens and chemicals known to be carcinogenic in
animal tests include lists by the National Toxicology Program (Table 13.13) and the International
Agency for Research on Cancers (IARC) which publishes a monograph series that evaluates the animal
and human data for widely used chemicals and chemical processes (Table 13.14). In reviewing these
different lists, it is of interest to note that rather than being identical, as one might expect, there can be
significant differences in what is viewed as a possible carcinogen depending upon the agency
promulgating the listing.
TABLE 13.11 Known or Suspected Carcinogens Identified by the ACGIH a
4-Aminodiphenyl
Confirmed Human Carcinogen (A1)
Coal tar pitch volatiles
Arsenic β-Naphthylamine
Asbestos Nickel, insoluble
Benzene Nickel subsulfide
Benzidine Uranium (natural)
Beryllium Vinyl chloride
Bis(chloromethyl)ether
Chromite ore processing
Wood dust (hard or mixed hard/soft woods)
Chromium(VI) Zinc chromates
Acrylonitirile
Suspected Human Carcinogen (A2)
Diazomethane
Antimony trioxide 1,4-Dichloro-2-butene
Benz[a]anthracene Dimethyl carbamoyl chloride
Benzo[b]fluoranthene Ethylene oxide
Benzo[a]pyrene Formaldehyde
Benzotrichloride Lead chromate
1,3-Butadiene 4,4′-Methylene bis(2-chloroaniline)
Cadmium 4-Nitrodiphenyl
Calcium chromate Oil mist, mineral
Carbon tetrachloride Strontium chromite
Chloromethyl methyl ether Sulfuric acid
Coal dust Vinyl bromide
Diesel exhaust Vinyl fluoride
a Including agents identified as carcinogens A1 or A2 in the Notice of Intended Changes for the TLVs.