TABLE 3.4 Examples of Select Carcinogens

2-Acetylaminofluorene

Dimethyl sulfate

Acrylamide

Ethylene dibromide

Acrylonitrile

Ethylene oxide

Aflatoxins

Ethylenimine

4-Aminobiphenyl

Formaldehyde

Arsenic and certain arsenic compounds

Hexamethylphosphoramide

Asbestos

Hydrazine

Azathioprine

Melphalan

Barium chromate

4,4'-Methylene-bis[2-chloroaniline]

Benzene

Mustard gas (bis(2-chloroethyl)sulfide)

Benzidine

N,N-Bis(2-chloroethyl)-2-naphthylamine

Bis(chloromethyl)ether

(chloraphazine)

1,4-Butanediol dimethylsulfonate (myleran)

a-Naphthylamine

Chlorambucil

ß-Naphthylamine

Chloromethyl methyl ether

Nickel carbonyl

Chromium and certain chromium compounds

4-Nitrobiphenyl

Cyclophosphamide

N-Nitrosodimethylamine

1,2-Dibromo-3-chloropropane

ß-Propiolactone

3,3'-Dichlorobenzidine (and its salts)

Thorium dioxide

Diethylstilbestrol

Treosulfan

4-Dimethylaminoazobenzene

Vinyl chloride

NOTE: Compounds on this list are classified as select carcinogens on the basis of OSHA Laboratory Standard criteria. See accompanying text for details.

these compounds to chloromethyl methyl ether, it is possible that these substances have comparable carcinogenicity, and it is therefore prudent to regard them as select carcinogens requiring the special handling procedures outlined in section 5.D.

Table 3.5 lists important general classes of chemicals for which some members (but not necessarily all) have been identified as being carcinogenic substances. Listed for each general class are representative compounds that are "reasonably anticipated to be carcinogens" based on animal tests, selected from lists of substances identified as carcinogens or potential carcinogens by OSHA, IARC, and the Annual Report on Carcinogens (U.S. DHHS, 1991) published by the National Toxicology Program.

The determination of whether a suspected carcinogenic chemical must be treated as a "particularly hazardous substance" in the context of a particular laboratory use will be affected by the scale and circumstances associated with the intended experiment. The laboratory worker must decide whether the amount and frequency of use, as well as other circumstances, are such that additional precautions beyond the basic prudent practices of section 5.C are required. For example, the large-scale or recurring use of such a chemical might suggest that the special precautions of section 5.D be followed to control exposure, whereas adequate protection from a single use of a small amount of such a substance may be obtained through the use of the basic procedures in section 5.C.

When evaluating the carcinogenic potential of chemicals, it should be noted that exposure to certain combinations of compounds (not necessarily simultaneously) can cause cancer even at exposure levels where neither of the individual compounds would have been carcinogenic. 1,8,9-Trihydroxyanthracene and certain phorbol esters are examples of "tumor promoters." Although not carcinogenic themselves, they can dramatically amplify the carcinogenicity of other compounds. It should also be understood that the response of an organism to a toxicant typically increases with the dose given, but the relationship is not always a linear one. Some carcinogenic alkylating agents exhibit a dose threshold above which the tendency to cause mutations increases markedly. At lower doses, natural protective systems prevent genetic damage, but when the capacity of these systems is overwhelmed, the organism becomes much more sensitive to the toxicant. However, there are differences between individuals in the levels of protection against genetic damage as well as in other defense systems. These differences are determined in part by genetic factors and in part by the aggregate exposure of the individual to all chemicals within and outside of the laboratory.

3.C.3.4 Reproductive and Developmental Toxins

Reproductive toxins are defined by the OSHA Laboratory Standard as substances that cause chromosomal damage (mutagens) and substances with lethal or



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