Carcinogens limitations

Group C Possible human carcinogen limited evidence of carcinogenicity in animals in the absence of adequate human data... 

A. Agent is probably a human carcinogen Limited human data Sufficient animal data PCBs, styrene oxide... 

B. Agent is possibly a human carcinogen Limited or inadequate human data Sufficient animal data Styrene, TCDD... 

NTP Cancer Classification—Reasonably anticipated to be a human carcinogen Limited evidence in humans sufficient evidence in animals NTP 1998... 

Chronic toxicity with proliferation Opportunity to determine carcinogenic Limited experience... 

Group C—Possible human carcinogen (limited evidence in carcinogenicity in the absence of human data... 

Probable human carcinogen = limited human or sufficient animal evidence using = limited animal evidence using lARC criteria or ERA guidelines for carcinogen... 

Reasonably anticipated to be carcinogens — limited evidence of carcinogenicity from human studies, the interpretation may be credible, but alternative explanations, such as chance, bias or confounding could not adequately be excluded or (2) sufficient evidence of incidence of malignant tnmors from studies in experimental animals in multiple species or strains or in multiple experiments with different routes of administration or nsing different dose levels or to an unusual degree with regard to incidence, site or type of tumor, or age at onset... 

Formaldehyde is classified as a probable human carcinogen by the International Agency for Research on Cancer (lARC) and as a suspected human carcinogen by the American Conference of Governmental Industrial Hygienists (ACGIH). This is based on limited human evidence and on sufficient evidence in experimental animals (136). Lifetime inhalation studies with rodents have shown nasal cancer at formaldehyde concentrations that overwhelmed cellular defense mechanisms, ie, 6 to 15 ppm. No nasal cancer was seen at 2 ppm or lower levels (137). 

Diethylstlbestrol [56-53-1] (DES)(7), which was first synthesized in the 1930s, is the most widely studied nonsteroidal estrogen and has been extensively reviewed. It is an extremely potent estrogen, possessing four times the oral potency of estradiol (3), but carcinogenicity problems have limited its use. 

Toluenediamine is classed as toxic. The oral LD q for animals is between 270—350 mg /kg body weight (45). TDA is readily absorbed through the skin and this is the major route of human exposure. Several studies have shown the 2,4 isomer of TDA to be carcinogenic for rats and mice, but tests on the 2,5 and 2,6 isomers were not positive. AH three of the isomers have been shown to be mutagenic (45). Results of limited studies on the reproductive ha2ards for male workers are equivocal, but animal experiments have shown TDA to cause adverse reproductive effects (45). 

Styrene is Hsted in the U.S. Toxic Substance Control Act (TSCA) Inventory of Chemicals. It is not confirmed as a carcinogen but is considered a suspect carcinogen. The recommended exposure limits are OSHA PEL 50 ppm, ACGIH TLV 50 ppm. For higher concentrations,... 

Succinic anhydride is extremely irritating to the eyes. It causes skin, mucous membranes, and respiratory tract irritation. It may be a sensiti2er. There is no evidence of carcinogenic activity in male or female tats given 50 or 100 mg/kg succinic anhydride (186) the Ames test is negative (187). LD q in rat 1510 mg/kg. There ate no estabflshed exposure limits for ACGIH TLV or TWA. 

Sulfur Polymer Cement. SPC has been proven effective in reducing leach rates of reactive heavy metals to the extent that some wastes can be managed solely as low level waste (LLW). When SPC is combined with mercury and lead oxides (both toxic metals), it interacts chemically to form mercury sulfide, HgS, and lead sulfide, PbS, both of which are insoluble in water. A dried sulfur residue from petroleum refining that contained 600-ppm vanadium (a carcinogen) was chemically modified using dicyclopentadiene and oligomer of cyclopentadiene and used to make SC (58). This material was examined by the California Department of Health Services (Cal EPA) and the leachable level of vanadium had been reduced to 8.3 ppm, well below the soluble threshold limit concentration of 24 ppm (59). 

Ethyl Carbamate. In November 1985, the Canadian Government indicated that it had detected ethyl carbamate [51-79-6] (urethane), a suspected carcinogen, in some wines and distilled spirits. Since that time, the U.S. distilled spirits industry has mounted a serious effort to monitor and reduce the amount of ethyl carbamate (EC) in its products. In December 1985, the Canadian Government set limits of 150 ppb in distilled spirits and 400 ppb in fmit brandies, cordials, and Hqueurs. The FDA accepted a plan in 1987 from the Distilled Spirits Council of the United States (DISCUS) to reduce ethyl carbamate in whiskey to 125 ppb or less, beginning with all new production in January 1989. 

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