International agencies

Acroleiu, iu lARC Monographs on the Evaluation of Carcinogenic Risk of Chemicals to Humans. Some Monomers, Plastics and Synthetic Elastomers andMcrolein, Vol. 19, International Agency for Research on Cancer, Lyon, France, 1979, pp. 479—494. 

It has been reported that because of concerns by some international agencies over the possibiUty that crystalline siUca might be a carcinogen, a 0.1% max sihca (crystalline) specification has been mandated in mineral fillers (26). 

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). 

Eadier reports of a link between testicular cancer and DMF exposure have not been corroborated ia a study of 4000 Du Pont employees (34). Very recendy, inhalation studies ia mice and rats have shown no oncogenic effect from DMF (35). The International Agency for Research on Cancer (lARC) has concluded that evidence associating DMF with cancer ia animals is "iaadequate," but has classified DMF as "possibly carciaogenic to humans" (Group 2B) (36). 

A comprehensive study of the tolerance of laboratory animals to vapors of 2-nitropropane was reported in 1952 (100). In a study pubHshed in 1979, rabbits and rats survived exposure to nitromethane for six months at 750 and 100 ppm, respectively, with no unexpected findings (101). Similarly, no compound-related effects were found for rabbits exposed to 2-nitropropane at 200 ppm or for rabbits or rats exposed at 27 ppm. Liver damage was extensive in male rats exposed at 207 ppm for six months, and hepatocellular carcinomas were observed. Subsequendy, the International Agency for Research on Cancer (lARC) found that there is "sufficient evidence" to conclude that 2-nitropropane causes cancer in rats but that epidemiologic data are inadequate to reinforce the conclusion in humans (102). The National Toxicology Program also concluded that it "may reasonably be anticipated to be a carcinogen" (103). 

I. K. O Neill, J. Chen, and H. Bartsch, eds.. Relevance to Human Cancer of N-Nitroso Compounds, Tobacco Smoke andMjcotoxins, lARC Scientific Pubhcation No. 105, International Agency for Research on Cancer, Lyon, Prance, 1991. 

Scientific PubHcation No. 19, International Agency for Research on Cancer, Lyon, France, 1978, p. 127. 

The International Agency for Research on Cancer (lARC) has classified DEHP (44) as "an agent possibly carcinogenic to humans." However this classification is based only on the rodent studies and does not take into account the more recent understanding of the underlying mechanisms. 

For all three compounds, biological data relevant to the evaluation of carcinogenic risk to humans are summarized in the World Health Organization International Agency for Research on Cancer monograph (70). 

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