Carcinogenic effects epidemiological reports

BCME is also found as an impurity (1-7%) in the related CMME. Fourteen cases of lung cancer, mainly of oat cell type, were reported in a chemical plant where exposure to CMME occurred. In the reported epidemiological studies, insufficient evidence is available to separate the carcinogenic effects of the two compounds. ... 

The possible carcinogenicity of nitrous oxide has been studied in dentists and chairside assistants with occupational exposures. No effect was observed in male dentists, but a 2.4-fold increase in cancer of the cervix in heavily exposed female assistants was reported. Other epidemiological reports of workers exposed to waste anesthetic gases have been negative. Carcinogenic bioassays in animals have yielded negative results. Nitrous oxide was not geno-toxic in a variety of assays. ... 

As far as carcinogenic effects are concerned, extensive epidemiological investigations have given no indication that the practically insoluble lead chromate pigments have any carcinogenic properties [3.139, 3.140]. Such properties have been reported for the more soluble zinc chromate and strontium chromate pigments. 

Hexane is currently under review for its carcinogenicity however, it is not classified as a carcinogen at the present time. A US Environmental Protection Agency (EPA) reference concentration of 0.2mgm was calculated based on an epidemiological inhalation study with an uncertainty factor of 300. Critical effects were reported to be neurotoxicity and electrophysiological alterations. 

A single epidemiological study reported no significant increase in cancer mortality in a group of men (n=427) occupationally exposed to an undetennined concentration of hydrazine in air (Wald et al. 1984). Although this study reported no evidence of a carcinogenic effect for hydrazine, the follow-up period was relatively short and only 49 deaths were observed. However, when the workers were observed for another 10 years, there was still no significant increase in cancer mortality (Morris et al. 1995). 

No doubt there are such epidemiological associations but some of those suggested may be fanciful. There is some experimental evidence that industrial exposure to lead can have carcinogenic effects [15] but Westerman et al [95] have reported, on the basis of the analysis of tissues, blood and urine, that they found no association between lead poisoning and multiple sclerosis, either early or late in the disease. 

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). 

Most of the data located concerning the health effects of heptachlor and heptachlor epoxide in humans come from case reports and occupational epidemiology studies of workers engaged either in the manufacture or application of pesticides. There is some information on people who have consumed heptachlor-contaminated food or dairy products, but no adverse health effects have been related to these exposures. The occupational studies involve exposures that are predominantly inhalation with contributions from dermal exposure, whereas all the animal studies were conducted using oral or intraperitoneal exposures. The occupational and case reports provide no quantitation of dose or duration of exposure, which makes it impossible to determine with any precision the effect levels for humans. There are no data that indicate that heptachlor or heptachlor epoxide are carcinogenic to humans. However, human studies are limited by the long latency period of carcinogenesis and by ascertainment and follow-up biases. 

Although a number of epidemiological studies have reported an increased risk of lung cancer among occupationally exposed beryllium workers, deficiencies in the studies limit any unequivocal conclusion. Specific criticisms concern the lack of consideration of latent effects, of smoking history, and of exposure to other potential carcinogens and the underestimation of expected lung cancer deaths in comparison populations. "... 

Nevertheless, the statistics presented in Table 4.5 must be interpreted with caution. As the evidence in Section 4.4.1 suggests, the comparatively low frequency of fatalities and low lost injury time in the UK and Sweden may be attributable to regulators in these two countries prioritising more readily identifiable effects of exposure to certain hazards (e.g., carcinogenicity or sensitisation) over less apparent effects (in terms of existing epidemiological studies or occupational health incident reports) that result from exposure to other hazards (e.g., reprotoxicity). 

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