Cancer/carcinogens methylene chlorid

Some VOCs are known human carcinogens (e.g., benzene, vinyl chloride). Others are animal carcinogens and may be human carcinogens (methylene chloride, trichloroethylene, tetrachloroethylene, chloroform, and p-dichlorobenzene). The unit risks for these compounds are shown in the table below (Unit risks reflect the probability of attracting cancer in a hypothetical population during lifetime exposure to lpgm of VOCs.)... 

Proposition 65 s warning requirement has provided an incentive for manufacturers to remove listed chemicals from their products. For example, trichloroethylene, which causes cancer, is no longer used in most correction fluids reformulated paint strippers do not contain the carcinogen methylene chloride and toluene, which causes birth defects or other reproductive harm, has been removed from many nail care products. In addition, a Proposition 65 enforcement action prompted manufacturers to decrease the lead content in ceramic tableware and wineries to eliminate the use of lead-containing foil caps on wine bottles. 

Most scientists would hold that these unknowns and uncertainties in the regulatory risk-assessment model would tend to favor risk overestimation rather than underestimation or accurate prediction. While this view seems correct, it must be admitted that there is no epidemiological method available to test the hypothesis of an extra lifetime cancer risk of about 10 per 1000 000 from methylene chloride in drinking water. The same conclusion holds for most environmental carcinogens. It is also the case that more uncertainties attend the risk assessment process than we have indicated above. 

In humans methylene chloride exposure has been associated with a wide variety of cancers in a number of cohort and case control studies pancreatic, prostate, lung, liver, cervical, breast, and astrocytic brain tumors have been reported. Limitations in these studies include small sample size, incomplete exposure information, and concomitant exposure to other carcinogenic substances. The lARC has stated that there is not a sufficiently consistent elevation of risk across studies to make a causal interpretation credible. In a recent study of 1473 workers, followed for nearly 50 years, methylene chloride exposure level was not related to mortality due to all causes, malignant neoplasms, or lung and pancreatic cancers. ... 

In contrast, the most common industrial halo-genated solvents such as methylene chloride, chloroform, perchloroethylene, and carbon tetrachloride have long been identified as suspected human carcinogens. Benzene and other aromatic hydrocarbons have also been associated with the causation or promotion of cancer in humans and animals. All of these substances are widely used because of their excellent solvent properties in a wide range of applications. Nevertheless, regulations have been issued in the United States, for example (under the Clean Air Act) to control many of these chemicals... 

The risk is of cancer Methylene chloride (MC), trichloroethylene (TCE), and perchloroethylene (PCE, or "perc"), which produce acute and/or chronic, non-cancerous health effects at sufficient concentrations, have also been classified as probable or possible human carcinogens by either the EPA or other governmental or international agencies (Ref. 3, Table 20 1)... 

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