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as a linear function of exposure and a quadratic function of age. For male bladder cancer, a straight-line extrapolation from the 1 % point of departure (LED1) yielded a risk at the MCL of 1 to 1.5 per 1,000. Considering the data on bladder and lung cancer in both sexes noted in the studies in Chapter 4, a similar approach for all cancers could easily result in a combined cancer risk on the order of 1 in 100. It is also instructive to note that daily arsenic ingestion at the MCL, approximately 100 µg in adults, provides a margin of exposure less than 10.

As discussed in Chapter 8, the subcommittee recognizes that human susceptibility to the adverse effects of chronic arsenic exposure is likely to vary based on genetics, sex, and other possible factors. Some factors, such as poor nutrition and arsenic intake from food, might affect assessment of risk in Taiwan or extrapolation of results in the United States.

Upon assessing the available evidence, it is the subcommittee's consensus that the current EPA MCL for arsenic in drinking water of 50 µg/L does not achieve EPA's goal for public health protection and therefore requires downward revision as promptly as possible.


EPA (U.S. Environmental Protection Agency). 1988. Special Report on Ingested Inorganic Arsenic: Skin Cancer; Nutritional Essentiality. EPA 625/3-87/013. U.S. Environmental Protection Agency, Risk Assessment Forum, Washington, D.C.

EPA (U.S. Environmental Protection Agency).  1992. Drinking water; national primary drinking water regulations-synthetic organic chemicals and inorganic chemicals; national primary drinking water regulations implementation. Fed. Regist. 57(138):31797.

EPA (U.S. Environmental Protection Agency). 1996. Proposed guidelines for carcinogen risk assessment. Notice.  Fed. Regist. 61(79):1795918011.

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