Water Resources in Rockland - Planning in a Changing World

Risks from arsenic at the Maximum Contaminant Level (MCL) for drinking water

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Estimated excess cancer risks per 100,000 people exposed at the MCL

Risks estimated based on cancer potency estimates from the US Environmental Protection Agency's Integrated Risk Information System (IRIS)

Estimated excess cancer risks per 100,000 people exposed at the MCL

Source: Craig Steinmaus, U.C. Berkeley, School of Public Health

Estimated cancer risk deaths per 100,000 people exposed at the MCL for each drinking water chemical carcinogen

Risks for arsenic based on the National Research Council's (NRC) 2001 cancer potency estimates

Estimated cancer risk deaths per 100,000 people exposed at the MCL of each drinking water chemical carcinogen

Source: Craig Steinmaus, U.C. Berkeley, School of Public Health

The number for arsenic deaths at the 10ppb mcl comes from the NRC 2001 Update on Arsenic in Drinking Water. While the authors of the update agreed that the extensive data from SW Taiwan provides a sound database on the effects of arsenic on humans, adequate for risk assessment, a number of sources of uncertainty in the data remain. Metabolism of arsenic varies markedly between individuals though it’s not clear how to account for that variability in a quantitative dose response analysis.

The choice of dose measurement (cumulative exposure, lifetime average exposure, peak exposure) is a source of uncertainty and the possible confounding impact of smoking adds to the uncertainty as well. Finally, Subcommittee members did not agree on the right background cancer risk to use, though the choice made to use US rather than Taiwanese background cancer incidence reflects standard epidemiological practice to use background incidence in the country of interest.

 

 
 

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