Arsenic in Drinking Water 2001 Update (2001) / Chapter Skim
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6 Hazard Assessment
6 Hazard Assessment
Pages 214-226
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From page 214... ...
The existing studies from Taiwan and Bangladesh, discussed in Chapter 2, have observed substantial increases in the risk of these medical conditions at levels of arsenic exposure that are within one to two orders of magnitude of the Tower levels of current regulatory concern in the United States. Pending 214
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From page 215... ...
The main end points for a quantitative risk assessment following exposure to arsenic in drinking water are lung and bladder cancers. The human data from southwestern Taiwan used by EPA in its risk assessment remain the most appropriate for determining quantitative risk estimates.
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From page 216... ...
The MOE can provide risk managers with information about the extent of apparent protection for the population. The MOE approach is complementary to more traditional approaches for determining a safe level of exposure, each approach providing different information to the riskmanagers (Presidential/ Congressional Commission on Risk Assessment and Risk Management 1997a,b)
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From page 217... ...
This is an important difference because the background rates for lung and bladder cancer are substantially different between Taiwan and the United States. Background rates for lung cancer in the United States are approximately 3and 2.3-fold higher than in Taiwan for females and males, respectively; and bladder cancer risks are approximately 1.4- and 3-fold higher in females and males, respectively, in the United States when compared to Taiwan.
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From page 218... ...
The MLEs of the lifetime excess risks for combined lung and bladder cancer incidence for females range from 9 per 10,000 from exposure to drinking water with arsenic at 3 ,ug/L to 60 per 10,000 from exposure to drinking water with arsenic at 20 ,ug/~. The corresponding risk estimates for males are ~ ~ to 72 per 10,000.
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From page 219... ...
in contrast, when the dose metric used in the Chilean data was the average arsenic concentration in drinking water from 1930 to 1994, the corresponding risk estimates were an order of magnitude higher. The previous Subcommittee on Arsenic in Drinking Water presented lifetime excess cancer risk estimates for bladder cancer mortality in males based on its analyses of the southwestern Taiwanese data (Chen et al.
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From page 220... ...
Also to account for intake from food directly, multiplied lower bound estimate by fraction of arsenic consumed per kilogram contributed by drinking water Adjustments for Used Taiwanese mortality data Used U.S. background inci- Decrease Mortality ver- for bladder and lung cancers; dence data for bladder and sus Incidence adjusted upper bound by 1.25 lung cancers from SEER for bladder cancer to reflect (2001 )
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From page 221... ...
The subcommittee also used a different statistical method than EPA to estimate lifetime cancer risks. The subcommittee has presented lifetime excess cancer risk estimates calculated using either the U.S.
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From page 222... ...
It has been suggested that, if the risks of bladder cancer from arsenic in drinking water were indeed as high as estimated in this report (see Table 6-~) , high cancer rates would have been anticipated in areas of the United States with increased concentrations of arsenic in groundwater, and these high rates would have readily attracted public-health attention.
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From page 223... ...
In accordance with its charge, the subcommittee has not conducted an exposure assessment and subsequent risk characterization and risk assessment. The theoretical lifetime excess cancer risks estimated by the subcommittee and presented in this report, however, should be interpreted in a public-health context using an appropriate risk-management framework, such as that proposed by the Presidential/Congressional Commission on Risk Assessment and Risk Management (1997a,b)
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From page 224... ...
1992. Drinking water; national primary drinking water regulations-synthetic organic chemicals and inorgaruc chemicals; national prunary ~ng water regulations implementation.
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From page 225... ...
Washington, DC: National Academy Press. PresidentiaVCongressional Commission on Risk Assessment and Risk Management.
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