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According to EPA's CWA recommended criteria, a level of 0.018 ug/L of arsenic is associated with a cancer risk of one in a million people exposed.  Therefore, a level of 0.18 is a risk of one cancer in one hundred thousand people and a level of 1.8 is a risk of one cancer in ten thousand people.   Therefore, EPA's SDWA Maximum Contaminant Level of 10 ug/L is greater than one cancer per ten thousand people exposed to that level.  And that's NOT factoring in the non-cancer risks associated with arsenic (e.g., heart disease) nor EPA's Science Advisory Board's new cancer slope factor (I believe the potency factor increased for bladder cancer by 15-20%). 

I'm not clear on why you think I'm not entitled to state my opinion that the SDWA level is high.  I'm a member of the public.

My entire point is that the SDWA level for arsenic presents a much higher risk than the CWA level for arsenic, a risk level (one in a million of cancer) that is typically the goal used for clean water in Oregon and most other states.   A consumer of water reading the annual report required under the SDWA could be easily confused into thinking he or she is obtaining information concerning the safety of the water when, in fact, that information has factored in the cost of treatment to allow for a much higher risk.

posted 2 years, 4 months ago
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I wanted to follow up on my on-air comment with more detailed information.  I mentioned the US EPA Safe Drinking Water Act  (SDWA) acceptable level of arsenic is 10 ug/L.  (This is the level to which the drinking water agencies compare their data and report it to you, the customer.  As I noted, these SDWA levels include, in some cases, the costs associated with treatment so they are not a "pure" indication of the risks of consuming that water.)

In contrast, under the federal Clean Water Act (CWA) -- which does not allow the factoring in of treatment costs -- EPA recommends 0.018 ug/L of arsenic level for protection of human health (from drinking and fish consumption).  

Similarly, Oregon currently has an arsenic level under the CWA of 0.0022 ug/L.  Last year, Oregon Department of Environmental Quality (inaccurately) recalculated this figure and generated a proposed level of 0.023 ug/L.   (All of these criteria are based on providing a risk of one cancer per million people exposed to the level of arsenic.)   Oregon DEQ is recalculating it yet again but the point is that regardless of which of these CWA numbers you take,  that number is considerably less than EPA's Safe Drinking Water Act level of 10 ug/L that factors in the costs of treatment.

Put another way, it means very little when your drinking water provider tells you that their tests show they have not exceeded the Safe Drinking Water Act level for arsenic because that level presents a high human health risk.

Nina Bell, Ex. Dir., Northwest Environmental Advocates, Portland, OR

posted 2 years, 4 months ago
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