Lowering the detection limit for arsenic: implications for a future practical quantitation limit

Exposure to arsenic (As) in drinking water is associated with an increased risk ol bladder, liver, kidney, ,ind skin cancers (Smith et al, 2002; NRG DIEGO P. FERNANDEZ, 2001). To mitigate these risks? the US Environmental Protection Agency AND JANET G. HERING (USEPA) revised the maximum contaminant level (MCL) for As in 2001. After considering possible standards ranging from 5 to 20 ug/L, USEPA set the MCL for As at 10 ug/L with a compliance date of January 2006 (USEPA, 2002). States have the option to set their own regulatory standards at or below the federal MCL; the New Jersey standard is 5 ug/L (NJDEP, 2004), and other states, such as California, are currently evaluating their state MCLs. These enforceable standards must be set as close to corresponding, nonenforceable healthbased standards as is feasible and be justified by a cost-benefit analysis. The federal health standard, the MCL goal (MCLG), is defined as the concentration of a drinking water contaminant at which there is no known or expected risk to health. The MCLG for As and all other carcinogens is set to zero because it is assumed that there is no threshold for cancer risk. In contrast, California's public health goal (PHG) for As is 0.004 ug/L based on an excess risk of 10"6 from lifetime water consumption of 2 L/d per person.