Health and Ecological Effects of Arsenic in Soil and Water
Arsenic Health and Ecological Effects: Soil and Water (1014015).  This technical report summarizes current knowledge of the human health and ecological effects of environmental arsenic and discusses use of this information in assessing risk and setting regulatory standards.  Since arsenic occurs naturally in coal, and thus in coal combustion products, arsenic risk assessment and regulation are important concerns for electric power producers.  In their detailed survey of the arsenic toxicity literature, authors of the report considered non-cancer and cancer human health effects related to inorganic and organic arsenic exposure via water, air, and soil—as well as toxicity to aquatic plants and animals.  Because inorganic arsenic species (arsenate and arsenite), commonly found in groundwater and soil, are much more toxic than organic arsenic compounds (monomethylarsonic acid and dimethylarsinic acid) also found in those media at much lower concentrations, the report focuses on inorganic arsenic toxicity and carcinogenicity.  Exposure to high levels (greater than 150 µg/L) of inorganic arsenic in drinking water in Taiwan has been associated with cancer of the lung, bladder, and skin.  Based on epidemiologic studies of Taiwanese exposed at this level, inorganic arsenic has been classified as a “human carcinogen” by EPA.  However, linear extrapolation of the Taiwanese results to lower dose exposures in the United States may be inaccurate:  arsenic carcinogenicity is believed to exhibit a threshold of action and/or a sublinear dose-response relationship at low doses.  Further EPRI research is underway to define the inorganic arsenic dose-response relationship for bladder cancer at low dose.  This research is important, the authors note, because “ . . . linear extrapolation of health risks observed in arsenic drinking water studies conducted outside of the United States to lower doses likely overestimates arsenic risk for U.S. populations, where arsenic exposures (e.g., from water and food) are significantly lower and nutritional intake is different.”  An accurate characterization of the dose-response relationship in the low-dose range will inform EPA’s arsenic cancer risk assessment, which is the basis for development of arsenic standards in water, soil, sediment, and air.  For more information, contact Ken Ladwig, (262) 754-2744, keladwig@epri.com.