ASSESSMENT OF EXISTING METHODS AND DATA DEVELOPMENT FOR REVISING WATER QUALITY CRITERIA FOR PROTECTION OF WILDLIFE FOR MERCURY

Mercury is considered a serious threat to wildlife in many areas. Numerous research and government policy initiatives aimed at examining and controlling the impact of mercury in the environment have been undertaken in recent years (e.g., U.S. EPA 1997a,b; U.S. EPA Mercury Action Plan). An important component of the action plan to reduce mercury pollution is the development of ambient water quality criteria (AWQC) for the protection of aquatic life and wildlife. Existing AWQC for the protection of wildlife are contentious. For example, the scientific rationale behind the wildlife Great Lakes AWQC for mercury has been particularly controversial (e.g., Meyer 1998). Initially, the Great Lakes Water Quality Initiative (GLWQI) had proposed a mercury criterion for wildlife of 0.18 ng/L, a level well below the typical mercury analytical detection limit of 200 ng/L and levels that naturally occur in the environment in many locations (Wiener and Spry 1996). Without much comment or scientific support, the mercury wildlife AWQC was subsequently raised to 1.3 ng/L in the final guidance. Recently, in the Mercury Report to Congress (U.S. EPA 1997a), the authors proposed that the wildlife AWQC be adjusted to 0.64 ng/L total mercury or 0.05 ng/L methylmercury. The updated total mercury value differs from the GLWQI value because the former is national in scope, and because of slight differences in how the existing exposure and toxicological information was interpreted (U.S. EPA 1997a).