How do we assess the environmental benefits from U.S. mercury emission control regulation?

There is a crucial need to document the impact and effectiveness of the regulation of anthropogenic mercury (Hg) emissions on human, wildlife and ecosystem health to ascertain the need for further controls. The impact of elevated methylmercury (MeHg) levels in fish on human and wildlife populations is well documented and is the driver for current and impending controls. Scientists and policy makers need to develop a monitoring framework to accurately evaluate the effectiveness of regulation. The monitoring strategy outlined below is the result of such an effort by a group of 32 Hg scientists from academia, industry, government and non-profit organizations. To monitor change in Hg loadings to aquatic systems and the resultant alteration in MeHg incorporation into fish and wildlife, the proposed monitoring strategy details the need for a comprehensive investigation (in air, water and the watershed) at 5-10 continentally- distributed locations (intensive sites). Additionally, it includes the more limited data collection at a larger number of sites (cluster sites) that are widely distributed across freshwater and coastal ecosystems, but associated with the intensive sites. At the cluster sites, wet Hg deposition would be measured in conjunction with seasonal sediment and water collections for total Hg and MeHg. Biota sampling would consist of yearling fish, piscivorous fish and piscivorous and insectivorous wildlife. To be successful, this program should begin without delay and last 15-20 years. Federal commitment and involvement would be required to maintain such a long-term monitoring effort. This monitoring framework would answer the question of whether change is occurring in atmospheric Hg input and how this change is reflected in a variety of aquatic ecosystems and in their organisms. In addition, this program would provide the information necessary to demonstrate the impact of Hg emission reductions from anthropogenic sources in the USA on fish MeHg concentration.