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Mercury (Hg) concentrations were monitored from 1999 to 2011 in largemouth bass (LMB) and yellow perch (YP) in 23 lakes in Massachusetts USA during a period of significant local and regional Hg emissions reductions. Average LMB tissue Hg concentration decreases of 44% were seen in 13 of 16 lakes in a regional Hg "hotspot" area. YP in all lakes sampled in this area decreased 43% after the major emissions reductions. Comparative decreases throughout the remainder of the state were 13% and 19% for LMB and YP respectively. Annual tissue mercury concentration rate decreases were 0.029 (LMB) and 0.016 mg Hg/kg/yr (YP) in the hotspot. In lakes around the rest of the state, LMB showed no trend and YP Hg decreased 0.0068 mg Hg/kg/yr. Mercury emissions from major point sources in the hotspot area decreased 98%, and 93% in the rest of the state from the early 1990s to 2008. The significant declines in fish Hg concentrations in many lakes occurred over the second half of a two decade decrease in Hg emissions primarily from municipal solid waste combustors and, secondarily, from other combustion point sources. In addition to the substantial Hg emissions reductions achieved in Massachusetts, further regional, national and global emissions reductions are needed for fish Hg levels to decrease below fish consumption advisory levels.

In June 1998 the New England Governors and Eastern Canadian Premiers (NEG-ECP) adopted a comprehensive regional Mercury Action Plan (MAP) with aggressive emission reduction and pollution prevention goals for the New England States, the Atlantic Provinces and Quebec. New Jersey and New York have also been active participants. The NEG-ECP MAP was motivated by, and based on, extensive data demonstrating the widespread and serious nature of mercury impacts in the region and the existence of many preventable sources of mercury pollution. The plan established a long-term goal of virtually eliminating anthropogenic mercury releases in the region with interim goals of a 50% reduction by 2003 and 75% by 2010. Policy and regulatory initiatives implemented under the NEG-ECP MAP have exceeded federal efforts addressing mercury and have resulted in substantial regional progress in reducing mercury pollution. Recent data indicates that the region has reduced mercury emissions by approximately 55% since the NEGECP MAP was adopted. The NEG-ECP MAP provides an important demonstration of what can be technologically, economically and politically accomplished and has influenced mercury reduction programs at the global scale. Scientific information played important roles in developing and implementing this plan. Key research areas where regional policy makers would benefit from additional information include improved: environmental indicators for tracking progress; mercury release inventories, especially on mercury product breakage and mobile sources; deposition sources, including in-region and out-of-region contributors; elemental mercury exposure and impact data; determinants of mercury levels in fish; ecological impacts of mercury; and data on the effectiveness of outreach efforts.

ObjectivePerchlorate inhibits the uptake of iodide in the thyroid. Iodide is required to synthesize hormones critical to fetal and neonatal development. Many water supplies and foods are contaminated with perchlorate. Exposure standards are needed but controversial. Here we summarize the basis of the Massachusetts (MA) perchlorate reference dose (RfD) and drinking water standard (DWS), which are considerably lower and more health protective than related values derived by several other agencies. We also review information regarding perchlorate risk assessment and policy.Data sourcesMA Department of Environmental Protection (DEP) scientists, with input from a science advisory committee, assessed a wide range of perchlorate risk and exposure information. Health outcomes associated with iodine insufficiency were considered, as were data on perchlorate in drinking water disinfectants.Data synthesisWe used a weight-of-the-evidence approach to evaluate perchlorate risks, paying particular attention to sensitive life stages. A health protective RfD (0.07 μg/kg/day) was derived using an uncertainty factor approach with perchlorate-induced iodide uptake inhibition as the point of departure. The MA DWS (2 μg/L) was based on risk management decisions weighing information on perchlorate health risks and its presence in certain disinfectant solutions used to treat drinking water for pathogens.ConclusionsCurrent data indicate that perchlorate exposures attributable to drinking water in individuals at sensitive life stages should be minimized and support the MA DEP perchlorate RfD and DWS. Widespread exposure to perchlorate and other thyroid toxicants in drinking water and foods suggests that more comprehensive policies to reduce overall exposures and enhance iodine nutrition are needed.

Mercury is a persistent, bioaccumulative toxin that adversely affects human beings and wildlife. Mercury, like many such toxins, is a multimedia pollutant that can readily transfer among air, water, and soils, and thus crosses the boundaries of traditional regulatory programs. Mercury can also be transported long distances in the atmosphere, creating transboundary issues that are regional and global in scope. Human exposure to mercury is largely attributable to the consumption of contaminated fish, with women of childbearing age, infants, and children at greatest risk. Because mercury persists in the environment, the risk of neurological or other impairments can span generations. Mercury, largely from anthropogenic sources, enters aquatic systems through a variety of pathways including direct deposition from the atmosphere, runoff, and wastewater discharges.