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Freshwater Fish in Mass. Lakes Show Reductions in Mercury Improvements Correlate to State's Zero Mercury Strategy
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Five years of testing on largemouth bass and yellow perch in over a dozen lakes and ponds by MassDEP have revealed encouraging news: the level of mercury in these species - although still too high - is declining, and this drop correlates with tighter regulatory controls on mercury pollution adopted by Massachusetts in recent years.
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 A potent toxin, mercury adversely affects people and wildlife, in particular the neurological system, kidneys, immune system and cardiovascular system. The brain and developing neurological system of the fetus and children are particularly sensitive to mercury and can be damaged by fairly low levels of exposure.
Since 1999, the MassDEP Office of Research and Standards, with technical and analytical support from the Bureau of Resource Protection's Watershed Group and the William X. Wall Experimental Station, has been testing the same subset of 17 lakes. The data reveal substantial reductions of mercury in fish tissue statewide, and the most significant reductions in the fish tissue were found in an area where the greatest reduction in mercury emissions occurred - the northeast region of Massachusetts.
Detailed results of this work will be published shortly and the Office of Research and Standards will continue monitoring efforts to assess longer-term trends in mercury levels. However, the results of those tests for both species are summarized here:
YELLOW PERCH: Nine of the lakes sampled for yellow perch were in the northeastern section of Massachusetts and in eight of these lakes, the drop of mercury concentrations in yellow perch averaged 32.4%, and the average for other remaining lakes statewide showed a drop of 15%.
LARGEMOUTH BASS: Eleven of the lakes sampled for largemouth bass were in the northeast region and mercury levels from seven of these decreased an average of 24%, and the decline over the other remaining lakes statewide was 19%.
Large Decreases Seen Within Mercury 'Hotspots' Mercury deposition modeling performed in 1998 demonstrated that the northeast region of Massachusetts was a mercury deposition "hotspot," with the highest rate of mercury atmospheric deposition in New England. Since that time, mercury emissions statewide have been reduced by about 70%, and by about 87% from sources located in the "hotspot" area. These reductions occurred as a result of new emission controls that were put in place at several trash incinerators in the mid-1990s, which, at the time, were the most protective emission limits in the country. In addition, some of the sources of mercury emissions in the northeast part of the state closed, including one trash incinerator and a medical waste incinerator.
Based on recent data from US Centers for Disease Control and Prevention, several hundred thousand newborns each year in this country are at-risk of mercury toxicity because of their mother's exposure to mercury. This equates to over 10,000 newborns at risk each year in the Commonwealth.
Once released into the environment, mercury persists and does not break down into harmless components like many other pollutants. It also bio-accumulates, or becomes concentrated, in fish tissue at levels up to a million times higher than in water. Although mercury is a natural element, the amount of this toxin circulating in portions of the biosphere is much higher than it was 100 years ago. Most human exposure to mercury is largely attributable to the consumption of contaminated fish.
To address mercury pollution, Massachusetts and other New England States and the Eastern Canadian Provinces developed a regional strategy: the New England Governors and Eastern Canadian Premiers Mercury Action Plan targeting mercury pollution. The goals of the plan are to reduce New England and Eastern Canadian mercury emissions by 75% as of 2010, with a long-term goal of virtual elimination. To further the goals of the regional plan, Massachusetts adopted its own multi-agency Zero Mercury Strategy in 2000. Under these strategies, Massachusetts has developed and is implementing one of the strongest programs to reduce mercury pollution and monitor environmental results in the nation, including strict but achievable control requirements on mercury releases from coal-fired utilities, trash and medical incinerators, and dental offices.
Long-term Monitoring of Native Fish Species
While regulations covering the control of mercury have grown stronger, the testing of lakes in the state has also evolved. Massachusetts has monitored fish contaminants since 1984; the primary goal of much of the early work was simply to identify fish populations that might pose unacceptable health risks. Since most sampling sites were not revisited, a long-term record of fish mercury conditions was not established and trends in mercury levels could not be evaluated.
Starting in the autumn of 1994, a more rigorous and comprehensive approach to the study of mercury in fish in Massachusetts was implemented.
The objective of this current work by MassDEP's Office of Research and Standards has been to establish a long-term monitoring network that will measure variation and long-term trends in mercury levels in fish. Data from a subset of lakes located in proximity to a number of historically large sources of mercury emissions in a high mercury deposition area has provided welcome and unexpected good news about the rapidity with which these valuable aquatic resources respond to major reductions in mercury inputs to the environment.
MassDEP will continue to monitor mercury concentrations from these water bodies to assess the environmental results of mercury reduction efforts. These efforts include limits on emissions from the Commonwealth's coal-fired utilities that take effect in 2008, as well as programs to reduce mercury pollution from consumer and industrial products and from dental offices that are currently underway in Massachusetts and the northeastern U.S. and Canada. MassDEP is also working to address the contribution of upwind, out-of-state sources to mercury deposition in Massachusetts through additional monitoring and modeling.
While this recent news is encouraging, the sobering facts are these: based on data from MassDEP's fish monitoring program, fish consumption advisories have been issued for over 100 specific water bodies in the state since the 1980s, and overall, about 50% of all tested water bodies have one or more species of fish with mercury concentrations that necessitate fish consumption advisories for the general population, including the sensitive subgroups women of childbearing age, pregnant women, nursing mothers and children.
Although substantial progress has been made, there is clearly further work to be done. Massachusetts, and the region as a whole, remain committed to continued implementation of mercury reduction efforts under the Massachusetts Zero Mercury Strategy and the New England Governors-Eastern Canadian Premiers Mercury Action Plan.
For more information see:
Toxic Effects of Mercury - http://mass.gov/dep/toxics/stypes/hgres.htm
Public Health Fish Consumption Advisory - http://db.state.ma.us/dph/fishadvisory/.
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