You may have heard or read in recent news articles that there is health advisory regarding consumption of some fish due to the potential for mercury contamination. While the advisory includes fish caught in most large water bodies including the Quabbin and Wachusett Reservoirs, there is no health concern for the drinking water provided by MWRA.  

MWRA very rarely detects any mercury, even with ultra-sensitive tests 20 times more sensitive than EPA requires.  Over the past decade , only three samples out of almost 250 detected any trace of mercury in the water. When mercury is detected, the levels found are just above the detection limit of 10 nanograms per liter (or parts per trillion). The levels found, between 10 and 14 parts per trillion, are about 1/200th of the drinking water standard of 2 parts per billion. 

Very simply, the data shows very few detections at extremely low levels.  In fact, these very low levels would be considered non-detectable under EPA’s drinking water quality reporting regulations.

The Massachusetts Department of Environmental Protection (DEP) has included the Quabbin and Wachusett Reservoirs on the state list of impaired water bodies due to the fact that historical samples of larger predator fish contained elevated levels of mercury and because the Department of Public Health has issued a fish consumption health advisory.

The fate of mercury on large water bodies such as Quabbin and Wachusett Reservoirs is complex.  Most large water bodies, even pristine lakes in far northern Maine and Canada, have elevated mercury levels in large predator fish, due to long term regional atmospheric deposition from coal burning power plants and trash incinerators.  Mercury bio-accumulates from algae, to small fish to larger fish, and can be found in large fish even when mercury levels are so low that no mercury can be found in the water itself.

For more information about mercury in the environment from the Department of Environmental Protection (DEP) and the Department of Public Health (DPH), visit:

DEP: http://www.mass.gov/dep/toxics/stypes/envnment.htm

DPH: http://www.mass.gov/dph/fishadvisories

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Posted December 2, 2011