Since January 2004, when the Department of Environmental Protection (MassDEP) and the Massachusetts Dental Society began promoting the installation of mercury amalgam separators in dental offices, mercury levels in wastewater sludge have dropped dramatically.

At the Massachusetts Water Resources Authority (MWRA) treatment plant on Deer Island in Boston Harbor, mercury levels have been cut nearly in half during that time, and are down by as much as three-quarters from a decade ago. The current level of about 2 parts per million (ppm) is 500 percent better than the state requires and 800 percent below U.S. Environmental Protection Agency (EPA) standards.

Even before the dental amalgam initiative, MWRA had been working aggressively with hospitals and other facilities to reduce the amount of mercury entering the greater Boston sewer system. As a result, its sludge was already well within government safety limits for use as a fertilizer and soil amendment. Today, with mercury levels down further, MWRA sludge is an even more attractive option for gardeners and landscapers.

When the mercury amalgam initiative began, dental facilities were seen as a significant yet controllable source of mercury. State officials estimated that amalgam waste accounted for half or more of the total mercury found in municipal wastewater across Massachusetts.

Much of this mercury - estimated at several hundred pounds per year - was being released to the environment when sewage sludge was incinerated or reused, or treated wastewater that still contained traces of mercury was discharged from treatment plants. Considering that one pound of mercury has the potential to render 2 million pounds of fish unsafe to eat, hundreds of pounds were a significant concern.

The type of mercury found in fish is extremely toxic. Developing fetuses and children are especially sensitive to mercury's harmful effects, including brain damage that can potentially affect development and learning. Each year, more than 400,000 newborns nationally - 8,000 of them in Massachusetts - are at increased risk because their mothers have been exposed to mercury, mostly from eating contaminated fish.

In Massachusetts, native freshwater fish are frequently so contaminated with mercury that the state Department of Public Health advises women who are pregnant or may become pregnant, as well as nursing mothers and children under 12, to avoid eating native fish caught anywhere in the state. More than 40 percent of the lakes and ponds tested have enough mercury in one or more fish species to prompt consumption advisories for everybody.

The aim of the amalgam separator program was to increase the use of pollution controls to effectively reduce mercury discharges from dental offices by up to 95 percent. Nearly 3,000 Massachusetts dentists either voluntarily installed these systems before 2006, or have complied with the regulations requiring amalgam separators that are now in effect.

Massachusetts continues to lead the nation in keeping mercury out of the environment. In-state releases are down by more than 60 percent since the late 1990s, thanks in large measure to regulatory efforts that cut mercury emissions from trash combustion by more than 90 percent and eliminated emissions from medical waste incinerators entirely.

More recently, MassDEP has implemented tough new regulations requiring four coal-burning power plants to control mercury emissions from coal-burning power plants by up to 95 percent in the next five years.

And just this fall, MassDEP and the state Department of Education began implementing the new Massachusetts Mercury Management Act, which bans the sale of specific commercial and consumer products, and requires schools to stop buying mercury-containing items.

But more still needs to be done nationally and globally, since the vast majority of mercury still finding its way into Massachusetts lakes and streams originates elsewhere. The Commonwealth and 22 other states have rejected a U.S. Environmental Protection Agency (EPA) decision to let companies buy and sell rights to emit mercury as a marketplace commodity, and are working together to push strong national mercury reduction measures.

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