Tons of mercury spewing from electric power plants pose “significant hazards to public health,” according to the EPA, which announced in December that it would draft new regulations to control emissions.

The determination, prompted by a suit by the Natural Resources Defense Fund, means the agency must propose rules to reign in the previously unregulated toxic emissions by Dec. 15, 2003. Final rules are to be issued in 2004.

“The greatest source of mercury emissions is power plants and they have never been required to control these emissions before now,” said EPA Administrator Carol Browner.

The action could also help with the Bay Program’s toxics goals. Mercury is one of the Bay Program’s chemicals of concern because of its potential to bioaccumulate in the food web.

In addition, recent research has suggested that fish in some of the watershed’s lakes and reservoirs may contain mercury concentrations high enough to warrant fish consumption advisories. Most of the mercury in those areas is thought to result from air pollution.

The new “Toxics 2000 Strategy” calls for ensuring that finfish and shellfish are safe to eat throughout the watershed. But accomplishing that goal for areas impacted by the deposition of airborne mercury would be difficult without federal action because much of the pollution originates from outside the watershed.

Mercury concentrations in the air typically are not high enough to be of concern. But when it drops to the ground, mercury accumulates in lakes and reservoirs, where it enters the food chain.

Power plants, especially those that burn coal, are the largest source of mercury releases, accounting for an estimated 40 tons getting into the air and water annually in the United States, according to a National Academy of Sciences study.

That report, issued last fall, concluded that while the health risks to a large majority of the population is low, as many as 60,000 babies may be exposed to unhealthy mercury levels annually because either they or their mothers ate fish contaminated with mercury. The report urged the regulation of power plant releases of mercury.

Exposure to mercury has been linked to neurological and developmental damage in humans. Fetuses and young children are particularly vulnerable. In addition, studies have suggested that some wildlife — such as loons, eagles and river otters — are affected when they eat mercury-tainted fish.

The EPA for more than six years has been debating whether to limit mercury coming from power plants as it has done for medical and hazardous waste incinerators and other sources.

Final decisions about how much utilities will have to reduce mercury emissions will be spelled out in the regulations. The EPA said cost-effective ways of reducing mercury emissions are available.

In a statement, the Edison Electric Institute said utilities are ready to work with the EPA on mercury reductions, but any future regulation should “have a sound scientific foundation.”

The EEI, which represents investor-owned utilities, said “key scientific and technological issues” remain to be resolved. It also took issue with Browner's assessment of the health risks from mercury.

Environmentalists, though, praised the action. “With this determination, the EPA can finally plug the loophole that has allowed power plants to escape the regulations that apply to every other major source of mercury,” said Andy Buchsbaum, water quality projects manager for the National Wildlife Federation. “Our challenge now is to work to make sure the final rule will be a strong one.”

The actual rulemaking will be handled by the incoming Bush administration.