The notification also states that a factual record is warranted to examine assertions that the EPA is failing to effectively ensure adoption in the 10 states of concern of total maximum daily loads (TMDLs) of mercury for waterways that do not meet water quality standards for mercury. The submitters assert that these permits and TMDLs must account for air emissions of mercury from upwind coal-fired power plants.

"U.S. coal-fired power plants are the largest source of mercury emissions in North America, spewing 48 tons each year,” said Dr. Elaine MacDonald with Sierra Legal in Toronto.

“The CEC's investigation will highlight the connection between mercury emissions from power plants and the thousands of mercury contaminated water bodies and ensure that the EPA cannot continue to ignore the impact of toxic air pollutants on water quality," MacDonald said.

The Secretariat did not recommend a factual record for the submitters' assertion that the United States is failing to impose controls on air emissions of coal-fired power plants through TMDLs or other Clean Water Act mechanisms.

The Secretariat noted that issues relating to control of mercury emissions from coal-fired power plants are currently under review in litigation challenging rules recently adopted in the United States under the Clean Air Act.

Earlier this year, the EPA enacted a regulation that places restrictions on power plant mercury emissions that environmental groups say are "minimal." They allege that the cap and trade system established under that regulation will allow coal-fired power plants to emit mercury for 10 years longer than the current provisions of the Clean Air Act would allow at the expense of public health.

Several environmental groups, including Waterkeeper Alliance, are currently challenging the EPA mercury regulation in a U.S. federal court. They are concerned about mercury emissions because the metal is a neurotoxin.

Exposure to high levels of metallic, inorganic, or organic mercury can permanently damage the brain, kidneys, and developing fetus, according to the Agency for Toxic Substances and Disease Registry (ATSDR), a U.S. federal agency.

Metallic mercury and inorganic mercury compounds enter the air from mining ore deposits, burning coal and waste, and from manufacturing plants, the ATSDR explains. It enters the water or soil from natural deposits, disposal of wastes, and volcanic activity.

Methylmercury may be formed in water and soil by the action of bacteria on metallic and inorganic mercury. Methylmercury builds up in the tissues of fish, and bioaccumulates up the food chain so that larger and older fish tend to have the highest levels of mercury.

In the past 10 years, the number of U.S. states issuing warnings against eating fish because of mercury poisoning has jumped from 27 to 45. One-third of all U.S. lakes and hundreds of thousands of river miles are affected by these advisories today, the submitters point out.

The CEC was established under the North American Agreement on Environmental Cooperation to address environmental issues in North America from a continental perspective, with a focus on those issues arising in the context of liberalized trade.