WASHINGTON — The Environmental Protection Agency on Wednesday proposed the first national standard for emissions of mercury and other pollutants from coal-burning power plants, a rule that could lead to the early closing of a number of older plants and one that is certain to be challenged by the some utilities and Republicans in Congress.

Lisa P. Jackson, the agency’s administrator, said control of dozens of poisonous substances emitted by power plants was long overdue and would prevent thousands of deaths and tens of thousands of cases of disease a year.

Ms. Jackson pointedly included the head of the American Lung Association and two prominent doctors in her announcement to make the point that the regulations were designed to protect public health and not to penalize the utility industry.

She estimated the total annual cost of compliance at about $10 billion, in line with some industry estimates (although some are much higher), and the health and environmental benefits at more than $100 billion a year. She said that households could expect to see their electric bills rise by $3 to $4 a month when the regulation was fully in force after 2015.