The Environmental Protection Agency released a plan Wednesday that would reduce emissions of mercury and other toxins from coal-burning power plants, drawing praise from health officials and condemnation from some industry representatives and lawmakers.

EPA Administrator Lisa P. Jackson said the “first ever” national standard for harmful power plant emissions “was 20 years in the making” and was required by the 1990 Clean Air Act. The plan would force plants to purchase scrubbers and other equipment to prevent 91 percent of mercury from coal from being released into the air.

“Today we’re taking an important step forward to protect the health of millions of Americans,” Jackson said in an address at the agency’s headquarters. She repeated the EPA’s position that controlling pollution prevents thousands of premature deaths as well as childhood asthma.

According to a report by the Congressional Research Service, coal-fired power plants are among the nation’s greatest sources of stationary pollution. In 2005, they accounted for 70 percent of emissions of sulfur dioxide, nearly half of the mercury and 20 percent of the nitrogen oxide.

Jackson estimated that the regulation would cost industry $10 billion by 2015, but said the health and environmental improvements would be worth more than $100 billion a year. She said electric bills would increase by $3 to $4 a month once the rule was fully implemented.

Reflecting the anticipated congressional battle, Sen. James M. Inhofe (R-Okla.), a frequent critic of the EPA, responded by introducing legislation that calls for a formal review of the agency’s regulations.

“EPA’s proposed utility [rule] today could, by itself, shut down up to 20 percent of America’s coal-fired power capacity,” he said. “When you add in all of the rules and regulations from EPA’s cap-and-trade agenda, the outlook for jobs and economic growth looks dire.”

Organizations that represent power plants seized on the projected cost of the cleaning equipment, which some say would exceed $10 billion, to denounce the standards. Scott Segal, director of the Electric Reliability Coordinating Council, called the proposal “one of the most expensive rules in the history of the agency.”

Segal said that the projected price tag does not include indirect costs and that the EPA did not take into account other recent rules for reducing greenhouse gases that could cause costs to overlap. The agency has adopted or plans to adopt numerous rules with compliance deadlines of 2015, he said, causing the industry to “face perhaps its costliest and most pressing challenge.”

In a statement, Segal cited an IHS/Global Insight report estimating that every $1 billion spent to comply with pollution standards will put 16,000 jobs at risk and reduce the nation’s gross domestic product by up to $1.2 billion.

A similar finding — in a report issued by the Council of Industrial Boiler Owners following EPA rules to reduce emissions of mercury from boilers — was challenged by the Congressional Research Service.

The CRS said the boiler owners did not consider costs that would be passed on to consumers by companies and the number of construction jobs that would be created by companies that install the cleaning equipment.

According to the nonprofit Clean Energy Group, a collection of electricity distribution companies that are in compliance with clean-air standards, 250 projects that would be required by the new rule would each create up to 200 construction jobs.

In a November letter addressing the anticipated proposal, the Building and Construction Trades Department said the “installation of equipment to control sulfur dioxide, nitric oxide, mercury and other hazardous air pollutants requires a wide range of . . . pipefitters, boilermakers, electricians, ironworkers . . . and laborers.”

Under the Clean Air Act, the EPA is required to identify industrial sources for 187 listed toxic air pollutants — including mercury, arsenic, chromium, nickel, hydrogen chloride and hydrogen fluoride — and to take steps to reduce them.

Industry representatives have complained that the agency is moving too fast too soon.

Jackson said the plan would give the industry up to four years to install scrubbers and other clean-air technology.

The proposal would replace the Clean Air Mercury Rule, a program from the George W. Bush administration that requires power plants to cut their mercury emissions by 70 percent.

In 2008, a federal court vacated that rule because it did not control other metals, such chromium dioxins that cause cancer.

The proposal will be open to public comment for 60 days after it is published in the Federal Register and will undergo public hearings in Atlanta, Chicago and Philadelphia. It is not expected to be final until late this year or early 2012.

Michael J. Bradley, executive director of the Clean Energy Group, said the EPA went out of its way to work with industry. “I’ve been in the business over 25 years, and I haven’t seen the EPA reach out like they have with this rule,” he said.

Charles D. Connor, chief executive of the American Lung Association, said the message of the new regulation is “start now, don’t wait” longer to control power plant emissions.

Jonathan Truwit, a doctor at the University of Virginia Hospital, described treating people with asthma and other lung diseases caused by industrial pollution.

“When I see young patients in the ICU, they’re gasping for air,” he said. “As a care doctor, I might be the last step. We can usually save the patient, but not always. It’s a tragedy when a person dies from asthma.”