WASHINGTON - The Environmental Protection Agency on Thursday set a new health standard that coal-fired power plants and other industries will have to meet on sulfur dioxide, a pollutant that triggers asthma attacks and other respiratory problems.

The EPA set the standard within a range that an independent panel of scientists suggested. This marks the first time the standard has been changed since the original one, issued in 1971.

The new rule sets the amount at 75 parts per billion over a one-hour period, a level that is aimed at protecting people who go outdoors from short-term exposures. The current standard is 140 parts per billion, averaged over 24 hours.

The EPA said that even brief exposure could create health problems, especially for children, asthmatics, and older people.

The agency also changed its rules to require more monitors in areas with the most sulfur dioxide pollution.

Sulfur dioxide comes mainly from coal-fired power plants. The EPA is in the process of tightening controls on other air pollutants from coal and other fossil fuels. It is expected to issue a final rule tightening the regulation of ozone, or smog, in September.

The EPA estimated that cleaner air as a result of the new standard would mean 2,300 to 5,900 fewer premature deaths and 54,000 fewer asthma attacks per year. It said the estimated cost to upgrade was about $1.5 billion.

Clean Air Watch, an advocacy group, gave the EPA "a B plus or A minus" on the new standard. It was slightly less strict than the group and the American Lung Association had recommended.

Dan Riedinger, a spokesman for the Edison Electric Institute, a power-industry group, called it "a very stringent standard. It will certainly have an impact" on the need to install new pollution-control devices.

Those controls will be put on power plants that burn coal, which is cheap but also is the most polluting fuel. Natural gas plants produce much less sulfur dioxide. The EPA said power plants accounted for 73 percent of the sulfur dioxide in the air.

Riedinger said it was too early to say how many plants would need more equipment. The industry also is expecting a separate revised rule on air pollution that applies specifically to the electric-power industry, and it also will require sulfur dioxide reductions.

The Edison Electric Institute had argued that research supported a less stringent standard.

Power plants have cut sulfur dioxide by 70 percent since 1980 under existing rules.