The Environmental Protection Agency is delaying indefinitely regulations to reduce toxic pollution from boilers and incinerators.
The move comes in response to a request from industry groups.
The announcement Monday was another setback for a rule that the agency claims will avert thousands of heart attacks and asthma cases each year. In February, the EPA announced changes to make it much cheaper to comply with the new standards without diminishing the public health benefits.
Industry groups, and congressional Republicans and Democrats, had been critical of the rule because of its expense and scope.
More than 13,000 large boilers would have to install pollution controls within three years of the regulation taking effect.
The EPA could not say when that would be. It said it would work as expeditiously as possible.