According to a statement from the EPA, the rules are “based on new information and analysis that became available after the rule was finalized”

The rules set mercury emission limits at 0.003 pounds per gigawatt hour, a slightly higher rate than the 0.002lb/GWh initially set by the EPA in December 2011.

Besides mercury, the adjusted rule also limits filterable particulate matter emissions from new coal-fired power plants to 0.09 pounds per megawatt hour and hydrogen chloride to 0.01lb/MWh.

Sulfur dioxide is limited to 1lb/MWh from coal-fired power plants and lead is restricted to 0.02lb/GWh.

“The updates are largely technical in nature and will have no impact on the sensible, achievable and cost-effective standards already set for existing power plants,” the EPA said.

“The updated standards only apply to future power plants and do not change the types of pollution control technology that plants would install.

“The updates ensure that emissions limits are achievable and that pollution levels can be measured continuously.”

The EPA stated that it did not project the updates would create any significant changes in costs, emission reductions or health benefits.

Industry groups had complained that the EPA's initial rule would have prevented new coal-fired power plants from being built since mercury emissions could not be reliably measured at such low concentrations.

The EPA received 20 petitions for reconsideration of the MATS and in July 2012 announced it would be reconsidering certain rules.

The EPA will take comment on today’s proposal and will hold a public hearing if requested.