Critics contend that the new emissions targets in a proposed Environmental Protection Agency rule for sulfur dioxides and nitrogen oxides carried downwind from powerplants in 31 eastern states and the District of Columbia could be difficult to achieve, but environmental advocates say the new proposal will result in cleaner air.

EPA says the proposed rule, which EPA Administrator Lisa Jackson signed on July 6, would cut SO2 emissions by 2014 by 70% from 2005 levels and trim NOx emissions by 52%. Gina McCarthy, EPA’s assistant administrator for air and radiation, says the proposal is a “large and important step in EPA’s effort to protect public health as well as help the states reduce air pollution and attain Clean Air [Act] standards.”

The regulation deals with interstate “transport” of emissions carried long distances, McCarthy says.

The proposal is a response to a 2008 federal appeals court decision that required EPA to rewrite the 2005 Clean Air Interstate Rule (CAIR). The new proposal “gets larger emission reductions more quickly than CAIR required,” McCarthy says. She says EPA also has begun work to apply the newly proposed SO2 and NOx “template” to another transport rule, which would help meet an ozone-pollution standard due out later this year.

EPA estimates the July 6 rule would avoid 14,000 to 36,000 deaths and produce $120 billion to $290 billion in annual benefits starting in 2014, compared with costs of $2.8 billion per year.

Power industry officials say the emissions targets would be difficult to achieve by the deadlines set in the proposal, the first of which will occur in 2012. A spokesman for the Edison Electric Institute says the proposal allows limited interstate emissions trading, which he calls “the most reasonable of the options on the table.” He adds, “However, the fact that EPA will put in place similar regulations in 2012 to deal with an even tighter air-quality standard leaves the power sector exposed to a great deal of regulatory uncertainty.”

Jeff Holmstead, a former EPA air official who authored the original CAIR rule, says, “It is not clear whether it will be possible to achieve the standards set by the rule while still providing affordable and reliable electric power.” But Bruce Nilles, the Sierra Club’s deputy conservation director, calls EPA’s proposal a “step forward for people who want clean air.” He adds, “While a thorough review and comment period remains to be completed, the Sierra Club is pleased to see this progress made.”