Environmental advocates Tuesday urged a panel of Environmental Protection Agency officials in Philadelphia to move quickly with the agency's proposed air toxins standards, which will limit mercury and other metals released from power plants.

One of the EPA's three public hearings on the rule, it was dominated by environmental advocates, doctors and new mothers who spoke of the potential of the new rule to reduce cases of asthma and cancer and cut down on developmental defects.

Mark Schmerling from Huntingdon Valley, Pa., took to the microphone with a large black-and-white photo depicting a plume of smoke from a coal-fired plant hovering over a church.

"I feel it's important for EPA to know that they have all the public support so that they can stand up to these industries," Schmerling said. "I want them to know that they're supported, that we stand behind them."

Most of the messages were the same: stand up to the power companies that are pushing for delayed enactment or more flexible standards.

Jeff McNelly from ARIPPA, a trade group representing Pennsylvania power plants that use waste coal to generate electricity, was one of the few industry representatives present. He said his group is looking over the hefty regulations and working on a detailed written comment to submit to the EPA. Tuesday, however, he wanted to file a complaint.

"It would be keen if we had some seat at the table to make some of these comments before the document's actually drafted," McNelly said. "And once we submit comments we're hoping (the EPA is) sincerely going to look at them."

A spokesman for Exelon, which owns PECO, called the rule "balanced, reasonable and long overdue," and offered a reminder that the power industry is not a monolith.

Industry experts says some smaller coal-fired power plants in Pennsylvania will likely close rather than undergo the multimillion-dollar updates necessary to meet the standards.

The rules, which are up for public comment until July 15, will be finalized in November. They're expected to go into effect between 2014 and 2015.