Six environmental groups in Pittsburgh marked National Clean Air Day Tuesday by urging the U.S. Environmental Protection Agency to follow through on plans to strengthen health-based smog controls.

At a news conference outside Children's Hospital of Pittsburgh of UPMC in Lawrenceville, leaders of the groups also called on Pennsylvania's Democratic Sens. Arlen Specter and Bob Casey to oppose legislation by Sens. Jay Rockefeller, D-W.Va., and Lisa Murkowski, R-Alaska, to block and delay EPA regulation of greenhouse gas emissions from coal-fired power plants and other industrial facilities.

"The Clean Air Act and the EPA have a 40-year track record of reducing pollution while allowing economic growth," said Randy Francisco of the Sierra Club. "It's time to start cleaning up the air and move away from older, dirty sources of energy."

Cassie McCrae, a campaign organizer for the Center for Coalfield Justice and the PA Alliance for a Coal Free Generation, said Mr. Rockefeller and Ms. Murkowski are ignoring a strong scientific consensus urging immediate controls of carbon emissions to reduce future climate change.

"What our senators need to hear from us is it is not acceptable to delay regulation," Ms. McCrae said. "Emissions regulations are needed. There is a public health threat and we need strong actions now."

The EPA is in the process of formulating regulations designed to reduce concentrations of ground-level ozone -- the primary component of unhealthy smog -- to between 60 and 70 parts per billion, a health-based standard that will protect human health. The Pittsburgh region is not in attainment for the existing, weaker, ozone standards.

"Ozone is a concern for children with asthma, and when pollution is high we see more respiratory symptoms and emergency room visits," said Dr. Fernando Holguin, clinical director of pediatric environmental medicine at Children's Hospital.

He is heading research to identify the environmental factors impacting asthma in the region. "Air pollution can lead to long-term consequences," he said.

Lucille Prater-Holliday, president of the Action Alliance of Neighbors United, said the group is launching the Green Community Action Team to help educate low-income and African-American communities about the link between pollution, economics and their health.

"There is not an understanding in our neighborhoods and we must bring more awareness to those who are often affected most by the pollution," Ms. Prater-Holliday said, noting that families of color are disproportionately affected by the lost work time and increased medical bills caused by asthma.

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