Environmental groups in New Hampshire and Maine want the EPA to investigate sulfur dioxide emissions at a power plant in Portsmouth.
Sierra Club chapters in the two states are mounting a petition drive.
It asks the EPA to look into the possible effect of the emissions on asthma cases in the Seacoast regions of the two states.
The groups contend that sulfur dioxide emitted by the Schiller Plant could be adding to respiratory illnesses, especially in Maine.
But Martin Murray, spokesman for PSNH says that an examination of the plant isn't necessary.