Though environmentalists consider the proposal modest, the suggested rules represent the federal agency's first attempt at monitoring refinery emissions, said Earthjustice attorney Emma Cheuse.
"EPA has a responsibility under the Clean Air Act to continue to reduce hazardous emissions that Americans are exposed to, and these rules are steps along the path to start doing that," Cheuse said.
Valero community liaison Chip Gross did not immediately return a request for comment.
While Attorney General Greg Abbott has not said what action, if any, he would take if the new rules are passed, "there's a good chance federal laws on air pollution will be sorted out here," said Adrian Shelley of Houston Air Alliance.
Abbott, who is running to replace Rick Perry as the next governor of Texas, often touts his record of having sued the EPA 27 times during his tenure as Attorney General.
The hearing Tuesday is the second and final of the EPA's 60-day public comment period on the proposal. During the first EPA hearing in Wilmington, California, in July, a man brought a jar of black gunk he said was particulate matter from a refinery that had been collected from an adjacent neighborhood.
The EPA is not expected to take any action before the end of the year.