Seeking to reassure major power plant and factory owners that impending regulation of climate-altering gases will not be too burdensome, the Environmental Protection Agency emphasized on Wednesday that future permitting decisions would take cost and technical feasibility into account.
Under the Obama administration, the E.P.A. declared that gases that contribute to global warming are a danger to human health and the environment and thus must be regulated under the Clean Air Act. The agency is starting with the largest sources of such emissions — coal-burning power plants, cement factories, steel mills and oil refineries — and then will extend the regulations to smaller facilities.
Utilities, manufacturers and oil companies have challenged the new rules, saying that the E.P.A. arbitrarily chose the plants it will regulate and that the Clean Air Act never envisioned limitations on carbon dioxide, a ubiquitous substance that is not in itself toxic or hazardous to health. The state of Texas has said it will not abide by the greenhouse gas regulations no matter how the E.P.A. decides to define or enforce them.
Gina McCarthy, the head of the E.P.A. office of air and radiation, said on Wednesday that the agency was simply following the law by beginning the process of regulating greenhouse gases, and that the facilities that will need to obtain permits starting in January are already complying with clean air rules for other pollutants.