NORTH LITTLE ROCK, Ark.—Arkansas environmental regulators took a wait-and-see approach Friday in considering whether to treat a chief culprit of global warming as air pollution.

The state currently excludes carbon dioxide from its definition of air contaminants and does not regulate CO2 emissions from industrial plants, businesses, automobiles or other sources.

Environmentalists asked the state Pollution Control and Ecology Commission to strike carbon dioxide from its list of exempted gases, which also includes water vapor, oxygen and nitrogen.

While commissioners agreed Friday that global warming has gained widespread acceptance as an immediate environmental threat, they adopted a recommendation proposed by industrial representatives and wholesale power users to wait on the federal government and Arkansas Legislature to complete its work to address global warming.

Teresa Marks, director of the state Department of Environmental Quality, also told commissioners she was concerned that any change in the definition would trigger regulations on carbon-dioxide emissions before the state has done the necessary scientific study or has the technology to put limits into place.

She said that without the exemption, the state might have to fall back on rules governing emissions of more than 25 tons a year, a standard not specifically established for CO2.

Carbon dioxide is a ubiquitous gas. Humans exhale this gas in the normal course of breathing. It also comes from the internal combustion engine and coal-fired power plants.

Federal and state regulations limit emissions of other pollutants, including sulfur dioxide and particulates, whose effects have been scientifically studied and quantified but the same scrutiny has yet to be applied to CO2, Marks said.

Only four states—California, Montana, Oregon and Washington—have established CO2 emission rates in regulating power plants in their jurisdictions.