AUGUSTA — Business groups squared off against environmentalists and health experts Tuesday during a hearing on a plan by the state Department of Environmental Protection to exempt Maine from some anti-smog regulations.

The change would ease the process of industries seeking to develop or expand in Maine by removing a requirement that they buy expensive emission offset credits. Maine is already meeting emission standards under the federal Clean Air Act. Also, the U.S. Environmental Protection Agency supports the proposal and has said that the plan will not allow for any additional pollution from Maine businesses.

Several people who testified against the proposal said that wasn’t good enough, namely because they believe federal ozone standards do too little to promote public health, while representatives from Maine’s pulp and paper industry say the changes are necessary to spur business development and job creation.

Since 1990, Maine has been part of an “Ozone Transport Region” that reaches from Maryland through the Pine Tree State. In an effort to prevent a net increase in pollution levels, industries within the region that emit smog-creating nitrous oxides or volatile organic compounds are required to purchase emission credits from defunct entities.

In the early 1990s, Maine’s coastal counties from York to Hancock exceeded federal ozone standards. But throughout the 1990s and into the 2000s, Maine’s air quality improved, according to Mark Cone, director of the Bureau of Air Quality.

By 2008, under the strictest standards ever for ozone standards, the entire state of Maine had fallen under federal ozone attainment limits, Cone said. Even when monitoring sites in Maine showed ozone levels exceeding the limit, the pollution could be traced to sources in other states, he said.

The DEP has requested the federal government grant the entire state a waiver, allowing Maine to opt out of the requirement that businesses purchase emission offset credits. The federal Clean Air Act allows parts of the Ozone Transport Region to opt out of the requirement, as long as they continue to meet federal clean air standards and aren’t contributing to the nonattainment of other areas.

Ed Miller, senior vice president for public policy at the American Lung Association, said an ozone level of 60-70 parts per billion is necessary to promote the public health. If that were the standard used by the federal government, he said, much of Maine would be placed in nonattainment.

“Maine’s air is not as healthy as it should or could be. In some cases, ozone levels are as high as possible without triggering the EPA’s nonattainment status,” he said. “We do not believe Maine people want to live in the unhealthiest environment allowed by law.”

Ivy Frignoca of the Conservation Law Foundation said ozone is also a danger to the environment by damaging vegetation, reducing crop yields, stunting tree growth and increasing the susceptibility of plants to disease. She said the state should wait until more current data is available before seeking to change the rules.

“The state is basing its exemption request on 2008 data, and we’re currently awaiting publication of the 2011 national emissions inventory,” she said. “It makes sense to wait.”

Cone said that because Maine is meeting all the federal standards, the credit-purchasing requirement is an unfair burden on the economy.

In Maine, major industry means pulp and paper. Representatives from that sector, including spokesmen from several of the state’s remaining mills, were the only members of the public to testify in support of the DEP’s proposed rule change, which they said was necessary to spur growth in the industry and make Maine more competitive.

Dixon Pike, a lobbyist for the Maine Pulp and Paper Association, said the proposal would ease that burden. He said the offset credit requirement deters mills and other businesses from investing in Maine.

“The science makes it very clear that the proposal is justified. We’re not jeopardizing environmental protection or risking the environment by this proposal,” he said. ”But we are removing some potential hurdles for investment by the mills and other facilities in the state.”

“The consequences of additional costs to obtain emissions offsets are not hypothetical,” said Ken Gallant, environmental manager for Verso’s Androscoggin paper mill in Jay. “Having to purchase offsets for a project can wipe out any potential return on investment.”

The EPA will continue taking public comment on Maine’s waiver request until Oct. 3.