Gas stations in seven southern and coastal counties in Maine will be required to sell cleaner-burning “reformulated gas” beginning June 1 as part of an agreement between the state and federal governments.

The U.S. Environmental Protection Agency announced Monday that only reformulated gas – a blend designed to reduce emissions of air pollutants – can be sold in York, Cumberland, Sagadahoc, Androscoggin, Kennebec, Knox and Lincoln counties starting in June.

Maine opted out of the federal government’s reformulated gas program in the late 1990s because of contamination caused by methyl tertiary-butyl ether, MTBE, which was one of the additives at the time. But MTBE is no longer used in gas, and the Maine Department of Environmental Protection asked the EPA to allow the state to rejoin the reformulated gas program.

Industry groups had supported Maine’s inclusion in order to allow the same type of fuel sold elsewhere in New England to be sold in southern Maine as well.

The emissions of reformulated gas contains fewer pollutants that cause ground-level ozone, or smog, which can cause breathing problems among the elderly, young children and the infirmed. Gas retailers in many cities are required to sell reformulated gas, but the program is optional elsewhere.

The EPA estimates that 30 percent of all gas sold in the U.S. is reformulated.