AUGUSTA, Maine — With ground-level ozone concentrations expected to reach unhealthy levels on Friday, state officials have issued an air quality alert for the coast from Kittery to Acadia National Park.

The unhealthy levels of ozone might continue into Saturday, too, according to the Maine Department of Environmental Protection, and the Down East coast and inland areas near the ocean are expected to be in the moderate range.

The air alert is meant for children and people suffering from respiratory diseases such as asthma, bronchitis or chronic obstructive pulmonary disease, but it also is aimed at healthy adults who exert themselves by exercising or working outdoors.

“When ozone reaches the unhealthy or sensitive groups range, a lot of people don’t realize that healthy adults who are exercising or working outdoors become an unhealthy group,” Martha Webster, an air quality meteorologist with the Maine Department of Environmental Protection, said Thursday afternoon. “You’re breathing more deeply, breathing more frequently and bringing more pollution into your body.”

At elevated ozone levels, affected people can experience reduced lung function and irritation, the department said in a media release.

“When this happens, individuals may notice a shortness of breath, coughing, throat irritation, and/or experience an uncomfortable sensation in their chest,” the release stated.

According to Webster, Maine’s overall air quality has improved since the 1990s. Still, on days such as Friday when the air quality is bad, the wind must be coming from the right direction to blow ozone and its precursors to Maine, she said.

The American Lung Association says that while the ozone layer found in the upper atmosphere shields the planet from much of the sun’s ultraviolet radiation, ozone air pollution at ground level causes serious health problems. Problematic ozone develops from gases that come out of tailpipes, smokestacks and other sources, according to the lung association, and when these gases come into contact with sunlight they form ozone smog. Winds can carry ozone far from its point of origin, which is how it ends up at bucolic places such as the top of Mount Cadillac on Mount Desert Island.

“The midwest has a lesser impact than it used to years ago,” Webster said. “Mostly what we’re focusing on is what’s happening in the northeast.”

She said that the Maine Department of Environmental Protection isn’t telling people not to go outside or exercise.

“We’re just saying pay attention to how you’re feeling,” Webster said. “Reduce the intensity or duration of your exercise, especially if you have a pre-existing condition.”

High temperatures generally are necessary for ozone to reach unhealthy levels, according to an official with the National Weather Service in Caribou. He said that the temperatures Friday along the coast from the New Hampshire border to Acadia National Park are predicted to be in the low 80s.

Additionally, thunderstorms are forecast for the afternoon, and rain is likely to alleviate the effects of ozone, the weather service official said, because with rainfall comes the circulation of cooler air.

For more information about air quality alerts, visit the Maine Department of Environmental Protection’s air quality forecast page or call 800-223-1196. For more information about heat-related illness or asthma, visit http://www.maine.gov/dhhs/mecdc/.