State health officials have issued an air quality advisory for today for the midcoast region and higher elevations up to Mount Desert Island.

Ground-level ozone is expected to reach unhealthful concentrations for sensitive groups today in midcoast Maine and at higher elevations from Port Clyde through Mount Desert Island, according to the Maine Department of Environmental Protection.

The advisory means that people with respiratory problems, such as asthma, as well as the elderly, children and even active adults, may experience reduced lung function or irritation due to ground-level ozone.

The DEP recommends that people in affected areas avoid strenuous activity, such as jogging, during midday; close windows and circulate air with a fan or air conditioner; and avoid using chemicals that can cause additional respiratory irritation.

Ground-level ozone is formed when pollution from fossil fuel combustion reacts chemically with intense sunlight. Ground-level ozone is most problematic on hot summer days.