State environmental officials have issued an air quality alert for parts of southern, central and eastern Maine due to unusual weather patterns that are trapping dirty air close to the surface.

The Maine Department of Environmental Protection is urging people with breathing problems or heart disease as well as the very young or elderly to limit prolonged, strenuous activity outdoors today because of potentially dangerous levels of airborne particulate matter.

The advisory for sensitive groups covers southern coastal and interior western Maine and extends along a swath from the Augusta area through Bangor to the Calais area. Conditions in midcoast, Down East, northern Maine and the western mountains are expected to be moderate.

Air quality advisories have, unfortunately, become fairly common in Maine during summer, when high temperatures combine with pollution to produce unhealthful conditions. But wintertime advisories are relatively rare.

A combination of factors is currently at work over New England, according to DEP air quality meteorologist Martha Webster.

First, winds are carrying soot and other pollutants up the coast from population centers to the south of Maine. These pollutants then combine with emissions from Maine sources, including home heating systems, idling cars, factories and power plants.

Finally, a high pressure system sitting off the coast is keeping this pollution closer to the ground, Webster said.

It’s not unusual, on very cold winter days, for air quality to reach moderate levels in Maine just from local sources, Webster said. But in this case, it is the contribution from southern New England and other population centers to the south that is driving up particulate levels to unhealthful levels.

“What is unusual is this is such a strong, regional event for the wintertime,” Webster said. The conditions could stay in place until Wednesday morning or later, depending on weather patterns, she said.

The last time air quality measures rose even to the top scale of the “moderate” category during winter in Maine was in 2005.

“Most people should be concerned when it reaches unhealthy for sensitive groups,” Webster said. “The more we learn about pollution in general, we see it is affecting health at lower and lower” pollution levels.

Officials in Massachusetts, New Hampshire and Connecticut have also issued air quality warnings for parts of their states, according to the U.S. Environmental Protection Agency.

Higher levels of soot and particulate matter can aggravate existing breathing or heart problems and irritate the respiratory systems in some people. Young children and the elderly are often particularly at risk.

The DEP recommends that sensitive persons avoid strenuous activity, such as jogging, and recommends that individuals take regular breaks. The department also recommends avoiding the use of aerosol products, paints and any cleaners that can further irritate the lungs.

The federal EPA also recommends that, during advisory days, people limit the burning of wood or charcoal, avoid burning leaves, trash or other materials and turn off lights to reduce electricity demand.

Air quality forecasts for Maine are available online at http://www.maine.gov/dep/air/ozone/. To receive automatic air quality alerts for specific areas, go to http://cfpub.epa.gov/airnow/index.cfm?action=airnow.enviroflash.

kmiller@bangordailynews.net

990-8250