Air pollution levels are expected to reach unhealthy levels today and tomorrow in southwestern Maine, according to the Department of Environmental Protection.

The agency said the regional air pollution event, unusual in winter, is due to particulate matter that has been building up in the northeast and spread into southern Maine. Rising levels of particulate matter, which can include liquid droplets or particles of smoke, soot and other pollutants, were detected here Sunday and were expected to reach unhealthy levels for sensitive people today and tomorrow.

The DEP said people with asthma or other respiratory diseases, children, the elderly, and people with heart disease should limit prolonged exertion.

Look at the DEP Web site for more information on the dirty air alert and particulate pollution.