The heat wave gripping Maryland is cooking up unhealthy levels of ozone air pollution, or smog.

With the thermometer hitting another record high of 97 degrees at BWI Tuesday, air monitors reported ozone levels that pose health risks for people with heart or breathing problems in hte Baltimore and Washington areas, but also in western Maryland and on the Eastern Shore. Individuals in those sensitive groups could experience health problems and are urged to limit their time outdoors.

Air quality reached "orange" levels, meaning a risk for sensitive groups, in Northeast Baltimore and in Davidsonville, Edgewood and Essex in the Baltimore area. Other areas registering sensitive air quality were Frederick County, Hagerstown in Washington County, Millington in Kent County and Beltsville in Prince George's County.  Ozone actually hit "red" levels, meaning a risk of causing discomfort and breathing problems even for healthy people exercising outdoors, in northern Virginia.  Southern Maryland and Montgomery County, it seems, enjoyed moderate to good air quality.  

Tuesday was the third time ozone pollution has gotten to orange levels this month, but the most extensive worsening of air quality. The other two times orange levels were reached Thursday in Padonia north of Baltimore and on Monday in Calvert County.  In May of 2010, by comparison, there were four days when ozone hit orange levels.

The stifling heat's forecast to hang around for at least another day, and air-quality forecasters are warning of another "Code Orange" day on Wednesday, a risk for sensitive individuals. 

Smog or ozone pollution forms when emissions from cars and trucks, power plants and other sources "bake" in sunny, windless skies.  Officials urge people to cut back on driving, using power mowers and painting, among other things, to reduce emissions when bad air days are predicted.

To learn more and stay up on the latest air-quality forecasts and readings, go here. 

(Worker laying asphalt in West Baltimore towels off perspiration. Baltimore Sun photo by Barbara Haddock Taylor)