For the first time this year, the Baltimore area is in for a three- or four-day stretch of air pollution high enough to be unhealthy for everyone, according to forecasters at the University of Maryland and the Maryland Department of the Environment.
"Code red" levels of ozone pollution were recorded at air monitors in Essex, Edgewood and Suitland late yesterday. Forecasters said that by early afternoon today, the entire metropolitan area will reach code red conditions for ozone. Pollution will stay high at least through tomorrow, forecasters predict.
Code red ozone levels can cause coughing, burning eyes and chest pain in healthy people, and are especially dangerous for children, the elderly and people with chronic respiratory or heart problems. People in those high-risk groups should stay indoors as much as possible today, while healthy adults should avoid strenuous work or exercise outdoors.
Ground-level ozone is a colorless, odorless gas created when fumes from vehicles, lawn mowers, boat engines, industrial smokestacks and other sources cook in the heat and sunlight of summer days. Maryland and other Mid-Atlantic states have some of the nation's worst ozone pollution because contaminants blow into the region from coal-burning power plants and factories in the Ohio Valley.
The latest bout of bad air is caused by a high-pressure system that is producing hot, windless days, allowing pollution to stagnate over the region. When that weather pattern occurs during the longest days of the year in late June, ozone levels typically soar as long hours of sunlight transform exhaust gases into harmful ozone, said MDE air expert Matthew Seybold.
The forecast calls for increasing clouds and winds Friday and Saturday. That could cause ozone levels to fall slightly, to "code orange" or moderately unhealthy, but there's a chance that the code red conditions could continue all week, forecasters said.
The string of unhealthy air days does not necessarily portend a long, hot summer of polluted skies. Last year, the region posted record low levels of pollution and only four code red days, three of them in a row in mid-June.
But with three unhealthy air days recorded in Central Maryland this month, the state will match the tally for all of last year if today's forecast is accurate.
Air pollution experts estimate that 60 percent or more of the pollutants that cause ozone are from domestic sources, such as cars and lawn mowers.
To help control pollution levels, the MDE asks residents to limit their driving, combining errands into one trip whenever possible. The agency also suggests taking public transportation or sharing a ride to work, avoiding using lawn mowers and other gasoline-powered machinery, and waiting until after dark to fill vehicle fuel tanks.