Mostly during the summer and early fall months, the Maryland Department of the Environment (MDE) and the Metropolitan Washington Council of Governments (COG) will issue air quality forecasts that may include ground level ozone warnings, which are announced by local television and radio stations.
Ozone is created by chemical reactions mainly between certain air-borne organic compounds and nitrogen oxides in the presence of sunlight and high temperatures. Various sources attribute motor vehicle pollution for between 20-40% of the ozone-causing pollutants in the Baltimore-Washington area.
Unhealthy concentrations can occur when weather is hot and sunny with little to no wind, and the highest ozone concentrations occur between 1 p.m. and 7 p.m. High concentrations of ozone can cause headaches, shortness of breath, coughing, and inflammation or irritation of the respiratory tract, especially during heavy physical activity. People with certain respiratory ailments (bronchitis, asthma, colds, pnuemonia) may have even more trouble breathing when the air is polluted. Not everyone is sensitive to ground-level ozone.
For more information about this region's ozone "action days" and alerts, you can check: