Ground-level ozone pollution, or smog, tends to be at its worst in the summer and later in the day, when the conditions required for its formation – sunlight and warm temperatures – are most prevalent.
Although smog-forming pollutants tend to originate in urban areas, they can be carried by the wind for long distances, even hundreds of miles, and form ground-level ozone in less populated areas. In Massachusetts, for example, it is not unusual for smog to be a bigger problem in the rural west-central part of the state or over Cape Cod than in larger cities.
The Department of Environmental Protection (MassDEP) has maintained a network of monitors to measure air concentrations of ozone for more than 20 years and issues a Daily Air Quality Forecast for ozone from the beginning of April through the end of September.
The MassDEP monitoring network is designed to characterize ambient air quality over wide areas. The ozone pollution at the monitoring site nearest where you live can provide a rough indication of pollution levels in your community, but keep in mind that prevailing wind patterns between you and the nearest monitor can affect actual conditions in your immediate neighborhood.
For a quick “snapshot” of air quality in your community and region, look at the map on the right, which uses a color-coded Air Quality Index (AQI) to tell you how clean or polluted the air is.