An air quality advisory has been issued for Thursday by the Massachusetts Department of Environmental Protection, which warns of elevated ozone levels in two eastern counties.
Essex and Suffolk Counties — the latter of which includes the City of Boston — will be under the air quality alert beginning at 11 a.m. Thursday and continuing for 12 hours.
The elevated ozone levels are expected to create potentially unhealthy conditions for people with heart or lung disease, older people, children, teenagers and people who are active outside, according to MassDEP.
The state has recommended that people who fit one of those descriptions try to limit outdoor activity and keep medicine handy, if needed. They also are urged to be mindful of symptoms, which could include coughing or shortness of breath.
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According to the Environmental Protection Agency, ground-level ozone is considered harmful, and is the result of pollutants reacting together in sunlight. Ozone, which is found in smog, is most common in cities during hot and sunny days, according to the EPA.
It differs from the ozone found in the upper levels of the atmosphere, which forms naturally and blocks some of the sun's UV rays.
The state maintains a live map of air quality in Massachusetts that may be found here.
