CONCORD, N.H. (AP) – Federal environmental officials are expecting the air quality to be unhealthy this weekend in Connecticut, Massachusetts, Rhode Island and parts of Maine, Vermont and New Hampshire.

Robert Varney, the Environmental Protection Agency’s regional administrator, says people should limit strenuous outdoor activity. Exposure to smog can cause serious breathing problems, aggravate asthma and other pre-existing lung diseases. Exposure also can make people more susceptible to respiratory infection.

The EPA expects more air quality alerts this summer because it has lowered the level of ground-level ozone – or smog – that triggers a public warning.