CONCORD, N.H. — Federal authorities say the air will be unhealthful in parts of New England, including southwestern New Hampshire and southern coastal Maine.

The Environmental Protection Agency said Connecticut and central and northeastern Massachusetts also will be affected Thursday. EPA Administrator Curt Spalding said the heat contributes to elevated ozone levels that can cause serious breathing problems, aggravate asthma and other lung diseases.

The EPA is asking employers to try to reduce electricity consumption by letting employees dress casually so air conditioners can be set to higher temperatures. Unnecessary lights and computers also should be turned off. Homeowners also should minimize the use of appliances, particularly during the day when power demands are highest.

The EPA also is urging people to reduce the use of gasoline powered engines which produce ozone.