Unhealthy air quality is expected for most of Connecticut, central Massachusetts and into coastal New Hampshire today and Saturday, the Environmental Protection Agency and the state Department of Energy and Environmental Protection announced.

The forecast for hot weather today is also expected to cause the demand for electricity in New England to reach high load levels, the EPA said in a news release.

“Everybody can help reduce smog-forming emissions by driving less, by using public transportation, and by setting air conditioner thermostats a few degrees higher,” Curt Spalding, administrator of EPA’s New England office, said.

Exposure to elevated ozone levels can cause breathing problems, aggravate asthma and other pre-existing lung diseases, and make people more susceptible to respiratory infection. When ozone levels are elevated, people should refrain from strenuous outdoor activity, especially sensitive populations such as children and adults with respiratory problems.

Ground-level ozone forms when volatile organic compounds and oxides of nitrogen interact in the presence of strong sunlight. Cars, trucks and buses give off the majority of the pollution that create ozone. Burning fossil fuels at electric generating units, particularly on hot days, also emit ozone precursors. Gasoline stations, print shops, household products such as paints and cleaners, as well as lawn and garden equipment also add significantly to the ozone problem.

The public is urged to help reduce ozone by using public transportation and carpooling, and avoiding the use of lawn mowers, chain saws and other small gasoline-powered engines. Due to the expected high demand for electricity, the EPA is asking homeowners and employers to reduce energy consumption by turning air conditioning to a higher temperature and turning off unnecessary lights, computers and appliances during the day.