Suffolk County has the worst smog in the state, but it's also among the cleanest when it comes to soot, according to a report released Wednesday by the American Lung Association.
Suffolk received its 15th consecutive "F" for ozone pollution -- the primary ingredient in smog -- in the group's annual State of the Air report.
"Unfortunately, Suffolk County has had the dubious distinction of having the worst ozone in the state for many years now," said Michael Seilback, vice president for public policy and communications at the American Lung Association of the Northeast.
The group's air quality grades are based on three years of monitoring data on ozone and particle pollution compiled by the U.S. Environmental Protection Agency.
Ozone is created in the atmosphere when vehicle and other emissions react with sunlight, while soot is made up of tiny particles of ash, diesel exhaust, aerosols and other materials. Both can cause health problems for those who breathe it, and both can exacerbate conditions such as asthma.
"Exposure to ozone can absolutely damage the lung," said Dr. Harry Steinberg, acting chief of the division of pulmonary critical care and sleep medicine for the North Shore-LIJ Health System.
From 2010 to 2012, Suffolk had 31 days during which high ozone levels made the air unhealthy for people with sensitivities, and three days when the air was unhealthy for everybody, the report found. The county had the highest weighted average for ozone in the state.
Seilback said much of Suffolk's smog isn't generated locally. Emissions from power plants and other sources in the Midwest follow wind patterns, pushing pollution into the New York metropolitan area, he said.
That phenomenon was the subject of a U.S. Supreme Court ruling handed down Tuesday that allowed the EPA to regulate pollution that begins in one state but reaches another.
Nassau County did not receive an ozone grade in the report because it does not monitor for the pollutant, according to the group.
But neighboring Queens County, which does monitor for ozone, also received an "F." Said Seilback: "We could look to the west and east, and know that air pollution doesn't stop at the county boundary."
Suffolk was one of six counties that received an "A" for its low levels of soot.
Nassau did not receive a grade on short-term particle pollution this year because of incomplete data, the group said.
The county received an "A" last year.
The state Department of Environmental Conservation issued a statement Tuesday saying that the entire state has met federal standards on particulate matter, while the New York metropolitan area has significantly reduced its levels of the pollution.