IRONTON — Lawrence County received a grade of “F” for the quality of its air in a report released Wednesday by the American Lung Association.

The failing grade for 2008 comes as a surprising reversal since the county received above average grades the previous two years.

The failing mark, given out as part of the association’s annual “State of the Air” report, listed Lawrence County as receiving the lowest marks possible in ozone and second lowest mark in particle pollution for both annual and short-term levels.

In both 2006 and 2007, the American Lung Association issued Lawrence County a grade of “B” each year for ozone and “C” for particle pollution.

This is the 10-year the American Lung Association has drafted the report. The last time the county receiving a grade of “F” for its air was in 2005.

To determine the grades, the health organization identified the number of days that air quality monitors located throughout Lawrence County experienced air quality designated as orange (unhealthy for sensitive groups), red (unhealthy), or purple (very unhealthy).

The color-coding system is taken from the U.S. Environmental Protection Agency’s Air Quality Index.

The EPA currently has air-monitoring equipment at the Ironton Health Department, the Ohio Department of Transportation garage and at a location on SR 141.

For 2008, Lawrence County registered 12 orange ozone days and nine orange 24-hour particle pollution days. Those numbers were much higher than 2007 when Lawrence County posted only one orange ozone day and six orange particle pollution days.

No “red” or “purple” days were issued in 2008.

Ozone is a gas formed when sunlight reacts with vapors emitted when motor vehicles, factories and power plants burn fuel.

It irritates the respiratory tract and causes health problems like asthma attacks, coughing, wheezing, chest pain and even premature death.

Particle pollution is a deadly cocktail of ash, soot, diesel exhaust, chemicals, metals and aerosols that can linger dangerously for hours to weeks on end.

The body’s natural defenses – coughing and sneezing – fail to keep the microscopic particles from burrowing deep within the lungs, triggering serious problems such as asthma and heart attacks, strokes, lung cancer and even early death.

‘‘Six out of 10 Americans right now as we speak live in areas where the air can be dirty enough to send people to the emergency room, dirty enough to shape how kids’ lungs develop and even dirty enough to kill,’’ said Janice E. Nolen, the association’s assistant vice president on national policy and advocacy.

Nationally, the report found that air pollution at times reached unhealthy levels in almost every major city and that 186.1 million people live in those areas.

The number is much higher than last year’s figure of about 125 million people because recent changes to the federal ozone standard mean more counties recognize unhealthy levels of pollution.

Wednesday’s notice by the American Lung Association comes on the heels of an April 1 EPA announcement that is was installing air testing equipment at Whitwell Elementary School to test outside air around the school.

The schoolyard testing will also sample for gases such as benzene and particulates such as hexavalent chromium, both of which are carcinogens that can lead to lung cancer, leukemia and Hodgkin lymphoma.

A 2007 study showed that the air surrounding both Whitwell and Dawson-Bryant High and Middle schools to be some of the worst in the entire country.

The Whitwell test is scheduled to be complete this summer.

The Associated Press contributed to this story.