The Charleston area air is a bit easier to breathe these days, and it will only get better as cargo and cruise ships switch to a cleaner fuel that will dramatically reduce air pollution, officials said Friday.

A new report by the American Lung Association shows that Charleston County air quality improved for ozone and short-term particle pollution. Last year, the association gave the county failing grades in both categories, but in the new report it received grades of "D" for ozone and "C" for short-term particle pollution.

"We have seen a definite decrease in ozone pollution across the state and nation," said Renee Shealy, assistant chief of the state Bureau of Air Quality Control.

Ozone comes from the burning of fossil fuels, Shealy said, which happens at coal-fired plants and in motor vehicles. Continued implementation of regulations to curb pollution from fossil fuel sources has made a difference, she said.

During warmer months, ground-level ozone is the state's most widespread air quality concern, said Myra Reece, chief of the state Bureau of Air Quality Control.

High ground-level ozone concentrations generally occur on hot, sunny days when the air is stagnant. Ground level ozone is formed when nitrogen oxide and volatile organic compounds react in sunlight. Ground-level ozone can create breathing problems, especially for children, people with asthma or other respiratory problems, and adults who work or exercise outdoors. It can cause tree and crop damage, Reece said in a statement released by the state Department of Health and Environmental Control.

The state ozone forecast is available on the Internet and by phone.

Shealy said the economic downturn may have played a role in the county's improved air quality because less fossil fuels are being burned. Ozone is characterized as smog. Particle pollution is not visible because it is so fine but for that reason it can be breathed deep into the lungs, she said.

Despite problems with air quality here as described in the lung

association report, atmospheric pollution in the Charleston area meets federal ambient air quality standards, she said.

Meanwhile, the 2,000 ships that visit the Port of Charleston will create dramatically less air pollution as they begin the switch to cleaner low-sulfur fuel, according to the South Carolina State Ports Authority.

"We were excited to see that one happen. That's real good news," Shealy said.

Last month in London, the United Nations' International Maritime Organization approved new rules that require ships to use cleaner fuels within 230 miles of the North American coast.

The new restrictions affect both cargo and cruise ships and will cut the level of sulfur in fuel by 98 percent, fine particulate matter emissions by 85 percent and smog-forming nitrogen oxide pollution by 80 percent, according to the U.S. Environmental Protection Agency. The requirements will be phased-in starting in 2012, officials said.

"This is a tremendously important step for clean air in the Charleston metro area. Requiring ships to use low-sulfur fuel will make a huge dent in port-related emissions," said Jim Newsome, SPA president and chief executive officer.

Those most at risk from air pollution are people with asthma, chronic bronchitis, emphysema, cardiovascular disease and diabetes. There are more than 100,000 people in the county who have at least one of those conditions, according to the lung association report.

The ozone level found in the upper atmosphere is beneficial because it shields us from much of the sun's ultraviolet radiation. However, ozone air pollution at ground level where people can breathe it is harmful.

Reach Prentiss Findlay at 937-5711 or pfindlay@postandcourier.com.