Concentrations of one of the most ubiquitous and dangerous air pollutants have declined throughout most of the nation in recent years, particularly in Southern California and the Southeast, according to a report released Tuesday by the U.S. Environmental Protection Agency.
Nationally, fine-particle pollution in 2003 dropped 10% from 1999 and reached the lowest recorded levels since nationwide monitoring began five years ago. In Southern California, Washington, D.C., and Chicago, where monitoring has occurred since around 1980, the levels were the lowest in more than two decades, the EPA report says.
However, an estimated 100 million Americans still live in areas that exceed federal health standards for fine-particle pollution. In the Los Angeles region, particularly in Riverside, the San Bernardino area and the San Gabriel and San Fernando valleys, levels of the pollutant remain among the worst in the nation.
In the report, the EPA called fine-particle pollution the country's "most pressing air quality problem."
Fine particles are microscopic pieces of soot spewed by a variety of sources, mostly carbon in diesel exhaust, sulfates from power plants, and nitrogen-based gases from cars. EPA officials said the drop in particle levels was due largely to decreased emissions from vehicles and industries, not from favorable weather conditions.
Scientists around the world have repeatedly shown that on days when amounts of fine particles rise, deaths from heart attacks, strokes, asthma and other respiratory diseases rise too. Medical experts suspect that they penetrate deep into the lungs, causing inflammation and disrupting neurological signals to the heart.
Environmental groups on Tuesday welcomed the report's findings but said that the Bush administration was hindering more progress by failing to impose long-delayed regulations on power plants, particularly in the Midwest and Northeast.
"Releasing the report at the same time they are delaying action on power plant standards is like telling a patient their cancer is beginning to shrink and then turning around and diluting their chemotherapy," said Dr. John Balbus, head of the health program at Environmental Defense, an environmental group. "To protect the millions at risk ... EPA must cut harmful pollution from power plant smokestacks."
The EPA said it would adopt a power plant regulation in March, although it wouldn't be implemented for at least five years.
The agency also is expected to soon designate areas that are violating a new health standard for the pollutant and order them to take steps to reduce emissions. As many as 244 counties in 21 states, including most of California's urban areas, are expected to be included.
The pollution levels declined 20% in the Southeast, 16% in Southern California and 9% in the industrialized area of the Midwest between 1999 and 2003, the report says. The Northeast is the only area with no decline. Levels there increased 1%.
One of the biggest declines over the last two decades has been in the Los Angeles region, where concentrations dropped about 40% between 1979 and 2003, the report says. Car and truck exhaust is the major source of fine particles in Southern California, and various state and regional antismog controls have led to the decline.
Still, the South Coast Air Quality Management District, which regulates pollution in Los Angeles, Orange, Riverside and San Bernardino counties, says that the problem is so severe that even if all measures in its air-quality plan are implemented, the region will still exceed the federal health standard for fine particles by 80% in 2010.
The EPA credited much of the improvement in the Southeast and Midwest to its acid rain regulation, which tightened controls on power plants in 2000. Emissions also have been reduced from diesel engines, including trucks, locomotives and off-road equipment such as tractors and bulldozers.
Allen Schaeffer, executive director of the Diesel Technology Forum, which represents engine and fuel manufacturers, said fine particles from diesel trucks had declined by two-thirds since 1990. By 2007, diesel trucks "will produce near-zero emissions thanks to clean fuels and advanced engine technologies," he said. The report "provides further evidence that our nation's air quality continues to take giant leaps forward," he said.
The EPA estimates that nationally, levels of the pollutant have improved more than 30% over the last 25 years and will drop another 10% to 20% in 10 years as new regulations for engines and power plants take effect.