Jane Kay, Chronicle Environment Writer – Friday, May 23, 2008 – San Fransisco Chronical
Microscopic air pollutants from trucks, cars, power plants and wood burning may pose greater health problems than previously believed, according to state researchers.
The new estimates were released Thursday in response to a request from the California Air Resources Board, which was seeking up-to-date research on premature deaths associated with inhaling particles one-thirtieth the width of a strand of hair.
Based on 60 studies worldwide and advice from a team of experts, including the World Health Organization, the researchers concluded that the new risk factor for fine-particle pollution is 70 percent higher than previously estimated.
The report, also reviewed by scientists at UC Berkeley, could serve as the basis for strengthening state – and perhaps federal – air-quality regulations.
“Particle pollution is a silent killer,” state Air Resources Board Chairwoman Mary Nichols said after receiving the report Thursday at a board meeting in Fresno.
Most of the premature deaths linked to California’s bad air occur in regions surrounding San Francisco Bay, Los Angeles and the San Joaquin Valley. The drop in fine particulates statewide in the last decade, particularly in cities, has been 30 percent.
One region that saw even greater improvement, the San Joaquin Valley, decreased 45 percent over the same time period due to new regulations, according to state air officials. The board added even more regulations Thursday by restricting wood burning to up to 35 days in the winter as well as requiring employers to start carpools.
Direct link
The state’s study found a direct correlation between increased pollution from specks of dust, soot, metals and soil and a greater number of hospitalizations, emergency visits and missed school days.
Health problems were generally related to respiratory illnesses and heart disease. Some studies reported bouts of asthma and bronchitis. Even small increases can affect children, the elderly and people with chronic diseases, researchers say.
The cost of hospitalizations, physician visits and lost work days connected to airborne specks of dust and tiny droplets could reach $70 billion a year, health officials said.
Numbers of premature deaths are difficult to estimate because the scientific knowledge isn’t far enough along to determine a safe level of the tiny particles. California’s average small-particle concentration is about 14 micrograms of PM2.5, or particles less than 2.5 micrometers in diameter, per cubic meter of air. The San Francisco Bay’s average over the past three years is 10.69 micrograms.
Assuming that a safe level is 7 micrograms of PM2.5 per cubic meter of air – half as clean as the state’s air – means that there would still be about 14,000 to 24,000 premature deaths every year in the state associated with these small particles, the study said. That is two to three times the number of deaths previously predicted.
Currently, the cleanest cities in the country generally measure 7 micrograms of PM2.5 per cubic meters of air in the atmosphere.
At that level, there would still be 1,800 to 3,200 deaths a year in the Bay Area; 8,100 to 14,000 in the Los Angeles region, and 2,000 to 3,500 in the San Joaquin Valley.
“The risk in a highly polluted area is similar to living with a smoker,” said Bart Croes, the board’s chief of research.
The forest fires burning in the Santa Cruz Mountains can cause serious health problems for people breathing in the smoke, he said. The assessments on premature deaths in the study include the effects of California fires in the last few years.
Fine particles – whether from fires or industrial emissions or traffic – penetrate deeply into the lung and inflame the lung tissue. There is evidence that they can cross the tissue into the blood stream, and accumulate in the organs.
Scientists today believe that it’s the size that causes the problem. However, research continues to see if materials in the particles such as metals or other toxic compounds may be the ones most responsible for the damage to the body.
Cancer study
Most of the studies used in the re-evaluation were epidemiological studies. Included in the report was an American Cancer Society study of 300,000 people in cities nationwide. Over 18 years, the cancer society looked at people who lived in cities that had low levels of small particulate matter and compared them to people who lived in cities with higher levels.
Researchers looked at diet, smoking habits and other factors in trying to isolate the pollution effects, which Croes noted was a difficult task.
As part of the assessment, they looked at changes in death rates during a coal-burning ban in Dublin, Ireland, sulfur dioxide reduction under new regulations in Hong Kong and a steel mill strike in Utah Valley.
Representatives of the Western States Petroleum Association said they hadn’t yet evaluated the draft of the study. The California Truckers Association, which is expected to comment, didn’t respond to queries from The Chronicle.
The air board will accept comments until July 11. The study could be accepted by the board as early as August.
See the study
Read the draft study on premature deaths associated with fine particulates:
E-mail Jane Kay at jkay@sfchronicle.com.