Air quality officials recommended Thursday that the Southland's system of health advisories, warning people of hazardous smog levels, be strengthened in the wake of new studies linking lung and heart problems to surprisingly small increases in air pollution.
"The data we are now seeing indicates that health advisories should be revised and issued for lower levels of pollution," said Shankar Prasad, health effects officer for the South Coast Air Quality Management District.
He said the studies also point to the need for stricter regulation of unpaved roads, construction sites and industrial yards where coal and other sources of soot and dust are stockpiled.
The studies--one by the Kaiser Foundation Research Institute and one by the California Environmental Protection Agency--found a correlation between hospital admissions for cardiopulmonary ailments and daily levels of ozone and particulate matter.
The yearlong Kaiser study, which is still being analyzed, looked at more than 10,000 hospital admissions in the Los Angeles Basin--making it the most comprehensive study of its kind conducted in the region, according to the AQMD, which paid for the project.
The most significant finding, common to both studies, is that rather small amounts of coarse particulate matter--or airborne grit--appear to be as hazardous to human health as other components of smog, such as ozone, that are emitted by gasoline and a host of other chemicals.
It has long been known that high levels of microscopic particle pollution are unhealthful because of their impact on lung function when they are inhaled. Once inside, they interfere with the lungs' capacity to clear themselves of bacteria and other damaging microorganisms.
The microscopic grit, however, comes in different sizes. Up to now, so-called fine particle pollution has been the prime focus of medical experts because these particles are inhaled more deeply than the larger, coarse particles.
Fine particles result from combustion in cars and factories. Coarse particles are produced by a variety of sources--from dirt roads and construction sites to diesel engines and industrial boilers.
"What we are seeing now, and that is new, is that coarse particles are an equal or greater problem," Prasad said.
The AQMD's monitors do a better job of measuring unhealthful levels of ozone than of particle pollution, he said.
In light of the studies, though, he recommended that smog alerts in the future be triggered by lower levels of both ozone and particulate concentrations.
For example, health alerts are now issued when particulates reach 150 micrograms per liter of air.
Prasad suggested that the AQMD consider issuing the alerts at a level as low as 50 micrograms per liter.
The Kaiser study, which covered Los Angeles, Orange, San Bernardino and Riverside counties, found that hospital admissions for chronic respiratory illnesses rose 7% for every 10-microgram increase in particulate pollution--even on days when the overall particulate level was well below 150 micrograms.
On the most severely polluted days, researchers said, admissions for all types of cardiopulmonary problems jumped 25%.
The second study--conducted by Cal/EPA in the Coachella Valley--turned up similar relationships between increases in particulate pollution and hospital visits for heart and lung problems.
Preliminary results of a 10-year study by USC environmental health researchers also suggest some evidence that the rate of lung development is slower for children growing up in areas of high ozone concentration.
The project, now half completed, is tracking 4,000 children from the fourth through the 12th grades in 12 Southern California communities.
"We are seeing small changes in lung functions related to ozone," said USC's Ed Avol. But the changes are so minor, he added, that it is too soon to say whether they represent a significant departure from normal ranges of development.