Waiting to Exhale
"We've made progress, but we still have very bad air. All you have to do is look outside to know that"John Froines
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In the last decade, after years of debate, environmental scientists amassed compelling evidence that links exposure to airborne particulate matter to an increase in the incidence of lung dysfunction, cardiovascular effects, cancer and allergic disorders. There is both excess mortality and morbidity associated with breathing particulate matter. But even the scientists themselves concede that the exact causes and number of people affected remain as hazy as the Los Angeles air. Enter UCLA School of Public Health Professor John Froines, the head of the Southern California Center for Airborne Particulate Matter, one of five centers funded by the U.S. Environmental Protection Agency to study the underlying basis of health effects associated with air pollution. Froines believes he and his center stand a good chance of clearing up that gray area, completing a critical step in establishing new environmental standards for air particles, both in terms of public health and far-flung economic consequences. Marshalling a multidisciplinary group of some 30 faculty members from UCLA and five neighboring institutions, the center is focusing on the epidemiology, toxicology, dosimetry (how particles deposit in the lung) and assessment of particulate exposure. But the challenges are daunting. "We've been using a very blunt tool to try to find a precise answer," Froines notes. For one thing, data on particulate exposure have typically come from monitoring stations covering expansive geographic regions. In addition, there's the problem of how to isolate the toxic culprit on, say, a diesel particle that might contain more than 1,000 chemicals. "You're looking for a needle in a haystack," says Froines. Worse, scientists do not even agree on whether putative ill-health effects are produced by certain chemicals adsorbed onto the particulates or the particles themselves. Center investigators will conduct research throughout the Southern California region, which is the nation's smoggiest region with the possible exception of Houston, TX. Froines' group is researching the culpability of polycyclic aromatic hydrocarbons and quinones, a class of organic compounds produced in fuel combustion, e.g., in triggering allergic-airway disease.
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"The evidence is strong that diesel is a human-lung carcinogen and is at least a factor in non-cancer effects such as asthma," Froines explains. Although California is poised to move forward with new regulations, Froines notes that pinpointing the exact causative agents within diesel particles would help to ensure that the proper strategy is adopted. Diesel heads the list of a host of particulates whose effects will be measured by the UCLA center in toxicological and human-exposure assessment studies. Using a fine-particle concentrator, researchers are examining how fine particulate matter affects people with impaired respiratory capabilities such as chronic obstructive-pulmonary disease and asthma. Moreover, the center is the nation's first to embark on constructing and employing a mobile-particle concentrator capable of conducting tests across a wide range of particle sizes. This is significant because fine (0.1-2.5µ in diameter) and ultra-fine (0.01-0.1µ) particles appear to be associated with more significant health effects than coarse (>2.5µ) particles. The aging of particles is a matter of considerable interest. "Ingesting a particle that has just been emitted might be very different from breathing in the same particle farther downwind of its source, for example, a freeway," notes Froines. The new concentrator will also be used in a variety of sites to study the effects of particles as they age. Meanwhile, concurrent epidemiological research at the center is comparing the effects of air pollutants on children across 12 communities. In addition, epidemiologists in the center are seeking to correlate traffic-density patterns with health effects from air-particulate exposure. So how long will Los Angeles remain in the gray area? As Froines puts it: "We've made progress, but we still have very bad air. All you have to do is look outside to know that." - D.G.
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