made progress, but we still have very bad air. All you have to do
is look outside to know that"
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.
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.
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
using a very blunt tool to try to find a precise answer," Froines
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
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
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
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?
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.