Fine particles may be health threat
By Jennifer Lauren Lee
Oct. 27, 2002 9:00 p.m.
The next time you drive on the freeway, you may want to hold
your breath.
Two new UCLA studies show that people who live, work or travel
within 165 feet downwind of a major freeway are exposed to
potentially hazardous concentrations of particles, which may lead
to future health problems.
Though the U.S. Environmental Protection Agency currently
regulates particles smaller than 2.5 micrometers in diameter, its
resources are not focused on regulating the smallest ““ and
potentially most dangerous ““ of these particles, according to
Yifang Zhu, a doctoral candidate in UCLA’s School of Public
Health and co-author of the studies.
“The ultra fine particles (less than 0.1 micrometers in
diameter) are very dangerous to people’s health, (perhaps)
more so than the larger particles,” she said.
When inhaled, these tiny toxic particles lodge themselves in
internal tissues, causing pulmonary inflammation, cardiovascular
problems and neurological changes.
Recent toxicology studies show that increased exposure to these
particles is linked to increased mortality and illness in those
exposed.
Motor vehicle emissions represent the most significant source of
ultra fine particles ““ making these studies an important
first step toward getting rid of these particles.
“We believe this is the first study conducted in the
United States that provides a detailed spatial profile of ultra
fine particles near freeways,” said co-author and
environmental health sciences professor William C. Hinds, in a
statement.
The studies, conducted through the Southern California Particle
Center and Supersite, assessed the concentration and
size-distribution of ultra fine particles near two major freeways
in the Los Angeles Basin.
The first study looked at the car-dominated Interstate 405,
where 93 percent of vehicles are gasoline-powered. The second study
focused on the 710 Freeway, where more than 25 percent of traffic
is composed of heavy-duty diesel trucks.
Hinds and Zhu conducted their study with an instrument that
simultaneously detects the number of ultra fine particles at that
location, the size of those particles, the wind direction and
speed, and a report of traffic conditions at the time.
After repeating these measurements at varying distances from the
freeways, Hinds and Zhu concluded that the number of these tiny
toxic particles just downwind of a major freeway is 25 to 30 times
greater than its concentration immediately upwind.
The particle concentration remains hazardously high up to 165
feet downwind of the freeway, decreasing rapidly with distance, and
falling to 30 percent of peak concentration at 330 feet.
Furthermore, the studies showed that concentrations of carbon
monoxide and black carbon (two other harmful pollutants associated
with vehicular emissions) were much higher just downwind of the
freeways, decreasing significantly (up to 80 percent) at a distance
of 330 feet away.
Zhu believes these are significant findings ““ especially
for a city with 10 million vehicles contributing to its daily
traffic.
“Think about how many hours people spend on
freeways,” she said.
According to Zhu, the data collected from these studies will be
used by future researchers to compare how gasoline and diesel
differ in their effects on the environment and on the people
nearby.
“We want to find out where these particles are coming
from,” said Wendy Hunter, the research and outreach manager
of SCPCS.
Hunter says that Hinds and Zhu are providing information for
other organizations such as the EPA and the California Air
Resources Board so that they can “create better regulations
for these particles.”
Researchers at the SCPCS are very concerned with finding out
more information about these ultra fine particles, according to
Hunter.
“Our primary goal is to increase human health,” she
said.
The studies were funded by the EPA and the California Air
Resources Board.
