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California Air Resources Board (ARB) and the South Coast Air
Quality Management District (SCAQMD) announced that exposure
to some air pollutants and toxic compounds may be ten times higher
inside vehicles than in ambient air. The two-year, $440,000 study
is the first ever to gather particulate data inside vehicles
and the first to collect real-time information under a range
of traffic and driving conditions.
 Dr.
Alan Lloyd, ARB Chairman said, "We're learning that peoples'
highest daily exposure to air pollutants may be during their
commute to and from work. Also, we have concerns about the potential
impact on bus riders, especially children. Therefore, I've asked
the ARB staff to collect more data to evaluate the risks."
The study's
objectives were to measure motorists' personal exposure to common
motor vehicle pollutants in Los Angeles and Sacramento, two areas
that have high levels of motor vehicle-generated air pollution.
Funded by
the ARB, with support from the SCAQMD, the study measured the
direct exposure to motor vehicle occupants from gaseous pollutants,
diesel soot and other fine particles. As part of the study, ARB
researchers also began looking at pollutant levels inside school
buses. Future ARB research may include projects that will better
define the pollutant levels to which children are exposed while
traveling to and from school.
Researchers
found levels of hydrocarbons and carbon monoxide were between
two and ten times higher inside vehicles than at roadside or
fixed monitoring stations. Researchers also found similar levels
of toxic compounds such as benzene, 1,3-butadiene, ethyl benzene,
toluene, xylene and MTBE, all considered toxic by the ARB and
USEPA. The variations depended on the pollutant, the type of
road and the level of traffic.
Researchers
found that as much as one-half of the pollutants inside test
cars were emitted by the vehicle ahead. In general, levels of
toxics and other pollutants are higher inside vehicles than in
outdoor ambient air because cars are surrounded by emissions
from other vehicles on freeways and streets.
"We know
that air pollutants in ambient outdoor air pose a health risk
to Southland residents," said Barry Wallerstein, SCAQMD
Executive Officer. "This study confirms that commuters face
an additional risk breathing the polluted air inside their cars."
According
to the research data, motorists who used air conditioning systems
and those who drove with their air vents open were exposed to
similar amounts of pollution.
Researchers
learned that people who use car-pool lanes were exposed to pollutant
levels well below those measured in other traffic lanes, possibly
because car-pool lanes are less congested and further removed
from the truck lanes. 
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