Air Inside Cars Found Dirtier Than Outside

The air people breathe inside their cars can be as much as 10 times more polluted than even the typical dirty outdoor air in the Los Angeles area, according to a study released Thursday by California air quality officials.

And the researchers found there is little that motorists and passengers can do to protect themselves other than staying away from rush-hour driving and, in particular, avoiding getting stuck behind diesel buses or older-model cars.

Other common tactics, such as opening or closing windows or vents and turning on air conditioning do not help, according to a new study of motorists driving on freeways in Los Angeles County and Sacramento.

Although car ventilation systems did show marginal success in filtering out tiny soot particles, the sort that belch from diesel trucks and buses, toxic gases such as benzene leaked into the vehicles no matter what, the research showed.

Breathing the Los Angeles region’s outdoor air is known to be bad for health, but the new study is the first to show how high the pollution levels are inside cars under a variety of driving conditions. Pollution levels of several dangerous pollutants are at least twice as bad inside cars as outside, and levels of others are 10 times worse.

“We’re learning that people’s highest daily exposure to air pollutants may be during their commute to and from work,” said Alan Lloyd, chairman of the California Air Resources Board, which conducted the study with the South Coast Air Quality Management District.

In the study, which cost $440,000, motorists were equipped with monitors to record the levels of pollution they breathed while driving. “We know that air pollutants in ambient outdoor air pose a health risk to Southland residents,” said Barry Wallerstein, the AQMD’s executive officer. “This study confirms that commuters face an additional risk breathing the polluted air inside their cars.”

The study found that a person standing alongside a freeway is actually exposed to less of some kinds of pollutants than a person driving a car. That is probably because the gases and particles spewed by traffic accumulate in the vehicles, which contain only a small volume of air in which they can be dispersed.

The fumes found inside the cars have been linked to a variety of respiratory problems, including lung cancer, asthma and allergies.

Because of the disturbing results, the California Air Resources Board has begun tests to explore the risks that children face in school buses.

Initial tests showed that the air inside buses is better than that inside autos, probably because there is a larger volume of air inside a bus. But because children are more susceptible than adults to lung problems and breathe in more air for their body weight, the board has decided to collect more data on the risk to youngsters traveling to and from school.

“We have concerns about the potential impact on bus riders, especially children,” Lloyd said.

Is there anything a motorist can do? “Drive in the carpool lane, avoid rush hour, report smoking vehicles and avoid the most congested traffic,” said Air Resources Board spokesman Jerry Martin. To report vehicles putting out excessive exhaust, motorists can call (800) CUT-SMOG.

During the tests, cars driven during rush hours contained nearly twice the pollutants of cars driven at less congested times.

People in carpool lanes breathed cleaner air. Their cars contained two to five times less pollution than those in regular lanes, probably because the lanes are less congested and farther from trucks.

More than half of the pollutants inside the test cars were emitted by the vehicle in front of them.

The two-year study was conducted on several Los Angeles County freeways. Beginning in El Monte, the motorists drove on Interstates 10, 110, 405, 605 and 91. Similar tests were also conducted in Sacramento. While the tests focused on freeways, the results on heavily traveled surface streets are likely to be similar.

In general, because California has gradually imposed standards reducing car exhaust, older vehicles tend to produce more pollution.

Hydrocarbon emissions from a 1999 auto are 90% lower than those from a 20-year-old car. Truck and bus engines built after 1990 emit less soot than older ones.

The worst pollutants found were tiny, inhalable particulates that come mainly from diesel vehicles and two compounds that are emitted mostly from gasoline-powered automobiles: benzene, which is known to cause leukemia, and 1,3-butadiene, which is a powerful carcinogen.

Diesel exhaust has been linked to lung cancer and allergies, and fine particles are believed to raise the risk of death from respiratory and cardiac diseases.

Concentrations of pollution inside the cars were compared with ambient air measurements, which are taken throughout the region at monitoring stations that are not located near freeways or factories.

The study revealed that a car driving behind a diesel bus contained up to 18,000 counts of fine particles per cubic meter of air. The normal range in the area is 2,000 to 4,000. A car behind a diesel delivery van contained 12,000, or up to six times the normal range.

For 1,3-butadiene, a car on a freeway contained 4.1 counts per cubic meter of air, 10 times worse than the ambient average of 0.4. For benzene, a car contained more than triple the concentration found in ambient air.

Other pollutants found in high concentrations were carbon monoxide, the fuel additive MTBE, ethyl benzene and toluene. All have been declared toxic air pollutants by the state air board and the U.S. Environmental Protection Agency.