Study Links Commuting, Cancer Risks

Here’s another reason to cut down that commute: All those hours spent on the freeway may increase your cancer risk.

In a study released in May, researchers for the South Coast Air Quality Management District found that commuters are exposed to two to four times the levels of certain toxic and cancer-causing chemicals as are found in outdoor air elsewhere. The longer they languish on the freeways, the more time they spend inhaling elevated amounts of benzene, formaldehyde, xylene, toluene and other compounds.

Air Samplers in Cars

The study, which involved mounting air samplers in 140 commuters’ cars during 1987-88, found that traveling with the windows rolled up was of little help in reducing levels of toxic gases.


However, air contaminants in older cars tended to be significantly higher than in newer ones, and cars moving at more than 30 m.p.h. had lower pollutant levels than those lurching along at less than 25 m.p.h.

While acknowledging that higher exposures do not always translate into equally higher risks, the study attempted to estimate the added risk of cancer for those whose daily drive to work and home takes a total of 1 1/2 hours--by no means an unusually long commute for area residents.

According to the study, the main added risk would come from benzene, an ingredient of gasoline that is emitted by vehicles. A known carcinogen, benzene has been associated with higher risks of leukemia.

According to air district data, the average area resident has about a 0.7 chance in 1,000 of getting cancer in his or her lifetime from benzene exposure. The person who commutes for 1 1/2 hours raises his risk of cancer from benzene exposure by about 15%, or to one extra chance of cancer in 10,000, according to the report.


About 30% of all people will get cancer sometime in their lives, and about 20% will die of it--meaning that people already have 2,000 chances in 10,000 of being killed by the disease. The in-vehicle exposures thus add only a little to this dreary forecast. But in an area with millions of people, the added risk could translate into hundreds or thousands of cancers that otherwise would not occur.

The in-vehicle report, and another study citing the Burbank area as a toxic “hot spot,” point out two shortcomings in the way that air quality is usually measured.

One is that pollution-control agencies are charged with monitoring the outdoor air that everyone breathes, although scientists have established that air within the home, office or car often contains more toxic contamination than air outside.

The other is that air monitoring focuses on areawide pollutants such as ozone, carbon monoxide and particulates, rather than on more exotic trace toxics that may raise the risk of cancer but vary greatly in concentration from one neighborhood to the next.


In the “hot spots” report last year, the Burbank area--including Glendale, North Hollywood and Van Nuys--was named as one of three areas in the South Coast basin that showed “significantly higher” concentrations of cancer-causing contaminants. The others were Hawthorne and Rancho Dominguez.

Researchers said cancer risks from airborne toxins in these areas, although low, were higher than other parts of the basin.

Burbank made the list principally because of elevated levels of benzene from heavy commuter travel through the area.