Review Finds Higher Rates of Some Cancers Near Some Los Angeles County Freeways
Southeastern regions of Los Angeles County near local freeways showed "unexpectedly high levels" of throat cancer and a type of lung and bronchial cancer, according to a review of reported cancer cases published in June in a book called "Cancers in the Urban Environment," the Los Angeles Times reports. Thomas Mack, chief of epidemiology at the University of Southern California Norris Comprehensive Cancer Center and director of the state Environmental Protection Agency scientific advisory committee, reviewed data of 84 cancer types reported to the Cancer Surveillance Program by county doctors between 1972 and 1998. Mack compared instances of cancer with census tracts, each of which contain information for about 5,000 people.
Mack in part found that higher levels of oropharyngeal carcinoma, or cancer of the mouth and throat, existed in several areas in and around Long Beach, including an area immediately east of the Long Beach Freeway between the two ports and the San Diego Freeway. His review also showed higher levels of small cell carcinoma of the lung and bronchus in some adjacent census tracts in the southeastern portion of the county, primarily in an area surrounded by the 710, 405, 105 and 605 freeways.
Seven of the nine census tracts between the ports and the 405 Freeway are considered high-risk areas for oropharyngeal carcinoma because they have cancer rates of more than 50% than the county average that cannot "easily be explained by chance," according to the Times.
Oropharyngeal carcinoma also appeared at higher levels than the county average in a strip of tracts a few census tracts farther east. Small cell carcinoma occurred more often in a horizontal strip of census tracts in south-central Long Beach and farther north in the area surrounded by the 405, 605, 105 and 710 freeways. Other high-risk tracts were found near the intersection of the 405 and 110 freeways.
The review also found that women were diagnosed with oropharyngeal cancer at a higher rate in four of the census tracts compared to men, who had higher rates in two census tracts, and both sexes showed higher rates in one tract.
According to the Times, small cell carcinoma and oropharyngeal carcinoma occur most frequently in smokers, but the cancers' presence also can be affected by race and ethnicity, as well as eating habits.
Several of the areas with instances of small cell carcinoma of the lung and bronchus are downwind of industrial facilities, oil refineries and manufacturing plants, as well as the 710 Freeway. Scientists have found evidence linking air pollution to lung cancer but have found no such connection with oropharyngeal carcinoma.
For most of the cancers included in the countywide review, there was "no evidence of environmental causes," and the review "provides no explanation" of potential causes for the higher levels of oropharyngeal and small cell carcinoma, the Times reports.
"I don't know that this is air pollution, but it is worth a shot to try to find out whether it is," Mack said. He added, "Neighborhoods may be at high risk because of the people that live there."
According to the Times, several experts agreed that the findings deserved more study. John Froines, director of the UCLA Center for Occupational and Environmental Health, said, "What this (book) should say is, 'OK, let's go look at these issues in more depth.'"
David Ropeik, director of risk communication at the Center for Risk Analysis at the Harvard University School of Public Health, said, "This is a hint, a clue, an important starting place to see what may be happening. This may or may not hold up as we do further study."
Francine Laden, an assistant professor of medicine at Harvard University's Channing Laboratory, said that the proximity of high-risk areas to freeways alone does not establish cause and effect. She said, "It's diseases that make sense, but this could be totally coincidence" (Schoch, Los Angeles Times, 9/3).