The average New Yorker faces little risk of cancer from a class of carcinogens found in the dust and smoke kicked up by the collapsed World Trade Center, according to a study published online Monday in the Proceedings of the National Academy of Sciences.
Researchers from the University of North Carolina-Chapel Hill and the Environmental Protection Agency measured cancer-causing chemicals called polycyclic aromatic hydrocarbons, or PAHs, in four places around lower Manhattan. The study didn't gauge the threat from other carcinogens or the danger to emergency workers and cleanup crews, who may have been exposed to higher levels.
Scientists examined air samples taken in the six months after the terrorist attacks using a test developed recently by researchers at UNC, said Stephen Rappaport, a professor of environmental health and an author of the article. In the days after 9/11, air concentrations of PAHs were about 65 times greater than normal -- among the highest levels ever recorded. The chemicals were produced by the fires that burned for three months at Ground Zero, by diesel trucks involved in the cleanup and by other cars in the city, Rappaport said.
PAH levels gradually returned to normal. For most people, such brief exposure to high levels of PAH should not increase the lifetime risk of cancer, which generally takes 10 to 20 years to develop. PAHs have been associated with cancers of the skin, lungs and bladder.
Many rescuers and laborers developed other health problems right away, however, including ''World Trade Center cough,'' believed to be caused by dust containing pulverized glass, cement and other irritants.
Doctors have screened nearly 12,000 cleanup and emergency workers for 9/11-related ailments, said Robin Herbert, co-director of Mount Sinai Medical Center's World Trade Center Worker & Volunteer Medical Screening Program.
About 75% of workers treated report persistent upper-respiratory ailments, such as sinus infections; 44% have lung complaints; and 40% have problems with mental health.
Herbert said she is glad that the overall cancer risk appears to be low. But she cautioned that more research is needed to confirm the results.
Rappaport noted that the air particles posed a greater threat to the babies of women pregnant at the time. A study published last year found that pregnant women exposed to the smoke and soot had twice the risk of a complication called intrauterine growth restriction, in which babies are born small.
Though the levels of PAH in outdoor air no longer pose a threat, scientists remain concerned that tiny particles may still be circulating in indoor heating and cooling systems. Rappaport said government researchers continue to monitor the problem.
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