CARCINOGENS that spewed out from the burning debris of the World Trade Center probably did not pose a health risk to most New York City residents.
But the infants of women who were pregnant on 11 September, or became pregnant soon after, may have faced an increased risk of birth defects. Also more than 1000 contractors, volunteers, police and firefighters, who spent months clearing up the debris at ground zero could be at higher risk of cancer. These are the conclusions of the first rigorous study in connection with the attack of a class of compounds called polycyclic aromatic hydrocarbons (PAHs). The study was conducted by a team led by Steven Rappaport of the University of North Carolina, Chapel Hill. Researchers suspect that these PAHs were among the most carcinogenic chemicals in the plume.
Investigators have struggled to assess the legacy of the plume created by the terrorist attacks. It was unprecedented in size and chemical complexity, and released an estimated 1 million tonnes of dust and smoke. And until now there have been few clues to the concentrations of PAHs released.
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However Rappaport and colleagues at the Environmental Protection Agency (EPA) in Research Triangle Park, North Carolina, have developed a way of using airborne particles trapped in suction filters designed to monitor other pollutants to estimate levels of the most carcinogenic PAHs released on 11 September.
Three days after the attack, they estimate air levels of nine PAHs were up to 200 times higher than normal: among the highest levels ever reported for an outdoor source. Levels halved during the following two weeks, and continued to halve every two weeks for the next six months (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0404499101).
The PAHs in the plume are unlikely to have increased cancers in the general public, Rappaport says, as in most cases the risk of cancer increases only after years of exposure. However, unborn babies are more sensitive to PAHs. Studies from the Czech Republic have linked the compounds to reduced fetal growth and head size. And a study conducted at the Mount Sinai School of Medicine in New York last August found that women who inhaled the 11 September plume were twice as likely to give birth to small babies (The Journal of the American Medical Association, vol 290, p 595).
Workers in the emergency services may also be at increased risk because they were exposed to far higher levels of PAHs than those captured by the EPA filters, albeit for relatively short periods, says Rappaport. But George Thurston at New York University in New York City, takes issue with that conclusion: 鈥淭hese people have been terrorised enough. The levels were high, but they were also very brief. I don鈥檛 think we know yet what the impacts are.鈥�