Last week, The Lancet ran a special 9/11 issue, and several studies published in the journal came to varied conclusions about the health effects of exposure to World Trade Center dust. The first study, led by Dr. David J. Prezant, Chief Medical Officer for the Fire Department of the City of New York (FDNY), suggested a link between cancer and exposure to the dust. The study evaluated certain health outcomes in over 9,800 male firefighters and showed that, seven years after 9/11, WTC-exposed FDNY firefighters had a 19 percent increased risk of cancer compared to WTC-non-exposed FDNY firefighters. Yet the researchers also found that WTC exposed participants had a 58 percent lower rate of lung cancer, compared to the general population; as it happens, all of the nine WTC firefighters with the disease were smokers. Though it did not reach a level of statistical significance, the study found a trend toward an increased risk of other cancers among the WTC-exposed firefighters, including prostate, stomach, colon, and thyroid cancer.
But ACSH s Dr. Josh Bloom is confused by the results. Logically, if there were going to be an increase in any sort of cancer among WTC firefighters, he says, it would be lung cancer. The fact that it was substantially lower in the responders should immediately set off alarm bells about the results; it illustrates the danger in leaping to conclusions based on uncontrolled studies. The higher rate of prostate cancer in the responders is also medically implausible, and this accounts for most of the overall 19 percent increase in all cancer. Neither of these figures makes any sense. When you see numbers like this, it is almost always due to a poor study design that leads to flawed data and, thus, misleading conclusions.
The study results violate the principles of epidemiology, adds ACSH s Dr. Elizabeth Whelan. The researchers are not looking at long-term, high-dose exposures. They re only investigating an isolated incident and identifying trends, not statistically significant results.
In another study, led by doctors from the New York City Department of Health and Mental Hygiene, the researchers found that rescue and recovery workers (RRW) were 55 percent less likely to have died from any cause, compared to the city s general population. These statistics were generated by an examination of the deaths of over 13,000 RRWs who participated in the WTC Health Registry between 2003 and 2009. However, the researchers admit, the reason for the lower death rate among RRWs is probably due to the fact that this healthy-worker cohort is usually in better health compared to the general population. (That is, as a rule, those who are employed tend to be in better healthier).
This is not to say that responders did not suffer from other physical and psychological maladies. A third study, from doctors at the Mount Sinai School of Medicine in New York, found a higher level of both physical and mental illness in this population. An analysis of the health records of over 27,000 WTC RRWs enrolled in the WTC Screening, Monitoring, and Treatment Program, revealed that the enrollees 9-year cumulative incidence of asthma was 28 percent. The incidences of sinusitis and gastroesophageal reflux disease (GERD) were 42 and 39 percent, respectively. The cumulative incidence for post traumatic stress disorder among RRWs was 32 percent; and for depression and panic disorder, the rates were 28 and 21 percent, respectively.
There s no question that many RRWs experienced health issues, including mental health problems, but to just assume that, because you were near the WTC on 9/11, you now have a higher risk of lung cancer is not based on epidemiology, biology, or even reality, says ACSH s Dr. Gilbert Ross. Some advocates for compensation for those exposed to WTC debris, and many politicians, seized upon these studies to justify federal compensation for cancer treatments among WTC workers, which is not currently covered by the Zadroga Fund. But speaking as the spouse of someone injured when the first building fell, and acknowledging that we have an instinctive desire to help all those involved on the day of that tragic event, he adds, there has to be a line drawn somewhere.
Dr. Whelan agrees. As far as I m aware, she says, single or short-term exposure to particulate matter does not provoke cancer. The ailments that some researchers claim were caused by exposure to WTC dust need continued follow-up. These data need do need to be considered, because we know that some cancers linked to environmental exposures have a long latency.