CHICAGO — The most comprehensive study of potential World Trade Center-related cancers raises more questions than it answers and won't end a debate over whether the attacks were really a cause.
The study suggests possible links with prostate, thyroid and a type of blood cancer among rescue and recovery workers exposed to toxic debris from the terrorist attacks. But there were few total cancers and even the study leaders say the results "should be interpreted with caution."
The study involved nearly 56,000 people enrolled in a registry set up to monitor health effects from those exposed to the aftermath of the trade center attacks. Most participants volunteered for enrollment, which could skew the results if people who already had symptoms were more likely to enroll than healthier people.
Cancers diagnosed through 2008 were included in the study, but that's just seven years after the 2001 attacks, and cancer often takes longer to develop. People diagnosed with cancer before the attacks were excluded from the study.
Cancer rates were compared with those in the general New York state population. But the researchers had no data on whether people in the study had risk factors for getting cancer, including a strong family history, or if they had existing cancer that wasn't detected until after the disaster. Participants are being monitored for health issues and may have gotten more cancer screening than other people, which also could skew the results.
The increased risks were seen only in rescue and recovery workers, who likely had more direct, sustained contact with potential cancer-causing substances in the dust, smoke and debris from the attacks. But cancers weren't more common in workers who had the most exposure — a finding that would seem to contradict the theory that contact was the cause.
The study comes just a few months after the federal government added dozens of types of cancer to a list of illnesses related to the trade center attacks that will be covered by a program to pay for health coverage.
The study results "won't settle the question because it's still too early," said Dr. Thomas Farley, New York City's health commissioner.