People who were involved in the rescue and recovery operation at the World Trade Center (WTC) are at an increased risk for certain types of cancer, including prostate, thyroid, and myeloma, study findings suggest.
The authors speculate that exposure to carcinogens released by the collapse of the buildings could explain the excess risk, although they admit that more data and longer follow up are needed.
"Given the relatively short follow-up time and lack of data on medical screening and other risk factors, the increase in prostate and thyroid cancers and multiple myeloma should be interpreted with caution," write Jiehui Li (New York City Department of Health and Mental Hygiene, New York, USA) and co-authors in JAMA.
Li et al analyzed information on 55,778 people enrolled in the WTC Health Registry in 2003-2004. This is an observational database of residents of New York State, of whom 21,850 were rescue and recovery workers following the WTC terrorist attack in 2001.
Between enrollment and December 2008 there were 1187 new cancer diagnoses, of which 37% were in WTC rescue/recovery workers.
For all cancers combined, the standardized incidence ratio (SIR) was 1.14 per 100,000 person-years in WTC rescue/recovery workers and 0.92 per 100,000 person-years in those not involved in rescue/recovery, a nonsignificant difference.
However, of 23 cancer sites investigated, SIRs were significantly increased in WTC rescue/recovery workers at three sites: prostate (SIR=1.43), thyroid (SIR=2.02), and multiple myeloma (SIR=2.85).
Cancers at these three sites were not increased in WTC non-workers.
The researchers note that the collapse of the towers exposed hundreds of thousands of people to dust, debris, pulverized building materials, and potentially toxic emissions. The dust, smoke, and aerosols contained known and suspected carcinogens including asbestos, silica, benzene, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, volatile organic compounds, and numerous metals.
However, using within-cohort comparisons, they found that the intensity of exposure to WTC-related debris was not significantly associated with site-specific cancers in either WTC workers or non-workers.
"At issue is whether dosages to exposed individuals were sufficient to cause excess malignancies and, if so, whether such excesses are epidemiologically detectable at present," write the researchers.
"Longer follow-up of rescue/recovery workers and participants not involved in rescue/recovery is needed with attention to selected cancer sites and to examine risk for cancers with typically long latency periods."
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