Association Between World Trade Center Exposure and Excess Cancer Risk

BACKGROUND:  The terrorist attacks of September 11, 2001, resulted in the release of known and suspected carcinogens into the environment. There is public concern that exposures may have resulted in increased cancers. This study was to evaluate cancer incidence among persons enrolled in the World Trade Center Health Registry (WTCHR).

METHODS:  Observational study of 55,778 New York State residents enrolled in the WTCHR in 2003-04, including rescue/recovery workers (N=21,850) and those not involved in rescue/recovery (N=33,928), who were followed up from enrollment through 2008. Cases were identified through linkage with 11 state cancer registries. Standardized incidence ratios (SIRs) adjusted for age, race/ethnicity and sex were computed with 2003-08 NYS rates as the reference, focusing on cancers diagnosed in 2007-08 as being most likely to be 9/11 related to exposure during September 11 and its aftermath. Within-cohort comparisons using Cox proportional hazards models assessed the relation between intensity of WTC exposure and selected cancers.

RESULTS:  There were 1,187 incident cancers diagnosed, with an accumulated 253,269 person-years (439 cancers among rescue/recovery workers and 748 among those not involved in rescue/recovery). The SIR for all cancer sites combined in the later period was not significantly elevated (SIR=1.14, 95%CI=0.99-1.30 among rescue/recovery workers vs. SIR=0.92, 95%CI=0.83-1.03 among those not involved in rescue/recovery). Among rescue/recovery workers, the SIRs had significantly increased by 2007-08 for 3 cancer sites and were 1.43 for prostate cancer (95% CI 1.11-1.82; n=67), 2.02 for thyroid cancer (95% CI 1.07-3.45; n=13), and 2.85 for myeloma (95% CI 1.15-5.88; n=7) in 2007-08. No increased incidence was observed in 2007-08 among those not involved in rescue/recovery. Using within-cohort comparisons, the intensity of WTC exposure was not significantly associated with cancer of the lung, prostate, thyroid, non-Hodgkin’s lymphoma or hematological cancer in either group.

CONCLUSIONS:  Among rescue/recovery workers enrolled in the WTC Health Registry, there was an excess risk for prostate cancer, thyroid cancer, and myeloma in 2007-2008 compared with New York State residents.  No elevations were found among those not involved in rescue/recovery work. No significant associations were observed with intensity of WTC exposures.  These early findings, however, were based on a small number of events, multiple comparisons and a short follow-up period. Longer follow-up for typically long-latency cancers and attention to specific cancer sites are needed.