The Association Between World Trade Center Rescue/Recovery Work and Physician Diagnoses of Obstructive Airway Disease

BACKGROUND: Adverse respiratory effects of work at the World Trade Center (WTC) disaster site have been widely documented and have shown consistent dose-response relationships. This study compares the number and timing of new cases of chronic obstructive airway disease (OAD) in highly-WTC-exposed versus lesser-WTC-exposed firefighters.

METHODS: New onset OAD was diagnosed by Fire Department of the City of New York (FDNY) physicians at treatment visits; individuals with a pre-9/11/2001 OAD diagnosis were excluded from analyses. Exposure was categorized by time of arrival for work at the WTC site as follows: (high) morning 9/11/2001 (n=1,582); (moderate) afternoon 9/11/2001 or 9/12/2001 (n=6,983); (low) 9/13-24/2001 (n=1,201). We modeled relative rates of incidence with respect to exposure intensity over the first ten years post-9/11/2001. We estimated the time(s) of changes in the relative rates from change point models using maximum likelihood. Age on 9/11/01, smoking history, retirement status, and season were included as covariates. We also examined the temporal relationship of OAD physician diagnoses to self-reported OAD symptoms.

RESULTS: Change points in the relative rates were observed at 15 months and 84 months post-9/11/2001. The relative incidence rates for the high versus low exposure group was 4.01 (95% confidence interval [CI] 2.62-6.16) prior to 15 months, 1.90 (95% CI 1.49-2.44) from months 16 to 84, and 1.20 (95% CI 0.92-1.56) thereafter. Similar results were found in sensitivity analyses modeling OAD by subtypes (asthma and non-asthma OAD). OAD symptoms were reported during months 1-15 in 69% of persons diagnosed with OAD during months 16 to 84 and 62% of persons diagnosed with OAD after month 84, but 71% of those reporting OAD symptoms during months 1-15 did not ever receive a physician diagnosis of OAD during the ten year follow-up period.

CONCLUSIONS: New physician diagnosis of OAD is associated with WTC exposure for at least seven years. Because most individuals receiving diagnoses later in the follow-up had reported OAD symptoms months or years earlier, we cannot rule out the possibility that the extended duration of the exposure-response relationship is partly due to delayed diagnoses. This is particularly likely for individuals first diagnosed in post-9/11/2001 years six and seven, as the FDNY WTC health program began to offer free coverage of OAD medications at that time, changing the incentive for diagnosis. Nevertheless, our results support recognizing OAD among WTC rescue workers as WTC-related even if diagnosed long after the exposure.