Exposure–response relationships for select cancer and non-cancer health outcomes in a cohort of US firefighters from San Francisco, Chicago and Philadelphia (1950–2009)

Abstract

Objectives To examine exposure–response relationships between surrogates of firefighting exposure and select outcomes among previously studied US career firefighters. Methods Eight cancer and four non-cancer outcomes were examined using conditional logistic regression. Incidence density sampling was used to match each case to 200 controls on attained age. Days accrued in firefighting assignments (exposed-days), run totals (fire-runs) and run times (fire-hours) were used as exposure surrogates. HRs comparing 75th and 25th centiles of lagged cumulative exposures were calculated using loglinear, linear, log-quadratic, power and restricted cubic spline general relative risk models. Piecewise constant models were used to examine risk differences by time since exposure, age at exposure and calendar period. Results Among 19 309 male firefighters eligible for the study, there were 1333 cancer deaths and 2609 cancer incidence cases. Significant positive associations between fire-hours and lung cancer mortality and incidence were evident. A similar relation between leukaemia mortality and fire-runs was also found. The lung cancer associations were nearly linear in cumulative exposure, while the association with leukaemia mortality was attenuated at higher exposure levels and greater for recent exposures. Significant negative associations were evident for the exposure surrogates and colorectal and prostate cancers, suggesting a healthy worker survivor effect possibly enhanced by medical screening. Conclusions Lung cancer and leukaemia mortality risks were modestly increasing with firefighter exposures. These findings add to evidence of a causal association between firefighting and cancer. Nevertheless, small effects merit cautious interpretation. We plan to continue to follow the occurrence of disease and injury in this cohort.

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“…Nonetheless, for the purposes of analysis, we assumed that the excess risk for the cancers analyzed is indeed caused by participation in the firefighter occupation (rather than genetics or some other exposure). The strongest evidence to date comes from Daniels, Bertke, et al, 2015, which looked at the incidence of cancer among career firefighters who were more and less exposed to fires, thus accounting for the fact that firefighters might have different characteristics from those in the general population (importantly, smoking prevalence and other lifestyle characteristics were not available in the data for these publications). If firefighting causes cancer, we should expect those who fight more fires to have higher cancer incidence.…”

“…If firefighting causes cancer, we should expect those who fight more fires to have higher cancer incidence. Daniels, Bertke, et al, 2015, describes a higher incidence of lung cancer among more-exposed firefighters but does not find strong associations with many other types of cancers. Many experts in the field believe that the strongest evidence for a direct link between firefighting and cancer is mesothelioma, which showed a twofold increase in incidence in the original Daniels, Kubale, et al, 2014 study.…”

“…The Daniels, Kubale, et al, 2014, andDaniels, Bertke, et al, 2015 studies specifically looked at cancer incidence among career firefighters, so these estimates might not apply to firefighters with different occupational roles (e.g., paid on call, paid per call, volunteer) because their risks can be very different. Information from the IAFF indicates that more than 85 percent of the places where people live in the United States are served by career firefighters.…”

“…There was also some evidence that firefighters younger than age 65 had an increased risk of developing prostate or bladder cancer. In a follow-up analysis, an association between total time spent at fires (fire-hours) and lung cancer and leukemia mortality were found (Daniels, Bertke, et al, 2015). Firefighters with more exposure to fires also had a lower incidence of colorectal and prostate cancers, which the authors suggested came from a "healthy worker survivor effect," 35 possibly enhanced by medical screening.…”

“…931, 2017), which tracks cancer cases among firefighters, allowing for more-detailed study of the risks of the job and how to prevent them (National Fallen Firefighters Foundation, 2017;Beilman, 2017). Daniels, Kubale, et al, 2014. b Daniels, Bertke, et al, 2015. …”