Development of a job-exposure matrix (JEM) for exposure to smoke particle mass among firefighters of the Fire Department of the City of New York (FDNY)

Objectives A refined job exposure matrix (JEM) based on incident types and severities and response characteristics was developed for firefighters to estimate quantities of smoke particles emitted during structural and non-structural fire incidents from 2010 to 2021. Methods The cohort included a subset of 3237 Fire Department of the City of New York firefighters who responded to at least one incident between 2010 and 2021, prior to retirement. Fire incident data included dates, type, severity (alarm level) and location. Response data included dates worked, firehouse, position titles and shift lengths for each firefighter. The quantity of smoke particle mass generated during structural and non-structural fires adjusted by individual firefighter engagement was computed using the United States Environmental Protection Agency AP-42 emissions framework. Correlations between years of employment, fire responses and career total particle mass concentration by firefighter were examined. Linear regression models were fit and corresponding R 2 values were calculated. Results Firefighters responded to a median of 424.7 (IQR=202.3-620.0) annual incidents/person; 17.6% were fire incidents (median=77.1; IQR=40.4-114.0). Structural fires were the most common type of fire incident (72.5% of annual incidents/person; median=55.9; IQR=29.6-85.5). Incident severity (alarm level) and firefighter engagement (position title) appeared to differentiate between high and low exposure regimes (R 2 =0.43). Incident severity explained most of the variability of particle exposures (R 2 =0.90). Conclusions Using the JEM, job-related smoke particle concentrations were estimated to vary by incident type, incident severity and firefighter engagement, highlighting the importance of using refined measures, so that future studies can more accurately evaluate associations between firefighting and health outcomes.