RESUMEN
OBJECTIVE: Coronary heart disease (CHD) is the primary cause of death among US firefighters during fire suppression. In other populations, exposure to respirable particles, including ultrafine particles, has been widely implicated as a risk factor for CHD. This study is the first to report detailed characterization of respirable particles released by combustion of an automobile and model residential structures under firefighter exposure conditions. METHODS: Characterization was performed when feasible during knockdown and routinely during overhaul. RESULTS: Ultrafines accounted for >70% of particles in all fire suppression stages, occurring in concentrations exceeding background by factors between 2 (automobile) and 400 (bedroom), consistent among all structures. CONCLUSIONS: Exposure to ultrafine particles during fire suppression should be considered a potential contributing factor for CHD in firefighters. Of major significance is their predominance during overhaul, where firefighters frequently remove respiratory protection.