Real-Time Assessment of Black Carbon Peaks Among Workers Exposed to Diesel Engine Exhaust Emissions

Abstract

Background Workers are commonly exposed to diesel engine exhaust (DEE) from diesel-powered engines and vehicles (DEVs), which contain harmful particulates such as black carbon (BC). This study aimed to characterize the peak BC exposures of workers operating or working near DEVs. Methods BC levels were recorded every minute from workers driving or working near DEVs using a portable aethalometer and were categorized by job type and activity. Peak BC levels were characterized using the occupational exposure limits for DEE (measured as elemental carbon) of 10 μg/m3 and 50 μg/m3 as cut-off values. Results Forklift operators, garbage collectors, and machine operators showed peak BC exposure levels surpassing 20 μg/m3, with average levels above 10 μg/m3. Despite their short exposure durations ('1 hour), these peaks contributed significantly ('60%) to the daily average BC exposure. The daily contribution rate of peak exposures above 10 μg/m3 to the average daily BC exposure often exceeded 50%. The ratio of peak levels above 10 μg/m3 and 50 μg/m3 to the arithmetic mean was negatively correlated with exposure duration, the proportion of exposure duration, and the daily contribution of peak levels. Conclusion Drivers of diesel-engine vehicles often experienced significant spikes in BC exposure, highlighting the need for real-time monitoring, which is recommended as a best-practice approach to identify and mitigate short-term peak exposures. © 2026 Occupational Safety and Health Research Institute.