Professional Drivers Exposure to Black Carbon in London; the Diesel Exposure Mitigation Study

Background: Despite the health risks of diesel engine exhaust, minimal research has been undertaken to quantify the exposures of professional drivers. To address this, we examined personal black carbon (BC) exposures of professional drivers in London under a range of occupational settings, vehicle types and driving conditions. Method: GPS-linked BC sensors were provided to 130 drivers (taxi drivers, couriers, heavy freight, waste removal and emergency services) for 96 hours, with measurements every minute. Drivers also completed a questionnaire, detailing their ventilation preferences, vehicle type and their number of working hours per day. Preliminary Results: Average driver exposure to BC was 3x higher at work (3.5 ± 2.9 µg/m3) compared to periods at home (1.1 ± 0.7 µg/m3). During work, drivers experienced high spikes in exposure, often exceeding 100 µg/m3. The highest exposed drivers were taxi drivers (6.0 ± 4.6 µg/m3), while the lowest were those in emergency services (2.0 ± 0.7 µg/m3). Window position influenced BC exposures, with concentrations being 2.5x higher for drivers with windows open versus closed. Across the same monitoring period ambient BC concentrations were 2.5 ± 1.8 µg/m3 at a London roadside and 0.8 ± 0.7 µg/m3 at the London background. Conclusion: We have performed the largest study of driver exposures to a proxy of diesel exposure (BC) in an urban environment. These data confirm the very high exposures experience by professional drivers in their working lives, but also indicate that simple measures, such as closing vehicle windows can significantly reduce exposures. Measurements made at fixed monitoring sites were not representative of driver exposure to BC.