Determinants of exposure to organic and elemental carbon, and polycyclic aromatic hydrocarbons, during asphalt paving

Asphalt paving is a source of carbonaceous particles originating from diesel exhaust and condensation of semi-volatile organic compounds from bitumen. While the latter furthermore serve as precursors for secondary organic aerosols and formation of ground level ozone over regional scales, emissions from asphalt are relevant for asphalt workers exposure and public health. Contemporary assessments of the total carbonaceous exposure is provided for elemental carbon (EC), particulate organic carbon (OC) and hazardous polycyclic aromatic hydrocarbons (PAH) in more than 90 personal exposures in Denmark. Measurement campaigns were designed to investigate effects of meteorological parameters, asphalt temperature and asphalt type, paving equipment and locations including highways, urban and rural road and parking lot with/without ambient traffic. Moreover, the exposures were divided into work tasks (operators of rollers and paving machines, foremen, and asphalt workers on the road) to evaluate their susceptibility to individual pollutants. Determinants of exposure included wind speed and wind direction, asphalt temperature and number of equipment operating. Geometric mean exposures varied from 0.81 to 2.16 μg m^-3 EC, 33-200 μg m^-3 OC, while the sum of the so called 16 priority PAHs varied from 86 to 4237 ng m^-3 at different locations. Diesel exhaust and bitumen particles partly exceeded current occupational exposure limit values, while PAHs were well below. Since diesel exhaust particles and bitumen fumes are carcinogenic and possibly carcinogenic according to IARC, respectively, a set of recommendations were formulated for mitigation of these pollutants of importance for human and environmental exposure.