Characteristics of Respirable Elemental Carbon (EC) Exposures of Household Waste Collectors

ABSTRACT

The objectives of this study to characterize exposure to respirable elemental carbon (EC), organic carbon (OC) and total carbon (TC) in relation to waste-handling activities and vehicle characteristics among workers who collect household wastes, and to examine the relationships among EC, OC and TC. A total of 72 household waste collectors were selected for exposure assessment over a full workday and most (70 of 72) exposures were collected from diesel emissions that underwent catalytic after-treatment by diesel particulate filters (DPFs). The exposure assessments were conducted from June through September 2014. Airborne EC and OC from the breathing zone were collected on pre-fired quartz filters and quantified using the thermal optical reflectance method. The average EC exposure level of the household waste collectors was 7.2 µg m^–3 with a range of 2.0-30.4 µg m^–3. A significant relationship between EC and TC exposure levels was observed (logTC = 0.38 × logEC + 3.22, p < 0.0001, adjusted R² = 0.23). EC level (µg m^–3), truck age (< 10 year-old vs. ≥ 10 year-old), type of waste collection job (collector vs. driver), current smoking status (yes vs. no) and month were found to significantly influence the level of TC exposure (n = 70, adjusted R² = 0.56, p < 0.0001). The average exposure to EC of household waste collectors can be categorized into the relatively low exposure group when compared to other DE exposure jobs. TC was not a best surrogate for DE exposure in household waste collection environments because it was affected by other OC interferences that were not generated from diesel engines.