Abstract

Large-scale use of leaded gasoline was an important source of the neurotoxin lead in the European environment. After a sequence of regulations on the allowed gasoline lead content and, eventually, a ban on the use of lead additives in gasoline, road transport was no longer considered a source of atmospheric lead. Currently a discrepancy exists between measured atmospheric lead concentrations and model-predicted concentrations, suggesting that lead emissions to the atmosphere may be underestimated. Recently it was suggested that lead emission from unleaded gasoline combustion is still an important source and may (partly) fill the gap between modelled and observed atmospheric lead concentrations. In this paper we assess the plausibility of the latter suggestion by following various emission estimation methodologies. The uncertainty of lead emissions from road transport is further reduced by chemical analysis of fuel samples. The result of our assessment is that lead from road transport fuel combustion is not the missing lead source needed to fill the gap between modelled and observed lead concentrations. Road transport is still a source of lead through brake wear and a small contribution from exhaust emissions but this contributes no more than 5-8% of the EU25 total emission. © 2009 Elsevier B.V. All rights reserved.

Abstract

Comparisons of measured and model-predicted atmospheric copper concentrations show a severe underestimation of the observed concentrations by the models. This underestimation may be (partly) due to underestimated emissions of copper to air. Since the phase out of asbestos brake lining material, the composition of brake lining material has changed and may contain up to ∼15% copper. This makes brake wear from vehicles potentially an important source of atmospheric (particulate) copper concentrations. In this paper, we reassess the copper emissions due to exhaust emissions and brake wear from road transport. Overall, our reassessments result in an estimate of total copper emission to air in UNECE-Europe of 4.0-5.5 ktonnes yr-1, which is substantially higher than the previous estimate of 2.8 ktonnes yr-1. Copper concentrations over Europe are calculated with the LOTOS-EUROS model using the revised emission data as model input. The results show that the revised emission estimates are a major step towards gap closure of predicted versus observed copper concentrations in ambient air. Brake wear emissions may be responsible for 50-75% of the total copper emissions to air for most of Western Europe. The hypothesis that road transport is an important source of copper emissions is tested and confirmed by (1) reviewing available literature data of chemically speciated PM data from road tunnel studies and (2) the gradient observed in copper concentrations from ambient PM monitoring going from rural sites to street stations. The literature review and observational data suggest that the majority of the emitted PM10 brake wear particles is in the PM2.5-10 size range. The results of this study indicate that modification of brake lining composition is an important mitigation option to reduce copper exposure of the population in Western Europe. © 2007 Elsevier Ltd. All rights reserved.