POLEMICS

The demand for urban mobility is steadily increasing and the growing number of vehicles in cities has major environmental consequences. Most of the urban areas in France suffer from poor air quality which results in increased morbidity and mortality rates among the urban population. Legislative authorities have tried to counteract this problem by imposing stringent emission limits on selected air pollutants, nitrogen oxides (NOx) and particulate matter (PM), which have been associated with adverse effects on human health. At the same time, modern cars are also required to produce less carbon dioxide (CO2) for reducing negative impacts on climate. Car manufacturers have responded to these emission regulations by introducing a series of in-engine modifications and exhaust after treatment technologies, e.g. the Diesel Particulate Filter (DPF) or Selective Catalytic Reduction (SCR) of NOx. New cars have nowadays to meet Euro 6 standard. In France, Euro 6 cars currently account for approximately 20% of the total fleet, with the share increasing to 40% and 60% by 2020 and 2025, respectively. Emissions of these cars are still poorly characterized, especially in view of recently discovered manipulation practices. We have recently conducted pilot emission measurements on Euro 6 passenger cars and have observed that, while emissions of pollutants subjected to regulations are indeed reduced, other non-regulated pollutants (e.g. organic nitrogen compounds and selected hydrocarbon classes) are emitted in substantial quantities. Many of the observed compounds are highly reactive in nature and will be rapidly transformed in the atmosphere potentially contributing to the formation of secondary organic aerosols (SOA). The atmospheric fate and toxicity of the mixture of pollutants emitted by Euro 6 light-duty vehicles is yet unknown. We have gathered an interdisciplinary team composed by emission specialists, atmospheric chemists, analytical mass spectrometry experts, toxicologists and air quality modellers that proposes to investigate the nature, the fate and the impacts of Euro 6 emissions combining in laboratory and real world measurements. Car exhaust will be measured at the tailpipe and after processing in static and dynamic simulation reactors. Primary emissions and oxidation products, both in the gas and the particulate phase, will be analysed using some of the most advanced on-line mass spectrometry techniques. Complementary studies on selected chemicals found in the exhaust will be carried out for elucidating degradation mechanisms and reaction products. The obtained kinetic and product information will implement air quality models. The genotoxic potential of primary and secondary particles will be assessed using standard in vitro assays. The consortium will thus provide a first comprehensive assessment on how the transition to a Euro 6 vehicle fleet will impact urban air quality.