Trends in primary NO2 and exhaust PM emissions from road traffic for the period 2000e2020 and implications for air quality and health in the Netherlands

Abstract Application of an oxidation catalyst mainly by diesel-fuelled passenger cars reduces harmful exhaust emissions of particulate matter (PM). As a side effect, the primary NO 2 /NO x emission ratio by these vehicles increased from 10% in 2000 (before the introduction of the oxidation catalyst) to between 55% and 70% in 2010. The impact of this evolution in traffic emissions was studied from both a health and a regulatory perspective. Primary NO 2 emissions from road traffic in the Netherlands is expected to increase from 8 kt in 2000 to 15 kt by 2015 and subsequently to decrease to 9 kt by 2020. Meanwhile, exhaust PM emissions from road traffic in the Netherlands will decrease from 7 kt in 2000 to 3 kt by 2020. The impact of exhaust PM on air quality and health was assessed according to the mass concentrations of elemental carbon (EC) in ambient air, as EC is a more sensitive indicator than PM. Monitoring data on the NO 2 /EC concentration ratios near road traffic between 2000 and 2010 indicate no significant change in ambient air quality. This indicates that health effects in epidemiological studies associated with long-term exposure to NO 2 concentrations are still valid. The health impact from the introduction of the oxidation catalyst was assessed by comparing the relatively higher NO 2 (“cost”) and lower EC (“benefit”) concentrations at street locations. “Relative” refers to traffic emissions in situations “with” and “without” the oxidation catalyst being introduced. The cost–benefit ratio in 2010 was in balance, but benefits are expected to outweigh costs by 2015 and 2020. It is concluded that the application of oxidation catalysts is beneficial from a health perspective, but from a regulatory perspective it complicates compliance with the average annual limit value of NO 2 . This indicates that additional local measures may be required in order to meet air quality standards at locations with high traffic intensities.