Effects of traffic policies on air pollution and health - an intervention study

Abstract

In the past decades substantial efforts have been taken to reduce air pollution emissions. However, increases in urban populations, number of cars and vehicle km travelled are a few trends that may partly offset their effectiveness. The EU has set air quality standards of which the standards for particulate matter (PM) and nitrogen dioxide (NO2) are the most important. Those are still exceeded especially near busy roads. Therefore, local policies have been implemented at busy urban roads. The aim of this thesis is to assess the effect of local traffic policy measures on 1) air quality; 2) oxidative potential of PM and 3) respiratory health of residents. Measurements of air pollution and respiratory health were conducted at eighteen locations (eight busy urban streets in five cities, six urban background locations and four suburban background locations) in the Netherlands before and two years after the policy implementations. In this study the LEZ was evaluated, which forbids entry of old heavy duty vehicles (trucks) to enter the LEZ, typically the inner-city. Additionally, a traffic recirculation plan was evaluated in one city (The Hague). Simultaneously at each location, six weekly air samples were collected spread over two six-month periods in 2008 and 2010. Respiratory health was assessed twice by spirometry, interrupter airway resistance and exhaled NO. Respiratory tests were performed in 661 residents in winter 2009 and 2011. In chapter 2, 3 and 4 we first compare the difference in concentration between major urban roads and background locations for a large range of air pollutants, prior to the introduction of the policies. High contrasts between busy streets and background locations in the same city were found for chromium (Cr), copper (Cu) and iron (Fe) (factor 2-3), indicative of non-tailpipe traffic emissions. In addition, high contrasts were found for soot and NOx (factor 2), indicators of combustion emissions. Contrast was lower for the regulated components. Oxidative potential of PM10 measured with the EPR assay showed the largest contrast between busy streets and background locations (factor 4-7). Chapter 5 presents an analysis of air pollution concentrations before and after the implementation of local traffic policies including the LEZ. Overall, the 2010-2008 concentration trends of traffic-related pollutants did not differ significantly for busy urban streets compared to suburban background sites outside of the LEZ. This suggested that LEZ policies directed at old heavy duty vehicles (trucks) did not substantially affect traffic-related air pollution concentrations. In the one street in The Hague, where in addition to the LEZ, traffic intensity was substantially reduced, soot, NOx and NO2 concentrations decreased significantly more than at the corresponding suburban background location. Changes in oxidative potential were not interpretable because of changes in laboratory practices. Chapter 6 describes the relation between changes in air quality and changes in the respiratory health status of residents. Especially in the one street in The Hague where traffic and air pollution concentrations was drastically reduced, lung function was improved with 3-5% in those residents compared to suburban background residents.