Research report (Health Effects Institute)
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Res Rep Health Eff Inst · Apr 2011
The impact of the congestion charging scheme on air quality in London. Part 1. Emissions modeling and analysis of air pollution measurements.
On February 17, 2003, a congestion charging scheme (CCS*) was introduced in central London along with a program of traffic management measures. The scheme operated Monday through Friday, 7 AM to 6 PM. This program resulted in an 18% reduction in traffic volume and a 30% reduction in traffic congestion in the first year (2003). ⋯ The most compelling lesson we take away from this study is that such work is impossible to undertake without a coherent multi-disciplinary team of skilled researchers. In conclusion, our study suggests that the introduction of the CCS in 2003 was associated with small temporal changes in air pollutant concentrations in central London compared with outer areas. However, attributing the cause of these changes to the CCS alone is not appropriate because the scheme was introduced at a time when other traffic and emissions interventions, which might have had a more concentrated effect in central London, were also being implemented.
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Res Rep Health Eff Inst · Apr 2011
The impact of the congestion charging scheme on air quality in London. Part 2. Analysis of the oxidative potential of particulate matter.
There is growing scientific consensus that the ability of inhaled particulate matter (PM*) to elicit oxidative stress both at the air-lung interface and systemically might underpin many of the acute and chronic respiratory and cardiovascular responses observed in exposed populations. In the current study (which is part two of a two-part HEI study of a congestion charging scheme [CCS] introduced in London, United Kingdom, in 2003), we tested the hypothesis that the reduction in vehicle numbers and changes in traffic composition resulting from the introduction of the CCS would result in decreased concentrations of traffic-specific emissions, both from vehicle exhaust and other sources (brake wear and tire wear), and an associated reduction in the oxidative potential of PM with an aerodynamic diameter < or = 10 microm (PM10). To test this hypothesis, we obtained, extracted, and analyzed tapered element oscillating microbalance (TEOM) PM10 filters from six monitoring sites within, bordering, or outside the area of the congestion charging zone (CCZ) for the 3 years before and after the introduction of the scheme. ⋯ PM10's oxidative potential after the introduction of the CCS did not change at the one urban background site within the zone. Yet compositional changes in PM10 were noted at the same site, including significant decreases in Cu and zinc (Zn) content, probably reflecting brake and tire wear (compared with increases in these metals at all sites outside the zone in the 3 years since the scheme's introduction). This pattern of results is consistent with observations of increased vehicle use throughout London in recent years and decreases in the number of vehicles entering the zone since the scheme's introduction.