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Modeled Air Pollution and Mortality Benefits of the London Congestion Charge: Spatial and Social Inequalities

2007; Lippincott Williams & Wilkins; Volume: 18; Issue: 5 Linguagem: Inglês

10.1097/01.ede.0000276530.41335.a6

1531-5487

Cathryn Tonne, Sean Beevers, Ben Armstrong, Frank J. Kelly, Paul Wilkinson,

Vehicle emissions and performance

ISEE-224 Objective: In February 2003, a traffic Congestion Charging Scheme (CCS) in London introduced a charge, currently £8 (US$16) a day, for driving into a designated Congestion Charging Zone (CCZ) between 7 am and 6.30 pm, Monday to Friday. The CCZ covers an area of approximately 21 km2 of central London, with a resident population of 232,000 (Greater London = 7.5 million). We modeled the impact of the scheme on traffic-related air pollution and mortality. Material and Methods: Annual average NOx and PM10 concentrations were estimated for the year before and after the introduction of the scheme using an emission-dispersion model. For both years, we assumed the same meteorological conditions and vehicle fleet as for 2003. The resulting 20 × 20 m resolution pollution maps were linked to small-area socioeconomic and population data. Associated changes in mortality by deprivation quintile were estimated using regression coefficients for NOx and PM10 derived from published cohort studies. Results: Before the CCS, mean NOx concentration was 77.1 μg/m3 and PM10 concentration was 26.7 μg/m3 across London as a whole. Concentrations of both pollutants were higher in more deprived areas, though the association with deprivation was stronger outside the CCZ than within it. Following the CCS, NOx concentration was estimated to have decreased by 2.7 μg/m3 (2.3%) within the CCZ and by 0.29 μg/m3 (0.4%) outside it. The corresponding figures for PM10 were 0.24 μg/m3 (0.8%) and 0.03 μg/m3 (0.1%). The reductions in NOx were greater in deprived areas across Greater London (P <.0001) but not within the CCZ (P = 0.94). The predicted improvement in life expectancy attributable to these pollution changes is modest. Conclusions: The CCS has had modest benefit on air pollution levels and related mortality in London. The greater improvement in more deprived areas, especially outside the CCZ, has made a small contribution to reducing socioeconomic inequalities in air pollution impacts.