The Central London Congestion Charging Scheme (CCS) has led to a modest increase in the life expectancy of Londoners, according to a joint study by King’s College, London and the London School of Hygiene & Tropical Medicine, which is published in today’s Occupation and Environmental Medicine journal.

The CCS was introduced in Central London in February 2003, to alleviate traffic congestion. To date, the impacts of the scheme on levels of traffic-related air pollution and the its effects on health have not been assessed. This is the first study to estimate the magnitude of the scheme’s impact on changes in life expectancy associated with air pollution. It also gives an indication of the extent to which a localized traffic intervention may influence socioeconomic inequalities in exposure to traffic pollutions, and the associated health effects.

Evidence from epidemiological research indicates that exposure to traffic is associated with higher death rates, a raised incidence of heart attacks, and impaired lung development in children.

The researchers used a combined emission-dispersion and regression modelling approach to estimate levels of nitrogen dioxide (NO2) and PM10 (particles of 10 micrometres or less) both before and after the introduction of the CCS. The period studied predates the westward extension which took place in 2007, and looks at the initial CCS, which covered approximately 21km2 and contained a resident population of 200,000 compared with the over 7 million residents of Greater London

Reductions in concentrations, although modest across Greater London, but were found to be greater in the charging zone wards, reflecting the localized nature of the scheme. Predicted benefits in the charging zone wards were 183 years of life per 100,000 people compared to just 18 years in the remaining wards. In London overall, 1,888 years of life were gained. More deprived areas within the zone had higher air pollution concentrations, but these areas also experienced greater air pollution reductions and mortality benefits compared to the least deprived areas.

The authors comment:

‘The Congestion Charging Scheme appears to have had a modest impact on air pollution levels, and associated life expectancy. It also appears to have led to a modest reduction in socioeconomic inequalities in air pollution exposures and associated mortality.’

The greater reduction in air pollution in the more deprived areas within the zone could help to reduce socioeconomic inequalities in air pollution impacts within the capital.

They conclude:

‘Exposure to ambient air pollution is associated with a broad spectrum of adverse health effects. In this analysis, we considered only the impact of exposure on all-cause mortality in adults. In addition to mortality, evidence supports associations between air pollution and lung cancer and cardiovascular morbidity in adults. Furthermore, considerable evidence supports an association between air pollution exposures and respiratory outcomes in children as well as pregnancy and infant health outcomes. The total benefit of a reduction in air pollution exposure on all probable adverse health outcomes is likely to be much greater than what we have estimated’.

Air pollution and mortality benefits of the London Congestion Charge: spatial and socioeconomic inequalities. Cathryn Tonne1, Sean Beevers (1), Ben Armstrong (2), Frank Kelly (1), Paul Wilkinson(2).

1 Environmental Research Group, King’s College, London.
2 London School of Hygiene & Tropical Medicine