The London Congestion Charge Scheme may have had a modest benefit on levels of air pollution and life expectancy in the capital, according to research from King’s College London to be published ahead of print in Occupational and Environmental Medicine.

Cathryn Tonne, Research Fellow in the Environmental Research Group (ERG) based in the School of Biomedical & Health Sciences, has been working with colleagues from the London School of Hygiene and Tropical Medicine on this project.

Extending the London Congestion Charge Scheme more widely and directly tackling vehicle emissions may see greater benefits for public health, say the authors.

The Mayor of London introduced the vehicle levy in designated areas five years ago this month, in a bid to ease traffic in central London during working hours. The Congestion Charge Zone originally covered an area of 21 km2, and a residential population of 200,000 people. It was subsequently extended west to a much larger area last year.

Impacts of air pollution

Cathryn Tonne describes how the work was carried out: `We focused on the original zone, and assessed the impacts of air pollution on health within the zone and across London as a whole. We used models of annual levels of air pollution based on measurements of changes in traffic flow across London.`

The researchers focused on nitrogen dioxide (NO₂) and particulate matter and the expected increase in life expectancy from reduced exposure to these pollutants.

‘The results showed that there was little change in pollutant levels in London as a whole. But there were more substantial falls in the charging zone. Levels of NO₂ fell the most,’ she explains.

There were smaller falls in particulate matter levels, which the authors ascribe to the comparatively large amount that comes from outside the capital and the fact that sources other than vehicles contribute to this form of pollution.

But the reduction in both pollutants was greatest in the most deprived areas of London. The estimated gains in years of life expectancy amounted to 1888 across London, overall.

The Congestion Charge did not set out specifically to improve health, and it covered a comparatively small part of inner London, say the authors.

But they conclude: ‘Policies affecting a larger geographical area and residential population, and which directly aim to reduce vehicle emissions, are likely to have larger public health impacts.’

Professor Frank Kelly, Director of the Environmental Research Group is hoping the team can undertake a follow-up study to examine the impact of the enlarged Congestion Charge Zone which includes the westerly extension.

Occupational and Environmental Medicine is an international peer reviewed journal concerned with areas of current importance in occupational medicine and environmental health issues throughout the world. It is part of the BMJ group of journals.

For more information please follow the link below to the published paper.

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Item date 28/02/2008