Assessing the health burden of long-term exposure to nitrogen dioxide and mortality in London

Abstract

Introduction The health impact of air pollution in London was previously based on fine particulate matter (PM2.5) alone. In this work, the mortality burden for PM2.5 has been updated and, for the first time, a scoping exercise performed for the potential mortality burden of long-term exposure to nitrogen dioxide (NO2) in London. Methods The methods for PM2.5 followed Committee on the Medical Effects of Air Pollutants recommendations. Methods for NO2 followed the same principles but used the coefficient recommended by the World Health Organisation. We assumed up to a 30% overlap with PM2.5, quantifying down to zero as the upper limit for the size of the effect (down to 20 μg m-3 in sensitivity analysis). Concentrations were modelled using the London Air Quality Modelling toolkit based on the London Atmospheric Emissions Inventory at a 20mx20m grid and then population-weighted at output area level. Estimates for individual London boroughs were summed to give the London figure. Results The total mortality burden of anthropogenic PM2.5 in London for the year 2010 was estimated to be 52,500 life-years lost, equivalent to 3,500 deaths at typical ages. Whilst much less certain than for PM2.5., the total mortality burden of NO2 was estimated to be up to 88,000 life-years lost, equivalent to 5,900 deaths at typical ages (assuming a 30% overlap between the effects of PM2.5 and NO2 and a counterfactual of 0 μg m-3. Some of this effect may be due to other traffic pollutants. The total mortality burden in 2010 from PM2.5 and NO2 if added, with caveats, gives a range from the 52,500 life-years lost, equivalent to 3,500 deaths at typical ages from PM2.5 alone up to as much as 141,000 life-years lost, equivalent to 9,500 deaths at typical ages. Conclusions Inclusion of estimates for NO2 potentially increases the estimated total mortality burden substantially, highlighting the importance of further research on the overlap in effects between NO2, PM2.5 and other traffic pollutants.