Report on estimation of mortality impacts of particulate air pollution in London.

It is widely accepted by the medical and scientific communities that there is a link between exposure to air pollution and the effects on health. These effects can vary in severity including mortality (death) and morbidity (the occurrence of illnesses throughout a life time). The evidence base from scientific studies shows that increased levels of fine particles in the air can increase risks of death. Increased exposure to particulates aggravates respiratory and cardio vascular conditions and research has shown that these particles can be inhaled deep into the respiratory tract. Less, however, is known about the health effects from long-term exposure to other pollutants such as sulphur dioxide, nitrogen dioxide and ozone. For this reason, this study has focused on the estimation of the mortality impact of fine particulate matter in London over a long-term basis. Airborne pollution in the form of fine particles (PM2.5) comes mostly from combustion sources; transport, domestic and industrial. The relationship between concentration and mortality rates, as recommended by the Committee on the Medical Effects of Air Pollution, is based on a large US study which estimated that for every 10 µg/m3 increase in average PM2.5 concentration there is a 6% increase in annual all-cause death rates. Applying this to population size data, average modelled PM2.5 concentrations and mortality rates for Greater London, we have estimated the mortality impacts of fine particles in London, and their geographical distribution. The study estimates the number of deaths in each Ward attributable to fine particles using average concentrations and demographic data by Ward. The study also estimates the change in life expectancy caused by pollution for the entire current London population. It is estimated that fine particles have an impact on mortality equivalent to 4,267 deaths in London in 2008, within a range of 756 to 7,965. A permanent reduction in PM2.5 concentrations of 1µg/m3 would gain 400,000 years of life for the current population (2008) in London and a further 200,000 years for those born during that period, followed for the lifetime of the current population. For the current population, this is equivalent to an average 3 weeks per member of the 2008 population, with the expected gains differing by age. It is unrealistic to believe that the estimated attributable deaths represent a subset of deaths solely caused by PM2.5, while all the remaining deaths were unaffected by pollution. Since everyone breathes the air where they are, a more realistic interpretation is that the risks are distributed across the whole population, with a total mortality impact of the concentrations equivalent to that number of deaths. Since the effects are long-term, there is also an implicit assumption that the results represent the impacts for concentrations that existed at the same levels in previous years. Those modelled concentrations include a proportion from natural sources that could never be eliminated, and it is unrealistic to expect even the man-made portion to be reduced to zero