See below for supporting papers
Update October 2013
We have been asked whether the methods used to develop estimates of the mortality burden, in a given year, associated with long-term exposure to current levels of particulate air pollution are similar to those used to calculate mortality (in a given year) attributable to other common public health risk factors such as smoking, obesity and alcohol.
Discussions with DH analysts suggest that, in most cases, the methodological approaches used are similar. Exceptions are statistics for diseases which are wholly attributable to a single risk factor (a notable example being alcohol and deaths from alcoholic liver disease). However, there are some differences in the language used to communicate the results.
COMEAP has no plans to change its preferred formulation for describing the mortality burden attributable to long-term exposure to particulate air pollution as "equivalent to" a given number of deaths (in a given year) together with information on the life lost to the population. This reflects the characteristics of air pollution as a contributory factor to mortality risk at ages at which deaths typically occur.
When comparing mortality effects, the number of attributable deaths does not give all the information that would be useful in such a comparison: information on the distribution of ages of attributable deaths is also important. Therefore, when estimates of mortality attributable to different risks are being compared the Committee considers that, if it is possible to do so simply, there are advantages in making it clear whether the other risks:
(a) share the characteristics of the effect of long-term exposure to air pollution on mortality, for example:
• contributing to deaths in combination with other risk factors,
• influencing deaths at older ages, as is typical for deaths from heart and lung disease
• involve some delay between exposure and effect
• cause sufficiently large effects on population mortality to change the size and age of the population over long periods so that estimates are best made for a specific year or time period rather than assuming the estimate is the same every year
(b) do not share these characteristics, for example risk factors which:
• are a direct and immediate cause of death and/or
• affect mortality at atypical ages (for example amongst children or young adults).
This report follows on from the report published by COMEAP in 2009 "Long-term exposure to air pollution:effect on mortality".The 2009 report focused on particulate matter, represented as PM2.5, as the air pollutant most strongly associated with increased risks of mortality and recommended coefficients expressing the relative risks of mortality associated with a 10 μg/m3 increase in PM2.5. It did not include calculations of the overall size of the potential effects of particulate air pollution on mortality in the UK.
The Committee has now carried out these calculations and, in this report, presents not only the calculations but also an overview of the methods used, assumptions made and the relationships between different ways of expressing the results.
Published 21 December 2010