The Committee on the Medical Effects of Air Pollutants (COMEAP) has previously provided advice on how the mortality effects of particulate air pollution can be quantified, with their recommendation being based on the link between levels of fine particulate air pollution (PM2.5) and deaths found in a large population study undertaken in the US. Since that time, a number of other studies have been undertaken, in the UK and elsewhere in Europe, and it is believed that a summary estimate of the results from available studies, published in the peer-reviewed scientific literature in 2013, is suitable to update their recommendation.
COMEAP report there is good evidence that PM2.5 plays a causal role in shortening life, however sources of pollutants, such as traffic, tend to emit a range of different pollutants, which makes it difficult, in population studies, to disentangle the effects of individual pollutants from each other. Therefore, it is likely that the coefficient linking PM2.5 concentrations with an increased risk of death reflects the effect of both PM2.5 and also, to some extent, of other pollutants, such as other size fractions of PM, nitrogen dioxide (NO2) and other components of the air pollution mixture.
The updated concentration-response function coefficient linking concentrations of PM2.5 with mortality is the same as COMEAP's previous recommendation, with a relative risk of mortality of 1.06 per 10 μg/m3 increase in PM2.5. However, the new summary coefficient has less statistical uncertainty associated with it (95% confidence interval 1.04 - 1.08) than their previous recommendation. This greater precision reflects the larger number of people included when the results of several studies are combined. However, the confidence interval does not reflect other uncertainties in interpreting the available evidence.
Source: UK Health Security Agency (UKHSA), 16 March 2022