This letter was originally published in issue 811 of Local Transport Today.

Alan Wenban-Smith’s categorisation of my exposure of the flimsy and contradictory nature of the Committee on the Medical Effects of Air Pollution’s analyses on particulates, as that of a “conspiracy theorist”, is inappropriate.

It was the committee not me, that pointed out the extraordinarily wide 75 per cent plausibility limits (one-sixth to double the values cited) and the committee, not me, that published Professor Hopke’s view that policy decisions should not be based on the (in my view disgraceful) use of the process of elicitation as used by the committee.

Where COMEAP went wrong was to press on with providing a quantified estimate of deaths linked to particulates, instead of telling the government that after years of work it could not establish a relationship between deaths and particulates with enough confidence to justify policy. Readers may care to make their own mind up about that in the light of the following:

1. The COMEAP reports generally refer to all anthropogenic particulates, not just to those from road traffic.

2. The COMEAP report of 2010 says anthropogenic particulates caused 29,000 premature deaths in the base year 2008 but with limits ranging from one-sixth to double that number. The report also says eliminating these (anthropogenic) particulates would save between 5.8 million and 66.2 million life years over 106 years, a vast range.

3. In 2014 I asked COMEAP for the mortality burden savings attributable to particulates from road traffic. Dr Sarah Robertson replied: “A number of sources, of which traffic emissions is only one, contribute to PM2.5 background concentrations in urban areas across the UK. Based on the modelled figures underpinning the COMEAP 2010 report, PM2.5 from local traffic sources contributes to approximately 16 days of the approximate 200 days loss of life expectancy in the UK attributable to anthropogenic PM2.5 in 2008. However, this does not represent the total contribution of traffic emissions to PM2.5 concentrations at UK urban background sites. Traffic is also a contributing source of regional primary and secondary PM2.5 concentrations. Detailed figures for traffic contributions to these aspects in 2008 are not available. However, extrapolating from modelled data for 2012 suggests that regional primary PM2.5 concentrations from traffic emissions equates to an additional seven days loss of life expectancy in the UK.” So, particulates from local and regional traffic contribute just 23 (in a range of four to 44 days), or ten per cent to the overall mortality burden of 200 days.

4. Particulates from exhausts are now a minor component of all particulates from traffic, which itself is a minor contributor to all anthropogenic particulates.

5. The LTT report of 2 October says COMEAP can find no “compelling narrative of adverse health effects from non-exhaust particulates from road traffic”.

Against that background, is it not reasonable to ask why COMEAP did not draw the same conclusion as at point 5 above with regards to particulates from exhausts? Namely, although it is reasonable to assume particulates are not good for us there is no compelling narrative linking particulates to premature deaths.

Of course, COMEAP was caught between a rock and a hard place. It may have sabotaged its very existence or been politically unacceptable for it to present such a conclusion. Heaven knows how much these studies have cost, but the cost to the nation of a policy that scarcely has any basis is vast.

As to Alan’s point about nitrogen oxides being the main concern associated with diesel, COMEAP concluded in 2018 that the effects of NOx could not be separated out from those of particulates. There is a very good summary of that by Air Quality News (https://tinyurl.com/y6x8sg3r). It cites COMEAP as finding, “The methodology of this present report allows for calculations to be made on the basis of either particulate matter known as PM2.5 or NO2, and using the higher of the two estimates. The results should not be added together as this would lead to an over-estimation of the effects. Using these two approaches, the range of estimates of the annual mortality burden of human-made air pollution in the UK is estimated as an effect equivalent to 28,000 to 36,000 deaths.”

Lastly, no one seems to have tackled the environmental damage that electric cars will do – all that lithium and those rare earth metals mined from sea beds and the difficulty of recycling 30 million toxic electric car batteries.

Meanwhile, Extinction Rebellion and a certain Swedish school girl caught the world’s attention by saying the world would burn in ten yours unless something is done. Bah, it’s been far warmer in the past and the world did not catch fire.

Strangely, I am a ‘green’ but I believe the greens have the wrong focus, possibly driven by a hatred of cars. In order of magnitude, the threat to the environment and human survival are: demographics, wars, plastics and effluent of all sorts tipped into the sea, pesticides, and habitat destruction.

Paul Withrington, Director, Transport-Watch