Forgive me for following up my letter. I do so because, in the same issue, we have (a) two experts disagreeing almost violently as to the efficacy of battery electric vehicles (“The route to zero emissions, or over-hyped”) and (b) under the headline, “No compelling evidence that brake and tyre dust harm health”, we have COMEAP declaring that there is “no compelling narrative of adverse health effect of exposure to non-exhaust particles from road traffic”.

Recapping, my previous letter: the “Great dirty diesel scare” was sparked by the COMEAP report of 2010. It claimed particulates were causing “29,000 premature deaths”. The same report says that the 75% plausibility limits range from one sixth to double the cited numbers. I pointed out that the finding was akin to a scientist stating that the average height of a man was six feet but with a plausibility range of one foot to 12 feet. Worse still the numbers depended on the disgraceful procedure of elicitation – asking experts, with no data, for their views as though there can be any “experts” with no data.

I go on to point out that the COMEAP report, “UK Plan for tackling roadside nitrogen dioxide concentrations”, of July 2017 has, under the heading “Estimating the mortality burden attributable to current concentrations of air pollutants”, the following admission: “Some Members do not think it appropriate to try to calculate an overall burden of the mortality associated with the air pollution mixture”. They were right, but overruled. 

In any event, the 2010 report contains a figure showing that particulates from local traffic are a minor contributor to the overall particulate burden. Worse still Engineering and Technology, March 2017 and the Air Quality Expert Group’s report, “Non-exhaust emissions from road traffic”, dated 2019 find that by as early as 2022 hardly any of the particulates from road traffic will be from exhausts! By that date it is unlikely that the battery electric vehicle will have made significant penetration. Hence the data represent a largely internal combustion engine powered fleet.

So, given the very wide plausibility limits cited by COMEAP, the technical disagreements, and the vanishingly small proportion of particulates which are from exhausts, the honest conclusion should be that there is insufficient evidence to justify any policy designed to reduce these, or any other particulates

We now have the amazing statement by COMEAP reported above, namely, “There is no evidence that non-exhaust particulates cause harm”. How on earth would they determine which particulates harmed health, I ask? I go on, if these non-exhaust particulates do not damage heath, and if particulates from exhausts are a vanishingly small proportion of the whole and if their impact on heath is entirely uncertain, why on earth are they destroying the diesel industry?

I conclude that COMEAP makes its claims in the knowledge that they play well with the often data free, anti-car and green lobbies which have such strong but misguided influence on policy.

Paul Withrington

A version of this letter was published in Local Transport Today on 16 October 2020.