- gasoline direct injection engines produce much more harmful particulate matter than current diesel engines (https://en.wikipedia.org/wiki/Gasoline_direct_injection#Emis...), plus some carcinogenic gases like benzoapyrene.
- a lot of the particulate matter emitted by cars comes from brake and tire wear, which even electric cars have (https://www.greencarcongress.com/2016/04/20160418-pm10.html).
So blaming it all on Diesel engines is a bit short-sighted...
One other point also is that tyre particulate emissions vary hugely according to composition and manufacture. So we will need both a switch to electric and proper regulation of tyres, then we’ll really be getting somewhere.
The paper about brake and tire wear you cited receive a Corrigendum about false attribution and conflict of interest because the author works in a motor tech:
The authors regret that as Victor Timmers did not carry out the research under the auspices of the University of Edinburgh, nor in collaboration or consultation with any personnel at the University of Edinburgh, the affiliation of “University of Edinburgh” has now been removed from this work at the request of the Institution. In addition, subsequent to the publication of the Paper, Victor Timmers has disclosed a potential Conflict of Interest with regard to the work, namely: “non-financial support from Innas B.V, during the conduct of the study”.
The authors would like to apologise for any inconvenience caused.
I carried it around with me for a few days in London, commuting in by train from the suburbs. There were two places that had the highest particulate levels. The first was in my kitchen when I was cooking (no comment!), and the second was on the London Underground. Particulates were far higher on the tube than on the street in central London. So high I would have thought it was a serious health risk for tube drivers. Presumably this mostly comes from the steel wheels on steel track. I don't know whether ingesting steel particulates is more or less healthy than other particulates though. Has anyone done any studies into whether tube drivers have higher rates of health problems than overground drivers?
Edit: table 1 of this paper confirms that the particulates on the underground are mostly iron: https://assets.publishing.service.gov.uk/government/uploads/...
Highly unlikely. Steel-on-steel is used because it lasts for YEARS without needing replacing due to wear.