In my previous working life I was involved in the supply of Certified Reference Materials used in calibrating analytical methods. The EC, through the JRC in Geel, issued a CRM produced from the material washed off the inside of one of the alpine tunnels. It contained a remarkably toxic mixture of organic, petrochemical and trace element pollution, much of it was from diesel truck exhausts (this was in the late 1980s).
To be honest I wouldn't drive any open car through the tunnels on a regular basis: this was BEFORE the concerns about micro particulates and other materials of recent concern.
Electric vehicles will cause less micro particulate pollution, as the use of brakes is significantly reduced due to regenerative braking.
I regularly ran a LWB van to Italy and back during the 20 year course of my last business. The Mont Blanc, my usual return route, was a truly scary tunnel in terms of pollution, probably because it was one of the oldest. It was like driving through thick fog at times and always a huge relief to get out. I would open all windows at the entrance barriers irrespective of outside temperature, take a few lung fulls of fresh air then close all windows and vents before entering.
