I haven’t seen this in the comments but its one reason I wonder why convertibles sell so well in the UK. I have a sun roof and i hardly ever use it because i hate the smell of exhaust. I may use the sunroof on a coastal road once in a while but not for long periods. I chose the car i drive because it has a hepa filtration system built into the climate control. I agree with comments about pollution but i must add that as a motorcyclist for a decade in London i blamed most pollution on short journeys like school runs. During school breaks the roads were much cleaner. So getting everyone to commute to work by bike won’t fix the problem when from experience most of the pollution is parents taking kids to school!