Petrol emissions are very nasty for humans - Benzine - big cancer causing substance.
Anyone sitting behind a vehicle in traffic is just gulping that stuff down.
Particulates are not good either, but then neither is the dust inhaled when Offroad, at the Crushjng plant etc.
I have to manage my Crushing crews with health checks, dust monitoring etc. any small particle you inhale can harm you. The more you inhale, the worse it can be.
Of course Silica is another big nasty - best be avoiding Desert and dusty beach driving.
Have a search for the following statistics - Lead Levels in Australia from about 1980 onwards. The graph trends downwards quite quickly as take up of Unleaded increases.
Now look at the instances of Cancer. Increases almost directly relative over the same timeframe. Only major environmental change - introduction of ULP (full of Benzine).

