Gasoline, a liquid at room temperature, is less viscous than water and therefore it also evaporates more easily. At room temperature gasoline will vaporize and move into the air space surrounding it - at high temperature it happens much more quickly.
The toxicity of gasoline is widely known. It is a solvent, causes cancers, nausea, brain damage... probably lots of other things to such as when it is inhaled causing respiratory damage and destroying the sense of taste and smell. (this is known from people inhaling it intentional for fun and then getting sick or sometimes dieing) Although doubtless many oil companies still might like to pretend otherwise this is so well researched there is no dispute.
This is unfortunate because of a real and tangible problem with car engines (or any combustion engine);
No combustion engine is perfect, and some are very far from perfect, thus not all the gasoline in a car's engine, or lawnmower, or leaf-blower, is actually burning. If an engine is designed well and in good condition, MOST (not all) of its fuel is burned, changing structure to (theoretically) less toxic substances before being exhausted. If it is worn, out of adjustment or poorly designed (older engines are typically worse for both reasons) then more gasoline is left unburn, escaping as gas into the air. New engines are better, though even a very "clean-burning" engine eventually becomes less efficient as it is used and knocked around with use. So even if EVERYONE drove new cars that were perfectly tuned, this is still in evidence. In reality, huge numbers of antiquated cars, poorly tuned cars, two-cycle leaf-blower and lawnmowers are throwing out lots and lots of this nasty substance!
All of us that live anywhere near anything burning gasoline are inhaling it every day!
This is why I oppose the automobile, and anything burning gasoline.