My parents always told me not to eat from the apple trees near the road, because some kind of bad toxic dirt might get through.
This sounds to be physically possible but not really probable in my view. In the time apples grow on the tree they never rot. The rotting procces starts as the apple falls down and damages - the wound will quickly change its colour and it begins to decay - from this I assume the peel is almost perfect defense against bacteria & toxic penetration.
I think the only danger may come from the dust microparticles spread by the cars - which can be easily washed by water or wiped off with a piece of cloth. Am I right? What about other types of fruit?