Thanks Simon hope ur car is back on the road soon,
On the subject of environmental tooxins...
I doubt you could get enough substance into the body thru ur tear ducts and eye surface to have a significant impact on your health.
the easiest and most common way to get material into your body from atmosphere is inhalation thru lungs (large surface area of fine blood capillaries) then absorption thru skin.
eyes dont have much surface area, u'd be more likely to have irritated eyes before you were poisoned.
just for some trivia... to be classified as "non-toxic" a compound needs to have no effect after being administered at an upper limit level of 2g per kg bodyweight.
which is 150grams of stuff for a 75kg person!!
Cheers
Ed