Just to clarify on #3 - from my original post: "while much smaller relative to everyone's car running on it". I didn't imply that the lead levels were equal or near to levels when everyone's car was running on it - I tried to state the exact opposite but, I'd clarify, the levels of lead in our environment is still well elevated from what it was prior to the introduction of leaded gasoline and lead is a heavy contaminant like mercury - it accumulates in your body and causes cumulative damage.

And to point #5 - the levels present in our environment directly contribute to how much childhood exposure you'll suffer.