You still have measurable lead levels in the air. Essentially the rain and gravity brings it down to the ground - mostly concentrated near roadways - where it

You still have measurable lead levels in the air. Essentially the rain and gravity brings it down to the ground - mostly concentrated near roadways - where it mixes with other dust and soil. From there it can then get cycled again into the air by agitation. It is unlike CFC gasses that tend to float up and are no longer present at ground level shortly after they stop being introduced. In this regard you still have lead present in the air in varying degrees 20 years after it stopped being introduced. The report cites 2% of 1990 levels nearly 20 years after it was outlawed.