Well honestly, I have to admit, I'd never previously considered the amount of lead added to the atmosphere by meteors. But considering it now... only about 6% of meteors are the metallic variety. I had to look up what the average chemical makeup of these is like, but it appears that they're mostly iron and nickel, with lead making up a small percentage of the remainder, probably less than 1%. So all and all, it doesn't seem like they actually deposit all that much lead.

Conversely, the connection between the use of leaded gasoline and lead levels in the environment is really very well documented and clear. We know that eliminating it from standard gasoline has made a profound difference. The volume of exhaust from small planes is of course dwarfed by the volume from cars and trucks, so the damage that's still occurring is significantly less, but it's still meaningful.

So... I don't have any solid data for you here, but my intuition is that a handful of meteors probably can't add close to as much lead to the atmosphere as millions of vehicles burning leaded gas.