> We estimate that piston-engine aircraft have consumed approximately 38.6 billion gallons of leaded avgas in the U.S. since 1930, excluding military aircraft use of this fuel, emitting approximately 113,000 tons of lead to the air.
Natural concentration of lead in atmosphere: https://www.dcceew.gov.au/environment/protection/chemicals-m...
Volume of atmosphere: https://www.reddit.com/r/askscience/comments/rf7tn/volume_of...
I'm neglecting the variation in density with altitude and assuming that all that 100 years of aviation lead is still there, so it might be way off.
>>> import pint >>> r=pint.UnitRegistry() >>> usa = r.Quantity(9833517,"km*2") >>> h = r.Quantity(35000, "ft") >>> v = usa * h >>> naturally = r.Quantity(0.1, "ug") / r.Quantity(1, "m * 3") >>> natural_total = naturally * v >>> natural_total.to('ton') <Quantity(11563.6821, 'ton')>
Natural total in USA, up to 35,000ft is 11,000 tons, and added is 113,000 tons.
So the leaded avgas has added 10x.
Assuming uniform distribution up to that height, and that it doesn't disappear. Neither of those things are true, especially as the lead is absorbed by people and animals.