Well, this is an another estimate: https://pubs.acs.org/doi/10.1021/acs.est.6b02910 https://pubs.acs.org/doi/10.1021/acs.est.6b02910 IQ damage of any amount is

Well, this is an another estimate: https://pubs.acs.org/doi/10.1021/acs.est.6b02910 https://pubs.acs.org/doi/10.1021/acs.est.6b02910 IQ damage of any amount is extremely significant and has subtle effects on society which are difficult to economically quantify, and given that many avgas burners basically do it for fun, seems mostly unjustifiable.