Two papers for your reading:

* March 2022 - https://www.pnas.org/doi/full/10.1073/pnas.2118631119 - "Half of US population exposed to adverse lead levels in early childhood"

* October 2011 - https://ehp.niehs.nih.gov/doi/10.1289/ehp.1003231 A Geospatial Analysis of the Effects of Aviation Gasoline on Childhood Blood Lead Levels

The two papers (plus others) taken together suggest that the impact is measurable (paper 2), perhaps to the tune of one or two IQ points on average per person exposed (me drawing a line from paper 1).

Granted, the latter point is my extrapolation, but there's enough of a foundation now for policy decisions to be made in advance of explicit research connecting these dots.