Lemmy See Your Wrists

Yes, but not because of guns. While the adverse effects of leaded gasoline were known in the 60s and leaded gasoline got banned in most countries, the US only phased it out in 1996. Which means that millions of people alive today are exposed as a child. This has a huge impact on IQ:

The average lead-linked loss in cognitive ability was 2.6 IQ points per person as of 2015. This amounted to a total loss of 824,097,690 IQ points, disproportionately endured by those born between 1951 and 1980.

Albeit, caveat, awry, segue, haphazard, and facsimile are all pronounced weirdly and incorrectly for those who learned a lot of English by reading.