Looks like 44% of homes (according to the US Census) in the US were built before 1970. The lead paint regulations went into effect in 1978.
That's a lotta potential for lead. I'm looking at a report from 2011, though. In theory that number has gone down a bit, but I'm sure it's not enough to breathe a sigh of relief.
TLDR - Evidence points towards a lead problem in the US.
We have fairly clear evidence that it's still a problem. Lead is a neurotoxin, and childhood exposure is linked to impulsive and violent behaviour. Mass-exposure seems to ramp up the violent crime rate (which is just induction: if
any one person is more likely to become violent due to lead exposure, exposing
everyone to it at the same time should logically lead to a crime wave later on. See evidence on leaded gasoline vs later crime waves).
The stuff also sticks around in the soil and kids ingest dirt or breathe in dust as a kid. In fact one of the lead researchers did a soil survey around New Orleans, and then compared that to the local police's crime hotspots map, there was a good correlation with contaminated soil and violent neighborhoods.
And you have anecdotal evidence: there are studies where they moved some poor families into good neighborhoods, and subsequently the academic performance and behavior of the kids is a lot better. Previously this has been cited as evidence of a
toxic social environment (e.g. blame the poor for holding each other down) but perhaps it's actually evidence of escaping a
literally toxic environment. To the extent that it's social, poor social behavior amplifies itself, however if everyone is
also being constantly dosed with neurotoxins, then the negative effects of the neurotoxins are also being amplified by the social effects.
So it's not like just pipes or paint are all you need to worry about. People living in lead-contaminated environments is an intergenerational catastrophe because of how that stuff causes mental retardation and anti-social behavior. Also, with many black neighborhoods being contaminated by this stuff, racism masks the extent of the problem: the right-wing say they are "naturally" violent and the left wing hold that "the system" makes them violent, while
both sides are missing the rather important element of the poor-mans environment being contaminated with neurotoxins.
Science for the win - once you determine an observable undeniable element, then
it's something you can do something about.https://rationalwiki.org/wiki/Lead-crime_hypothesisOne example is that Sao Paulo in Brazil switched to ethanol instead of gasoline decades ago (because the place is the location of the major sugar refineries and the price of sugar crashed, leaving them with very cheap ), and it was a localized thing. Sao Paolo
alone experienced a large unexplained crime reduction, while all the areas which continued to use leaded gasoline didn't experience any such crime reduction.