On Melissa Harris-Perry on Sunday, the host and her panelists discussed a recent Mother Jones article that presented evidence that lead exposure in children leads to lower I.Q.s and violent crime.
"The rise of emissions from leaded gasoline between the 1940s and the 1970s may have had a significant impact on the increase in crime rates from the 1960s through the late 1980s. When lead emissions went down, so did crime, with the appropriate time lag," Harris-Perry said.
A similar correlation was found for teen pregnancy.
While correlation is not causation, findings show that "even the smallest bit of lead exposure has a significant effect of the I.Q. levels on the children under six."
And, she said, her home in New Orleans lies in the middle of an area that shows high levels of lead in the soil and in old homes.
"Lead emissions mostly affect children, right, so it affects their brain development," said Kevin Drum, political blogger for Mother Jones and author of the lead exposure article. "Now, we've known for a long time that lead affects I.Q. and school scores. But in the last ten years or so, there's been a whole new line of evidence suggesting that it also affects areas of the prefrontal cortex of the brain. And those are areas that affect emotional regulation, judgment, impulse control, aggression. Things like that. All the things that you would think, hey, that might actually lead to more violent crime. And sure enough, when you look at the, when you look at the graphs you put up there, it sure does."
He went on to cite a study that started in 1981 at the University of Cincinnati, which followed 400 children, measuring lead levels in their blood every six months.
"The higher the lead level [in the blood], the more likely to be arrested for violent crime," Drum said.
Harris-Perry asked whether that might simply be because lead levels were higher in areas of poverty and other sociological indicators related to poor school performance and arrests of people "who are more likely to be policed."
Howard Mielke, research professor at the department of pharmacology at Tulane University, said that the most convinced data came from MRIs, which show brain damage in individuals with higher levels of lead as children.
"How much lead does it take to be lead poisoned?" Harris-Perry asked.
"Very small amounts," Mielke said, going on to explain that children exposed to a mere six micrograms of lead daily are a focus of concern.
Harris-Perry voiced concerns over lawmakers and officials who could theoretically one day use that as evidence against people who haven't even yet committed crimes.
Watch the video, via MSNBC, below.