The Molecule Made Me Do It

Several weeks have passed since the Michigan Primaries, and as the cameras and political spotlight left the state, the country that was once so outraged by the lead levels of Flint’s water has largely turned its attention to other issues. Meanwhile, the residents of Flint continue to work to improve their water quality, and they are turning their focus to combatting the future effects of the poison that entered their bodies and brains through the kitchen faucet. This post is the first of several that will explore the current state of knowledge about lead, its effects, the severity of the problem, and how it can be solved.


The country has, for the most part, accepted that lead is a substance we do not wish to find in the body. The public health community has achieved success in limiting our exposure by outlining some of the impacts that it has on our health. Lead has been removed from gasoline and paint in line with goals set forth by organizations like the CDC. At the Center for Health Advancement, though, we look beyond the health impacts to find how interventions affect our health and other sectors, like education and crime. Here, we explore how the effects on our health contribute to the effects on crime.


The 1960s, ‘70s, and ‘80s saw dramatic increases in crime, followed by steep declines in the ‘90s and 2000s. The criminology and sociology fields have offered myriad explanations, from New York’s use of the Broken Windows Theory, to abortion rates, to the War on Drugs, to economic cycles. It was only in the last decade or so that economists and public health researchers started analyzing the role that lead toxicity may have played in the rise and fall of crime across America and internationally. Now, even the Brennan Center for Justice at New York University School of Law, which focuses on poverty, policing, and incarceration, has highlighted studies that indicate reductions in lead levels have caused over half of the reduction in crime seen in the past 25 years.


The evidence connecting lead levels in blood to criminal activity is startling and rapidly growing. It started with a realization that the rise and fall of crime rates mirrored that of lead levels almost perfectly, just 20 years later. A regression analysis indicated that lead levels could explain approximately 90 percent of the variation in crime levels 23 years later at the national level. Certainly, though, one correlation does not necessarily indicate causation. These results were tested by assessing the relationship between lead and crime at the state, city, neighborhood, and even individual level within the United States and across other countries that had data for both crime and blood lead levels. Time after time the results showed this consistent association in which higher levels of lead in the blood were connected to higher rates of crime in the future.


The research challenged a number of ideas that had been held as fact. Everyone knew that big cities had higher crime rates that smaller ones. Most assumed that there was just some urban characteristic that led city-dwellers to commit crimes. However, it was found that larger cities tended to have higher traffic density and thus higher rates of lead being spewed from exhaust as the cars burned leaded gasoline. Once lead levels were reduced, and the disparity in levels was mostly wiped away, it turned out that the size of a city could not actually predict the level of crime therein.


Not all of the research is based on these population-level studies. The neuroscience field has analyzed the ways in which lead actually interacts with the brain to yield some of these results. Lead simultaneously impedes the development the prefrontal cortex (the area of the brain responsible for regulating emotions, controlling impulses, and paying attention) and inhibits the ability of different parts of the brain to communicate with each other. With that information, it becomes easier to understand how the inability to control emotions or impulses might lead an individual to commit the types of violence observed in these crime rates.


Ultimately, lead is toxic and has devastating effects on an individual’s health and mental development, especially in young children. However, beyond those effects, the mental impact can contribute to the likelihood that an individual with lead exposure will commit crimes. This is indicated by chemical, neurological, and population-based studies.


Lead is a forcing factor in public health. Add more and public health gets worse; take it out of the environment and health outcomes improve. You can talk all day about individual solutions—midnight basketball, longer prison sentences, gun control, anger-management classes—but the real reason crime went way up and then came way down is because of contextual factors, and the single most important contextual forcing factor is lead.


Even after the spotlight has turned away from the water in Flint, lead is continuing to get a lot of attention. Let’s hope that this attention makes a difference for the many communities still suffering from a public health hazard that’s been overlooked for too long.

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