Many factors cause a person to turn to crime. It may be due to his financial situation, moral upbringing, or even his social background. But did you know that gasoline with lead was thought to have contributed to making an individual turn to a life of crime?

The Lead-Crime hypothesis stated that exposure to lead found in every item like house paint and automotive gasoline could make a person vulnerable to psychological defects. These defects were believed to have led the individual to commit crimes.

The Lead-Crime Hypothesis

Lead, a chemical component used in multiple daily items, has a chemical composition similar to calcium. Lead can penetrate the blood-brain barrier, and it is scientifically proven that if lead finds its way to the brain, especially of a developing child, it can cause significant damage to the organ. It can also severely interfere with the brain’s development, specifically a substantial reduction in IQ and self-control. (Source: Manhattan Institute)

Lead could have also been the silent culprit assisting in the development of criminals, as hypothesized by economic analyst Rick Nevin. In 1994, as a consultant to the US Department of Housing and Urban Development, Nevin was working on a financial analysis of lead paint hazard regulations.

Nevin was researching the costs and benefits of removing lead paint from old houses as researchers at the time were linking lead exposure in children may lead to complications like lower IQ, hyperactivity, behavioral issues, and learning disabilities.

After speaking with a client who suggested that maybe there is a correlation between lead exposure and violent crime, Nevin took on further research altogether, leading him to his Lead-Crime Hypothesis. (Source: Mother Jones)

The hypothesis states that lead exposure at young ages causes problems like learning disabilities, ADHD, and impulse control problems. This causes people to commit crimes as adults, and particularly violent crimes. (Source: Brookings)

The Biggest Source of Lead in the Environment

As Nevin continued his research, he discovered that lead found in the paint used in old houses was nothing compared to the lead content found in automobile gasoline. Lead emissions from vehicles grew steadily from the 1940s until the 1970s.

Researchers charted the rise and fall of atmospheric lead content caused by the rise and fall of lead gasoline consumption. It produced an inverted U-pattern, peaking in the seventies and sharply falling in the eighties due to the Clean Air Act.

Nevin and other researchers noted that the violent crime rates were strikingly similar to the inverted U-pattern of lead gas consumption. The only difference was that the pattern of crime rates was offset to lead consumption by twenty years, supporting the hypothesis that children exposed to high levels of lead were more susceptible to commit violent crimes.

Nevin further hypothesized that violent crime rates are higher in big cities than small towns, and the explanation is that there were more cars emitting lead in a small area compared to cities with fewer cars and more open spaces.

The Clean Air Act helped curb the violent crime rates as lead content significantly dropped. Oil and gas companies adopted more environmentally-friendly materials. (Source: Mother Jones)