The role of the environment in criminal behavior
Police and prisons aren’t the only ways to fight crime; economist Rick Nevins found a direct causality between atmospheric lead (created primarily by leaded gasoline emissions and lead paint) and criminality as well as other deleterious psychological, physical, and behavioral effects. The causality is so blatant that Tulane University researchers Howard Mielke and Sammy Zahran found that when neighborhood maps of lead contamination and crime statistics in New Orleans were overlapped, they were nearly identical.
Economy and police tactics is not enough to explain the drop in violent crimes
New York City and many other urban centers across the United States saw dramatic drops in relatively high violent crime rates over the past two decades. Former mayor Rudy Guiliani and his Compstat-loving police commissioner Bill Bratton credited tough police tactics, “broken window” strategies (the idea that cracking down on smaller crimes deters larger, more violent crimes), and maintaining a comprehensive database of crime statistics with the exponential drop in crime across NYC. But violent crime reached its zenith in 1990 and was already in a steady decline by the time Guiliani and Bratton came to power. Cities in other parts of the country were statistically following suit too, only without NYC’s beefed-up policing. Criminologists used economic factors, Roe v. Wade, population size, the prison industry, and crack cocaine’s declining popularity in an attempt to explain falling urban crime rates, but none of them held the same econometric consistency or merit as Nevin’s lead contamination theory. Several case studies that had the informational luxury of tracking subjects from womb to adulthood found that childhood exposure to lead almost always resulted in adults more prone to violent criminal tendencies.
The drop in blood lead contamination
The time frame also coincided perfectly. Children in the 1940’s and 50’s were exposed to the greatest amounts of atmospheric lead and later grew up to commit violent crimes in the late 60’s through the 1980’s. Lead wasn’t removed from gasoline until the EPA passed the Clean Air Act in 1970, which subsequently saw blood lead levels in children falling by 75% between the years 1976 and 1991. And because blood lead contamination has been linked to reduced IQ levels and aggressive and delinquent behavior, statisticians saw crime rates falling with lead levels. The phenomenon was not limited to New York City or even the United States either; Nevins found that in places like Australia, West Germany, Canada, Finland, and the United Kingdom, blood lead level graphs always matched up to violent crime graphs. Households and neighborhoods with high levels of lead contamination also have environmental factors that further contribute to criminal behavior: lower-income neighborhoods frequently fall victim to poor city planning, often being crammed between highways in bleak, industrial sectors of the city where unkempt streets and hallways produce great amounts of lead-ridden dust and debris.
Nevin, R. (2000). How Lead Exposure Relates to Temporal Changes in IQ, Violent Crime, and Unwed Pregnancy Environmental Research, 83 (1), 1-22 DOI: 10.1006/enrs.1999.4045
Reyes, J. (2007). Environmental Policy as Social Policy? The Impact of Childhood Lead Exposure on Crime The B.E. Journal of Economic Analysis & Policy, 7 (1) DOI: 10.2202/1935-1682.1796