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Preschool blood lead levels correlate with later criminality

Long-term, worldwide trends in crime levels correlate powerfully and consistently with changes in environmental levels of lead, according to a new study by economist Rick Nevin. Lead is a potent neurotoxin that is already strongly linked to delinquent behavior (see related articles, Crime Times, 2003, Vol. 9, No. 1, Page 7 and Crime Times, 1995, Vol. 1, No. 3, Page 4).

Lead levels in different countries fluctuated over the past century as these countries increased or decreased their use of leaded gasoline and paints. Using a range of sources, Nevin tracked these changes over several decades in the U.S., Britain, Canada, France, Australia, Finland, Italy, West Germany, and New Zealand. Because different countries used and then phased out lead-containing paint and gasoline at different times, blood lead levels in their populations also rose and fell at different points. Nevin compared these peaks and valleys to trends in crime rates and age-specific arrest rates in each country, predicting that children exposed to higher levels of lead during the crucial preschool developmental years would show higher rates of offending when they reached their late teens and early 20s (the peak years for criminal behavior).

Nevin’s data strongly supported this prediction. “It is stunning how strong the association is,” he commented in the Washington Post. “Sixty-five to ninety percent or more of the substantial variation in violent crime in all these countries was explained by lead.” In particular, murder rates were strongly associated with high rates of severe childhood lead poisoning.

The association between lead levels and crime held true decade after decade, despite important sociological and societal changes. Nevin notes, for example, that his data can explain why juvenile arrest rates in the U.S. skyrocketed in the 1960s (two decades after the dramatic increase in leaded gas usage after World War II), even though the percentage of children living in poverty dropped dramatically during this time. Decreases during the late 1970s and the1980s in the numbers of U.S. children with severe lead poisoning also correlated with dramatic drops in violent crimes during the late 1990s—defying sociologists’ almost-universal predictions of increasing rates for that period—while countries that did not phase out leaded gas until later, such as Britain, had high crime rates in the 1990s.

Nevin says a competing theory by Steven Levitt, which suggests that rising rates of abortion caused crime rates to drop in the 1990s by reducing the number of unwanted children, cannot explain the rise in U.S. crime rates between 1973 and 1991. He also notes, “Britain legalized abortion before the USA, but violent crime rose in Britain and across Europe and Oceana in the 1990s despite rising incarceration rates, rising or unchanged police per capita, and declines in the age 15-19 share of the population.”

Nevin says, “The association between crime and preschool blood lead should lend urgency to global efforts to eliminate preschool lead exposure.” He notes that more than 30 countries still use leaded gasoline, and that children and pregnant women also come into contact with lead through contaminated waste sites, industrial emissions, lead-glazed ceramics, on-the-job exposure, water from old pipes, and other sources.

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“Understanding international crime trends: The legacy of preschool lead exposure,” Rick Nevin, Environmental Research, Vol. 104, No. 3, July 2007, 315-36. Address: ricknevin@verizon.net.

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“Research links lead exposure, criminal activity,” Shankar Vedantam, Washington Post, July 8, 2007.

Related Article: [2009, Vol. 15] [2009, Vol. 15]