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When crime rates dropped sharply and unexpectedly across the United States during the 1990s, many were left baffled at the precipitous plunge. Though city officials may be quick to credit police efforts, there’s another theory gaining momentum. According to Lauren Wolf’s new article for Chemical and Engineering News, studies show that lead exposure may have caused spikes in criminal activity. The toxic substance was banned and regulated in the 1970s, which could account for the drop in violent crime.

lead poisoning, lead exposure, 1990s crime rate, criminal behavior, violent crime, Chemical and Engineering News, lead-induced crime, lead ban, EPA lead ban, lead-based paint,Image via Wikimedia

In 1973, the EPA instituted a ban to phase out all lead in gasoline, which resulted in a dramatic 98 per cent reduction of lead levels in the air. Five years later, lead-based paint was also banned from being used in newly built homes. As a result, children who were born before the ’70s and reached adulthood in the ’90s were exposed to greater levels of lead exposure than children born later. Those children, says Wolf, grew up “with healthier brains and less of a penchant for violence.”

Experts believe those dramatically reduced levels of lead poisoning in children born after the 70s could explain the plunge in crime rates. Though critics point out that correlation does not necessitate causation, scientists say that it’s more than just a coincidence, citing studies that lead poisoning causes greater aggression in lab animals. In addition to the possibility of triggering violent tendencies, researchers have long observed other lead-induced neurological damage, such as lower IQ scores, kidney damage, and antisocial tendencies.