“Prevailing theories of violent crime properly implicate a host of social, economic and psychological variables,” says Masters. But these factors alone do not explain why American counties have rates of violent crime that vary from less than 100 to over 3000 per 100,000 population. To explain this variability, Masters decided to focus on two metals: lead and manganese. Both were plentiful in some parts of the country but not others. Furthermore, there was solid scientific evidence that both could alter brain chemistry in a way that could cause learning disabilities, poor impulse control and aggressiveness, he says. Recent research has strongly linked lead with lower IQs in some urban children. Prolonged exposure to low levels of lead can also impair a person’s ability to be deterred by the threat of punishment, says Masters. Manganese might not be as well-known as lead, but it too has been associated with behavioral disturbances, including loss of impulse control and outbursts of violent behavior under stress. Like lead, it is pervasive. Neuroscientists believe that manganese inflicts its damage by lowering the amount of serotonin in the brain.
Masters poured over the U.S. Environmental Protection Agency’s Toxic Release Inventory. Breaking this information down county-by- county, he factored in crime report data from the Federal Bureau of Investigation, alcoholism statistics from the Department of Health and Human Services and socioeconomic and demographic data from the Census Bureau. When this massive number-crunching job was done, the findings were nothing short of shocking. “In counties with no reported releases of lead or manganese and below-average deaths from alcoholism, rates of violent crime are below average. That is, 216 per 100,000 compared to the national mean of 298.” By contrast, there were 920 violent crimes per 100,000 in the 52 counties where toxic releases from both metals were present and where there were also above-average rates of alcoholism. Even in counties with a below-average number of alcohol-related deaths, the violent crime rate was about twice as high when lead and manganese were present. The effect of metals and other compounds that damage nerve function may be especially important in explaining why rates of crime have differed so widely by geographical region and by ethnic group, he says. “Our analysis shows that neurotoxic metals significantly contribute to rates of violent crime.”
First Posted: THURSDAY, SEPTEMBER 4, 2008