Excess manganese reduces brain levels of the neurotransmitters serotonin and dopamine, while increasing serotonin concentrations elsewhere in the body. Both human and animal studies link low brain serotonin to impulsive violence, and altered dopamine levels are implicated in a wide range of aberrant behavior. Despite the bans on leaded gasoline and paint, studies reveal high levels of lead in the soil along heavily traveled urban automobile corridors. Additional sources of lead and other toxic heavy metals include industrial plants, aging public water systems, water pipes within homes, and leaded paint in older homes. Children are particularly susceptible to these toxins, Masters et al.
Research also shows that nutritional deficiencies exacerbate the effects of toxins.
The effects of toxins, the researchers add, are magnified by alcohol. And indeed, Masters' research shows a strong relationship. Masters et al. created a dataset of all U.S. counties, integrating the U.S. Environmental Protection Agency's Toxic Release Inventory for lead and manganese, crime reports from the FBI, alcoholism statistics from the federal government, and socioeconomic and demographic data from the Census Bureau. The converging evidence linking heavy metal pollution to criminal behavior, Masters et al. say, may point crime prevention efforts in new and more productive directions. Encourage vitamin supplementation for children, and particularly for those at serious risk of deficiency.