Here Masters cites a wealth of studies showing how lead and manganese cause changes in the development of the brain, and in the functioning of neurotransmitters in the brain. Different pollutants harm the brain differently. Lead in the brain damages glia, a kind of cell associated with inhibition and detoxification. Manganese has the effect of lowering levels of serotonin and dopamine, which are neurotransmitters associated with impulse control and planning. Masters emphasizes that children who are raised from birth on infant formula and who are not breast fed will absorb five times as much manganese as breast-fed infants.
Calcium deficiency increases the absorption of manganese.
Masters says toxic metals affect individuals in complex ways. For example, because lead diminishes a person's normal ability to detoxify poisons, lead may heighten the effects of alcohol and drugs. For the neurotoxicity hypothesis to hold up, individuals must receive doses of toxic metals sufficient to be associated with violent behavior. He also argues that aging water delivery systems very likely contribute lead and manganese because lead pipes and even iron pipes contain these toxins. For example, it has been thoroughly documented that uptake of lead is greatly increased among individuals who have a diet low in calcium, zinc, and essential vitamins.