For example, uptake of lead is greatly increased among individuals who have a diet low in calcium, zinc and essential vitamins. Thus, Masters argues, amounts of lead and manganese that wouldn't harm a well-nourished individual may poison undernourished children. The calcium needs of pregnant or breast-feeding women are higher than average, which creates a particular problem for minority women. And non-Hispanic black women get only 467 milligrams of calcium per day, compared to 642 mg for white women, government studies show. Because of increased manganese absorption by babies who drink infant formula and who are not breast fed, Masters considers infant formula toxic.
White infants are more than three times as likely to be breast fed as black infants.
Masters cites studies showing that alcohol increases the uptake of toxic metals, at least in laboratory animals, and probably has a similar effect on humans. If the neurotoxicity hypothesis is valid, then measures of environmental pollution should correlate with higher rates of violent crime. He also examined demographic and socioeconomic variables for each county. As Masters says, neurotoxicity is only one of many factors contributing to violence, but he believes it may be especially important in explaining why violent crime rates differ so widely. Masters says that traditional sociological approaches cannot explain why the availability of hand guns or drugs triggers violent behaviour in only a small proportion of the population, a proportion that varies greatly from place to place.