The figure below, borrowed from Matthew Yglesias, shows that poor children, especially poor black children, have higher concentration of lead in the blood than other middle class children.
Lead poisoning is a serious problem, causing cognitive delay, hyperactivity, and antisocial behavior. If poor children do less well in school and on standardized tests, it may be, in part, because of the environmental toxins to which they are disproportionately exposed.
See also a previous post in which I argue that lead poisoning remained a mother’s problem until the China toy scandal put middle class children at risk, at which point the state stepped in to ensure children’s safety.
Also see this post on race and toxic release facilities.