Pollution is extremely widespread in the United States, as shown in Figure 1, which maps the location of two types of toxic waste sites in the United States in 2015. The blue dots show the location of Toxic Release Inventory sites, which are factories that are required to report their emissions to the Environmental Protection Agency (EPA) because they are using certain EPA-identified toxic chemicals. The red dots show the location of “Superfund” sites, which are the most contaminated federal toxic waste sites. Superfund sites are generally no longer operating, and the EPA is in the process of cleaning them up. Although we do not currently have comprehensive evidence on which pollutants are harmful and what type of exposure causes negative health effects, the evidence we do have is worrisome and suggests a source of inequality that has not yet been explored in depth. Namely, since African American, Hispanic, and low-income families are more likely to live in close proximity to toxic waste sites, where housing is less expensive, it is possible that exposure to pollution—which more affluent families can avoid because they can afford more costly housing—is one mechanism through which poverty produces negative cognitive and health outcomes over time. In the study described in this article, David Figlio, Jeffrey Roth and I examine whether prenatal proximity to Superfund sites is associated with negative cognitive and developmental effects through childhood and into adulthood .1 These effects can have long-term consequences on socioeconomic outcomes such as academic achievement and adult income, as noted in several other articles in this issue including those by Ariel Kalil and Helena Duch in this section, and by Anna Aizer and Margot Jackson in the section on poverty and parenting young children.