Association for Public Policy Analysis & Management

Although industrial plants exist in every major city of the United States releasing billions of pounds of toxic substances annually, there is little evidence about how these pollutants might harm child development. There are currently about 21,800 TRI sites operating across the United States and the Environmental Protection Agency estimates that 59 million people (about 19 percent of the population) live within one mile of a TRI site, including millions of children (EPA, 2014). Although there is sufficient evidence to classify many chemicals as developmental neurotoxicants, and an increasing number of papers show that pollution harms academic achievement (e.g. Persico, Figlio and Roth, 2016; Sanders, 2012; Bharadwaj, Gibson, Graff Zivin, and Neilson (2014); etc.), it is not clear which of these chemicals impact cognitive development the most.

There is increasing evidence that the developing human brain is highly vulnerable to toxic chemical exposures, particularly during the prenatal, perinatal and early postnatal periods, as well as in early childhood (Rice and Barone, 2000; Bearer, 1995). During these sensitive periods, chemicals can cause permanent brain injury at low levels of exposure that would have little or no harmful effects in an adult (Grandjean and Landrigan, 2014; Bearer, 1995). There is also evidence that exposure to neurotoxins early in life may affect cellular growth, maturation, differentiation, and migration pathways, as well as gene expression and synapse formation, in the developing brain. However, much more research on how specific chemicals and combinations of chemicals cause different adverse outcomes in the human brain is needed, since much of this research is done in animals and in vitro cell cultures.

Using population-level data that follows cohorts of children born in the state of Florida between 1994 and 2002, we examine the effects of living near different categories of environmental toxicants by comparing siblings who live within one mile of a TRI site that emits environmental toxicants. Using the timing of plant openings and closings (and family moves), we compare children who are exposed to different types of pollution (i.e. volatile organic compounds (VOCs), heavy metals, or polycyclic aromatic hydrocarbons (PAHs)) to their unexposed siblings to see which types of toxicants are most likely to cause low achievement. We will focus on airborne toxic releases because people living close to a plant may be more likely to be exposed to them than to water or ground releases. We find that living within 1 mile of a TRI site while the site is operating substantially lowers children’s test scores. The results on test scores are largest for heavy metals and Polycyclic Aromatic Hydrocarbons (PAHs).

In addition, different types of toxicants are distributed unevenly across neighborhoods in Florida. Thus, we also examine racial and socioeconomic inequalities in exposure to different types of environmental toxicants. Conditional on living within one mile of a TRI site, Black children and low income children are more likely to live in neighborhoods where TRI facilities emit heavy metals than White and higher income children.