Health and human capital effects of lead exposure
Date
2020
Authors
Keyes, Christopher James, author
Zahran, Sammy, advisor
Mushinski, David, committee member
Cutler, Harvey, committee member
Manning, Dale, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
The legacy of lead in the United States is complex and intertwined with public health. As concerns over the toxicity of lead increased with time, policy makers responded with a series of national policies aimed at minimizing the risk of lead exposure across society. One such policy, the Clean Air Act (CAA), set a timeline for the removal of lead from gasoline beginning in 1975. This policy would target the anti-knock lead additive tetraethyl-lead (TEL), which was used to boost gasoline octane and improve engine performance (Needleman, 2000; Reyes, 2007). Over the following two decades, the flow of lead entering the environment from automobile emissions decreased precipitously. This dissertation exploits a natural experiment in lead exposure arising from the differential phase-out of leaded gasoline across states under the CAA. Though the policy was implemented at the national level, enforcement took place at the producer level, creating exogenous variation in lead emissions from automobile exhaust across states and over time. Since lead dust from automobile emissions was a significant source of lead exposure over the period, we leverage this spatial and temporal variation as a quasi-random vector of lead exposure. Chapter one summarizes the CAA, and the historical significance of the policy as it relates to public health. Using blood lead levels (BLLs) from The Second National Health Nutrition and Exercise Survey (NHANESII) as a bio-marker for lead exposure, this paper models the lead exposure effect of the policy. Combining annual gasoline sales and gasoline lead concentrations at the state level, the steps taken to construct the variables proxying for lead exposure following the CAA are detailed at length. The empirical strategy applied in this chapter is used to identify the causal effect of the phase out on lead exposure, and is carried over in the following two chapters. Much of the research focusing on the effects of lead exposure emphasize the risk faced by children, who are particularly susceptible to even minute quantities in the first five years of life. Chapter two tests the hypothesis that lead exposure in childhood impacts cognitive ability and the presence of abnormal latent preferences toward risk and uncertainty in adulthood. Applying the identification strategy detailed in Chapter one, to a nationally representative sample of individuals born during a period of significant reductions in leaded gasoline emissions, we find considerable evidence supporting the causal effect of childhood lead exposure and later in life outcomes. Across a series of tests, we find that BLLs in childhood are a significant predictor of: 1) IQ loss, measured with standardized test scores; 2) increased likelihood of low-IQ outcomes in exposure levels; and 3) increased abnormal risk response across a series of situations involving uncertain outcomes. The results presented in this paper illustrate the significance and persistent affect of early in life lead exposure. An underappreciated medium of child exposure to flow and legacy sources of lead is in-utero transmission of lead from mother to infant. Transmission of lead to the fetus occurs via diffusion across the placental barrier over the course of a pregnancy. Chapter three estimates the causal effect of maternal lead exposure on birth outcomes during the initial period of the phase out. Results show consistent evidence that fetal exposure to lead through the maternal blood lead pathway significantly depresses infant health. Our findings suggest that an increase in maternal blood lead: 1) decreases infant birthweight; 2) increases the risk of low and very low birthweight; 3) shortens gestation length; 4) increases the risk of prematurity; and 5) increases the risk of a low APGAR score. A back of the envelope calculation of the economic benefits of the phase-out of leaded gasoline through the reduction of healthcare-related costs involved in treating low birthweight infants, are in the tens of billions annually. It might be tempting to assume that lead exposure is a rear-view problem, at least in the United States, as BLLs in children have fallen since the 1990s, coincident with a series of actions that banned lead from paint, plumbing, food cans and automotive gasoline. However, the flow of lead into the environment continues from various point source polluters as well emissions from aviation gasoline used by an estimated 160,000 piston-engine aircraft (Kessler, 2013). Though the benefits to public health attributable to national policies are immense, the stock of legacy lead and present day flow sources of environmental lead remain a persistent threat to public health.
Description
Rights Access
Subject
gasoline
Pb
tetraethyl
lead
emissions
TEL