Executive Summary

Pollution exposure in the United States is extremely common and widespread. Many of the Toxic Release Inventory and Superfund sites that the Environmental Protection Agency monitors are located near population centers. African American, Hispanic, and low-income families disproportionately live and attend school near pollution sites.  In addition, these groups are more likely to live in older homes with degrading paint and pipes that release lead into air and drinking water. Proximity to pollution sites and lead in homes causes cognitive impairments, behavioral issues, and lower test scores among children. Over a lifetime, these deficits in human capital accrue through lower educational attainment, wages, and productivity. The prevalence of pollution exposure is a significant obstacle to improving health, education, and economic growth in the United States.

Given these effects, effective regulation of pollution is an investment in economic growth and productivity. To maximize the benefits of interventions, they should be targeted at cleaning up pollution near cities where the greatest numbers of people are exposed. Targeting early stages of cognitive development, from gestation through childhood, would also allow for better long-term outcomes. Finally, any plan to reduce pollution should account for multiple sources of pollution by using a variety of strategies, such as the following:

• Raise Clean Air Act standards to close racial gaps in pollution exposure
• Change zoning laws to keep children, schools, and daycares away from toxic sites
• Accelerate cleanup of Superfund, Toxic Release Inventory, and other toxic sites.
• Remediate homes with flaking lead paint to reduce blood lead levels in children
• Increase lead screenings for children and use results to target homes for remediation
• Use infrastructure spending to replace HVAC systems in schools and lead pipes in homes

Introduction

Millions of tons of hazardous waste have been produced in the United States in the last 100 years and have been dispersed into the air, into water, onto land, and under the ground. 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 (TRI) sites, which are factories or government facilities that are required to report their emissions to the U.S. Environmental Protection Agency (EPA) because they are releasing certain toxic chemicals that are known to be harmful to human health. The red dots show the location of Superfund sites, which are the most contaminated federal toxic waste sites. ¹ 1The Comprehensive Environmental Response, Compensation, and Liability Act (P.L. 96-510, 1980), which is now known as Superfund, is the largest and most expensive federal program to clean up toxic waste in the United States. Superfund sites are toxic waste sites bad enough that the EPA puts them on a National Priority List, and if potentially responsible parties refuse to participate, is ultimately responsible for cleaning them up. There are currently about 1,344 Superfund sites and 21,800 TRI sites operating across the United States. 221.5 million people had a TRI site operating in their zip code in 2016. Nearly 22% of all public schools were within one mile of a TRI facility in 2016, and these sites exist in both urban and rural areas.

FIGURE 1

Although we do not currently have comprehensive evidence on which pollutants are most harmful, the evidence we do have is worrisome and suggests a source of inequality that has not yet been explored in depth. African American, Hispanic, and low-income families are more likely to live near sources of pollution like toxic waste and TRI sites. ² 2See, for example, Banzhaf, Ma and Timmins (2019) for a review of the environmental justice literature showing that Black, Hispanic, and low-income individuals are more likely to live near toxic sites and other sources of pollution. There is growing evidence that exposure to pollution is an important mechanism through which poverty produces negative cognitive and health outcomes. In addition to having worse quality school buildings, children who attend school near a major highway are also more likely to be low-income or Black than children attending school elsewhere (Heissel, Persico and Simon 2021). ³ 3Air pollution from cars and trucks is much higher closer to a highway. In Florida, 32% of children who attend school near a major highway are Black, compared with 22% of the overall state population. Low-income, Black and Hispanic children are also more likely to live near Superfund sites and to attend school near TRI sites (Persico, Figlio and Roth 2020; Persico and Venator 2021). Thirty-three and a half percent of children in families in Florida living near Superfund sites are Black and 38.2% are Hispanic, as compared with 22% and 24% of the overall population (Persico, Figlio and Roth 2020). Low-income children are up to 12 times more likely to have elevated blood-lead-levels than their wealthier peers (EBLLs) (CDC 2005; 2014), ⁴ 4I define a child as having an elevated BLL (EBLL) if their highest BLL is ≥5 µg/dL, the upper reference interval value per the 2012 guidelines by the Centers of Disease Control and Prevention for lead poisoning (CDC 2013). I use the terms “elevated BLL” and “lead poisoned” interchangeably. and African American children ages 1–5 are more than twice as likely to be lead-poisoned than their white peers (CDC 2005). In addition to being more likely to live near toxic sites, low-income individuals might be less able to avoid exposure to pollution, for example, by buying an air purifier (Graff Zivin and Neidell 2013).

Why should prenatal and early life exposure to pollution affect long run outcomes? According to the “fetal origins” hypothesis, prenatal health conditions can have large impacts on health and brain development that reverberate into adulthood (Currie and Almond 2011; Currie, Almond and Duque 2016). Such effects are persistent and occur through “fetal programming” that occurs in the womb through brain development or epigenetic mechanisms, which are just beginning to be explored. The basic idea is that pollution might interfere with the translation of genes into proteins in a way that affects brain development and later health. A large literature has shown that early life experiences matter to a variety of health and other (non-health) outcomes, such as IQ and wages (Almond, Currie and Duque 2016). In Section II, I discuss how children are exposed to lead and other types of toxic pollution. In Section III, I review the empirical evidence on lead, how exposure to pollution affects children’s long run outcomes, and how pollution might shape the macroeconomy. In Section IV, I discuss the evidence surrounding different potential ways to intervene, taking into account costs and benefits of different approaches. Finally, I draw some conclusions from these studies of pollution and policy recommendations in Section V.

How children are exposed to lead and other types of mixed toxic pollution

Children and adults are exposed to harmful pollution in a variety of ways, including air pollution from cars, power plants, and factories that surround schools and homes. However, I will focus on lead pollution since there is more evidence that lead is especially harmful to human development. TRI sites like coal-burning power plants often emit lead into the air, which is also a byproduct recycling, mining, and other industrial processes. Superfund sites and brownfields also contain lead, ⁵ 5Brownfields are another type of polluted site that are not considered toxic enough to be admitted to the National Priority list. so people might unwittingly walk on contaminated soil, which they then track back into their homes. Lead also pervades the soil near roadways and in cities because gasoline contained lead until it was gradually removed beginning in 1978 (Currie and Aizer 2017; Reyes 2007).

Since the de-leading of gasoline, lead-contaminated household dust is considered the most important high-dose source of lead for children in the United States today (Lanphear et al. 2002; Zartarian et al., 2017). Much of this is due to the degradation of interior paint, especially in housing built before legislation was passed in 1978 that required manufacturers to remove lead from paint. However, lead can also be tracked into homes through contaminated soil or nearby industrial sources.

Besides degraded paint and contaminated soil, lead is also found in the pipes of a substantial number of American households. According to the EPA, an estimated 6.5 million to 10 million homes and businesses nationwide still get water through older service lines that contain lead (EPA 2016). These lines could potentially expose children to lead unless the water is treated or compounds are added to coat the pipes’ interior to prevent lead from leaching. Unfortunately, there are no nationwide empirical studies that compare exposure to lead through water versus lead dust, so it is difficult to gauge how important the contribution of lead pipes is to overall lead poisoning in children in the U.S.

Recently, the water crisis in Flint, Michigan became emblematic of the problems associated with lead pipes in low-income areas. In 2014, Flint decided to switch its water source from Lake Huron to the more corrosive Flint River as a cost-saving measure. Unfortunately, Flint did not use anticorrosive agents to prevent the more acidic water from leaching lead out of the local pipes, which were largely made of lead. In addition, the new water source contained Legionnaire’s disease, which was not removed before the water reached residents. Grossman and Slusky (2019) find that after the Flint water switch, fertility rates decreased by 12% and there was a 5.4% decrease in birth weight. Low birth weight is associated with increased risk of childhood disability and worse long run outcomes (Black, Devereau and Salvanes 2007; Elder et al 2020). The experience of Flint residents is only one example of the damage caused by lead contamination and a small fraction of the total costs nationwide.

Background: The Link Between Pollution and Long Run Economic Outcomes

A variety of causal papers have examined how pollution in particular affects human capital outcomes, like educational attainment, health, mortality, and wages, even at levels below current regulatory standards (Graff Zivin and Neidell 2013). Because pollution exposure is not randomly assigned, the papers I summarize here use natural experiments to estimate the causal effects of pollution on a variety of outcomes. A natural experiment is a situation in which some external event, such as the cleanup of a toxic waste site, or an idiosyncrasy like the direction of wind on a given day, or a sudden unexpected change in policy “assigns” participants randomly to potential treatment and comparison groups. The idea is that researchers can use this as-good-as-random variation from something that happens unexpectedly to identify the effects of a treatment like pollution on outcomes. Natural experiments allow researchers to estimate treatment effects in circumstances such as pollution exposure where random assignment is impossible or unethical.

A growing literature has shown that children exposed in utero to pollution exhibit higher infant mortality (Currie and Neidell, 2005), lower birth weight (Currie et al., 2015), and a higher incidence of congenital anomalies (Currie, Greenstone, and Moretti 2011). Pollution exposure also increases mortality among the elderly (Anderson 2020; Deryugina et al 2019; Hollingsworth and Rudik, forthcoming). In addition, there is evidence in the medical literature that certain types of pollution (like lead) might interact with genetic factors to produce poor academic performance and cognitive disabilities, such as specific learning disabilities, speech and language impairments, intellectual disability, and autism (Miodovnik, 2011; Jurewicz et al, 2013).

However, a growing literature also shows that prenatal pollution exposure affects children’s outcomes in school. Almond, Edlund, and Palme (2009) study the effects of fallout from the Chernobyl nuclear accident on schooling outcomes in Sweden. They find that children who were exposed to airborne radiation during gestation have worse academic outcomes later in childhood. Sanders (2012) finds that higher county-level measures of air pollution during gestation (making assumptions about location and timing of birth) in Texas negatively affects later test scores. Bharadwaj, Gibson, Graff Zivin, and Neilson (2017) compare Chilean siblings’ differential exposure to air pollution during gestation during a period of rapid economic development in Chile, making use of three air quality monitors in Santiago. They find that children exposed to more carbon monoxide (and correlated pollutants like coarse particulate matter [PM₁₀]) air pollution during gestation have worse test scores in school than their siblings. An increase of one standard deviation in carbon monoxide (CO) leads to a 0.034 standard deviation decrease in fourth grade math scores.

Other recent studies investigate the effects of postnatal exposure to hazardous waste on cognitive development. Aizer, Currie, Simon, and Vivier (2015) exploit a change in Rhode Island’s rules regarding residential lead abatement to investigate the effects of lead exposure in early childhood on children’s test scores. Rau, Urzua, and Reyes (2015) conduct a difference-in-differences analysis using a case study from a toxic dump in Arica, Chile, to study the effects of postnatal exposure to hazardous waste on academic achievement. These studies find evidence of deleterious effects of exposure to air pollution, nuclear fallout, and lead on children’s human capital development.

In one recent study, David Figlio, Jeffrey Roth, and I use population-level data on all children born in the state of Florida between 1994-2002 to examine whether prenatal exposure to Superfund sites is associated with negative cognitive and developmental effects later in childhood. We compare siblings who faced different toxic exposures during gestation because the EPA cleaned the local Superfund site between births. We find that prenatal exposure to Superfund pollution has long-term consequences on outcomes such as academic achievement, behavioral incidents in school, repeating a grade, and cognitive disability when compared with the unexposed sibling in the same family.

The effects were relatively large in magnitude. Children living within two miles of an uncleaned Superfund site had a 23% increase in the likelihood of cognitive disabilities including learning disabilities, autism, intellectual disability, and speech and language impairments. They also had a 42% increase in the likelihood of being suspended from school and a 45% increase in the likelihood of repeating a grade relative to the average for public school children in Florida. The effect on test scores was about one-third to one-half of the estimated effect of being in a small class in the famous Project STAR experiment (Krueger 1999).

Some recent studies find that contemporaneous school bus pollution affects students’ test scores and respiratory health (Austin, Heutel and Kreisman 2019; Beatty and Shimshack 2011). Retrofitting 10% of school bus engines to be cleaner increased English test scores by 0.009 standard deviations. Currie et al (2009) also finds that days of high carbon monoxide increase absences from school. Marcotte (2017) also finds that students score 1%-2% lower on math and reading scores on days of high particulate matter and pollen on the day of the exam.

In another recent paper, Joanna Venator and I explore what happens when a Toxic Release Inventory site opens or closes near a school. There are currently about 21,800 TRI sites operating across the United States, and the EPA estimates that 59 million people (about 19% of the population) live within one mile of a TRI site (EPA 2014). We find that nearly 22% of all public schools were within one mile of a TRI facility in 2016. Using detailed Florida public school data, we assess how children’s outcomes change when a TRI site opens or closes within a mile of their school. The comparison group is composed of students attending schools between one and two miles away from a TRI site at the same time in the same zip code. We find that exposure to pollutants in schools has significant, negative impacts on test scores and being suspended or absent from school.

We also find that a TRI site opening within one mile of a school is associated with lower performance on school accountability measures, meaning that there is an increase in the likelihood that a school’s ranking on these measures drops one or more levels. These findings reveal that even short-term exposure to pollution after early childhood causes test scores to drop. This suggests that pollution could be harmful to children at all stages of development. In addition, assigning rewards and sanctions to schools based on test scores raises important questions of fairness, particularly if the schools serving the highest fractions of Black or low-income children are the ones most affected by local pollution.

Over 6.4 million U.S. children attend public school within 250 meters (about the length of three American football fields) of a major roadway. In another new paper (2021), David Simon, Jenni Heissel, and I investigate pollution exposure of students who graduate from elementary to middle school or from middle school to high school. We compare children who switch from a school that is upwind from a highway to a school that is downwind of a highway and find that attending a school downwind of a highway is associated with a 0.04 standard deviation lower test scores, a 4 percentage point increase in behavioral incidents, and a 0.53 percentage point increase in the rate of absences over the school year. Children who attend school near a major highway are again more likely to be low-income or minority than children attending school elsewhere. My research demonstrates how proximity to major sources of pollution worsens educational outcomes in the United States.

EVIDENCE ABOUT LEAD POISONING

A growing literature indicates that low-income children are more likely to live near sources of toxic waste (Currie, Greenstone, & Moretti, 2011; Persico, Figlio, & Roth, 2016) and up to 12 times more likely to have elevated blood lead levels (EBLLs) (CDC, 2005; 2014). Recent research highlights the deleterious effects of EBLLs on children’s brain health (Meyer, McGeehin, & Falk, 2003), as well as on educational and behavioral outcomes (Amato et al., 2013; Ferrie, Rolf, & Troesken, 2015; Gazze, 2016; Miranda, Maxson, & Kim, 2010; Nilsson, 2009). Children who swallow or breathe in large amounts of lead from pipes, pollution, paint, soil, and many other sources can develop widespread brain damage that causes encephalopathy, coma, and sometimes death (Meyer, McGeehin, & Falk, 2003).

Even low levels of lead exposure have been linked to negative educational and behavioral outcomes, like lower test scores, suspensions from school, and crime (Aizer et al. 2018; Aizer and Currie 2017; Blackowicz et al. 2016; Feigenbaum and Muller 2016; Ferrie, Rolf, and Troesken 2012; Grönqvist, Nilsson, and Robling forthcoming). Specifically, Aizer et al. (2015) and Gazze (2016) show that policies aimed at reducing lead hazards in homes are associated with improved test scores and decreased enrollment in special education, respectively. Aizer et al. (2015) use the timing of state policies designed to reduce lead hazards in homes to estimate the effects of removing lead on student achievement. They find that the falling racial gap in childhood lead levels after housing remediation in Rhode Island accounted for half of the total decline in the Black-white test score gap over the same period.

Lead poisoning has also been linked to crime in several high-quality studies. Feigenbaum and Miller (2016) use the pH of water as an instrument for lead exposure at a time when nearly all pipes were made of lead (between 1921 and 1936). More acidic or basic water leaches lead out of pipes, but the pH of water does not affect cognition or behavior otherwise. They find that people living near more lead pipes with more acidic or basic water had higher homicide rates than people living near water with a neutral pH of 7. Reyes (2015) uses the removal of lead from gasoline under the 1970 Clean Air Act as a natural experiment. The regulations were implemented such that there was substantial variation in how much lead was in the air across states over time. Children exposed to lead through gasoline had higher rates of crime in adulthood.

Using population-level data on children’s blood lead levels matched to school records in Rhode Island, Aizer and Currie (2019) find that children who lived in areas of high lead levels in the soil are more likely to engage in antisocial and delinquent behavior in school compared to children who lived in areas with lower lead levels in the soil. Finally, Hans Grönqvist, J. Peter Nilsson, and Per-Olof Robling (2020) use detailed administrative data from Sweden to investigate the effects of removing lead from gasoline. They find that children exposed to more lead had worse academic outcomes and were more likely to commit crimes. While a recent unpublished meta-analysis suggests that there might not be an effect of lead on crime, the paper includes a variety of poor-quality studies that might bias the estimates downwards (Higney et al (2021).

Early life exposure to such pollution has worse effects, including cognitive disabilities (Persico, Figlio, and Roth 2020; Gazze 2016). In a recent paper, Ludovica Gazze, Sandra Spirovska and I (2021) find that because lead-poisoned children have lower achievement, are more disruptive, and engage in risky behavior, lead poisoning might have spillover effects onto children who are not themselves exposed to lead. We show that children attending school with 10% more lead-exposed peers in a cohort are 1.6% more likely to be suspended and 10% more likely to be chronically absent from school. In addition, children with more lead-exposed peers are less likely to graduate high school or take the SAT. We estimate that lead costs $208 billion for a single birth-year cohort. Together, these studies highlight how exposure to environmental pollution is a mechanism through which poverty produces negative cognitive and health outcomes over a lifetime.

EVIDENCE ON HOW POLLUTION AFFECTS LONG RUN OUTCOMES

Evidence on how pollution affects children’s long run outcomes is rarer, but troubling nonetheless. One recent paper shows that children who were exposed to less lead after Sweden removed lead from gasoline were more likely to graduate high school and have higher wages in adulthood (Grönqvist, Nilsson, and Robling forthcoming). Black, Bütikofer, Devereux, and Salvanes (2013) study the effects of radiation exposure in utero from nuclear weapons testing in the 1950s and 1960s. They find that children who were exposed to radiation during gestation had lower IQ scores, educational attainment, and earnings in adulthood. Pollution has also been shown to affect test scores on the day of high stakes exams in Israel, as well as educational attainment and long run wages (Ebenstein, Lavy and Roth 2016). Isen and colleagues (2017) compare cohorts of children in counties with substandard air quality that had to reduce air pollution after the Clean Air Act. They find that cohorts exposed to more air pollution in early life is associated with a 0.7% decrease in the number of quarters worked and a 1% decrease in mean annual earnings. In a recent working paper, Voorheis (2017) also finds that pollution exposure in early life is associated with modestly lower college attendance and wages.

In a new working paper, I compare siblings who were in utero before and after a Toxic Release Inventory site opened or closed within one mile of their home. I find that children who were exposed prenatally to industrial pollution have lower wages, are more likely to be in poverty as adults, have fewer years of completed education, and are less likely to graduate high school (Persico 2020). In addition, another recent working paper by Colmer and Voorheis (2020) shows that early life pollution exposure worsens intergenerational economic mobility. In other words, early life parental pollution exposure harms the outcomes of children born to these parents as well. Thus, a growing body of evidence suggests that pollution exposure can cause people to fall into poverty, and potentially, to stay there for generations.

Pollution also affects labor market outcomes, such as hours worked and labor supply. Hanna and Oliva (2011) compare residents before and after a local oil refinery closed in Mexico City. They find that a 1% increase in sulfur dioxide levels decreased hours worked by 0.72%. Carson, Koundouri, and Nauge (2011) use the variability of arsenic levels in drinking water tube wells in Bangladesh to estimate the effect of arsenic on labor supply. They find that arsenic pollution leads to an 8% reduction in labor supply overall, likely because people are getting sick and staying home. Recent evidence has also shown that worker productivity is harmed by air pollution in outdoor conditions (Graff Zivin and Neidell 2012), indoor call centers (Chang, Graff Zivin, Gross and Neidell 2016), investor behavior (Heyes, Neidell and Saberian 2016), and indoor pear packing facilities (Chang, Graff Zivin, Gross and Neidell 2016).  Graff Zivin and Neidell (2012) find that a 10 parts per billion decrease in ozone concentration increases agricultural worker productivity by 5.5%. This implies that ozone levels well below federal air quality standards has a significant impact on worker productivity.

Thus, there is growing evidence that exposure to pollution affects long run outcomes, like educational attainment, IQ, wages, adult poverty, and engaging in work. There is also evidence that pollution affects workplace productivity and labor supply. The effects of early life pollution exposure are also quite persistent, potentially affecting future generations of children.

HOW POLLUTION MIGHT SHAPE THE MACROECONOMY

While the health effects of pollution have been studied for decades, we are just beginning to realize the extent to which pollution impacts educational attainment, worker productivity, disability, and wages. All of these are inputs to the economy generally. In addition, we now know that pollution affects a variety of outcomes even at levels below regulatory thresholds in the United States. Since pollution is so widespread, pollution exposure should be viewed as a factor of production since it negatively influences the way people can produce things. Growing evidence suggests that environmental regulation may also contribute to economic productivity such that regulation can be seen as an investment in economic growth (Graff Zivin and Neidell 2013).

In addition, there is evidence that pollution might contribute to generational poverty, which also affects economic growth. If children’s neurological development is compromised by pollution before they are born, those children potentially will not be as productive as they might have been. They might not invent the next supercomputer or metal alloy. In addition, it is difficult to see how children in the U.S. can have an equal opportunity to succeed if such a large proportion of the population suffers from pollution exposure.

Because there is little work on this topic, it is hard to know how much this impacts innovation and total economic growth in the United States, but the costs are likely to be high. While it is difficult to extrapolate how lead exposure might affect labor market outcomes, my coauthors Gazze and Spirovska and I (2021) attempt a back of the envelope calculation for the effect of one lead poisoned peer in a cohort of 220. We find that being exposed to one additional lead poisoned peer is associated with $71 in lost earnings per student from lower graduation rates alone. This estimate does not include the additional costs of behavioral issues, yet it implies a spillover effect of a lead poisoned child of $15,549 on their 219 school peers. As half a million young children appear to still be poisoned by lead each year (Aizer et al. 2018) and lead-poisoned students appear to be quite dispersed across schools, these spillovers total almost $8 billion per birth-year cohort. Reyes (2014) estimates the direct social cost of lead poisoning at $200 billion per birth-year cohort. Thus, we estimate that the costs of lead exposure are about $208 billion dollars per birth cohort when including the spillover effects of lead (but without including costs to the greater economy). However, this figure does not account for the costs of deaths that pollution causes among infants and the elderly or lost wages (and tax revenues) from this, but there is evidence that both lead and other types of air pollution cause increased mortality among these groups (Hollingsworth and Rudik 2021; Deryugina et al 2019).

A plan for the best way to intervene, taking into account costs and benefits

We now know that pollution can have lasting effects on children who are exposed, even before they are born. We also know that pollution continues to affect adult health and productivity, even at levels currently produced in the U.S. under the Clean Air Act. So, what can we do? There are three general insights from the empirical literature that can help us target our interventions.

First, cost-benefit analysis suggests that reducing pollution in the most densely populated places in the United States will have the greatest net benefit. The more people there are, the more costly it is to have pollution nearby. This is particularly of concern given that pollution has spillover effects onto unexposed children and that in densely populated places there are more interactions with more peers (Gazze, Persico and Spirovska 2021). Thus, it might make sense to have even stronger air quality regulations in cities than in more sparsely populated areas. Unfortunately, most TRI sites that release large quantities of pollution are currently located in and around major cities. Until they are cleaned up, these TRI sites will continue to emit pollution that affects millions of people.

Second, intervening earlier in critical periods of cognitive development like gestation and early life is better. Moreover, there might be dynamic complementarities either in learning, or behaviorally (e.g., parents might reinforce behavior). The basic idea is that because skills beget skills, children who benefit from early investments might benefit more from later human capital investments. These are not well understood, but they could be important to long run outcomes. Thus, pregnant women and children should be targets of interventions to prevent lead poisoning and toxic pollution exposure to prevent negative long run outcomes for young children.

Third, any plan should include a variety of strategies. The sources of pollution that affect outcomes are varied and widely distributed. There is no silver bullet that will solve this problem once and forever. Thus, any plan should consider the variety of possible ways people are exposed to pollution, and solutions to prevent exposure will follow from that.

In the following sections, I discuss some potential solutions. First, I suggest raising the Clean Air Act standards, eliminating the disparities in air quality that exist between different races, and preventing the manipulation of pollution measurement so that we have a more accurate picture of how much pollution there is. Second, I discuss the benefits (and costs) of additional funding for cleaning up Superfund and other toxic sites. Third, there is the potential to change zoning laws to keep schools and daycares away from sources of pollution (and vice versa). Fourth, I review the evidence surrounding remediating homes with lead paint, which is considered to be a primary vehicle for childhood lead exposure. Fifth, I examine the evidence around lead screening programs. Sixth, I discuss the potential for upgrading school HVAC and indoor air quality systems and giving schools drinking water or air filters. Finally, I examine the evidence for replacing lead pipes.

RAISING THE CLEAN AIR ACT STANDARDS

Because many types of air pollution both harm child development and also cause global climate change (due to co-emissions of greenhouse gases), we are discovering that emissions are extremely costly. A recent paper by Shapiro and Walker (2020) finds that policy regulating pollution is more lenient than is efficient in most markets. They recommend tightening pollution standards for incumbents in the market since incumbents face weaker standards than entrants into the market. Alternatively, they suggest charging a facility-specific tax equal to the marginal damages from their annual emissions.

Perhaps the most cost-effective strategy to the problem of pollution in the long run is simply to make the standards under the Clean Air Act more stringent. An important topic for future research would be to estimate where the Clean Air Act thresholds should be, given the recent evidence on how damaging pollution is at current regulatory standards. We should consider strengthening the nation’s air quality standards by lowering the primary annual fine particulate matter (PM_2.5) standard.

However, because pollution exposure is unequal, this would still not solve the problem of environmental justice. Thus, we could revise the way we classify areas with substandard air quality in a racially sensitive way by requiring that pollution exposure be near the same for non-Hispanic whites and non-whites within a state. In other words, we could require the closing of large gaps in exposure between racial and ethnic groups on penalty of fines until the problem is remediated. A similar set of rules exists in the Individuals with Disabilities Education Act (IDEA) for preventing overdiagnosis of disabilities among non-white children. This change would force the closure of many coal-fired power plants, which would further lessen children’s exposure to lead.

The U.S. also needs to take seriously the issue of air pollution measurement manipulation. There has been recent evidence that municipalities strategically place and turn off monitors to avoid Clean Air Act violations, and that true air quality in many places is worse than pollution monitors would indicate. Grainger and Schreiber (2019) find that monitors are often strategically positioned by local regulators to avoid pollution hotspots. In addition, Zou (2021) finds that polluters often engage in strategic behavior with monitoring systems wherein air quality is worse on unmonitored days and that monitors are strategically shut off during times of high air pollution (Mu, Rubin and Zou 2020). To address the bias in pollution monitoring, the EPA could start using satellite data rather than monitors to assess fines and disproportionalities in air quality.

CLEANING UP SUPERFUND AND OTHER TOXIC SITES

About one in four (or >80 million) Americans live within 3 miles of a federal Superfund site (U.S. EPA, 2012), a location with particularly high levels of environmental toxicants, and about 11 million Americans, including 3-4 million children, live within one mile of a Superfund site (Steinzor and Clune, 2006). Recent evidence suggests that prenatal exposure to Superfund sites leads to worse academic outcomes and a greater likelihood of cognitive disabilities, and that low income, Black, and Hispanic children are more likely to live nearby (Persico, Figlio and Roth 2020).

According to our back-of-the-envelope calculation, the Superfund program would pay for itself in 38 years through reduced special education costs for specific learning disabilities alone. ⁶ 6We calculated this estimate assuming that the typical Superfund site would cost $27 million to clean up over nine years, and relying on Chambers et al.’s (2003) estimate that the spending ratio for a child with a specific learning disability (SLD) is 1.6 relative to the average “regular education” student; that a typical child with a SLD receives special education services for the SLD for eight years; and assuming a four percent annual discount rate. However, this calculation is fairly conservative. It does not take into account other potential co-benefits, such as raised test scores, housing values, educational attainment, and reduced cancer rates. Thus, the Superfund program is likely quite cost effective and should be well-funded so that site cleanup can proceed more rapidly. (The average length of a Superfund cleanup for sites within 2 miles of children in our sample was 7.7 years). One could also consider funding the cleanup of other types of toxic sites that did not make it on to the National Priority list, such as CERCLA brownfield sites.

CHANGING ZONING LAWS TO KEEP SCHOOLS AND DAYCARES AWAY FROM SOURCES OF POLLUTION (AND VICE VERSA)

Another lower-cost option for reducing children’s exposure to pollution is through zoning. Stricter regulations on where new point source emitters are allowed to locate would prevent industrial sites that plan to release large amounts of pollution from opening near schools and large population centers. Likewise, changing zoning laws could keep schools, daycares, obstetrics, neonatal wards, children’s hospitals and the like in population dense places away from sources of pollution.

REMEDIATING HOMES WITH LEAD PAINT

Given that the primary source of lead exposure in children is believed to be from lead paint, it stands to reason that remediating homes with flaking lead paint might lead to the biggest benefits. Furthermore, we can target such remediations based on the likelihood of having lead paint in the home based on housing age. The U.S. Department of Housing and Urban Development (HUD) estimates that 87% of houses built before 1940 in the U.S. have lead paint, compared to 69% of houses built between 1940 and 1959 and 24% of houses built between 1960 and 1977 (HUD, 2011).

Several studies have estimated the effects of lead abatement programs on blood lead levels in children. Sorensen et al. (2019) compare outcomes in counties before and after they implemented lead hazard control grants and find that fewer children were lead poisoned and test scores improved after counties implemented lead hazard measures. Clark et al. (2011) examined the effects of HUD-supported interventions in housing and found that after the interventions between 22 and 43% of children had reduced blood lead levels (except for children with normal blood lead levels below 6 μg/dL at pre-intervention) over the next three years. Another study found that homes with all replacement windows had 41% lower interior floor dust lead levels, with windowsill dust lead levels being 51% lower (Dixon et al. 2012). Galke et al. (2001) evaluated lead hazard control grants in the Northeast and Midwest regions. They found that immediately after the intervention, floor and window lead dust decreased about 50% and 88%, respectively. One year later, resident children’s age-adjusted blood lead levels had declined from 11.0 to 8.2 μg/dL. In another paper, Leighton et al. (2003) found that mean blood lead levels of children in remediated New York City housing declined significantly from 24.3 to 12.3 μg/dL at a 10- to 14-month follow-up.

However, Gazze (2020) simulates the impact of several lead screening policies, as well as remediations. She finds that remediating homes only after finding children with elevated blood lead levels there (as it is currently prescribed in many states) is not cost effective because of the uncertainty in turnover of residents at each address. Gazze (forthcoming) also finds that state lead abatement mandates lead to families with children being 11.3% less likely to live in old houses, and that these mandates decrease the prices of old houses by 7.1%, with little evidence that most of these mandates actually induce remediations. Thus, these mandates have important distributional consequences, with lower income families more likely to live in older homes. Any future lead remediation policies should account for potential distributional effects on lower income residents.

LEAD SCREENING

Another concern is that most children are still not being tested for lead. While the Centers for Disease Control and Prevention (CDC) recommends that children be tested before 72 months of age via a blood test in a doctor’s office, according to the CDC in 2017, only 18.7% of U.S. children were tested for lead. While Medicaid mandates that children be tested and several states have created universal testing areas, in empirical studies, there is still relatively low compliance of less than 60%, even given universal screening mandates (Gazze 2020; Gazze, Persico and Spirovska 2021).

Free, universal lead screening could help solve this problem, particularly in areas that are likely to have lead hazards based on having more houses built before 1978. Gazze (2020) finds that households are sensitive to the distance to lead screening providers and that opening a lead testing provider in every zip code without a provider would increase lead screenings and prevention efforts. Gazze (2020) also finds that incentivizing screenings for lead by providing households with an incentive, such as a travel subsidy, might be a cost-effective way of identifying and preventing lead poisoning.

Testing children for lead poisoning can also be used to target houses for lead remediation. At least one program like this exists in North Carolina, and Billings and Schnepel (2018) find that interventions that reduce children’s exposure to lead are associated with positive long-run outcomes for those children. They find that children who qualify for the program have a 0.184 standard deviation decrease in antisocial behavior for adolescents and a 0.117 standard deviation increase in primary and middle school educational performance, compared to children who just do not qualify for the program. Together, these studies show the benefits of lead screening and the need for greater availability and incentives for lead screening.

UPGRADING SCHOOL HVAC SYSTEMS AND GIVING SCHOOLS DRINKING WATER FILTERS

The COVID-19 pandemic has changed the way we understand building ventilation and its importance in keeping us safe from viruses and bacteria in the air. It has also brought into sharp relief the disparities that exist between school building quality in richer and poorer neighborhoods. According to the Government Accountability Office’s national survey of school districts (U.S. GAO 2020), about 54% of public school districts need to update or replace multiple building systems or features in their schools. They estimate that about 36,000 schools need HVAC updates, and 41% need to update or replace heating, ventilation, or air conditioning. They also find that capital construction expenditures were on average $300 less per student in high poverty districts ($719 per student), compared to low poverty districts ($1,016 per student). This funding disparity reflects fewer resources to spend despite the greater needs of lower income districts in most cases. Whereas wealthier districts make up state funding shortfalls through raising local taxes, high-poverty districts are more likely to rely on state funding and have difficulty making up the difference in lean years.

Why is it so important to invest in school infrastructure now? There is evidence that school ventilation protects children from contracting COVID-19 and other viruses in schools (Prather et al 2020; EMG 2020). Research suggests that COVID-19 spreads in schools in situations where there are high case rates in the surrounding community, and children can still catch COVID-19 in school buildings that are not properly ventilated (Goldhaber et al 2020; Harris, Ziedan and Hassig 2021).

I recently released a causal study with Kathryn Johnson (2021) showing that higher air pollution can make people more likely to get sick with and die from COVID-19. Because air pollution harms the immune system, it can increase the likelihood of infection from airborne diseases. It also can exacerbate existing cases of COVID-19 by harming the immune systems of infected people. We used the variation in pollution caused by a rollback of environmental enforcement during the pandemic to estimate the effects of increased pollution on county-level COVID-19 deaths and cases. We find that counties with more Toxic Release Inventory (TRI) sites saw an 11.8% increase in air pollution on average following the EPA’s rollback of enforcement, compared to counties with fewer TRI sites. We also find that these policy-induced increases in air pollution are associated with a 53% increase in cases and a 10.6% increase in deaths from COVID-19.

So how much might HVAC system upgrades in schools help? In a recent study, Gilraine finds that putting air purifiers in classrooms led to a 0.2 standard deviation increase in test scores for children, compared to children in local schools that did not get the air purifiers (Gilraine 2020). This is similar to the effect of small class sizes in the famous Tennessee Project STAR experiment. He estimates that the annual cost of installing air purifiers throughout a school is $1,000. Similarly, Stafford (2015) finds that indoor air quality renovations at schools in Texas improved test scores by 0.15 standard deviations. This suggests that air filtration, like that offered by modern HVAC systems, could improve children’s academic and behavioral outcomes long after the COVID-19 pandemic has concluded. Low-income children stand to be impacted the most by improvements in air quality, since there is evidence that their school buildings are in worse shape in many places and they are more likely to live near sources of pollution (Persico, Figlio and Roth 2020). While it is difficult to make comparisons across samples, Dahl and Lochner (2012) find that a $1,000 increase in income from the Earned Income tax Credit leads to a 0.06 standard deviation increase in tests scores. This implies that removing pollution might have similar effects to increasing family income by $3,333. Upgrading HVAC systems in schools would stem the spread of COVID in the short term and see long-term improvements in test scores from reduced exposure to pollution.

REPLACING LEAD PIPES

Similar actions could be taken with regard to replacing lead pipes in schools and providing students with water that has been purified through water filters to prevent lead poisoning at school. There is less evidence about how lead pipes lead to elevated blood lead levels and worse outcomes. However, Hanna-Attisha et al. (2015) estimate that the percent of children with elevated BLLs at 5ug/dL or above doubled in Flint from 2.4% to 4.9% after the switch to the Flint River water source. The Flint water crisis has also been linked with lower fertility rates and poorer birth outcomes (Danagoulian & Jenkins, 2018; Grossman & Slusky, 2019; Wang et al., 2018), even though households engaged in avoidance behavior, such as using bottled water (Christensen et al., 2018).

Dave and Yang (2020) exploit a switch in water treatment in one of the treatment plants in Newark, New Jersey, and show that exposure to drinking water contaminated by lead during gestation is associated with worse birth outcomes. In another study, Ferrie, Rolf, and Troesken (2012) use the pH of water as an instrument for lead exposure at a time when all pipes were made of lead. They find that people who lived near low-pH or high-pH water (water that is acidic or basic) had Army General Classification Test scores that were 0.33 standard deviations lower than people who lived in places where the water pH was 7 during World War II.

While it is unclear what the contribution of lead pipes is to total lead poisoning in America, it is still likely that replacing lead pipes is a worthwhile endeavor. An estimated 6.5 million to 10 million homes and businesses nationwide still get water through older service lines that contain lead (EPA 2016), which is likely to affect a substantial number of pregnant women and children.

Conclusions

Given the mounting evidence that pollution is much more harmful to babies, children, and workers than previously supposed, even at current levels, more action should be taken to protect America’s future workforce. Because pollution affects human capital development and worker productivity, it also affects the economy generally. Thus, regulation should be seen both as a vital public health intervention as well as an investment in our economy.

The best course of action would be to utilize a variety of strategies, such as those I have outlined here. Of the possible courses of action, raising the Clean Air Act standards and making those standards more racially sensitive is likely to have the biggest impact on the largest number of people. There is ample evidence that pollution regulation is inefficient from being too lax and that more stringent measures would strengthen America’s health and productivity. This is especially true because air pollution has been increasing in recent years, as shown in Figure 2. While PM_2.5 pollution had been falling for years, it began rising again in 2017. Clay and Muller (2021) find that pollution has increased 5.5% overall in the U.S. since 2016, which coincided with a decline in enforcement. Furthermore, NOAA (2020) reported that atmospheric carbon dioxide just reached the highest monthly reading ever recorded in May 2020 at a time when pollution was expected to fall because of the COVID-19 pandemic.

FIGURE 2

Second, changing zoning laws to keep children, schools, and daycares away from toxic sites is likely to yield substantial benefits. We need to stop putting pollution-emitting sites near places where children and pregnant women congregate. Third, cleaning up Superfund and other toxic sites more quickly is likely to yield substantial returns on investment in terms of future wages and productivity. Fourth, remediating homes with flaking lead paint so that future children are not poisoned and increasing lead screenings to identify children who have been lead poisoned are likely to be very beneficial. In addition, states should use lead testing results to target homes for remediation.

Finally, there are two beneficial interventions supported by President Joe Biden’s infrastructure bill: upgrading school building facilities, like HVAC systems, and replacing lead pipes. There is also debate over whether these things should be part of President Biden’s infrastructure bill. ⁷ 7Wasson, Erik. “Biden Infrastructure Plan’s Chances Gain as GOP Preps Offer.” Bloomberg.com, May 17, 2021. While replacing lead pipes might not be as impactful as some of the other interventions I outlined, it is likely worth doing, especially if we can replace pipes in a targeted way in municipalities where the water utilities have worse records of corrosion control. In addition, the evidence suggests that improving school building quality stands to be both a timely and wise investment that is likely to pay dividends in years to come.

The overall cost of pollution in the U.S. are extremely high in terms of worse health and educational outcomes for children, lost productivity for workers, and unrealized innovations from effected populations. Fortunately, the price of mitigating pollution is small relative to the potential gains to be made. Higher environmental standards, cleaning up TRI and Superfund sites, and removing sources of lead in older homes will go a long way to building human capital in the U.S.

Table 1: Outcomes of Pollution Exposure

[table id=7 /]

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