Impacts of Lead Exposure on Health, Fertility, and Education

The Issue:

Lead is both a major public health hazard and an extremely useful material, especially for use in fossil fuel-burning engines and in pipes that transport water. While we have mostly stopped adding lead to fossil fuels, historically-installed lead pipes remain a key part of our infrastructure. As a result, the Biden administration has proposed in its infrastructure bill to eliminate all lead pipes at an estimated cost of $45 billion. And there are options for eliminating the last remaining sources of lead in fuels. Are the benefits worth the cost? The negative effects of ongoing lead exposure on children have been studied since at least the 1960s and there is a growing understanding that lead exposure is an important driver of criminal and delinquent behavior. Moreover, there is abundant research in economics showing the impact of lead on health, fertility, and educational outcomes. The conclusions of this literature are an important part of the cost benefit analysis for removing the remaining sources of lead exposure.

Continued usage of lead water pipes and remaining leaded fuels raise the risks of higher infant mortality, lower fertility, and cognitive difficulties.

The Facts:

• Studies of the impact of leaded gasoline have shown that lead causes cognitive difficulties, particularly in boys, and decreases fertility. Lead gets in the air first and then the topsoil when engines burn liquid fossil fuels to which it has been added to improve their efficiency. It impacts children and adults who breathe the airborne dust or play in lead-contaminated soil in public parks or urban gardens around their homes, even years after lead was phased out from gasoline for on-road vehicles. Researchers have studied the effects of lead in this context by comparing individuals who grew up in areas that had high levels of lead to those who grew up in areas that had low levels. However, establishing that lead levels cause negative outcomes has been complicated because people with high exposure to lead also tend to live in poorer communities, with lower-quality schools and less access to health care. One way in which researchers have addressed this is by using the original 1944 Interstate Highway System Plan (as designed, not necessarily as implemented). Whereas actual implementation may have been correlated with local preferences for transportation and environmental quality, the recommended plan from the federal government was essentially externally imposed. Using this, one study finds that living in counties with topsoil lead levels above the national median doubles the probability of 5-year-old boys having cognitive difficulties, such as problems with learning, remembering, concentrating, or with making decisions. Using a similar strategy, another study finds that airborne lead decreases fertility. The researchers estimated that if counties with lead concentration above the median were to decrease to the levels of lead of those below the median, then general fertility rates would be 7.8 births per 1,000 women per year higher.
• As of July 2021 the last country selling leaded gasoline (Algeria) has stopped. But lead is still added to the fuel that powers small piston-engine aircraft (not jet aircraft) and to some fuel for automotive racing. The continued usage of these leaded fuels leads to measurable concentrations of lead in exposed populations. For instance, when researchers looked at blood lead data from over a million children and their proximity to 448 nearby airports in Michigan, they found that blood lead levels in children increase with proximity to airports and increase when the wind is in the direction from the airport to homes. Blood lead levels in these Michigan children also declined right after 9/11/2001 when air traffic volume decreased. In the case of race cars, researchers used the fact that two major racing organizations (NASCAR and the Automobile Racing Club of America) switched from leaded to unleaded gasoline in 2007 to compare changes in population outcomes, before and after deleading, between those who live near racetracks and those who live further away. The researchers find that proximity to racetracks using leaded gasoline increases lead in the air, raises elevated blood lead rates, and increases elderly mortality. While NASCAR and ARCA now use unleaded fuel, leaded racing fuel can still be legally purchased in the U.S. and remains widely used in both professional and amateur races. 
• Lead exposure through water infrastructure happens when acidic (lower pH) drinking water passes through lead pipes. Since lead pipes have been in use for well over a century, economic historians have extensively studied this channel and linked lead exposure with increased child mortality and lower intelligence test scores. Studies use the variation across cities in water acidity and the types of service pipes to determine the extent of lead exposure for different locations. Researchers have estimated that in 1900, the decline in exposure to lead from decreasing water acidity in cities with lead-only pipes by going rom a pH of 6.675 to 7.3 would have been associated with a decrease in infant mortality of 7%–33% — at least twelve fewer infant deaths per 1,000 live births. Looking at where World War II enlistees lived in 1930, Army General Classification Test scores were six points lower where pH was 6 relative to a neutral pH of 7.
• There are several twenty-first century examples of public health emergencies stemming from high lead levels in drinking water in the United States. The water crisis in Flint, Michigan has been the focus of intense attention. The city switched its water source in 2014 to the Flint river, which doubled the rates of children with elevated blood lead levels (>5 μg/dL), compared to no change outside of Flint. Comparing changes in Flint to other large cities in Michigan, I find that fertility rates decreased by 12% and that overall health at birth also decreased. Another study finds that low birth weight rates in Flint increased by 1.8 percentage points (15.5%). Others find reduced test scores, additional disciplinary actions, and increases in special needs for exposed students. While these findings are subject of debate (see here and here), the health and fertility effects described are broadly consistent across many cities and settings and do not rely on Flint alone. Washington, D.C., for instance, had a crisis of high water lead levels that peaked in 2001. The higher lead levels there were associated with higher rates of miscarriage and fetal death, even though the blood level elevations measured (≈5 μg/dL) were previously considered low enough to not be harmful. More recently, Newark, New Jersey had its own localized lead water crisis in 2016. Researchers found that prenatal exposure to lead in Newark significantly raised the probability of low birth weight or preterm births by approximately 1.4 to 1.9 percentage points (14-22 percent). The adverse effects were largely concentrated among mothers of lower socioeconomic status.