Researchers have known for decades that lead poisoning damages brains and worsens crime, but millions of Americans still drink contaminated water every day. Here’s how we can fix that.
Most discussion of the Biden administration’s new infrastructure bill focused on its plans to crisscross America with high-speed railways, or on its commitment to roll out high-speed broadband to every household. Less attention was given to the $45 billion it earmarked for replacing the lead pipes that much of the country’s water supply travels through. Though less glamorous than many other elements of the bill, it’s probably this that involves the greatest benefit to Americans’ long-run well-being, and the prosperity of the country itself.
We’ve known for decades that lead exposure causes serious health problems. It lowers people’s IQ, and even seems to increase people’s propensity to commit crimes. Unlike bans on DDT or chlorofluorocarbons, we can’t just pass a law to get it out of our lives. More than anything, getting rid of lead is a practical problem. And it’s one that we might finally be ready to solve.
The status quo & the current pace of change
We know lead is really bad. There is compelling evidence that lead increases the risk of heart disease and hypertension in adults, reduces the ability of children to learn and attain high levels of education and, as a consequence, lowers earnings over a person’s lifetime if they have been exposed to lead during their childhood.
But the most famous negative effect of lead pollution is that it makes people more likely to commit crimes, including violent ones. Working this out has taken decades of research. In 1996, a pediatrician and child psychiatrist called Herbert Needleman published an influential study which measured lead accumulation in the body and its relationship with antisocial behaviour. He followed up on 212 boys over 4 years, from the age of 7 until 11, collecting data using X-ray spectroscopy to measure the amount of lead they had accumulated in their bones, as well as reports of their behaviour from their teachers, their parents and the children themselves. Boys who had higher levels of lead accumulation showed significantly higher levels of aggression, delinquency and anxiety.
The toxic effects of lead seem largely, but not entirely, due to its ability to mimic calcium ions in the body. Crucially, this mimicry means that lead is able to traverse the barrier that separates our blood circulation and the fluid in our brains, which enables it to set off a spiral of further consequences.
Calcium ions are extraordinarily important in the brain and nervous system, as they act as signals that trigger various functions in neurons, such as the production and release of neurotransmitters. So the presence of lead, by mimicking the appearance of calcium ions, alters the normal development of the nervous system. Lead disrupts the shape and structure of neurons, and interferes with the formation of synapses, which connect neurons to their targets.
Most severely, its ability to mimic calcium causes calcium overload in brain cells, which damages mitochondria and triggers ‘apoptosis’, which is a regulated procedure in which cells package up their contents and commit suicide. The damage that lead unleashes in the brain occurs primarily in the prefrontal cortex, hippocampus and cerebellum – areas of the brain that are involved in memory formation, impulse control and cognitive function. Over time, individuals who have been continuously exposed to lead during their childhood display higher rates of impulsivity and aggression than those who were not exposed, and in turn, these changes are strongly believed to be responsible for antisocial and delinquent behavior.
Needleman’s study was one of the earliest and most influential – other researchers followed up. Recent research asserts that up to 56% of the decrease in violent crime that occurred in the US during the 1990s was a result of reductions in lead exposure in children born after 1973, when the Environmental Protection Agency introduced new regulations that began a phased reduction in leaded gasoline. Hundreds of other studies link lead with crime and behavioural problems ranging from poorer test scores to antisocial behaviour, as well as to poor health.
These later studies work hard to disentangle cause and effect. Lead pollution is often highest in poorer neighbourhoods, or where those in groups facing discrimination live – how can we be sure that the wide range of negative effects we see is down to lead, and not the other trials that poorer or marginalised groups face?
Economist James J. Feigenbaum and sociologist Christopher Muller look at homicide rates between 1921 and 1936, comparing cities based on their proximity to lead refineries. An important part of the study was that it made use of measurements of acidity in the water. Because of the chemistry of lead, more of it leaches into water that contains higher levels of acidity. So the authors compared cities with lead pipes and a range of pH levels to cities without lead pipes and a range of pH levels.
They found that cities that used lead pipes had, on average, 24% higher rates of homicides compared to cities that did not. In cities with lead pipes they found that when the water’s pH dropped from 7 to 6 (i.e., became more acidic), homicide rates increased by 10%, after controlling for additional confounders. This study was effective because populations within cities were exposed to lead in the same way – through the shared water system.
Over time, the evidence has become overwhelming. The impact of lead pollution on human physiology, and therefore behaviour, is huge, and negative. Reducing lead pollution has costs, but it has enormous positive impacts – according to Elise Gould, economist at the Economic Policy Institute:
“Even under the most conservative analysis, for every dollar spent on controlling lead hazards, at least $17 would be returned via improved health outcomes, increased IQ, higher lifetime earnings, increased tax revenue, less spending on special education and reduced criminal activity.”
Solving the problem: pipes
We have already removed a lot of lead from people’s lives. Lead has been removed from gasoline and paint. But to replace all of the nation’s lead pipes, first we’ll have to know where they are.
Every year, there are at least half a dozen pieces written in major news outlets that call for larger efforts to tackle lead exposure in the United States. After all, the evidence of the harms is clear and the solutions seem simple. Yet, every piece asks the same question: Why does lead exposure continue to be a problem if the solutions really are straightforward?
The fact that this has been a challenge for so long and continues to be a major question today suggests that maybe there are several layers to the problem. The first layer might relate to actions that directly move the world to a better state, while the second layer to actions that indirectly move us into a better state; these are actions that require larger investments up front but have benefits that are multiplied over time.
For instance, suppose the cost of excavating and replacing one household’s lead pipes is $4,000. If we doubled the amount of public resources for this task, we can expect to replace roughly double the number of pipes. But the problem is, we don’t often know whether a given house will have lead pipes, as we often have records that are incomplete. We could invest resources, funds and time into manufacturing new hardware that could verify whether lead pipes are present at these sites before we incur unnecessary costs to excavate them. And if we wanted to go a level further, we might invest in scientific research to develop more accurate hardware to detect lead more reliably. As we go further, to higher levels of the problem, we would require a cost-benefit analysis to justify investing resources in the lower levels.
It is worth noting that, across the United States, many cities are embarking on efforts to extract lead proactively, to prevent situations where exposure could reach dangerous levels. But we are still decades away from having lead-free infrastructure, at current rates of remediation. The American Water Works Association estimates that there has been a 40% reduction in the number of lead service lines over the past 30 years. But without Biden’s big infusion it would still have been 45 years before we replaced all lead pipes in the US.
If the government is going to successfully replace pipes, what does it need to do? One major challenge lies in the contractual terms that are set between states and local governments and contractors who remove lead piping. Take Flint, Michigan, as an example of the problem: contractors were paid for every excavation, and in cases where lead pipes were present, the contract would also pay the cost to replace pipes. You might be able to guess what went wrong. Many unnecessary excavations were carried out, which in turn slowed down the replacement of the pipes that were confirmed to contain lead. The head of public works in Flint estimated the number of lead lines to be around 10,000 in 2017, but by December of 2018, the contractor had a hit rate of only 15%: they only found around 1,500 lead lines in the 10,500 excavations that were performed.
There were other problems too. Most water systems add ‘corrosion inhibitors’ to pipes – chemicals that react with lead ions in the piping to form a layer of protective coating, or direct current to prevent the lead from being corroded and seeping into the water supply. But while these methods are cheap in the short run, they require real-time monitoring, and with slight changes in pH and temperature, the protective coatings wear down quickly and disappear.
If local governments partnered with economists who study industrial organization, that could help them understand which public procurement practices they could implement to optimize funding. In this sense, it is important that metrics on project performance are available for city officials (and the public) because when this data is not observable or only selected metrics are public, it is difficult to determine whether a project was expensive. Like any other public procurement, setting project benchmarks can also help calibrate costs of lead replacement across the country.
In most states, public funding for lead service lines replacement only covers the public side (known as partial replacement), leaving the rest of the remediation costs to homeowners (i.e., paint, internal plumbing and service line from the curb to the house). Many households or landlords might be unable to cover the costs of replacement or can find the process of finding certified contractors and building permits overwhelming. If the Biden proposal is aiming to remove 100%of all lead pipes, it will be important to require and fund full replacements.
Karen Baehler, political scientist at the American University, conducted an analysis of more than 3,000 lead pipe replacements in the District of Columbia with the goal of mapping replacements to socioeconomic data. Partial and voluntary full replacements took place across the eight wards in DC, the administrative subdivision of the city, between 2009 and 2018, where the District of Columbia Water and Sewer Authority required customers to pay for the replacement on private property if they were interested in a full replacement.
It is no surprise that the proportion of full replacements was significantly lower in poorer wards, but the most interesting finding of the report was the seven-fold increase in the number of participants in the voluntary full replacements between 2013 and subsequent years. This was the result of an outreach program for home renovators to participate in the replacement program before applying for a renovation permit. Policy nudges like these are very likely lower in cost to implement compared to the amount homeowners will incur for replacement costs (between $2,500 to $15,000 per household), making them very effective policy interventions.
Solving the problem: data
Solving the problem will involve more than spending money on pipes. Indeed – it will involve more than finding the right pipes and replacing them. We know lead pollution is going on, we know people are affected by it and we know how bad the effects are. But we don’t always know exactly where it’s coming from and where it’s going.
A major challenge for the implementation of cost-effective lead abatement programs is the lack of high-quality data in blood lead levels and other related variables. The main national survey that researchers and policy-makers use to track progress on lead is the National Health and Nutrition Examination Survey (NHANES). This annual survey has been collecting data on blood lead levels since 1976 and is used to establish the Blood Lead Reference Value to identify lead poisoning in children, which is currently set at the value of 5 μg/dL.
But there are major problems in this data. For example, in the third wave of the survey, data on birth weight (which is highly correlated with cognitive development) was missing in nearly half of the values in the sample. Other variables correlated with lead exposure, such as the poverty index, were also missing in significant proportions. The lack of data on these important variables hampers our ability to draw valid inferences from the data and target health interventions effectively.
And because lead concentrations in the blood are evidence of past exposure, higher-quality data that tells us where lead is currently at high concentrations is also needed to prevent future exposure. For instance, many states across the Rust Belt lack data on the precise locations of lead in their water systems, despite being aware of its presence. In Wisconsin, 154,000 pipes have been categorized as lead, but nearly twice as many are labelled as unknown material. In Flint, the location of an estimated 10,000 lead pipes was uncertain. Without access to sensible record keeping, it is hard to imagine remediation programs that are targeted precisely.
The hurdles Biden’s billions will need to clear
Since the 1970s, US regulations have sought to reduce or eliminate sources of lead exposure—including from paint, water, air and soil—to prevent lead poisoning, particularly in children. The ban on leaded gasoline in the US was a major step towards this goal, with blood lead levels in children decreasing by 77% between 1976 and 1991.
It is encouraging to see lead abatement as a policy issue by the US government and promise significant sums of funding to deal with a problem that continues to affect many Americans: lead in drinking water. In recent days, the Senate parliamentarian (the official advisor to the US Senate) cleared the path to use budget reconciliation as a mechanism to pass this proposal, which will allow Democrats to bypass the two-thirds requirement needed in the Senate. But the journey is not over, and Biden’s infrastructure proposal will need to clear several hurdles before becoming a reality.
Using these funds to fully remove lead pipes will not only require a cash injection to the Environmental Protection Agency’s programs, but a significant amount of detective work to locate where the pipes are. Some of this is already happening in Toledo, Ohio, where city officials have partnered with a water analytics firm to narrow down the location of hazardous pipes, but more is needed to ensure that future funding and policy will encourage cities to initiate full replacement of pipes, either by incorporating mandates as part of the Lead and Copper Rule or through other policy.
The consequences of lead exposure directly impact America’s human capital, impairing children’s cognitive development and worsening crime rates. Removing lead from our infrastructure and environment will be a costly process, but given the large social returns, the cleanup time should be now. After all, lead poisoning is entirely preventable.