Starting in 2014, the impoverished city of Flint, Michigan, experienced the highest-profile lead exposure crisis in recent American history.

Lead levels in Flint’s children spiked after the city failed to properly treat a new water source. Eventually, the state of Michigan and city of Flint were forced to agree to a $641 million settlement for residents affected by the lead poisoning, and several state officials, including former Gov. Rick Snyder, were criminally indicted for their role in exposing children to lead.

While estimates differ, a prominent study found that the share of screened Flint children under the age of 5 with high lead levels reached 4.9 percent in 2015, up from 2.4 percent before the problems with lead contamination began. According to the CDC guidance at the time, a level of lead in blood that would be considered high was 5 micrograms per deciliter (µg/dL) (the agency has since lowered the threshold to 3.5 µg/dL). That said, no level of lead exposure is considered safe, and even exposure well below public health recommendations can be quite harmful. That nearly 5 percent of young children in Flint faced exposure to rates that high is a travesty.

As scandalous as the Flint lead crisis is, it’s sobering to know that it may be just the tip of the iceberg globally.

A recent systematic evidence review, widely cited and respected in the field, pooled lead screenings from 34 countries representing two-thirds of the world’s population. The study estimated that 48.5 percent of children in the countries surveyed have blood lead levels above 5 µg/dL.

Let me repeat that: Flint became the symbol of catastrophic lead exposure in the United States. The breakdown of a long-neglected system was so terrible that it led to headlines for months and even became an issue in the 2016 presidential election. Yet children in low- and middle-income countries are, per this estimate, 10 times likelier to have high blood lead levels than children in Flint were at the height of the city’s crisis.

The lead problem is global. It’s catastrophic in scope and hurting children’s ability to learn, earn a living when they grow up, and function in society. Yet lead has gotten comparatively little attention in the global public health space. Charities globally are spending a total of just $6 million to $10 million a year trying to fight it. For comparison, individuals, foundations, and corporations in the United States alone spent $471 billion on charity in 2020.

Childhood lead poisoning is a tragedy — and it is one that would be relatively inexpensive for the world to fix.

What lead does to humans

Lead is soft, plentiful, and easy to mine and manipulate, which is why humans have been harnessing it for various purposes for thousands of years. Ancient Romans used lead for everything from water piping to pots and pans to face powder to paint to wine preservatives.

Today, common uses of lead still include cookware, paint, and piping, along with lead acid batteries (a technology still used for most car batteries, even in hybrids), and plane fuel. For decades, a major use of lead was as an additive to gasoline meant to prevent engine knocking. While the US started phasing out leaded gasoline for passenger cars in 1973 — and only finished in 1996 — the last country to officially abandon it, Algeria, did so last year.

The reason we phased it out is that — as we have known at least since Roman times — lead is extremely bad for humans.

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“Lead causes toxicity to multiple organs in the human body,” Philip Landrigan, a doctor and professor at Boston College who conducted key studies on the effects of lead in the 1970s, told me. “In infants and children, the brain is the big target. But we also know very well that adults who were exposed to lead — especially people exposed occupationally [and thus exposed to high amounts] — are at very substantially increased risk of heart disease, hypertension, and stroke.”

Lead exposure can be quite deadly. Some of the best evidence here comes from a recent study examining Nascar’s decision to ban leaded gasoline from its cars in 2007. Overall, mortality among elderly people fell by 1.7 percent in counties with Nascar races after the races stopped using leaded gas. The authors estimate that Nascar and other leaded gas races had caused, on average, about 4,000 premature deaths a year in the US.

The biggest costs of lead, though, are its effects on the brains of children. The developing brain is, in Landrigan’s words, “exquisitely sensitive” to the effects of lead. “It damages neurons; the active cells in the brain that we use for reflexing, running, and jumping, everything,” he explains.

The effects of lead “seem to concentrate in the prefrontal cortex,” Bruce Lanphear, a leading medical researcher on lead’s effects based at Canada’s Simon Fraser University, told me. That part of the brain is smaller in adults who were exposed to lead as children, he added. Neuroscientists believe the prefrontal cortex plays a key role in executive functioning: the ability of people to choose behaviors in pursuit of conscious goals rather than acting on impulse. “It’s what distinguishes us from other animals, what makes us human,” Lanphear said.

For just about any variable you can imagine related to human behavior and thinking, there is probably research indicating that lead is harmful to it.

High lead exposure reduces measured intelligence substantially. “If we compare kids at the lower and higher end [of lead exposure], we saw a 5-8 point IQ difference,” Aaron Reuben, a psychologist at Duke University and lead author on a study looking at a cohort in New Zealand, told me. Higher lead levels are associated with higher rates of ADHD and negative changes in personality.

Reuben says his research has found that kids exposed to lead are “less conscientious, less organized, less meticulous. They’re a little less agreeable; they don’t get along as well with others. They’re more neurotic, meaning they have a higher propensity to feel negative emotions.”

In recent years, some writers have embraced a theory that declining lead exposure (mostly due to the gradual removal of lead from gasoline) was a leading factor in the drastic decline in crime, especially violent crime, in the United States in the 1990s. Whether or not lead explains that specific historical phenomenon, several high-quality studies have found a relationship between high lead exposure and crime and delinquency.

One found that Rhode Island schoolchildren exposed to lead were dramatically likelier to be sent to detention. Another, looking at the introduction of lead pipes in the late 19th century, found that cities with the pipes had considerably higher homicide rates. A third, looking at reductions in lead in gasoline in the late ’70s and early ’80s, found that the phase-out led to a 56 percent decline in violent crime.

This evidence is suggestive, not definitive. A recent meta-analysis argued that when you take into account the likelihood of publication bias (that is, that studies showing a strong effect of lead on crime are likelier to be published than studies finding little effect), the effect size could be quite small and not explain any of the decline in homicide rates in the US.

But the idea that lead has a high social cost does not hinge on a specific narrative about crime. Lead appears to be consistently costly across outcomes from IQ to personality to impulse control to elderly mortality.

“Lead has been really bad and very significant in the history of social behavior,” Jessica Wolpaw Reyes, an economist at Amherst College and author of that last paper, summed it up to me.

Lead exposure is still very common in the developing world

The story of lead exposure in the United States and other rich countries in recent decades has in fact been enormously positive. Yes, there have been disastrous lapses as in Flint, but they stand out precisely because they are such an exception to recent trends.

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A recent paper from CDC researchers estimated that from 1976 to 1980, fully 99.8 percent of American children aged 1 to 5 had levels of lead in their blood of over 5 micrograms per deciliter. From 2011 to 2016, the share was down to 1.3 percent. In a major triumph for environmental public health, high-level lead exposure went from the norm to an aberration in just four decades, in large part due to the abandonment of lead in gasoline.

As bad as things are in developing countries today, lead exposure in those nations is much less prevalent than it was in the US 40 years ago — a sign of global progress. That said, lead exposure in developing countries appears to be quite high compared to exposure in rich countries today.

Several experts I spoke to pointed to the 2021 evidence review led by Bret Ericson that I referenced above as the best summary of what we know about how common lead exposure is in low- and middle-income countries. In 34 nations, which together account for over two-thirds of the world’s population, the researchers were able to find blood lead surveys they considered reasonably representative of the country’s children, usually conducted by nonprofits or government agencies.

Overall, those studies estimated that 48.5 percent of children had high lead levels (defined as above 5 ug/dL). Levels of exposure varied greatly, with surveys in a few countries (like Tanzania and Colombia) not finding any children with blood lead levels above 5 ug/dL, and other countries showing huge majorities with levels that high. In Pakistan, for instance, over 70 percent of children had high blood lead levels.

Lead levels this high imply incredible amounts of damage to health and well-being. The Global Burden of Disease study published in the Lancet in 2019 estimated that about 900,000 people die due to lead annually, representing 21.7 million years of healthy life lost. One attempt to quantify the economic costs of lead in low- and middle-income countries estimated that in 2011, the burden was around $977 billion annually, or 1.2 percent of global GDP.

Lead in poor countries comes from everything from batteries to turmeric

While the numbers above give a sense of the lead problem’s scale, they are not definitive. One consistent message I heard from experts is that we simply need a lot more data on lead in low- and middle-income countries.

The Ericson evidence review concluded, “there is a paucity of rigorous data on lead exposure in the general populations of [low- and middle-income countries].” Most countries in Africa, and several in Latin America and Central Asia, did not have data usable for the review.

Lead experts also disagree about what the primary sources of lead exposure in developing countries might be. Pure Earth, the largest nonprofit working on lead contamination in developing countries, has generally focused on reducing exposure from informal recycling of lead-acid car batteries. In many developing countries, such recycling happens in mom-and-pop operations in backyards, with no protection for the recycling workers or neighboring residents from the resulting fumes.

But more recently, Pure Earth has also been working on reducing exposure from cookware and spices. Stanford researchers Jenna Forsyth and Stephen Luby have found that turmeric spice in Bangladesh is very often cut with lead chromate. That’s right: The turmeric that Bangladeshis use for cooking often has lead added to it. Lead is very heavy, and in lead chromate form, it’s a vibrant yellow, which makes it an easy way to adulterate and amplify the color of turmeric. The problem likely spans beyond just Bangladesh. Consumer Reports has found that even in the US, grocery stores were selling turmeric cut with heavy metals.

Environmental scientists have worried for years about lead exposure from ceramics in Central America, where traditional processes often use lead for glazing. But Pure Earth’s Richard Fuller told me that ceramics in India often contain lead too, and in many low-income countries, aluminum cookware is contaminated as well. Aluminum pots and pans in these contexts “are generally made in local recycling places where the recyclers are throwing all this scrap metal in,” he said. “It’s almost impossible for them to not get lead in.” In turn, that lead can seep into food cooked using these tools.

But other, smaller organizations focus on different lead sources. Lead Exposure Elimination Project (LEEP), founded in 2020, has mostly focused to date on lead paint. Just as lead can make turmeric more vibrant, it can make yellows and whites in paint more vibrant too. “We decided to start with lead paint because it seemed like a significant source of exposure, and there’s an obvious approach to tackling it, which is regulation,” Lucia Coulter, a medical doctor and LEEP’s co-founder, told me.

Tackling lead paint requires introducing new laws and enforcing old ones. Jerry Toe, an official at Liberia’s Environmental Protection Agency (EPA) who has worked with LEEP on lead paint, told me that while the country had adopted a law banning lead paint in 2004, the Liberian EPA had still not formalized any regulations deriving from it by 2019, when he came to the issue. It took a LEEP study in Malawi for regulators in that country to conduct regular monitoring of lead levels in paints for sale.

Imran Khalid, a researcher at Pakistan’s Sustainable Development Policy Institute and director at the World Wildlife Fund Pakistan, has had a similar experience. “The implementation [of lead regulations] is quite poor,” he told me. “Our environmental laws are primarily lip service.”

Khalid has been working with LEEP on paint sampling studies in which he and other researchers obtain paint from stores and test it for lead. Zafar Fatmi, a professor at Aga Khan University in Karachi, said that in his initial testing, around 40 percent of paints had high levels of lead.

Khalid notes that some high-lead paint comes from major multinationals, which makes enforcement a challenge. “For a country like Pakistan that’s already going to the IMF [International Monetary Fund] again and again” asking for loans, he explains, “people become very hesitant [about criticizing multinationals] when environmental issues come up.”

And there are other possible sources in poor nations as well, including some of the same ones still plaguing rich countries. “A lot of homes in African countries still have lead pipes, and nobody is talking about getting rid of them or what problems they’re creating,” Jerome Nriagu, a professor of environmental health sciences at the University of Michigan and one of the first US researchers to raise alarms about lead in Africa, told me.

An urgent need for more funding and more data

Last year, the effective altruist research group Rethink Priorities released a comprehensive report attempting to assess how many groups were working on lead exposure in poor countries and how much more could be done on the issue. Their answers: Not many are working on this, and those that are could likely use millions of dollars more every year to spend on effective projects.

Pure Earth, formerly known as the Blacksmith Institute, is by far the largest player, but it spends just $4 million to $5 million a year on lead. “Summing estimated budgets of other organizations, we believe that donors spend no more than $10 million annually on lead exposure,” Rethink Priorities’ Jason Schukraft and David Rhys Bernard conclude.

Much of that funding comes from government sources like the US Agency for International Development and the Swedish equivalent Sida. Outside support for nonprofits, there’s not much public evidence that international aid agencies are investing in lead abatement. With some notable exceptions, like the Center for Global Development, groups working on global health have largely ignored the issue.

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Ten million dollars a year, tops, is not much money at all to spend fighting global lead poisoning, even with increased investments directed by donors in the effective altruism community toward Pure Earth and LEEP. “It’s a fairly small community, and it’s remarkably small given the scale of the problem and the scale of the impacts,” Pure Earth’s Fuller said. That helps explain why effective altruist groups like Rethink Priorities and GiveWell have become interested in lead alleviation. It’s a neglected area, where each additional dollar can go a long way.

So what else could be done with more money and resources? One simple answer is better research. When I asked Fuller and his colleague Drew McCartor what additional studies they’d do if they could, they immediately said basic lead exposure surveys in affected countries and basic sourcing analysis to see where lead is coming from in those countries.

We have such poor data on how many people (especially children) are being exposed to lead and on how they’re being exposed to lead, that improving that data could in turn significantly enhance nonprofits’ ability to target interventions effectively. If, say, lead pipes are a bigger source of exposure in sub-Saharan Africa than previously thought, that would change how Pure Earth and other groups allocate funds; likewise, a finding that lead paint is not a significant source of exposure might change LEEP’s approach.

Rethink Priorities concluded that “existing and potential new NGOs in the area currently have the capacity to productively absorb $5 to $10 million annually in additional money,” and that sums above that amount might be productively usable too.

That’s just not a lot of money in the context of US foundations or even foreign aid budgets — especially for something we know is severely injuring children and killing adults in the developing world.