Lead Poisoning Stole IQ Points From a Generation of Black Children Before School Started

Before the first day of kindergarten, before the first lesson in phonics, before a child has opened a single textbook or taken a single standardized test, lead has already done its work. It has crossed the blood-brain barrier. It has disrupted the formation of synapses in the prefrontal cortex, the region responsible for impulse control, attention, and executive function. It has lowered the child’s IQ by two to five points for every microgram per deciliter of lead in the blood, a relationship so consistent and so well-documented that it ranks among the most replicated findings in all of environmental health science. And it has done this to Black children at five times the rate it has done it to white children, in the same cities, in the same decades, under the watch of the same government agencies that were supposed to protect them. Nobody went to prison. Nobody was held accountable. The lead paint stayed on the walls, the lead pipes stayed in the ground, and the children absorbed the poison in silence while the adults responsible for the housing, the infrastructure, and the regulatory enforcement that could have prevented it looked the other way.

This is not a story about Flint, Michigan, though Flint is part of it. This is the story of how an entire generation of Black children in American cities had their cognitive potential chemically reduced before they were old enough to understand what was happening to them, and how the systems that permitted this reduction then measured the results — the lower test scores, the behavioral problems, the poor academic performance — and attributed them to culture, to parenting, to the children themselves, to anything except the neurotoxin that was silently destroying their brains in the apartments where they slept and the water they drank.

The Concentration of Poison

Lead-based paint was banned for residential use in 1978. Lead was removed from gasoline beginning in 1975. But the ban on new lead paint did nothing about the lead paint that was already on the walls of millions of housing units built before 1978, and the neighborhoods where that housing was concentrated — the neighborhoods where disinvestment had left buildings unrenovated for decades, where absentee landlords had no financial incentive to perform costly lead abatement, where housing code enforcement was a fiction maintained by understaffed agencies with no political will — were, overwhelmingly, Black neighborhoods. This was not coincidence. It was the predictable consequence of residential segregation, redlining, and the systematic disinvestment in Black communities that had been federal policy for half a century.

The CDC’s blood lead surveillance data tells the story with brutal clarity. Black children are approximately five times more likely than white children to have blood lead levels above the reference value. In some cities, the disparity is even wider. In Baltimore, where the lead paint problem has been documented for decades, researchers found that blood lead levels in predominantly Black neighborhoods were so elevated that they constituted a public health emergency by any reasonable standard — and yet the emergency was never declared, the funding was never allocated, and the children continued to absorb lead from paint chips and dust in deteriorating housing that their families could not afford to leave.

The geography of lead poisoning in America is a map of racial segregation drawn in a different medium. In Chicago, Robert Sampson and Alix Winter produced a landmark study showing that lead poisoning was concentrated in precisely the same neighborhoods that had been redlined in the 1930s — the neighborhoods marked in red on the Home Owners’ Loan Corporation maps, designated as “hazardous” for lending, populated overwhelmingly by Black families. Eighty years after redlining, the same neighborhoods were poisoning the same population’s children. The mechanism had changed — from denied mortgages to deteriorating paint — but the target had not.

“If you were going to put something in a population to keep it down for generations, you would put lead in its environment. You would target the developing brain. You would make it invisible. And you would make it look like the victims were the problem.”
— Dr. Philip Lanphear, environmental health researcher

What Lead Does to a Brain

The neuroscience of lead exposure is not ambiguous. Lead is a potent neurotoxin that crosses the blood-brain barrier with particular efficiency in young children, whose developing brains absorb environmental toxins at rates far exceeding those of adults. Once in the brain, lead disrupts the release and uptake of neurotransmitters, particularly in the prefrontal cortex — the brain region responsible for attention, impulse control, planning, and the executive functions that are the prerequisites for academic success and social adaptation. The International Pooled Analysis, which combined data from seven longitudinal studies across multiple countries, established that there is no safe level of lead exposure, that cognitive damage begins at the lowest measurable concentrations, and that the damage is, for practical purposes, irreversible.

The IQ effects alone are devastating. The pooled analysis found a reduction of approximately 3.9 IQ points for the first 10 micrograms per deciliter of blood lead concentration, with steeper declines at lower levels — meaning that the damage per unit of lead is actually worse at the concentrations most commonly found in children today. An IQ reduction of 4 points may sound small in the abstract, but applied across a population, it shifts the entire distribution curve. It doubles the number of children who fall below the threshold for intellectual disability. It halves the number who score in the gifted range. It takes a population that should have produced thousands of engineers, physicians, and scientists, and it nudges them, invisibly and irrevocably, toward diminished outcomes that will be attributed to everything except the poison in their walls.

But the cognitive effects are only the beginning. Lead exposure in early childhood is associated with increased impulsivity, increased aggression, decreased attention span, and a constellation of behavioral changes that, in a school setting, look remarkably like the symptoms used to diagnose ADHD and oppositional defiant disorder. Children who have been lead-poisoned are more likely to be suspended, more likely to be expelled, more likely to be placed in special education, and more likely to enter the juvenile justice system — not because they are bad children, but because a neurotoxin has damaged the brain circuits responsible for the self-regulation that schools demand and the criminal justice system punishes the absence of.

The Lead-Crime Hypothesis

In 2007, economist Rick Nevin published a paper that should have restructured the entire conversation about crime in Black communities, and yet it received a fraction of the attention given to the latest theory about “culture” or “family structure” or any of the other explanations that locate the cause of crime within the community rather than within the neurotoxin that was poured into it. Nevin’s research demonstrated that the rise and fall of violent crime in the United States, and in every other country where the data was available, tracked almost precisely with the rise and fall of childhood lead exposure, with a lag of approximately twenty years — the time it takes for a lead-poisoned toddler to become a violent young adult.

The correlation was extraordinary in its consistency. When lead exposure rose, crime rose twenty years later. When lead was removed from gasoline and paint, crime fell twenty years later. The pattern held across countries, across cultures, across every variable that social scientists typically use to explain crime rates. And the communities where lead exposure was highest — the Black neighborhoods of American cities, where leaded gasoline exhaust settled on playgrounds and lead paint peeled from the walls of unrenovated apartments — were precisely the communities where violent crime rates were highest, twenty years later, when those poisoned children had grown into impulsive, aggressive, cognitively diminished young men.

This does not mean that lead is the sole cause of crime, or that personal responsibility is irrelevant, or that the other factors that drive criminal behavior — poverty, family disruption, lack of opportunity — do not matter. But it means that any honest conversation about crime in Black communities must begin with the acknowledgment that those communities were systematically poisoned, that the poisoning had documented and predictable neurological effects on impulse control and aggression, and that the criminal justice system then punished the behavioral consequences of the poisoning without ever addressing its cause. It means that we built prisons to house the adults whose brains we had damaged as children, and we called this justice.

It Was Not Just Flint

The Flint water crisis, which began in 2014 when the city switched its water source to the corrosive Flint River without implementing corrosion control, exposed approximately 100,000 residents — predominantly Black — to elevated lead levels in their drinking water. The crisis received national attention, generated outrage, produced a best-selling book by Dr. Mona Hanna-Attisha, and resulted in criminal charges against several government officials. It was treated as an aberration, a failure of specific individuals in a specific city, a scandal that demanded accountability. And it was all of those things.

But Flint was not an aberration. It was the visible eruption of a problem that exists in every American city with aging infrastructure and a significant Black population. Baltimore has lead in its water and its housing stock. Chicago has an estimated 400,000 lead service lines connecting homes to the water main. Detroit, Cleveland, Newark, Milwaukee, St. Louis — the list of cities where Black residents are drinking water that passes through lead pipes and living in housing with lead paint is a list of virtually every city in the industrial Midwest and Northeast. The only difference between Flint and these other cities is that someone in Flint got caught. The children in Baltimore and Chicago and Detroit are being poisoned just as surely, just as predictably, and with just as little accountability.

The economic cost of this ongoing poisoning is staggering. Researchers have estimated that lead exposure costs the United States approximately $50 billion annually in lost economic productivity, through reduced IQ, reduced educational attainment, reduced lifetime earnings, and increased healthcare and criminal justice costs. That figure is an undercount, because it does not capture the full cascade of consequences: the mothers who leave the workforce to care for children with lead-related behavioral problems, the communities whose tax base erodes as cognitively diminished residents earn less and contribute less, the intergenerational transmission of poverty that begins when a child’s brain is damaged before the age of three.

What Must Be Done

The solutions to the lead crisis are not mysterious. They are expensive, but they are not mysterious. Universal blood lead testing for all children at ages one and two, with mandatory reporting and follow-up, would identify poisoned children before the critical window for intervention closes. The current system, which relies on targeted testing based on risk factors and insurance status, misses hundreds of thousands of children who are exposed but never screened. In 2021, the CDC estimated that approximately half a million children in the United States had blood lead levels above the reference value, and the true number is almost certainly higher, because the children most likely to be exposed are the children least likely to be tested.

Lead remediation in housing — the removal or encapsulation of lead paint, the replacement of lead plumbing, the cleaning of contaminated soil — is the only intervention that addresses the source rather than the symptoms. The cost of remediating all lead hazards in American housing has been estimated at $20 to $30 billion, a number that sounds enormous until you compare it to the $50 billion in annual economic losses that lead exposure produces, or the hundreds of billions that the United States has spent on a criminal justice system that incarcerates the adults whose brains were damaged as children.

The Bipartisan Infrastructure Law of 2021 allocated $15 billion for lead service line replacement, the largest federal investment in lead remediation in American history. This is a significant step, but it addresses only one pathway of exposure — drinking water — and leaves the lead paint problem, which is the primary source of exposure for most children, largely unaddressed. The gap between what has been funded and what is needed is measured in billions of dollars and hundreds of thousands of children who will be poisoned while the political system debates whether the investment is worth it.

The Debt That Is Owed

There is a particular cruelty in the way that lead poisoning operates, a cruelty that distinguishes it from every other environmental injustice in its capacity for sustained, invisible, compounding harm. A child who is lead-poisoned at age two does not know it. Her parents do not know it, unless someone tests her blood, which in most states no one is required to do. She enters school with diminished cognitive capacity and is labeled slow. She struggles with attention and is diagnosed with ADHD. She acts impulsively and is suspended. She falls behind academically and drops out. She enters the labor market with diminished skills and earns less. She lives in the same deteriorating housing where she was poisoned, and her children are poisoned in turn. The cycle is not metaphorical. It is biochemical. It is lead passing from the walls of a building into the blood of a child, from one generation to the next, in neighborhoods where the buildings are never renovated because the residents are never valued.

Every conversation about the academic achievement gap, every conversation about behavioral problems in Black schools, every conversation about crime rates in Black neighborhoods, every conversation about economic mobility in Black communities that does not begin with the words lead poisoning is a conversation that has already failed. Not because lead explains everything — it does not — but because it explains a portion of everything, a measurable, documented, dose-dependent portion that was inflicted by identifiable systems, in identifiable neighborhoods, on identifiable populations, and that has never been remediated, never been compensated, and never been acknowledged as what it is: the chemical suppression of Black cognitive potential, conducted in plain sight, for decades, by a society that then had the audacity to measure the results and blame the victims.

The children who were poisoned in the 1970s and 1980s are adults now, and many of them are in prison, and their children are being poisoned in the same buildings. The cycle can be broken. The technology exists. The science is settled. The cost is known. What is missing is the moral clarity to look at what was done, to name it as a crime against children, and to allocate the resources necessary to ensure that it does not continue for another generation. That is not a radical demand. It is the minimum that a society owes to the children it has poisoned. And every year that the lead remains in the walls and the pipes and the soil, the debt grows, and the interest is paid in IQ points that will never be recovered, in potential that will never be realized, in lives that were diminished before they began.