Scientists disagree for a living and peer review keeps the data in check. A toxicologist and an epidemiologist looking at the same chemical will often arrive at different conclusions even if the differences are small, and the people who study children’s health are just as critical with each other’s work as anyone else in science. So when close to fifty of them put their names on a single document about chemicals and children’s brain development and say the same thing, that document is worth reading. Agreement is the exception in this field, not the norm.
The document that reflects this is from July 2016, created by a group calling itself Project TENDR. They published a consensus statement in Environmental Health Perspectives, the peer-reviewed journal of the National Institute of Environmental Health Sciences. The authors were not activists looking for a cause. They were children’s environmental health researchers, developmental toxicologists, pediatricians, and scientists who work inside regulatory agencies. Among the signatories were the American College of Obstetricians and Gynecologists, the Endocrine Society, and the Child Neurology Society. The list of individual authors reads like a faculty roster from the top of the field.
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The short list they could all stand behind
The statement does not try to go after every synthetic chemical a child encounters. The authors were deliberate about that. They picked a small number of substances where the evidence was strong enough that the group of scientists put their signature on it. Five made the core list: lead, mercury, organophosphate pesticides, polybrominated diphenyl ether flame retardants (the PBDEs once common in furniture foam and electronics), and air pollution. Phthalates were added as an example of a chemical class where the human evidence is still growing but already concerning enough to mention.
The list was not a catalog of everything that might be bad. It is a set of prime examples, chosen because the epidemiological, toxicological, and mechanistic studies lined up for each one. These are the chemicals where the science was done, and where, in the authors’ view, regulation had not kept up.
Organophosphate pesticides are on that list. The same scientists who flagged lead and mercury put a class of agricultural and household pesticides in that same category of concern. For a parent trying to sort out real risks it’s the kind of thing worth understanding alongside how pesticide exposure affects children specifically during the years when the brain is still forming.
Why children are the wrong group to be casual about
The thought behind the statement is based on what developmental biologists settled long ago, which is: a child’s brain is not a small adult brain. It is a construction site. Neurons are migrating to their final positions, connections are forming, and the whole sequence runs on a schedule that has narrow windows where specific things have to happen at specific times. A chemical that interferes with one of those steps is not something that shows up the next morning. It changes how a system gets built, and the result becomes visible years later.
This starts before birth. The authors make it clear that exposure begins in utero, which is why obstetricians signed a statement about brain development. A pregnant woman’s contact with these chemicals also means the fetus comes in contact as well.
The same amount that an adult body processes of these chemicals without much consequence is different than a system that is still building itself. That is the core of why the statement treats children as a separate question rather than a smaller version of the adult one.
The conclusion that made it a call to action
In addition to the scientists naming chemicals, they made a structural claim. Their words: the current system in the United States for evaluating scientific evidence and making decisions about environmental chemicals is fundamentally broken.
It’s hard to argue with once it is laid out, because the vast majority of chemicals in industrial and consumer products have undergone almost no testing for developmental neurotoxicity. A substance can be widely used, showing up in national biomonitoring surveys in the bodies of most Americans, without anyone having seriously studied what it does to a developing brain. The default in the United States is that a chemical is presumed acceptable until proven otherwise, and the proving part rarely happens. The TENDR authors argued that for substances capable of disrupting brain development, that default has the logic backwards.
This is where the statement crossed from science into advocacy, and the authors were open about it. They called it a call to action, and they wanted businesses to remove these chemicals from supply chains and products. They wanted a different framework for assessing new ones, one that does not wait for a generation of children to serve as the evidence.
Which of these a parent can do something about
Some of these chemicals reach a child through decisions a parent makes in their own kitchen and yard. Others reach the child through the air outside the house or the pipes in the wall, which is hard to have any control over. Knowing the difference can help turn a scientific statement into something you can practically use during the week.
Organophosphate pesticides are the most actionable item on the list. They show up as residue on conventionally grown produce and in products people spray around the home and garden without thinking they are neurotoxic. The evidence here is not weak, and three separate birth-cohort studies, published together in Environmental Health Perspectives, found that children with the highest prenatal organophosphate exposure scored measurably lower on cognitive tests, with one cohort showing roughly a seven-point IQ difference between the highest and lowest exposure groups, an effect on the same level of damage done by lead. A family can lower a child’s contact with these pesticides in practical ways: washing or peeling produce, choosing organic for the fruits and vegetables that tend to carry the heaviest residue, and not reaching for the household bug spray or lawn treatment when a child plays in the yard. None of this requires drastic changes, and the link between these specific pesticides and the developing brain is exactly why the choices around pesticides and children are worth a closer look than a parent might give them otherwise.
Flame retardants are more challenging to reduce but still doable. The PBDEs named in the statement were phased out of new furniture and electronics over the past decade, but two things complicate that. Older couches, foam, and electronics in many homes still contain them, and they migrate into household dust and the air indoors. And the chemicals that replaced them, a class of organophosphate flame retardants, have their own harmful evidence, so newer does not mean safer. The ways to address are: dealing with dust through regular vacuuming with a good HEPA filter, washing hands before eating, and replacing the most degraded old foam furniture when it is realistic to do so.
Then there is the part that is challenging to address. Lead in old paint and old plumbing, mercury that accumulates in certain (mainly large) fish, and air pollution from traffic and industry are not problems that mindful shopping fixes. A family can test old housing for lead, be selective about high-mercury fish during pregnancy and early childhood, and run air filtration indoors, but the bulk of these heavy metal exposures are structural. They are the reason the TENDR authors wrote a policy document instead of a shopping guide. The honest message is that prevention runs on two tracks at once, the household track and the policy track, and the second one is why scientists felt they had to speak up.
How much weight a consensus statement can carry
A consensus statement is a strong thing and a limited thing at the same time, and being honest about both is the only way to use it well.
The strength is in the agreement itself. When this many independent experts, sign the same statement saying a specific chemical contributes to neurodevelopmental harm, the question of whether the hazard is real becomes mostly settled. Lead is not controversial anymore by any stretch. The statement puts organophosphate pesticides and PBDE flame retardants in that same settled category.
The limit is that none of this speaks to any one child. Consensus on a population-level hazard is not a diagnosis and not a prediction about an individual. A chemical can be a genuine contributor to neurodevelopmental risk across millions of children and still leave any particular child unaffected, because individual outcomes depend on dose, timing, genetics, and a long list of other factors the statement never claims to resolve. The authors were making a case about policy and prevention, not about reading any single family’s history backwards.
The hazard is real enough that reducing a child’s contact with the named chemicals is reasonable. The uncertainty about individuals is wide enough that the goal is sensible prevention rather than worry about damage already done. Reducing what you can reduce, during the years when it matters most, is a defensible response to exactly this kind of evidence.
The full statement is public, and is worth reading in the authors’ own words rather than anyone’s summary of it, including this one.
Common questions
What neurotoxin is of greatest concern for children’s health?
There is no single answer that every scientist would give, because the chemicals differ in how strong the evidence is and how avoidable the exposure is. Lead remains the most thoroughly documented, with a long record tying it to lower IQ and behavioral problems at exposures once thought safe. Among the chemicals a family encounters through food and the home rather than through old paint and pipes, organophosphate pesticides carry some of the strongest evidence, with multiple birth-cohort studies linking prenatal exposure to measurable cognitive deficits. The TENDR consensus treats lead, mercury, organophosphate pesticides, PBDE flame retardants, and air pollution as the prime examples worth acting on, rather than ranking one above the rest.
Which chemicals did the TENDR consensus statement name?
The 2016 statement named five as core examples: lead, mercury, organophosphate pesticides, polybrominated diphenyl ether (PBDE) flame retardants, and air pollution. Phthalates were added as a chemical class with emerging human evidence. The authors chose these because the epidemiological and toxicological studies pointed the same direction for each, not because they are the only chemicals of concern.
Can chemical exposure during pregnancy affect a baby’s brain?
The TENDR scientists state plainly that exposure begins in utero, which is why obstetricians and gynecologists signed the statement. The developing fetal brain is sensitive to certain chemicals during specific windows, and several of the chemicals on the list, organophosphate pesticides among them, show their strongest associations with harm from prenatal rather than later exposure. This is the reasoning behind advice to reduce contact with these specific chemicals during pregnancy.
How can I reduce my child’s exposure to these chemicals?
The chemicals split into ones a family controls and ones that are mostly structural. For organophosphate pesticides, washing or peeling produce, choosing organic for high-residue fruits and vegetables, and avoiding household and lawn pesticides while children are around all lower contact. For flame retardants, controlling household dust and replacing the most degraded old foam furniture helps. Lead, mercury, and air pollution are harder to address through individual choices, though testing old housing for lead and limiting high-mercury fish during pregnancy and early childhood are reasonable steps. The realistic goal is reducing what you can during the years when a child’s brain is still forming, which is where exposure reduction does the most good.
Are these chemicals still legal and in use?
Many are, and the flame retardant case is more complicated than a simple phase-out. Some PBDEs were pulled from new products, but they persist in older furniture and electronics already in homes. More to the point, manufacturers replaced them largely with a different class, organophosphate ester flame retardants, and a 2019 peer-reviewed analysis co-authored by a former director of the National Institute of Environmental Health Sciences concluded that swap was likely a regrettable substitution, meaning the replacements appear about as concerning as what they replaced. Those newer flame retardants have themselves been associated with lower IQ in children, and human exposure to them now often runs higher than peak PBDE exposure ever did. On the pesticide side, several organophosphates remain in agricultural and consumer use, though restrictions on specific ones like chlorpyrifos have shifted over time. Part of the TENDR authors’ argument was that this pattern, where a phased-out chemical is replaced by a barely-tested cousin, is exactly what a functioning regulatory system would prevent, which is why they framed the statement as a call for policy change rather than only individual caution.
Source: Project TENDR: Targeting Environmental Neuro-Developmental Risks. The TENDR Consensus Statement. Environmental Health Perspectives, 2016; 124(7): A118–A122. DOI: 10.1289/EHP358. Available at PubMed Central and via Project TENDR.