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These Chemicals Are Lowering Our IQ | Bruce Lanphear | AFP 49

The following is based on a conversation with Bruce Lanphear, a professor in Health Sciences at Simon Fraser University.

How Does Low-Level Lead Exposure Silently Trigger Adult Cardiovascular Disease?

While historic public health efforts focused heavily on lead’s impact on pediatric brain development and IQ loss, modern epidemiological data reveals that lead exposure is actually the primary environmental risk factor for coronary heart disease deaths globally. Lead stored in the skeleton (accounting for ~95% of an adult’s total lead burden) slowly leaches back into the bloodstream as bone density turns over, particularly during menopause or aging. Once circulating, lead induces systemic inflammation, contributes to arterial plaque build-up (atherosclerosis), and promotes high blood pressure (hypertension). Because lead exposure is ubiquitous across entire populations, its small individual physiological impact accumulates into a total mortality count that rivals or exceeds large individual risk factors like smoking.

Why Are Low-Dose Environmental Exposures Often More Dangerous at a Population Level Than High-Dose Poisons?

This phenomenon is explained by the Prevention Paradox. High-risk behavior (such as active cocaine use) dramatically increases an individual’s immediate risk of an adverse health event like a heart attack. However, because only a tiny fraction of the population uses cocaine, the absolute number of community heart attacks caused by it remains small. Conversely, widespread, low-level environmental contaminants—such as ambient air pollution, pesticides, or legacy lead—confer a subtle risk percentage increase per individual. Because 100% of the population is continuously exposed to these low doses, the absolute burden of chronic illness, premature births, and cognitive decline generated across millions of people vastly dwarfs the disease footprint of high-risk individual behaviors

What Does the Latest Science Say About Fluoridated Water and Pediatric Brain Development?

While topical fluoride (such as in toothpaste) provides clear benefits for oral health and enamel protection, systemic ingestion via public water fluoridation has come under intense scientific scrutiny. Recent systematic reviews and prospective mother-child cohort studies measuring maternal urinary fluoride during pregnancy consistently demonstrate an inverse relationship with child cognitive development. High maternal fluoride intake during fetal neurodevelopment correlates with measurable IQ point deficits in children. Because modern populations already receive high topical fluoride exposure via dental products, scientists and toxicologists are urging independent regulatory reviews to re-evaluate whether mass drinking water fluoridation still meets safety and efficacy thresholds for developing infants.

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Cleaned Transcript

Jeroen Schreel: Welcome to Apple Finch Pudding, your gateway into the world of science. Today’s guest is Bruce Lanphear, a professor at Simon Fraser University whose work focuses on environmental toxins. Welcome, Bruce.

Bruce Lanphear: Thank you. Glad to be here.

Jeroen Schreel: Before we start, do you have a fun science fact for our listeners?

Bruce Lanphear: Yeah, it’s actually a little bit drawn out. What I wanted to share is that the element lead was originally used to determine the age of the Earth. Clair Patterson measured the decay of uranium into lead to calculate the Earth’s age. However, he couldn’t get accurate results until he created an ultra-clean laboratory back in the 1960s because the Earth was already so heavily contaminated—the same challenge researchers face today when measuring microplastics.

To accomplish his work, he began asking questions: How much more lead do we have in our bones today compared to our pre-industrial ancestors? How much lead was in the atmosphere 2,000 years ago compared to now? Ultimately, all of this led him to realize: “We have so heavily contaminated the Earth, we have got to do something about it.”

Even though human blood lead levels have declined by roughly 95% over the past 40 to 50 years, we are still 10 to 100 times more heavily exposed to lead today than our pre-industrial ancestors. The levels we have are not inherently “low.” Because of what we observe with lead regarding behavior, learning abilities, premature birth, and heart disease, we don’t even know what a truly “normal” baseline is. We can only identify what is typical in a lead-contaminated environment. We could say the same for plastic-contaminated environments. It is typical, but is it normal? That is a question we need to keep asking.

Jeroen Schreel: That’s very interesting. You have a big focus on lead, and you mentioned it affects how we function and think. What do you mean by that, exactly?

Bruce Lanphear: Early evidence demonstrated that children exposed to higher amounts of lead performed worse on reading, math, and general IQ tests. That data was heavily used to drive how we regulate lead. In the 1970s, when the U.S. EPA was established, lead was designated as a primary criteria air pollutant.

Lead was initially removed from gasoline because it poisoned catalytic converters, not because it was toxic to humans. Around the same time, however, growing scientific evidence showed its toxicity to human health. It was long known that massive doses could kill people, but researchers like Herb Needleman, Phil Landrigan, and Joel Schwartz began investigating lower levels. They found that exposure levels previously assumed to be safe were actively reducing children’s learning abilities.

The developing brain is probably one of the most sensitive organs in existence. When environmental epidemiologists evaluate a new chemical, one of our first thoughts is: “Can we study this in a pediatric population to see if it impairs brain development?”

Jeroen Schreel: How severe are these learning disabilities and developmental issues?

Bruce Lanphear: At extraordinarily high exposures, it can be severe enough to drop a child’s IQ below 85. But more broadly, we see whole-population shifts. Consider a blood lead level of 5 μg/dL. Roughly one in three children globally currently has a blood lead level exceeding 5 μg/dL (equivalent to 50 parts per billion in blood). At that concentration, children lose an average of about 5 IQ points.

When you shift an entire national population’s IQ distribution downward by 5 points, you trigger roughly a 60% increase in the number of children falling below an IQ of 70—the threshold where individuals struggle to participate in the workforce or live independently. It isn’t just affecting one isolated child at a time.

Furthermore, lead is only one contributor. Mercury, air pollution, specific pesticides, and poor nutrition also diminish cognitive potential. What worries me most is that these chemical exposures cluster in lower-income neighborhoods. In communities where I’ve worked, children don’t just live in housing with legacy lead paint; they also live near highway emissions, in multi-unit buildings with monthly cockroach pesticide treatments, and around older furniture leaching PBDE flame retardants. Society often blames genetics, parents, or teachers for poorer educational outcomes in disadvantaged areas, but widespread toxic exposure is a massive, understated factor.

Jeroen Schreel: You have stated that many chronic diseases are man-made. What evidence brought you to that conclusion?

Bruce Lanphear: Lead is a prime example. Most people aren’t aware that lead is a primary risk factor for coronary heart disease and heart attacks—the leading cause of global mortality. In a 2018 study, we published findings showing that lead was a leading risk factor for fatal coronary heart disease. We usually hear about cholesterol, obesity, and smoking. Those are valid, but lead exposure proved to be just as critical.

If you smoke, your risk of coronary heart disease roughly doubles. Going from the 10th to the 90th percentile of population blood lead levels carries a comparable relative risk. Yet overall, lead accounted for more total deaths than smoking. Why? Because only ~20% of adults smoked, whereas 100% of the population was exposed to lead.

As epidemiologist Geoffrey Rose explained, small risks spread across massive populations dwarf huge risks confined to tiny groups. Consider cocaine: using cocaine increases your heart attack risk over 20-fold in the subsequent 24 hours. Ambient air pollution increases individual heart attack risk by only 5% to 10%. But air pollution causes far more total heart attacks than cocaine annually because everyone breathes polluted air, while very few use cocaine.

Jeroen Schreel: Gasoline lead was phased out decades ago. Where is modern lead exposure coming from?

Bruce Lanphear: In adults, ~95% of lead is stored long-term in the bones (~70% in children). During the peak of leaded gasoline in 1970s Britain, the typical male carried about 150 milligrams of lead in his skeleton—equivalent to three paperclips. A lead-poisoned worker carried about 500 milligrams. As women age into menopause, bone turnover accelerates, triggering a notable surge in circulating blood lead levels as historical deposits leach back into the bloodstream.

Interestingly, between 1968 and 1978, public health agencies observed an unexpected 20% drop in U.S. coronary heart disease deaths. At the time, health officials couldn’t fully explain it. Recent epidemiological mapping demonstrates that this historic decline in heart attacks and hypertension tracks almost perfectly with the phase-out of leaded gasoline.

Bruce Lanphear: Occupational exposures are much easier to trace than general environmental exposure. My father had ALS (Lou Gehrig’s disease). I had two uncles with Parkinson’s disease—one was a welder exposed to high levels of manganese, and another was a machinist exposed to trichloroethylene (TCE). A third uncle died of bladder cancer after working at a chemical dye factory.

High workplace exposures stand out clearly. Environmental exposures—like low-level air pollution, heavy metals, or widespread agricultural pesticides—are harder to isolate per person, but they affect entire populations. The Lancet Commission on Pollution and Health estimated that 1 in 5 global deaths is directly attributable to toxic chemicals and pollution.

Jeroen Schreel: One in five deaths is an incredible number. Why is there so little public awareness or funding assigned to this?

Bruce Lanphear: According to World Bank estimates, lead exposure alone causes roughly 5.5 million premature deaths annually. Yet in 2023, total global international aid earmarked for lead poisoning prevention was approximately $15 million. Contrast that with HIV/AIDS, which caused ~1 million deaths globally that year and received $8 billion in international aid.

Medical care focuses downstream on clinical treatments—stents, hypertension drugs, and symptom management. Environmental epidemiology moves upstream to ask: “Why are people developing hypertension in the first place?”

I once surveyed over 1,000 pediatricians across 10 medical conferences. I asked them: “If you had to allocate public funds, would you invest in enhancing treatments for childhood leukemia, or in researching how to prevent childhood leukemia?” 99.5% voted for prevention research. Yet, less than 1% of the National Cancer Institute’s childhood cancer budget goes toward environmental prevention. The institutional medical-industrial ecosystem is organized around profitable downstream pharmaceutical treatments rather than upstream prevention.

Bruce Lanphear: As a society, we must also re-evaluate how we handle healthspan and mortality. When my father was diagnosed with ALS in 2007, I looked at his history. He had three distinct population-level risk factors: severe head trauma from a scooter accident, childhood lead exposure growing up above a garage, and pesticide exposure from living downwind of—and working at—a golf course. While you cannot state definitively that those factors caused his specific case, each factor elevated his baseline risk.

Since ALS was incurable, we prioritized how he wanted to live out his remaining time. Most lifetime healthcare expenditures occur in the final six months of life, often inside intensive care units. My father chose to die at home. He lived in a co-housing community, surrounded by family and friends singing and visiting. His passing was peaceful, community-centered, non-medicalized, and fundamentally inexpensive. Maximizing quality of life and healthspan is far more vital than simply prolonging medicalized survival.

Jeroen Schreel: There seems to be a major shift underway toward prioritizing healthspan over raw lifespan.

Bruce Lanphear: Absolutely. Right now, society places the total burden on the individual to research clean eating, avoid pesticides, and find time to exercise. But we can design environments that make healthy choices automatic.

For example, a randomized controlled trial provided participants with free public transit passes and access to a car-share service. Over three months, the intervention group lost an average of 8 pounds simply by walking more, whereas the control group gained weight. Walkable urban environments, accessible public transit, reduced air pollution, and widely available organic foods systematically extend population healthspan while lowering long-term national medical expenditures.

Jeroen Schreel: If someone goes outside to exercise, are they risking higher exposure to outdoor air pollution?

Bruce Lanphear: Unless there is an acute hazard like wildfire smoke or severe respiratory illness, the physiological benefits of outdoor exercise generally outweigh the risks. Studies show that exercise helps offset some metabolic risks associated with PFAS (“forever chemicals”) exposure.

However, localized air pollution sources remain a problem. General vehicular pollution is measured via particulates, sulfur dioxide, nitrogen dioxide, and ozone. But niche exposures persist—for instance, small aviation airports still burn leaded avgas. Children living downwind of general aviation airports exhibit up to 25% higher blood lead levels.

Agricultural pesticide drift is another systemic issue. Studies demonstrate that pregnant women living near active farm fields face elevated rates of premature births and higher incidences of neurodevelopmental disorders like autism in their children.

Jeroen Schreel: Many people assume indoor environments are safe, but everyday consumer exposures exist. What about fluoride?

Bruce Lanphear: We must distinguish between topical fluoride toothpaste and systemic fluoride added to municipal drinking water. Dental research demonstrates that topical application (toothpaste) drives dental health benefits, not ingested water. A October 2024 Cochrane review evaluating fluoridation studies conducted since 1975 found that water fluoridation provided minimal to no additional benefit in reducing tooth decay in modern populations where fluoride toothpaste is widely used.

Concurrently, a growing body of scientific literature—including prospective mother-child cohort studies measuring fluoride in maternal urine during pregnancy—consistently links higher prenatal fluoride exposure with lower IQ scores in children.

When administering population-wide public health interventions where individuals cannot opt out (such as drinking water additives), safety and efficacy standards must be exceptionally high. Formula-fed infants, in particular, receive very high relative fluoride doses when formula is mixed with fluoridated tap water. Independent scientific reviews need to re-evaluate water fluoridation policies based on current neurotoxicity data.

Jeroen Schreel: What worries you most about the current landscape of environmental health?

Bruce Lanphear: What worries me most is our reliance on obsolete regulatory systems. Current frameworks assume chemicals have “safe thresholds” and often rely on a few small, industry-funded animal studies to clear a new compound for market entry.

Once a chemical is commercialized, the burden of proof flips. Regulators then require dozens or hundreds of independent human epidemiological studies showing clear harm before taking action to restrict or ban it. Proving specific real-world toxicity for complex, multi-exposure conditions like ADHD or autism requires tracking cohorts over a decade while controlling for countless variables. The system is structurally designed to protect industrial chemicals rather than public health.

We need proactive frameworks. As critical green-technology metals like lithium expand worldwide, we should establish baseline national biomonitoring now and levy small fees on industrial manufacturing profits to fund independent, long-term toxicological safety research.

Jeroen Schreel: What practical, short-term steps can individuals take in their daily lives to reduce toxicity?

Bruce Lanphear: You don’t need to change everything overnight. Incremental, sustainable changes make a big difference over time:

  • Air Quality: Use a portable HEPA air filter indoors, particularly if ambient PM2.5 levels exceed 5 μg/m3 or during wildfire events.
  • Diet & Food Prep: Cook meals from scratch using whole ingredients whenever possible. Choose organic produce when accessible, avoid canned foods lined with synthetic resins, and minimize ultra-processed, heavily packaged products.
  • Lawn Care: Eliminate cosmetic pesticide and herbicide use around homes and gardens.
  • Personal Care Products: Reduce the use of synthetic cosmetics and fragrances. Nail polishes, synthetic perfumes, and scented dryer sheets frequently contain phthalates and endocrine-disrupting chemicals. Use wool dryer balls instead.
  • Kitchenware & Apparel: Transition away from plastic food storage containers and non-stick cookware. Choose natural textile clothing like cotton and wool over synthetic fabrics when feasible.

Jeroen Schreel: Buying organic food or natural fabrics can be expensive. How do we make this accessible?

Bruce Lanphear: Advocating for living wages and equitable economic structures is a public health necessity. When families have adequate financial resources, they can afford healthier food and cleaner living environments, which yields long-term healthcare savings for society.

Jeroen Schreel: What is your final take-home message for our audience?

Bruce Lanphear: While it is sobering that so many chronic health conditions are man-made, it is also deeply empowering. It means we don’t have to wait for expensive future drug developments to transform human health. By applying what we already know today to clean up our environments, food, and water, we can prevent a vast amount of disease, disability, and premature death.

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