Environmental Toxins and the Midlife Brain

What I Want Every Woman to Know

TL;DR: Environmental toxins — mold, mercury, PFAS, plastics, pesticides, air pollution — are an important contributor to cognitive decline and they are everywhere. Exposure alone doesn’t determine your outcome; what matters just as much is your “terrain”: your hormones, metabolic health, nutrition, and what else your body is managing, especially in midlife when menopause is already reshaping brain metabolism. Toxins don’t need to be labeled “neurotoxic” to reach your brain, and different forms of the same toxin (like the three types of mercury) behave completely differently in the body.

The practical approach: stop ongoing exposure first, target the highest-impact sources rather than chasing perfection, support your body’s natural elimination routes, and reserve testing for when something’s actually wrong rather than routine fishing. The goal isn’t a toxin-free life — it’s understanding what matters, reducing what you reasonably can, and building enough resilience to handle the rest.

Anne and Beth live in the same house, drink the same water, breathe the same air — but have ended up with very different health scenarios. Anne developed headaches, fatigue, poor sleep, and brain fog. Beth reports feeling perfectly fine.

Testing results appeared paradoxical. Beth had a marginally higher measured toxicant level but feels okay. Anne’s levels were a bit lower, but she struggles.

We want medicine to hand us a number that separates safe from unsafe.

For each type of toxin, not only do we need to know the dose and duration, we also need to know hormones, genetics, nutritional status, metabolic health, immune function, gut health, liver and kidney function, prior exposures, and whatever else your body happens to be handling at the same time.

But that would make understanding and managing toxins easy. It is not.

For a woman in midlife, everything matters.

Note: This is a long and dense article. Here’s the principle I want you to keep in mind as you read it: exposure is only half the story. The other half is the woman being exposed. A toxin acts on the terrain of a woman’s body and brain health. In other words, toxin exposure must be considered in the broader context of whole health.

Environmental toxins are everywhere.

Some toxins occur naturally — mycotoxins from certain molds, for instance. Others are man-made: mercury and lead, industrial chemicals like PFAS and PCBs, plastic-associated compounds like BPA and phthalates, pesticides and herbicides, solvents, and the mixture of particulates and combustion byproducts we lump together as air pollution.

These toxins don’t behave alike, and exposure doesn’t automatically mean illness. But calling all of this “environmental toxin exposure,” and leaving it at that, undersells how much of it is genuinely capable of interfering with human biology.

So the useful question is not “have I had environmental toxin exposure?“

You have.

It’s “what have I been exposed to, how much, for how long — and what does that mean for me?“

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Neurotoxins aren’t the only toxins that affect your brain

Some environmental toxicants are explicitly neurotoxic — they interfere directly with neurons or nervous-system function. Others are cytotoxic, disrupt hormones, alter immune signaling, generate oxidative stress, injure blood vessels, or impair mitochondria, the structures that generate most of our cellular energy.

Those distinctions are clinically important. But your body doesn’t operate as a set of silos, independent of each other. A toxicant that disrupts thyroid physiology can eventually show up as fatigue, mood changes, or brain fog. A chemical that damages vascular health changes the blood supply your brain depends on. Chronic oxidative stress and mitochondrial dysfunction can occur in every cell of the body.

This is the whole point of systems medicine: a chemical doesn’t need the label neurotoxin for its downstream effects to reach your brain.

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Menopause changes the terrain

For generations, we treated menopause as something that happened to the ovaries. Your brain disagrees vehemently.

Neuroscientist Dr. Lisa Mosconi has used PET imaging to track women’s brains across the menopausal transition. Estrogen isn’t just a reproductive hormone — it participates directly in brain-energy metabolism, helping neurons use glucose for fuel.

In her TED talk, Mosconi shows PET scans of the same woman’s brain at 43, before menopause, and eight years later, documenting roughly a 30 percent drop in brain energy levels. Her broader body of research shows that this shift in brain metabolism tracks with the menopausal transition itself, independent of chronological aging.

Meanwhile, the rest of the body is shifting too: blood pressure and lipids can rise, insulin sensitivity and body composition can change, visceral fat tends to increase, bone loss accelerates, and the sex hormones that help regulate immune function are in flux.

A 52-year-old woman isn’t her 42-year-old self plus ten birthdays. The terrain has changed.

So the question isn’t whether a chemical somehow becomes more toxic after menopause — it’s what happens when a brain and body already navigating major metabolic and hormonal shifts absorb additional neurotoxic, endocrine, inflammatory, or mitochondrial stress on top of that.

There isn’t a single number for a lifetime of exposure.

Think about forty or fifty years of living: the houses you’ve lived in, the water you’ve drunk, the cities, the workplaces, the food, the cookware, the cosmetics, the plastics, the pesticides, the renovations, the smoke, the mold, the dental work, the hobbies.

Different compounds move through the body on entirely different timelines. Some clear quickly once exposure stops. Others accumulate in specific tissues for years. And nobody encounters chemicals one at a time under laboratory conditions, isolated from everything else.

This is why I find total environmental load clinically useful, even though it isn’t a single validated number on a lab report. It’s a way of asking how many environmental toxicant demands are arriving in a system that already has other work to do.

Toxins I see most commonly

Mold and mycotoxins

“Mold” isn’t one substance, and neither is “mycotoxin.”

Ochratoxin A, produced by certain Aspergillus and Penicillium species, is best known for kidney toxicity, but experimental research also links it to neurotoxic effects involving oxidative stress, mitochondrial injury, and neuroinflammation.

Trichothecenes, including T-2 toxin and DON, interfere with protein synthesis and cellular barriers, and affect immune and gastrointestinal function; research also points to effects on the blood-brain barrier and nervous system.

Zearalenone is particularly relevant for women because it can interact with estrogen signaling.

Gliotoxin, associated with Aspergillus, is immunotoxic and pro-oxidative.

What I want you to notice isn’t the names themselves — it’s how differently each one behaves. One leans toward mitochondria and nerve tissue, another toward the immune system, another toward estrogen receptors, at exactly the stage of life when your own estrogen signaling is already in flux. “Mold toxicity” isn’t one biological event, which is why “I have mold” tells me almost nothing on its own.

This matters especially if you’re in the thick of perimenopause or menopause, when brain fog, fatigue, and mood shifts get waved away as “just hormones.” Sometimes they are. But if you’ve had water damage, a musty basement, or a smell you can’t place, mold deserves a seat at that table too — not just estrogen.

Mercury isn’t one thing either

Methylmercury is the form we usually think of with contaminated fish. It’s efficiently absorbed and readily reaches tissue, including the brain — and large predatory fish accumulate more of it as mercury concentrates up the food chain.

Elemental mercury behaves differently: poorly absorbed if swallowed, but mercury vapor is readily absorbed through the lungs and crosses into the brain. Dental amalgams — the “silver fillings” — are roughly 50 percent elemental mercury and continuously release small amounts of vapor, especially during chewing.

The FDA recognizes amalgam as a source of low-level mercury exposure and advises avoiding new amalgams in certain higher-risk groups, including pregnant and nursing women, young children, people with pre-existing neurological disease, impaired kidney function, or known mercury sensitivity [1].

Inorganic mercury crosses into the brain less readily but can accumulate elsewhere, particularly the kidneys. And these forms aren’t sealed off from one another — methylmercury can undergo demethylation, becoming inorganic mercury as the body processes it.

Fish mercury and filling mercury are not the same exposure. They enter the body differently, travel differently, and land in different tissue. So a mercury result isn’t answered by “is it high?” It’s answered by asking what form, from what source, sitting in what tissue.

Let me share a case which illustrates an uncommon scenario. One of my patients blood mercury labs came back quite high. Turns out she eats a lot of fish and takes a fish-oil supplement. To segregate where the high mercury was coming from, we had her stop the fish oil supplement but continue eating fish for three months and then retested. Sure enough, her blood methylmercury levels declined to half the (still high) level, but her inorganic mercury levels shot up.

This is to be expected — methylmercury slowly demethylates into inorganic mercury in the body. But a confounding factor was that this patient also had dental amalgams: the elemental mercury vapor they release gets oxidized into inorganic mercury once it’s absorbed, which is a separate pathway to the same endpoint.

Granted, this is an N of 1, and I have not had this scenario with other patients, but it happened, so I am sharing it with you. I don’t recommend drilling out intact amalgams if a well-trained dentist tells me they don’t need to be removed, as removal itself can temporarily spike mercury-vapor exposure. Suffice to say that taking good quality supplements and deciding when it’s time to remove dental amalgams requires a thoughtful approach.

PFAS, PCBs, and the persistence problem

PFAS is a family of thousands of chemicals; PFOA and PFOS are the best studied. Research links PFAS exposure to changes in cholesterol, immune function, liver biology, and thyroid-hormone regulation.

Given how common thyroid disease is in midlife women, it is important to notice that fatigue, weight changes, and brain fog are classic menopause complaints, but they’re also classic thyroid complaints. PCBs and dioxins are older persistent pollutants that can linger in the environment and food chain long after their use was restricted.

Persistence changes the math, because yesterday’s exposure can continue to be a problem indefinitely — and body fat is one of the places it persists. Certain fat-soluble persistent pollutants accumulate in adipose tissue, and during significant weight loss, some can mobilize back into circulation.

Researchers are also investigating some environmental chemicals as obesogens, capable of influencing fat-cell development, endocrine signaling, inflammation, and metabolism. Body composition shifts substantially for many women around menopause, and it’s worth knowing that fat isn’t just a calorie warehouse — it’s biologically active tissue that can both store certain pollutants and be altered by them.

Plastics: heat is the variable that matters

BPA, BPS, phthalates, and other plastic-associated compounds can interfere with endocrine signaling. Now, I don’t need you to purge every piece of plastic from your life, but there are easy reductions available.

I don’t microwave food in plastic when glass or ceramic will do, and I don’t drink from a disposable water bottle that spent an afternoon baking in a hot car — heat increases migration of some compounds into what you’re eating or drinking. The same logic applies to piping-hot, fatty takeout sitting in a plastic container. Please don’t let these details cause distress; this is just low-effort exposure reduction.

Glyphosate and pesticides

“Pesticide” covers an enormous family of compounds. Organophosphate insecticides are well established as neurotoxic at sufficient exposure. Glyphosate is a different story and deserves its own discussion because of its ubiquitous nature.

Human biomonitoring suggests it clears the body relatively fast once exposure stops — one study estimated a urinary half-life of roughly 5½ to 10 hours [2]. That sounds reassuring until you notice the obvious catch: a chemical doesn’t need a long half-life if you keep encountering it.

Researcher Stephanie Seneff has proposed a mechanism worth knowing, although it remains debated. Because glyphosate is structurally related to the amino acid glycine, she has argued it may sometimes interfere with glycine-dependent proteins, substituting for glycine at susceptible sites — and has consequently proposed supplemental glycine as a strategy that might reduce this interference [3].

There’s real biochemical evidence that a critical glycine residue strongly influences how susceptible the plant and bacterial EPSPS enzyme is to glyphosate [4]. What hasn’t been established in human trials is that supplemental glycine meaningfully accelerates glyphosate clearance or prevents clinical effects in people.

But glycine is a very useful amino acid and has many other beneficial properties, the most critical being its contribution to better sleep, so I will often recommend its use. I also recommend talking to your HOA to see if a “green” pesticide or other measures to control weeds can be employed.

And don’t forget what you breathe

Air pollution is now recognized as a potentially modifiable dementia risk factor. PM2.5 — fine particulate matter small enough to penetrate deep into the lungs — is one major component, alongside nitrogen dioxide and other combustion products.

It isn’t only outdoor air, either. Gas stoves generate nitrogen dioxide and other combustion pollutants. Wildfire smoke carries fine particles and chemicals. Gasoline fumes contain volatile organic compounds. Paint, solvents, adhesives, and renovations can substantially change indoor air quality.

We spend enormous energy worrying about what goes into our mouths while breathing roughly twenty thousand times a day. The lungs deserve some of that attention. We have known combustion produces pollutants. We’re now getting much better at quantifying the exposure and asking what decades of relatively low-dose exposure might do.

Is this an argument for an induction cooktop? In a way, yes. I, myself, have a gas stove right now, and there is something satisfying about cooking food on gas because we have always done it this way.

But our houses are also now more sealed than before, and our stove ventilation may not be effective, giving us higher NO2 exposure than is good for us over decades.

Why does the brain care so much?

Because it’s expensive tissue — it demands extraordinary amounts of energy, precisely regulated blood flow, and exquisitely coordinated electrical and chemical signaling. Toxicants that interfere with mitochondria, generate oxidative stress, promote neuroinflammation, or disrupt neurotransmitters, vascular function, or the blood-brain barrier are landing on a system with very little margin for error.

Now place those insults next to a menopausal brain that’s already adapting to shifting estrogen signaling and energy metabolism. That doesn’t add up to toxin + menopause = cognitive decline. It adds up to something more realistic: multiple stressors converging on the same vulnerable system.

Toxins play an important role in cognitive decline

I’m trained in ReCODE, Dr. Dale Bredesen’s framework for identifying and reducing contributors to cognitive decline, and environmental toxins and biotoxins are one recognized category within it.

Bredesen describes a toxin-associated, or “Type 3,” pattern that he has said occurs more often in patients carrying the ApoE3 allele than ApoE4 — in his own words, “the ones who have ApoE4 tend to have more inflammation and the ones who have ApoE3 tend to do more poorly with toxins,” making Type 3 the harder subtype to treat [5]. His 2015 published research on Alzheimer’s subtypes corroborates this, describing the toxin-associated (“cortical”) pattern as typically ApoE4-negative [6].

That doesn’t mean carrying ApoE3 proves you have a toxin problem, or that if you have ApoE4 you don’t need to address toxins. It means when cognition is changing, I want environmental contributors considered carefully and individually.

When a woman tells me her brain fog started around menopause, I don’t reflexively blame her hormones. I don’t reflexively blame toxins either. I ask what else changed in her life at the same time — a move, a renovation, a new job, a leak that never got properly fixed.

I also don’t need toxins to explain everything. A woman can have declining estrogen, insulin resistance, sleep apnea, nutrient insufficiency, and significant mold exposure. Removing one contributor doesn’t erase the others — it just gives her brain one less problem to solve.

When do I test for toxins?

When a woman comes to me with concerns of cognitive decline, environmental contributors are already part of what I’m considering. My interest sharpens when there’s unusual fatigue, headaches, neuropathic symptoms, sleep disturbance, new sensitivities, or symptoms spanning several systems at once.

Then I want the story: When did this start? Did you move? Was there a leak? Did the office flood? Was your house renovated? What do you do for work? What are your hobbies? What do you eat on repeat? What’s in your water? Where do you feel worse — and, maybe most revealing, where do you feel better?

A toxin lab panel gives me the numbers. I combine it with her symptoms and history to formulate the full context.

The first rule of detox: turn off the faucet

If water is pouring across your kitchen floor, buying a better mop isn’t your first move. If you’re living in a water-damaged environment, supplements alone won’t fix it. If mercury is elevated, find the source. If drinking water is contaminated, address the water. If the exposure is occupational, protection from continued exposure is the treatment.

My sequence: identify, reduce or remove, support physiology, treat specifically when appropriate, reassess. You cannot meaningfully detoxify something you’re continuously putting back in.

Reduce what matters most

Environmental health can turn into an exhausting hunt for microscopic perfection. I don’t recommend that. Start with large, repeated, avoidable exposures: fix water intrusion, control mold and moisture, improve indoor air and ventilate when cooking, reduce smoke exposure, know what’s in your drinking water and filter for the contaminants you have.

Use a water filtration system. Use a HEPA air filter in rooms where you spend the most time.

Choose lower-mercury fish more often rather than cutting fish out entirely — SMASH (salmon, mackerel, anchovies, sardines, herring) is a useful shorthand for lower-mercury options. Skip the microwaved plastic. Don’t leave a water bottle baking in the car. Wash produce. Trim unnecessary pesticide, solvent, and fragrance exposure.

Then look beyond the kitchen. The art studio, workshop, salon, farm, renovation site, or shooting range may matter far more than the plastic straw you’ve been agonizing over.

Emunctories and the universal detox protocol

An emunctory is a route through which the body eliminates waste: the bowel, the kidneys and urinary tract, the skin through sweat, the lungs through gases and volatile substances.

When naturopathic doctors talk about keeping the emunctories “open,” we mean something very practical. Before asking the body to mobilize more of the unwanted material, I want the ordinary routes of elimination working well. Are your bowels moving regularly? Are your kidneys functioning appropriately? Are you well hydrated? Are you eating enough protein and micronutrients to support hepatic biotransformation? Are you moving, circulating, sweating, sleeping?

Mobilization without adequate elimination is counterproductive. That’s what I mean by a gentle detox — not starvation or purging or a juice cleanse. Reduce the incoming load, nourish the pathways that process it, keep the emunctories functioning, and use targeted interventions when the toxicant and the woman in front of me call for them. That’s my universal detox protocol for the toxin burden we all carry.

Upping your detox game with sauna

Your skin is your largest organ, and it is an excellent excretory route. Sauna can help excrete certain toxins through skin very effectively.

A systematic review found arsenic, cadmium, lead, and mercury in sweat, and in people with higher exposures or body burdens, sweat concentrations sometimes exceeded plasma or urine levels — the authors concluded that sweating deserves consideration as a route for toxic-element elimination, while calling for better therapeutic trials [7].

A more recent sauna study measured multiple toxic elements, including lead and mercury, in sauna-induced sweat [8]. There are studies that show that exercise produces greater sweat concentrations of several metals than passive sauna — a useful reminder that movement and sweating belong in the same conversation [9].

But sauna has another story worth telling. Heat exposure has been studied for cardiovascular, vascular, and metabolic effects, and observational Finnish research has linked frequent sauna use with lower risks of cardiovascular and neurocognitive disease.

I don’t think of sauna as simply a machine for sweating out chemicals — for the right patient, it can be part of a broader strategy involving circulation, cardiovascular health, heat adaptation, relaxation, and elimination. The right dose still depends on her blood pressure, hydration, medications, and cardiovascular status.

Should you get tested for toxins?

It depends.

If you feel terrific, think clearly, sleep well, function well, and have no meaningful exposure history, you don’t need to go fishing through ever-larger lab panels hoping to find something wrong.

My threshold changes when a woman isn’t well — cognitive changes, unexplained fatigue, neurological symptoms, a suspicious exposure history, a multisystem illness that isn’t adding up, or a family history of dementia.

In my practice, when I test because the history gives me a reason to look, I frequently find meaningful toxicant exposures. Then the real questions start: Is this level significant? Does it fit her symptoms? Where is it coming from? What else is going on physiologically? Will addressing it change how she feels and functions?

That’s different from fishing because it answers a clinical question.

The most important thing isn’t a number on a lab

Go back to Anne and Beth from the beginning. Beth had the higher measured toxicant level. Anne had the lower one. Who’s more affected? You still don’t know.

Now let’s find out more.

Beth is active, metabolically healthy, sleeping eight hours, well nourished, carrying relatively few other physiological stressors. Anne is in the roughest stretch of menopause — sleeping five hours, glucose dysregulated, nutrient-depleted, constipated, inflamed, carrying a history of prior exposures, with cognition already shifting. The lower exposure appears to carry greater consequence in Anne.

That’s where environmental medicine becomes systems medicine. Dose, body burden, and biological resilience make a huge difference. A reference range on a lab report can’t tell the whole story, because the toxicant never exists apart from the person carrying it — what it affects, what else is happening in her body, and what capacity she has to process, eliminate, and recover from it.

I don’t want a healthy woman finishing this article concerned and immediately ordering twenty toxin tests. I want her making smarter choices about the environment she lives in. But if your health is changing — particularly if it feels like your brain is changing — I don’t want environmental toxins dismissed without a second look.

Midlife is an extraordinary opportunity to shape the decades ahead. We can address blood pressure, insulin resistance, hormones, sleep, muscle, nutrition, exercise. We can protect careers, relationships, and mental health. And we can pay attention to the environment the biology has to function inside of.

The goal is not a toxin-free body in a toxic world. It’s something far more achievable: understand the exposures that matter, reduce what you can, keep your body’s routes of elimination working, investigate intelligently when something isn’t right, and give your brain and body as much resilience as possible for the years ahead.

Sources

“Dental Amalgam Fillings.” U.S. Food and Drug Administration. https://www.fda.gov/medical-devices/dental-devices/dental-amalgam-fillings
“Exploring the half-life of glyphosate in human urine samples.” PubMed. https://pubmed.ncbi.nlm.nih.gov/30293930/
Seneff, S. “Glyphosate Substitutes for Glycine: Does It or Doesn’t It?” stephanieseneff.net. https://stephanieseneff.net/glyphosate-substitutes-for-glycine/
“Site-directed mutagenesis of a conserved region of the 5-enolpyruvylshikimate-3-phosphate synthase active site.” ScienceDirect. https://www.sciencedirect.com/science/article/pii/S0021925818545804
Bredesen, D.E. Interviews on ApoE genotype and toxin-associated (“Type 3”) Alzheimer’s: The Jordan Harbinger Show, “How to Make Alzheimer’s Just a Bad Memory,” Aug. 4, 2018, https://www.jordanharbinger.com/dr-dale-bredesen-how-to-make-alzheimers-just-a-bad-memory/; and Dr. Jill Live!, “Dr. Jill Interviews Dr. Dale Bredesen on Reversal of Alzheimer’s Disease,” Aug. 26, 2021, https://www.jillcarnahan.com/2021/08/26/75-dr-jill-interviews-dr-dale-bredesen-on-reversal-of-alzheimers-disease/
Bredesen, D.E. “Metabolic profiling distinguishes three subtypes of Alzheimer’s disease.” Aging (Albany NY), 2015 Aug;7(8):595-600. https://pubmed.ncbi.nlm.nih.gov/26343025/
“Arsenic, cadmium, lead, and mercury in sweat: a systematic review.” PubMed. https://pubmed.ncbi.nlm.nih.gov/22505948/
“Effect of water filtration infrared-A (wIRA) sauna on inorganic ions excreted through sweat from the human body.” PubMed. https://pubmed.ncbi.nlm.nih.gov/36207634/
“Excretion of Ni, Pb, Cu, As, and Hg in Sweat under Two Sweating Conditions.” PubMed. https://pubmed.ncbi.nlm.nih.gov/35410004/

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