Hidden toxins poisoning our brains

Garcia showing a plastic toy that was collected from a Hawaii beach. — Gabriela Campos/The New York Times

IN a dimly lit basement laboratory at the University of New Mexico, Marcus Garcia dug through a bin overflowing with plastic detritus – cracked water bottles, frayed fishing nets, a child’s toothbrush, a faded Pokemon mug.

“Yes!” he exclaimed, brandishing a cracked pipette tip, its once-pristine plastic yellowed by years of sun and saltwater.

Months earlier, Garcia had plucked this relic from a remote Hawaiian beach during a research expedition.

For a scientist who uses pipette tips daily, the discovery was surreal: a tool of modern medicine now emblematic of humanity’s plastic plague.

Garcia, a post-doctoral fellow in pharmaceutical sciences, works alongside toxicologist Matthew Campen in one of the world’s most foreboding research fields: tracing how microplastics – particles smaller than 5mm – invade our bodies.

Their February 2024 study in Nature Medicine sent shockwaves through the scientific community.

Analysing human brain tissue, they found 50% more microplastics in 2024 samples compared to 2016 – with dementia patients’ brains harbouring significantly higher concentrations.

“This isn’t just accumulating in our environment,” Campen warned. “It’s bioaccumulating in us – and fast.”

Campen, who runs a lab at the University of New Mexico that has found microplastics in human brains, placentas, testes and other organs. - — Gabriela Campos/The New York Times

The lab’s findings read like a horror anthology.

Microplastics have infiltrated placentas, testes, breast milk and even newborns’ first stools.

Preliminary data suggests preterm babies’ placentas contain more particles than full-term ones, despite shorter gestation periods.

Yet critical questions remain unanswered: What dose is toxic? Which plastics pose the greatest risk? And how are they bypassing our biological defences?

To unravel this, Campen’s team turned to an unlikely resource: the dead.

Analysing 24 human brains donated post-mortem, they estimated a median concentration of 5,000 micrograms of microplastics per gram of tissue – roughly 7gm per brain, equivalent to five plastic bottle caps.

Brains from dementia patients showed markedly higher levels, a phenomenon Campen theorises could stem from a compromised blood-brain barrier.

“Nobody’s thrilled to learn their cerebellum doubles as a landfill,” Campen quipped. “But this is just the baseline. Production’s skyrocketing – imagine the numbers in 2034.”

Using atomic force microscopes, Campen identified shard-like fragments as tiny as 200 nanometres – 400 times thinner than a human hair – that slip past the body’s defences.

Earlier studies, relying on lower-resolution tools, missed these ultrafine particles, suggesting that exposure has been grossly underestimated.

“Think of it like this,” Campen explained. “Previous research spotted boulders. We’re finding sand – and it’s everywhere.”

Christy Tyler, an environmental scientist at New York’s Rochester Institute of Technology, notes that plastics now pervade every ecosystem: “They’re in soil, rain, Arctic ice, food chains. Everywhere.”

Campen’s team traced most brain microplastics to polyethylene, the dominant plastic of the 1960s, implying decades of environmental degradation.

Even if production halted today, existing waste – over nine billion metric tonnes globally – would keep fragmenting into our bodies for centuries.

The lab’s work intersects jarringly with Garcia’s Hawaiian fieldwork.

In July 2023, he joined volunteers hauling 816kg of plastic waste – including syringes, bleach bottles and lab equipment – from a single beach.

A researcher studying microplastics content in samples at the lab. - — Gabriela Campos/The New York Times

“You’d find a toy shovel, then realise it’s from the ’80s,” Garcia recalled. “This isn’t just trash. It’s a timeline of human recklessness.”

Back in Albuquerque, PhD student Teya Garland donned a respirator and fed coloured plastic chunks into a cryogenic grinder, its banshee wail reducing them to dust.

These particles, sourced from Hawaiian debris, will soon be fed to mice in landmark experiments probing neurological damage.

“We’re simulating decades of human exposure in months,” Garland said.

Early animal studies hint at dire outcomes: inflammation, hormonal disruption, developmental delays. Yet human risks remain murky.

“Is 5,000 micrograms harmful? 50,000? We’ve no idea,” Campen admitted.

While Campen downplays risks from “fresh” plastics – like those shed by water bottles – others urge caution.

Tracey Woodruff, a reproductive health expert at UC San Francisco, warns nanoparticles from synthetic fabrics or food containers may still wreak havoc: “Reducing exposure isn’t paranoia. It’s prudence.”

The science is fraught with caveats. Current tools struggle to distinguish microplastics from natural lipids, leading some to question Campen’s estimates.

“Their brain concentrations seem high,” Woodruff acknowledged, “but the upward trend aligns with plastic production curves. That’s undeniable.”

Since the 1950s, global plastic production has doubled every 10–15 years. By 2050, projections suggest 12 billion metric tonnes will clog landfills and ecosystems – enough to bury Manhattan under a 3km-high mound.

For Campen, the Hawaii pipette tip epitomises this legacy: “It’s a relic of our throwaway culture. And a warning.”

The lab now hunts for pre-1970s brain samples to compare plastic loads.

“Imagine a Victorian-era brain preserved in formaldehyde,” Campen mused. “That’s our holy grail.”

In adjacent labs, mice nibble pellets laced with Hawaiian plastic dust. Researchers monitor their cognition in mazes, memory tests and social behaviours.

Early data suggests impaired learning at high doses – a potential parallel to human neurodegenerative diseases.

“We’re not just studying toxicity,” Garland said. “We’re mapping how plastics age in the environment. A bottle discarded today might become brain-invasive nanoparticles in 2070.”

As Garland’s mice maze their way towards answers, humanity faces an uncomfortable truth: we’re unwitting participants in the largest toxicological experiment in history.

“Plastics are the new leaded petrol,” Campen said. “By the time we grasp the damage, it’ll be in our grandchildren’s bones.”

For Garcia, combing Hawaiian beaches, the urgency is visceral.

“Every pipette tip I find – that’s our waste. Our hubris. And unless we change, our epitaph.” — ©2025 The New York Times Company

This article originally appeared in The New York Times.