Experts are warning that we could be facing a plastic-fuelled public health crisis based on alarming levels of microplastics in our bodies and growing evidence of their health effects.

Defined as shards of plastic less than five millimetres in size, microplastics are everywhere, from the summit of Everest to the deepest ocean trenches. They have been found in 1,300 animal species, including in the breath of dolphins.

They are in our food, our water, our air – and they have been detected throughout the human body, including the blood, lungs, liver, breast milk, testicles and recently the brain. We inhale them, consume them and swallow them – from the air, from seafood, from table salt, from alcohol, from bottled water, from our microwaved lunch.

Studies estimate that 10 to 40 million tonnes microplastics are put into the environment every year – and this number is expected to double by 2040.

But how are they affecting our health? Let’s look at the science.

Brain deep-dive

In February this year, a paper in Nature Medicine that found that our brains may contain as much as 7 grams of tiny plastic shards – about the same weight as a plastic spoon. This is a much higher concentration (7 to 30 times more) than in other organs like the liver or kidney.

In addition, the study found that levels of microplastics in the brain are increasing over time, by about 50% between 2016 and 2024.

Further, microplastic levels were 3 to 5 times higher in the brains of people with dementia diagnosis – though the sample size was low (12 patients) and this is an association so does not prove causation.

This week, a new commentary in the journal Brain Medicine delves into alarming evidence of microplastics in the brain and discusses its health implications.

“The dramatic increase in brain microplastic concentrations over just eight years, from 2016 to 2024, is particularly alarming,” notes lead author Nicholas Fabiano from Canada’s University of Ottawa. “This rise mirrors the exponential increase we’re seeing in environmental microplastic levels.”

The authors express particular concern about microplastic particles smaller than 200 nanometres in width. These particles are largely composed of polyethylene (the most commonly produced plastic, accounting for 34% of the total plastics market), and are small enough to potentially cross the blood-brain barrier – a layer of cells that acts like a filter to keep harmful substances out of the central nervous system.

However, the researchers note that there is still so much we don’t know about how microplastics may enter and affect our organs, citing the findings around dementia patients as an example.

“Is dementia weakening the blood-brain barrier, allowing more microplastics to enter?” they ask. “Or do microplastics, once inside, trigger microinflammation and make it harder for the brain to clear proteins, potentially worsening neurodegeneration?”

With so many unknowns, what do we know so far about the link between microplastics and human health?

Health crisis?

How microplastics harm our health is not yet fully understood, but the last 5 years has seen a flurry of research, mostly using animals and cell cultures.

Exposing lab mice to microplastics, for example, can lead to disruption of the gut biome, inflammation, lower sperm quality and testosterone levels, and negative effects to learning and memory.

Microplastics also adversely affected human tissue grown in the lab to resemble lungs. A 2022 study tested the effects of microplastic fibres on these organoids and found that the exposure significantly reduced the number and size of airways forming in the tissues. The researchers linked this inhibited growth not to the microplastic fibres themselves, but to the chemicals they released, thus suggesting that microplastics are a form of air pollution that could be inducing stress in our lungs.

A broader 2024 review of microplastics and their effects on different organ systems found that they can cause “oxidative stress, inflammation, immune dysfunction, altered biochemical and energy metabolism, impaired cell proliferation, disrupted microbial metabolic pathways, abnormal organ development, and carcinogenicity”.

But that’s in non-human studies – and some of the exposure levels were much higher than we would experience in everyday scenarios.

So what about humans?

Microplastics in humans

With limited human data, clear answers may be some years away. However, evidence is beginning to emerge, especially over the last 12 months.

A 2024 study found that people with microplastics in their blood vessels were 4.5 times more likely to have a heart attack or stroke, or to die, than people without them. Similarly, a paper in Environmental Science & Technology found that patients with inflammatory bowel disease had 1.5 times more microplastics in their stool samples than their healthy counterparts.

For both studies, this is an association, not a clear causation.

In another paper published last year in the Journal of Exposure Science & Environmental Epidemiology, researchers review the presence of microplastics in the urinary tract, finding them in 54% of urine samples, 70% of kidney samples and 68% of bladder cancer cases. They report that the microplastics caused toxicity and inflammation, reducing cell survival.

“The documented cytotoxic effects of microplastics, alongside their ability to induce inflammation, reduce cell viability and disrupt signalling pathways, raise significant public health concerns relating to bladder cancer, chronic kidney disease, chronic urinary tract infections and incontinence,” the authors write.

One of the researchers, Liam O’Callaghan from Australia’s Bond University, says much more research is needed.

“We know microplastics are found in cancers, but do they have anything to do with forming the cancers? We don’t know yet.”

Another new study, which will be presented at an American Academy of Neurology conference in April, links microplastics to disability.

After studying 218 US coastal counties, the researchers found that the average percentage of thinking and memory disabilities was 15.2% in areas with high levels of microplastics compared to 13.9% in areas with the lowest levels.

For mobility disabilities, the percentages were 14.1% vs 12.3%; for self-care disabilities, it was 4.2% vs 3.6%; for independent living disabilities, it was 8.5% vs 7.7%.

“Our study found [that] in coastal communities with higher levels of microplastics in the water, there were higher rates of disabilities that can affect a person’s life in many ways through thinking and memory, movement and their ability to take care of themselves and live independently,” says Sarju Ganatra from Lahey Hospital and Medical Center in Burlington, Massachusetts, US.

Importantly, the study does not prove that microplastics are the cause of disabilities – it only shows an association.

What action can we take?

Though the jury is still out on exactly how microplastics affect our health, it’s clear that we need to change the way we use plastic – by consuming much, much less of it.

For example, the Brain Medicine commentary outlines the evidence for switching from bottled to tap water.

“Bottled water alone can expose people to nearly as many microplastic particles annually as all ingested and inhaled sources combined,” says Brandon Luu from the University of Toronto in Canada. “Switching to tap water could reduce this exposure by almost 90%, making it one of the simplest ways to cut down on microplastic intake.” 

Other significant microplastic sources include plastic tea bags, seafood, alcohol and processed foods. As a result of industrial processing, chicken nuggets have been found to contain 30 times more microplastics per gram than chicken breasts.

Many cosmetics are also imbued with microbeads, while clothing made from synthetic materials like acrylic and polyester shed microplastics during wear and washing. Reducing consumption of these products will help reduce microplastic intake.

Luu also points out the importance of the containers we eat from.

“Heating food in plastic containers – especially in the microwave – can release substantial amounts of microplastics and nanoplastics,” he explains. “Avoiding plastic food storage and using glass or stainless steel alternatives is a small but meaningful step in limiting exposure.”

Ventilating and vacuuming your home can also reduce inhalation of microplastics in the dust on surfaces and in the air.

“While these changes make sense, we still need research to confirm whether lowering intake leads to reduced accumulation in human tissues,” Luu says.

Luu and colleagues also note that “one of the most hopeful aspects of the findings to date is the lack of correlation between age and microplastic accumulation, suggesting that despite ongoing environmental exposures, the body has mechanisms to clear these particles over time through sweat, urine, and feces”.

In addition, we need to better understand our exposure to microplastics. Monitoring projects already exist; in Europe, 75 organisations are part of the CUSP collaboration which runs 5 large-scale projects to quantify microplastics exposure.

This pollution also needs to be addressed on a structural level through legislation. The US state of California recently became the first government entity in the world to test drinking water for microplastic – but what about closer to home?

“While several initiatives have been introduced across Australia to address plastic waste – such as the banning of plastic bags by Coles and Woolworths, restrictions on single-use plastics, the Victorian container deposit scheme, and the longstanding South Australian container deposit scheme – specific legislation targeting microplastics remains absent on a national scale,” write University of New South Wales researchers in a 2024 review of microplastics in Australia.

They also explore the legislative measures and policies of other countries to recommend ones to implement in Australia. These include:

1. clearly defining micro- and nanoplastics;
2. requiring industries to redesign goods to minimise plastic;
3. restricting or replacing microplastics in cosmetic products and pharmaceuticals;
4. and identifying chemicals (such as additives in plastics) that generate microplastics, among many others.

“The government should also provide more funding exclusively for microplastics research and arranging training, workshop for academic, non-governmental organisations (NGOs) to mitigate the looming threats of microplastics pollution,” they conclude.

David Puder, co-author of the Brain Medicine paper, agrees: “We need more research to wrap our heads around microplastics – rather than wrapping our brains in them – since this could be one of the biggest environmental storms most people never saw coming.”