Microplastics are tiny plastic particles — smaller than 5 mm, down to the nanometre scale — that have worked their way into our water, food, air, and now our own bodies. Whether they actively harm human health is still being established, but the picture has changed sharply since 2019: microplastics have now been found in human blood, placenta, lungs, arteries, and breast milk, and in 2024 they were linked for the first time to serious cardiovascular events in people.
If you’re dealing with a chronic condition that won’t shift, this is a source of exposure worth understanding — because you can be doing everything “right” with your food storage and still be quietly accumulating plastic.
Most of us picture plastic pollution as the visible stuff: bottles, bags, the debris in the stomachs of fish and seabirds. But a 2017 IUCN report found that microplastics make up a larger share of ocean plastic pollution than any of that visible waste (Boucher & Friot, 2017). Because they’re so small, they slip through water filtration systems and end up in our soil, air, oceans, and food supply.
What are microplastics and nanoplastics?
Microplastics are not one specific material — they’re small fragments of plastic from many sources. “Primary” microplastics are defined as pieces 5 mm or smaller, and they degrade further, down to around 1.6 micrometres. Nanoplastics are far smaller again, around 100 nanometres — small enough to cross biological barriers that larger particles can’t.
They come from sources such as:
- Microfibres shed from synthetic clothing
- Microbeads in exfoliants and cosmetics
- Industrial plastic pellets
- Degradation of larger items — electronics, car tyres, drink bottles, food packaging, fishing nets, plastic bags
How do microplastics get into your body?
Three main routes: you eat them, you breathe them in, and to a lesser extent they cross the skin. Diet is the one most people can act on, so it’s worth knowing which foods carry the most.
A useful example is the humble tea bag. Many bags are sealed with polypropylene, a thermoplastic that softens with heat — exactly the conditions you create when you brew. Researchers at McGill University found that a single plastic tea bag can release billions of microplastic and nanoplastic particles into one cup of hot water (Hernandez et al., 2019). In that study the tea leaves were removed first, so this was the bag alone, and both cut and uncut bags were tested across four brands to rule out the cutting process.
Which foods and drinks contain the most microplastics?
Based on studies so far, the highest dietary sources include bottled water, seafood and shellfish, table salt, tea brewed in plastic-sealed bags, and beer. These are the foods that have been tested — microplastics almost certainly appear in most foods to some degree.
- Bottled water tends to contain more microplastics than tap water; among tap water, untreated contains more than treated, and freshwater surface sources the least (Koelmans et al., 2019).
- Seafood — in one survey, 11 of 25 commercial fish species tested positive. Cod tests positive more often than herring, though herring tends to carry higher amounts (Lenz et al., 2016).
- Shellfish — one study estimated high-shellfish eaters take in around 11,000 particles a year, versus roughly 1,800 for low consumers (Van Cauwenberghe & Janssen, 2014).
- Table salt — a consistent, if small, source.
- Beer — plastic concentrations were found to be higher than in the municipal water used to brew it, pointing to the brewing or packaging as the entry point (Kosuth et al., 2018).
How much plastic are we actually eating?
You’ll often see the claim that people eat “a credit card’s worth of plastic” — about 5 grams — every week. It’s a striking image, but treat it as a rough, widely-quoted estimate rather than a precise figure: it came from modelling assumptions that later analyses have questioned, and the real number is genuinely uncertain. The honest position is that we’re all ingesting some microplastic regularly, and we don’t yet have a reliable weekly amount.
Are microplastics actually bad for your health?
This is where the science has moved the most, and where the old headlines are now out of date.
Back in 2019, the World Health Organisation stated that microplastics “don’t appear to pose a health risk at current levels” — but that assessment rested on very limited data and an acknowledgement that far more research was needed. Since then, the evidence has caught up:
- They’re in us. Microplastics have now been documented in human placenta (Ragusa et al., 2021), blood (2022), lungs, liver, breast milk, and follicular fluid.
- Human cardiovascular link. In 2024, a New England Journal of Medicine study examined plaque removed from the carotid arteries of patients. Those with microplastics and nanoplastics in their plaque had a markedly higher rate of heart attack, stroke, or death over the following roughly three years than those without (Marfella et al., 2024). This is observational — it shows a strong association, not proof that the plastic caused the events — but it’s the first direct human evidence that microplastics may be a cardiovascular risk factor.
- Mechanistic and animal data. Plastics are well-established endocrine disruptors. In animal models, plastic-derived compounds have produced effects across multiple generations: in one rat study, exposed animals that were then bred showed reproductive disease, tumours, and obesity in three subsequent generations (Manikkam et al., 2013). These are animal findings, and they don’t translate one-to-one to humans, but they’re a plausible signal of harm worth taking seriously.
Put together honestly: microplastics are a plausible and increasingly evidenced contributor to chronic disease, not a proven single cause of any one condition. That’s a more defensible — and more useful — position than either “harmless” or “the cause of everything.”
Why microplastics may matter for chronic, hard-to-solve cases
In clinical practice, it’s not unusual to see markers associated with plastic and petrochemical exposure turn up in a client’s functional test results — including in people who’ve already swapped their plastic containers and bottles for glass and stainless steel. That often surprises them.
Microplastics help explain it. You can clean up the obvious plastic in your kitchen and still take plastic in through tea, packaging, seafood, water, and the air. For someone with a chronic condition that hasn’t responded well to treatment, cumulative environmental load — microplastics included — is one factor worth investigating rather than assuming it’s been ruled out.
How can you reduce your microplastic exposure?
You can’t avoid microplastics entirely — they’re everywhere — but a few changes cut down the dietary load, which is the part you control most:
- Ditch plastic tea bags. Use loose-leaf tea and a teapot or stainless steel infuser. Ideally choose organically grown leaves.
- Rethink bottled water. Filtered tap water generally carries less plastic than bottled.
- Cut plastic food packaging where you reasonably can, and don’t heat or microwave food in plastic — heat is what drives shedding.
- Watch the hidden plastics — coffee cup lids, sealed tea bags, cling film — not just the obvious bottles and containers.
The bottom line
We always expected microplastics in the ocean and in seafood. Finding them in honey, salt, and now human arteries is what makes this a genuine and growing problem. The evidence that effects may carry across generations, and influence gene expression, is especially worth watching — some of the chronic disease we see today may trace back several generations and compound over time.
If you’ve been battling a chronic condition without much success, microplastic exposure is one avenue worth looking into. And a simple first step: swap the tea bags for a teapot and loose leaves.
Frequently asked questions
Do tea bags contain plastic? Many do — they’re commonly sealed with polypropylene, a plastic that softens with heat. One study found a single plastic tea bag can release billions of micro- and nanoplastic particles into a cup of hot water.
Is bottled water worse than tap water for microplastics? Studies to date suggest bottled water tends to contain more microplastics than tap water, and treated tap water tends to contain less than untreated.
How much microplastic do we eat? The often-quoted figure is around 5 grams a week — “a credit card” — but that’s a debated estimate based on modelling, not a reliable measured amount. We know we ingest some regularly; the exact quantity is uncertain.
Can microplastics affect your heart? A 2024 New England Journal of Medicine study found that people with microplastics in their artery plaque had a higher rate of heart attack, stroke, or death than those without. It shows an association, not proof of cause, but it’s the first direct human evidence of a cardiovascular link.
Can you avoid microplastics completely? No — they’re in water, food, and air. But you can reduce your intake with steps like using loose-leaf tea, filtered water, less plastic packaging, and never heating food in plastic.
References
- Boucher, J. & Friot, D. (2017). Primary Microplastics in the Oceans. IUCN.
- Hernandez, L. M. et al. (2019). Plastic Teabags Release Billions of Microparticles and Nanoparticles into Tea. Environmental Science & Technology.
- Koelmans, A. A. et al. (2019). Microplastics in freshwaters and drinking water. Water Research.
- Lenz, R. et al. (2016). Microplastics in fish. Marine Pollution Bulletin.
- Van Cauwenberghe, L. & Janssen, C. R. (2014). Microplastics in bivalves cultured for human consumption. Environmental Pollution.
- Kosuth, M. et al. (2018). Anthropogenic contamination of tap water, beer, and sea salt. PLoS ONE.
- Manikkam, M. et al. (2013). Plastics-derived compounds promote transgenerational disease. PLoS ONE.
- Ragusa, A. et al. (2021). Plasticenta: First evidence of microplastics in human placenta. Environment International.
- Marfella, R. et al. (2024). Microplastics and Nanoplastics in Atheromas and Cardiovascular Events. New England Journal of Medicine.
- World Health Organisation (2019). Microplastics in drinking-water.
