Microplastics

Tiny pieces of plastic — smaller than 5mm, often invisible without a microscope. Nanoplastics are smaller still. They come from larger plastic items breaking down over time, from synthetic textiles shedding in the wash, from tyre wear on roads, and from plastic packaging shedding into food.

Microplastics aren't deliberately added (with the exception of cosmetic microbeads and glitter, now banned in many countries). They're a side effect of using plastic — plastic breaks down. The more plastic we use, the more microplastics shed into the environment, food, water, and air.

Usually no label. The hint is plastic packaging, synthetic fabric content, and 'microbeads' in older personal care products (now mostly banned). The 'nylon-6, nylon-66' content of plastic tea bags is one example.

Bottled water (a major source — one study found about 240,000 particles per litre on average), tap water (less but still present), plastic tea bags, food packaged or stored in plastic, synthetic clothing fibres in washing machine wastewater, indoor air and household dust.

Mainly ingestion (food and water) and inhalation (indoor air, dust from synthetic textiles). Some skin contact but absorption is usually minimal.

Microplastics have been detected in human placentas. Studies on fertility and pregnancy outcomes are emerging. The science is genuinely early — the practical move during pregnancy is reduce the high-yield sources (bottled water, heated plastic) without panicking about exposures you can't fully control.

Microplastics have been detected in human testicular tissue. Studies are emerging on associations with sperm quality. Real but still-developing evidence.

Higher concern in principle due to development and lower body weight, but the evidence base is too new for confident statements. Bottle-fed babies receive a higher dose if formula is prepared in plastic bottles with hot water (some studies have measured this). Glass bottles avoid this.

Microplastics have been detected in atheromatous plaque in cardiovascular patients (Marfella et al., NEJM 2024). The same study found higher cardiovascular event rates in patients whose plaque contained microplastics. This is one of the strongest human-health signals to date.

Strongest: microplastics are universally present in human bodies (placenta, blood, lung, atheroma). The NEJM 2024 atheroma study is the most-cited recent human-outcome paper. Toxicology studies in animals show inflammation, oxidative stress, and tissue effects from microplastic exposure. The science on health outcomes at typical exposure levels is still developing — this is the fastest-moving topic in this guide.

Genuinely uncertain. Universal exposure means everyone is in the experiment. The sensible position: reduce the addressable big-source items (bottled water, heated plastic, plastic tea bags) without trying to eliminate microplastics from your life — that's not realistic.

Filtered tap water in glass or stainless steel. Loose-leaf tea or paper tea bags. Glass or ceramic for hot food and drinks. Natural-fibre clothing where practical (also helps with synthetic textile shedding). A washing machine filter that catches synthetic fibres reduces release into wastewater.

Some sources are easy (bottled water, plastic tea bags, heating plastic). Others are hard or impossible (indoor air, all synthetic textiles, all plastic packaging). The goal is reduce, not eliminate.

If you regularly buy bottled water, switch to a filtered jug or under-sink filter. That single change reduces microplastic intake more than most other actions.

Treat this as 'reduce sensibly while the science develops.' The biggest individual levers — bottled water, heated plastic, plastic tea bags — are easy. The biggest lever overall is societal: less plastic produced and discarded. Don't chase perfect; chase practical.

NIH on microplastics, WHO microplastics report, NEJM Marfella et al. on microplastics in atheromas, Stanford Medicine on microplastics and human health. See References below.