Where microplastics come from
Primary microplastics are manufactured at small size — microbeads in cosmetics (now banned in many countries), pellets in industrial supply chains, and microfibers shed from polyester, nylon, and acrylic clothing during washing. Secondary microplastics form when larger plastic items fragment under UV, mechanical abrasion, and weathering. Studies have detected microplastic particles in human blood (Leslie et al. 2022, Environment International), placenta (Ragusa et al. 2021, Environment International), and lung tissue (Jenner et al. 2022, Science of the Total Environment).
The biggest exposure pathways
Per the published exposure literature, the largest single per-event source for most adults is plastic tea bags — Hernandez et al. 2019 (Environmental Science & Technology) measured ~11.6 billion microplastic particles released per nylon/PET pyramid bag at brewing temperature. Bottled water averages ~113 particles per 16oz serving (Mason et al. 2018, Frontiers in Chemistry). Microwaving food in plastic containers releases ~1.4 million particles per minute (Hussain et al. 2023, Environ Sci Technol). Other sources include sea salt (~36 particles/day per Karami 2017), shellfish (~30 particles/serving), and inhaled airborne dust (~50,000/year baseline per Cox 2019).
Health evidence
The strongest causal-direction evidence to date is Marfella et al. 2024 (NEJM): patients with microplastics detectable in carotid artery plaques had a 4.5x higher rate of cardiovascular events (heart attack, stroke, or death) over 34 months of follow-up compared to patients without detectable plastics. Multiple smaller studies have linked microplastic exposure to oxidative stress, endocrine disruption (via the BPA/phthalate plasticizers they carry), and gut microbiome changes. The evidence base is rapidly growing.
What you can actually do
Complete elimination isn't possible (atmospheric deposition is global), but the avoidable pathways (plastic tea bags, bottled water, microwaving plastic, sea salt, polyester clothing) account for the bulk of high-exposure ingestion in most households. Use the microplastic exposure calculator to identify your top 3 reduction swaps based on your actual habits.
Primary sources: Cox et al. 2019 (Environ Sci Technol), Mason et al. 2018 (Front Chem), Hernandez et al. 2019 (Environ Sci Technol), Marfella et al. 2024 (NEJM), Leslie et al. 2022 (Environ Int), Ragusa et al. 2021 (Environ Int).