The Plastic
Particles measuring 1 nanometer to 5 millimeters. Fragments of the synthetic world breaking down into something small enough to cross the blood-brain barrier, embed in arterial plaque, and pass through a placenta to an unborn child.
What Are Microplastics?
The EPA defines microplastics as particles roughly 1 nanometer to 5 millimeters in size — small enough to be invisible to the naked eye, large enough to carry toxic chemical cargo.
Primary microplastics are manufactured small — for cosmetics, biomedical applications, industrial abrasives. Secondary microplastics are plastic products that have fragmented: water bottles, packaging, synthetic fabrics, and tires ground down by road friction.
What makes them dangerous is not just their size. Microplastics act as chemical sponges, concentrating persistent organic pollutants, heavy metals, and endocrine-disrupting compounds from the surrounding environment — then delivering them directly into living tissue.
Key Numbers
1 nanometer
Minimum size — small enough to cross the blood-brain barrier
5 mm
Maximum classified size — still invisible to the naked eye at the smaller end
6×
Increase in microplastic intake by organisms since 1990 (ACS Environmental Science & Technology 2024)
1,300+
Species in which microplastics have been detected, including humans (Science 2024)
Where They Come From
Synthetic Textiles
A single wash of polyester clothing releases up to 700,000 microfibers. They pass through wastewater treatment and enter waterways. Fleece, nylon, and acrylic shed continuously with wear and washing.
Tire & Road Wear
Tire abrasion against road surfaces generates particles that enter stormwater runoff. Tire wear particles are among the largest sources of microplastics in urban waterways, carrying zinc, PAHs, and benzothiazole.
Single-Use Plastic
Plastic bottles, food packaging, and bags degrade in UV light and physical abrasion into progressively smaller fragments. Warm beverages in plastic cups leach nanoplastics directly. Heated plastic containers accelerate release.
Ocean Degradation
Larger plastic in oceans fragments over decades under UV radiation and wave action. The resulting microplastics enter the marine food chain, accumulate in fish and shellfish, and return to humans as food. The ocean contains an estimated 5 trillion pieces of plastic.
Drinking Water
Microplastics have been detected in both bottled and tap water worldwide. Standard municipal water treatment removes most microplastics but not all — particularly nanoplastics. Bottled water carries its own contamination from the container itself.
Air & Dust
Microplastic fibers have been detected in indoor air, outdoor air, and even in the atmosphere above remote mountain ranges. Indoor environments concentrate fibers from textiles, carpets, and furniture foam. Inhalation is a direct exposure pathway.
How They Enter the Body
🍽️ Ingestion
The primary route. Contaminated food and water, seafood containing gut contents, table salt, honey, beer, and bottled water are all documented sources. The average person ingests an estimated 5 grams of plastic per week — the weight of a credit card.
- → Seafood and marine-origin food
- → Drinking water (tap and bottled)
- → Food stored or heated in plastic
- → Table salt, honey, beer
- → Frontiers in Nutrition 2021 review
💨 Inhalation
Airborne microfibers and particles are inhaled directly into the respiratory tract. Occupational exposure in textile and rubber manufacturing is documented. Indoor environments — with synthetic carpets, fabrics, and foam — can have higher microplastic air concentrations than outdoors.
- → Indoor air from synthetic textiles
- → Outdoor air near industrial sites
- → Tire dust resuspended by traffic
- → Atmospheric deposition even in remote areas
- → Environ Pollut review 2022
🖐️ Dermal Absorption
Nanoplastics — at the smallest size range — can potentially penetrate intact skin, particularly when assisted by personal care products, cosmetics, and the chemicals they carry. This route is less studied but increasingly documented for nanoscale particles.
- → Cosmetics with microbeads (now banned in U.S.)
- → Skincare products in plastic packaging
- → Nanoscale particle skin penetration
- → Contaminated soil contact
- → PMC9920460 — exposure review
Nowhere Is Untouched
Microplastics have been detected in locations that should settle any remaining debate about whether this is a niche or localized problem.
Human Brain Tissue
Concentrations of microplastics in human brain tissue increased 50% in less than a decade, according to a 2025 University of New Mexico study published in Nature Medicine. The brain tissue examined post-mortem showed measurable accumulation of nanoplastics.
Arterial Plaque
A landmark 2024 NEJM study (Marfella et al.) found microplastics embedded in arterial plaque in over 300 patients undergoing endarterectomy. Patients with microplastics in their plaque had 4× higher risk of heart attack, stroke, or death within 3 years.
Human Placenta & Breast Milk
Microplastics have been detected in human placentas, meaning contamination is occurring before birth. They have also been found in breast milk, indicating the contamination continues through early infancy. No developmental threshold of safety has been established.
Human Bone Tissue
A 2024 study published in The Innovation Medicine detected microplastics in the insides of human bones, suggesting accumulation that occurs over years or decades. The long-term structural and immune implications in bone marrow are not yet characterized.
Remote Mountain Snow
Microplastics have been detected in snow and ice in the Swiss Alps, Arctic sea ice, and Antarctic snow — confirming atmospheric transport of microplastics to locations with no local plastic source. Contamination is now planetary in scale.
Ocean Depths
Microplastics have been found in deep-sea sediment in the Mariana Trench — the deepest point on Earth. They contaminate deep-sea organisms, enter the marine food web, and resurface in seafood consumed by humans. The cycle is global and multi-generational.