Tiny plastic particles, known as microplastics, have been found throughout the human body—including the brain, blood, lungs, liver and even lower limb joints. In fact, a 2025 study in Nature Medicine found that the typical adult brain had the equivalent of a plastic spoon’s worth of micro- and nanoplastics. To effectively understand plastic toxicity in the human body, it is crucial to understand from current scientific research how plastic is relevant to disease development and what standards are in place to help regulate these microplastics in the environment.
What Are Plastics Made Of, and Why Are They Used Everywhere?
Plastics are synthetic products that are typically made of organic polymers and other chemical additives, such as bisphenols, phthalates, and flame retardants, giving plastic products unique properties. They are used in most containers and packaging materials; in most of the fabrics that make clothing, bedding, carpeting, and towels; in the construction of buildings and motor vehicles; and in many of the materials used in health care settings to prevent the spread of infection, among many other uses. Plastics are thus used in a variety of commercial applications because of their low cost, ease of production, versatility, and hydrophobicity.
What Happens to Plastic Waste? The Rise of Microplastics & Nanoplastics
Plastic never goes away—it just breaks down into finer and finer particles:
- Microplasticsare plastic particles typically <5 mm in size
- Nanoplastics are even smaller, often <1 µm
These tiny plastics come from two main sources: primary microplastics, which are manufactured at a small size, like in cosmetics and paints, and secondary microplastics, which result from the breakdown of larger plastic items, such as bottles, plastic packaging, and synthetic textiles. These environmental pollutants represent between 60% and 80% of the waste present in the marine environment and 90% of the waste floating on the seas and oceans. Microplastics and nanoplastics prevail in the oceans, remote islands, and polar regions—pervading every ecosystem in the world.
Microplastics in the Human Body: What We Eat, Breathe, and Absorb
Micro-/nanoplastics are even found in the water we drink, food we eat, clothes we wear, and the air we breathe. In fact, scientists have estimated that adults ingest the equivalent of one credit card per week in microplastics, and studies in animals and human cells suggest microplastics exposure could be linked to cancer, heart attacks, reproductive problems and a host of other harms.
We should care about micro-/nanoplastics because studies have shown that they have infiltrated the human body, lodging themselves in everything from the brain, testicles, heart, stomach, lymph nodes and placenta. They have also been detected in urine, breastmilk, semen and meconium, which is a newborn’s first stool.
Evidence of Human Exposure & Accumulation of Microplastics
Several studies have confirmed not just exposure, but accumulation of micro‐/nanoplastics in human tissues or body fluids:
It is important to note, however, that the research on micro‐/nanoplastics is just at the cusp, and as such, many key questions remain about exactly how much exposure is harmful, the mechanisms of damage, and how to translate lab findings to population health risks.
Brain, Liver, and Kidneys
A 2025 University of New Mexico study with found plastic accumulation in the brain, appearing to increase by 50% in the past eight years and showing much higher concentrations of microplastics and nanoplastics than in the liver or kidneys. Further, brain tissue from people who had been diagnosed with dementia had up to 10 times as much plastic in their brains as everyone else—but while there is a clear correlation, the study design cannot show whether higher levels of plastic in the brain caused the dementia symptoms as they may simply accumulate more due to the disease process itself.
Respiratory System
Inhalation of airborne microplastics is a recognized exposure route. Some human/animal studies indicate lung inflammation, impaired lung function, oxidative stress.
Heart Disease
A scoping review of studies shows MNPs (micro/nanoplastics) are cytotoxic, immunotoxic, genotoxic in cardiovascular cells; they have been found in human cardiovascular tissues (arteries, thrombi, blood) in multiple studies.
Another study in The American Heart Association noted that people living in U.S. coastal counties next to waters with high microplastic levels had significantly higher rates of Type 2 diabetes, coronary artery disease, and stroke compared to those in less polluted waters.
Arterial Plaque
Researchers examined plaque removed from carotid arteries of ~257 people and found plastic particles (mainly polyethylene, and some PVC). Notably, people with these plastic particles in their plaques had a 4.5× higher risk of a heart attack, stroke, or death over ~3 years compared to those without.
Immune System and Inflammation
A systematic review on nanoplastics and immune disruption (2015‑2025) found that exposure in in vitro and in vivo studies leads to oxidative stress, imbalanced cytokine (immune signaling) profiles, and activation of pro‑inflammatory pathways. Another review of microplastics effects on immunity noted that microplastics are taken up by immune cells, disrupt intracellular signaling, and can lead to tissue damage via generation of reactive oxygen species (ROS).
Digestive System and Gut Microbiome
Microplastics have been found in human feces; some studies suggest that people with inflammatory bowel disease (IBD) have higher concentrations of fecal microplastics than healthy controls. There are also findings of altered gut bacterial communities, chronic intestinal inflammation in animal/cell models.
Standards that Cover Microplastics in the Environment
Microplastics are ubiquitous in nature and therefore affect both wildlife and humans. They have been detected in drinking water and in numerous foods (e.g., honey, salt, and marine organisms). Microplastics can be transferred into food product when bees pick up microplastics from contaminated food and the environment, and in the ocean plastic particles are being eaten by marine life—a study found microplastics in 98.9% of seafood samples.
While the full extent of the environmental and health impacts of microplastics are not yet known, implementing standards to govern microplastics samples in the environment are essential for research. Documents, such as ISO/TR 21960:2020, ISO 24187:2023, ISO 5567-27:2025, and ASTM D8333-20, detail specifications for the detection, sampling, and analysis of microplastics in the environment—particularly in water and other environmental matrices.
ISO/TR 21960:2020 – Plastics — Environmental Aspects — State of Knowledge and Methodologies
ISO/TR 21960:2020 covers environmental aspects of plastics including microplastic generation. This technical report summarizes the state of knowledge and outlines methodologies for assessing microplastics and macroplastics in various environmental matrices (like land and water) and biota. It gives an overview of testing methods, including sampling from various environmental matrix, sample preparation and analysis.
ISO 24187:2023—Principles for the Analysis of microplastics present in the environment
ISO 24187:2023 describes the principles to be followed in the analysis of microplastics in various environmental matrices. This includes the unique particle size classification of plastics, the use of certain apparatus with regard to sampling, sample preparation, and the determination of representative sample quantities.
ISO 5667-27:2025—Water quality – Sampling – Part 27: Guidance on sampling for microplastics in water
ISO 5567-27:2025 specifies the basic methods for sampling suspended microplastics in water (domestic water, freshwater, seawater, treated wastewater and untreated wastewater), for their subsequent characterization. Suspended particles can also include synthetic or semi-synthetic polymeric materials (such as rubber).
ASTM D8333-20 – Standard Guide for Collection of Microplastic Samples in Aquatic Environments
ASTM D8333-20 covers sampling procedures for detecting microplastics in water bodies (relevant for exposure analysis). The standard provides a standardized method for preparing water samples, including drinking water, surface waters, and wastewater, for microplastic analysis.
You can find these standards and more on the ANSI Webstore.