We live in a world full of plastic. From grocery bags to polyester clothes, from food packaging to children's toys, synthetic polymers have become nearly impossible to avoid. What once seemed a marvel of modern convenience has revealed a far darker side: tiny fragments of plastic, known as microplastics, are now everywhere—in the air we breathe, the water we drink, the food we eat, and even inside our own bodies.
Microplastics are defined as plastic particles smaller than 5 millimeters in diameter. Many are far tinier—the smallest measure less than the width of a human hair and are called nanoplastics. These infinitesimal fragments originate in two main ways: they are either intentionally manufactured for use in products like cosmetics and industrial abrasives, or more commonly, they are the result of larger plastic items breaking down over time through wear, weathering, and chemical degradation. For example, plastic in the ocean gets pounded into rocky shores by waves, and UV from the sun photodegrades plastics into tiny pieces.
Because of their tiny size, microplastics don’t stay put. Car tires create them on roadways; synthetic fabrics shed microfibers with every wash; paint, packaging, and countless other products like furniture shed microscopic fragments in every environment they touch. Over time, these pieces disperse into the air, soil, waterways, and oceans—a global cascade of microscopic pollution.
Once dispersed, microplastics move with startling ease. In the atmosphere, they can travel vast distances, carried by winds and air currents. Scientists have documented microplastic fibers in polar regions, remote forests, and deep ocean waters—places humans seldom tread. Their small size and low mass make airborne microplastics especially prone to long-range transport, even reaching the upper atmosphere. This mobility means that microplastics are not just a localized problem; they are a planetary one.
Inside Our Bodies
In recent years, researchers have discovered that microplastics are not merely an external pollutant. They have entered the human body. Tiny plastic fragments have been found in people’s blood, lungs, reproductive organs, brains, placentas, and breast milk—evidence that these particles are infiltrating vital tissues.
The UCSF Magazine feature “The Plastic Inside Us” notes that science is still struggling to understand the full implications of these findings, but the mere presence of microplastics in internal systems alarms many experts. While a direct causal link between microplastics and specific diseases has not been conclusively established, emerging evidence suggests potential harm in key physiological systems.
There are several ways microplastics make their way inside us. The most obvious is ingestion: microplastics have been found in processed foods, fruits, vegetables, salt, bottled water, and even tap water worldwide—meaning we consume them daily, often unknowingly.
But another, less visible route is inhalation. We breathe them in as part of the fine particulate matter that surrounds us.
Airborne Microplastics
Air doesn’t just carry pollen, dust, and soot. It also carries microplastics. These airborne particles originate from the very products we use and the infrastructure we rely on: clothes made of synthetic fibers release microscopic strands when worn or washed; car tires shed plastic particles through friction with the road; building materials, paints, and even household fabrics emit plastic fragments as they age and degrade.
Invisible to the naked eye, these airborne microplastics are now recognized as a significant route of human exposure. When suspended in the air, particularly in indoor environments, they can be inhaled deeply into the lungs with every breath. Some estimates suggest that individuals in typical settings may inhale tens of thousands of microplastic particles each day.
Once inhaled, the smallest particles travel deep into the respiratory tract. Unlike larger dust particles that may lodge in the upper airways and be expelled through mucous or coughing, microplastics are small enough to bypass these defenses and penetrate into the bronchioles and alveoli—the tiny air sacs where gas exchange occurs.
Once lodged in lung tissue, microplastics have the potential to cause inflammation, oxidative stress, and cellular damage. Animal and cell studies consistently show that microplastics can trigger immune responses and tissue irritation, leading to scarring and impaired lung function. Some research also suggests that they may act as carriers for other toxic chemicals, including plastic additives like phthalates and PFAS, which can leach out and further disrupt cellular processes.
Respiratory impacts are not the only concern. Emerging evidence from reviews of thousands of studies suggests that exposure to inhaled microplastics could be associated with increased risk of lung cancer, chronic inflammation, and even systemic effects such as colon cancer or reproductive harm, although the mechanisms remain poorly understood and under intense investigation.
Chemical Intruders
Microplastics are more than inert particles. Many are composed of polymers embedded with chemical additives to improve flexibility, durability, or flame resistance. Some of these additives, like bisphenol A (BPA), phthalates, and certain PFAS, are known endocrine disruptors, meaning they can mimic or interfere with hormonal signaling in the body.
When microplastics enter the body by ingestion or inhalation, these chemicals may desorb from the plastic matrix and interact with cells and tissues. Although our understanding of these interactions is still evolving, there is concern that they could contribute to developmental disorders, metabolic disruption, reproductive abnormalities, and even cancer.
Importantly, because microplastics can carry both physical and chemical risks, their biological impact is multifaceted: they can act as tiny abrasive particles that physically irritate tissues, and as vectors that ferry harmful chemicals into sensitive biological systems.
What We Know (and Don’t) About Health Effects
Scientists agree on one thing: humans are exposed to microplastics continuously and globally. The fundamental questions now are about how these exposures translate into disease and damage. Many studies to date have been in animals or lab models, and human evidence remains early and correlative.
Research suggests that microplastics can elicit oxidative stress, which is a biochemical imbalance that damages DNA, proteins, and cellular membranes. They can also cause chronic inflammation, a known precursor to many diseases, including cardiovascular disease and cancer. In the lungs, sustained inflammation can lead to fibrosis, or scarring that permanently reduces lung function.
While definitive human health outcomes linked directly to microplastics are not yet established, many researchers view the signs as a warning, not reassurance. The fact that plastic fragments and associated chemicals are found in critical organs, combined with biological changes seen in laboratory studies, points to a need for deeper investigation and precautionary action.
A Future with Plastic, but Not at Any Cost
Microplastics are essentially an unintended consequence of the plastic age: a global cascade of microscopic pollution that has become invisible to our senses yet intimately present in our bodies. Their ubiquity underscores how profoundly human technologies have reshaped Earth’s environment and, increasingly, our internal biology.
Scientists and policymakers are now grappling with how to mitigate this exposure. Strategies range from reducing plastic production and improving waste management to developing new materials and filters that capture microplastics before they disperse. While individual choices, such as reducing use of synthetic textiles and plastic water bottles, can help reduce some exposure, systemic solutions will be needed to address the scale of the problem.
Above all, the story of microplastics is a reminder that our embrace of convenience and disposability has hidden costs—costs that may be borne not just by ecosystems, but by our own bodies. As research continues to unfold, the challenge will be to balance the materials we rely on with an understanding of their long-term implications for health and the environment.
In your home, a HEPA air purifier can minimize your exposure and your family's exposure to airborne microplastics and nanoplastics, thereby reducing the amount that enters your body.
Resources:
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