Published in JAMA (October 2025)
By Dr. Kari C. Nadeau and colleagues
The New Age of Plastic Pollution
For decades, the global debate on plastics focused on oceans, wildlife, and waste. But new evidence shows that the plastic problem is much closer — inside the human body.
A recent article in The Journal of the American Medical Association (JAMA), led by Dr. Kari C. Nadeau, a leading environmental health researcher at Harvard, summarizes alarming findings: microplastics — tiny particles less than 5 millimeters in size — have been detected in multiple human organs and tissues.
This growing body of research suggests that plastic pollution is no longer just an environmental issue; it has become a direct human health concern.
What Are Microplastics?
Microplastics are the result of plastic breakdown. Over time, sunlight, heat, and friction turn larger plastic waste — bottles, packaging, textiles, tires — into microscopic fragments.
They can also be intentionally produced, such as microbeads used in cosmetics, toothpaste, and industrial abrasives. These particles are small enough to travel through air, water, and soil — and ultimately, into our bodies.
How Do They Enter the Human Body?
According to the JAMA article, there are three main pathways of exposure:
- Inhalation:
Tiny airborne plastics, especially those below 2.5 micrometers (PM₂.₅), can penetrate deep into the lungs. Sources include clothing fibers, vehicle tire wear, and urban dust. - Ingestion:
Studies have detected microplastics in bottled and tap water, sea salt, seafood, fruits, vegetables, and even tea bags made with synthetic mesh. The average person may ingest tens of thousands of microplastic particles each year. - Placental and neonatal exposure:
Perhaps most concerning, microplastics have been found in placental tissue, breast milk, and newborn stool, suggesting exposure begins before birth.
Where Are Microplastics Found in the Body?
Recent scientific studies, summarized by Dr. Nadeau’s team, have detected microplastics in nearly every human organ tested so far:
- Lungs and airway tissue
- Blood and lymphatic system
- Liver, kidneys, and spleen
- Heart and major blood vessels
- Colon and gastrointestinal tract
- Placenta, breast milk, and reproductive organs
- Brain and central nervous system
These findings confirm that microplastics can circulate throughout the body, cross biological barriers, and lodge in tissues for unknown periods.
Can They Harm Human Health?
While the field is still young, evidence from both laboratory and clinical studies points toward multiple possible health risks.
1. Inflammation and oxidative stress
Microplastics can cause cells to release inflammatory molecules and reactive oxygen species (ROS), damaging DNA, proteins, and cell membranes.
2. Endocrine disruption
Many plastics contain chemical additives — such as phthalates and bisphenol A (BPA) — that interfere with hormonal signaling, affecting metabolism, fertility, and development.
3. Cardiovascular risk
A recent study cited in the JAMA article found polyethylene and PVC particles in carotid artery plaques of patients. Those with plastic-contaminated plaques had a significantly higher risk of heart attack, stroke, or death within 34 months.
4. Neurotoxicity and brain inflammation
Animal and organoid studies show that nanoplastics may cross the blood–brain barrier, potentially contributing to neuroinflammation and neurodegenerative processes.
5. Effects on liver and gut
Experiments on liver organoids showed even low doses of polystyrene microplastics can impair cell viability and increase liver enzyme activity, suggesting hepatotoxic effects. Similarly, microplastics can disturb gut microbiota balance, promoting intestinal inflammation.
An Unfolding Global Health Problem
Plastic production has skyrocketed from 2 million tons in 1950 to over 430 million tons per year today — and only about 9% is recycled.
As plastic waste breaks down, it forms micro- and nanoplastics that persist for centuries.
Dr. Nadeau’s article calls this “a planetary boundary issue” — warning that exposure is now so widespread that almost no population is untouched. The convergence of environmental pollution and human biology has created a new, invisible form of exposure: plastic inhalation and ingestion as part of daily life.
What Science Still Doesn’t Know
Despite the clear detection of microplastics in human tissues, many key questions remain unanswered:
- How much plastic does the average person accumulate over time?
- What size, shape, or type of plastic is most harmful?
- What are the safe thresholds for exposure?
- How do microplastics interact with existing diseases or medications?
Researchers are also working to standardize methods to detect and quantify microplastics in biological samples, since results can vary widely between studies.
Policy and Public Health Implications
The authors emphasize that microplastics are both a scientific and policy challenge.
They advocate for:
- Reducing plastic production, especially single-use plastics.
- Banning microbeads in cosmetics and cleaning products.
- Improving waste management and recycling infrastructure.
- Monitoring exposure through public health systems.
- Developing international treaties to limit plastic pollution from production to disposal.
Dr. Nadeau notes that the world urgently needs a legally binding global plastics treaty — one that addresses not only waste but also chemical additives, emissions, and occupational exposure.
The Bigger Picture: From Environment to Human Health
For years, plastic pollution was seen as an environmental issue — affecting oceans, fish, and wildlife. Now it’s clear: it’s also a human health issue.
Plastics are not inert. Their chemical makeup, ability to carry toxins, and capacity to enter cells mean they could influence diseases ranging from cardiovascular disorders to cancers and metabolic syndromes.
The message from the JAMA authors is simple but urgent:
“We are living in a plastic age. Understanding and reducing human exposure is essential to protecting health.”
What You Can Do
While large-scale policy change is essential, individuals can reduce personal exposure by:
- Using reusable glass or stainless steel containers instead of plastic bottles.
- Avoiding microwaving food in plastic or wrapping hot foods in plastic film.
- Choosing natural-fiber clothing over synthetics.
- Supporting legislation aimed at reducing single-use plastics.
Every small change contributes to lowering environmental and biological plastic load.
The Takeaway
Microplastics are no longer just floating in the ocean — they’re circulating in our blood.
Their presence in vital organs underscores a new frontier in environmental medicine.
As Dr. Nadeau and her team conclude, the next decade will be critical: scientists must determine how these particles affect our biology, and governments must act to curb exposure before it becomes a global health crisis.
The plastic age has left its fingerprints inside us — literally. What we do next will determine whether those traces remain harmless or become a legacy of disease.