Microplastics and Nanoplastics: Invisible Threats to the Human Body

Microplastics and nanoplastics—tiny plastic particles less than 5 mm and 1000 nm in size, respectively—have become an invisible but ubiquitous presence in our daily lives. Found in food, water, dust, and even the air we breathe, these particles are increasingly raising alarm among scientists due to their potential impacts on human health. A recent review published in eBioMedicine by researchers from Imperial College London and the UK Health Security Agency explores the biological pathways and potential consequences of long-term exposure to micro- and nanoplastics (MNPs) across multiple organ systems.

A Hidden Epidemic of Plastic Exposure

The average person encounters microplastics unknowingly, every single day—whether through bottled water, indoor dust, seafood, or even table salt. But what happens once these particles enter our bodies?

This comprehensive review examines emerging evidence from the past decade on how MNPs may affect human health, particularly focusing on eight organ systems: respiratory, digestive, cardiovascular, hepatic, renal, nervous, immune, and endocrine. Although most findings are based on animal studies and in vitro human cell models, the article underscores growing concerns about systemic toxicity and the urgent need for human-centered research.

Mapping the Damage: What the Science Reveals

Respiratory System

Inhalation of airborne plastic fibers—especially ultrafine ones—can cause chronic inflammation and pulmonary fibrosis. Animal studies also suggest the formation of lung nodules, with some human tissue samples revealing traces of plastic in the bronchoalveolar fluid.

Digestive System

MNPs affect gut microbiota, leading to intestinal inflammation, dysbiosis, and metabolic disturbances. Some gut microbes may even metabolize certain plastic types, which could alter nutrient absorption or trigger immune responses.

“The ingestion of microplastics is no longer speculative—it’s a documented reality,” the authors note.

Cardiovascular and Circulatory Systems

In rats and zebrafish, MNP exposure has been linked to reduced heart rate, endothelial cell damage, and oxidative stress in cardiac tissues. Studies suggest translocation of particles from the digestive tract to the bloodstream and into the heart itself.

Liver and Kidneys

Accumulation of MNPs in the liver and kidneys results in fibrosis, enzyme dysfunction, and metabolic irregularities. Animal models consistently show elevated markers of inflammation and cellular stress.

Nervous System

Preclinical studies indicate neurotoxicity, including alterations in neurotransmitter levels and disruption of the blood–brain barrier. These changes could have implications for neurodegenerative diseases and cognitive function.

Immune and Endocrine Systems

Exposure to MNPs has been shown to activate inflammatory cytokines, such as IL‑1α, and disrupt immune balance between T-regulatory and Th17 cells. Furthermore, endocrine disruption has been observed—especially due to additives like bisphenol A (BPA) and phthalates—leading to imbalances in hormones like testosterone and insulin.

Mechanisms of Toxicity: How Plastic Harms the Body

Across organ systems, several common pathways of MNP toxicity emerge:

• Oxidative stress and mitochondrial dysfunction
• Cell membrane disruption
• DNA damage and mutagenesis
• Formation of protein coronas that alter cellular uptake
• Triggering of apoptosis (programmed cell death)

These biological effects are observed consistently in multiple tissue types, suggesting that the threat of MNPs is not confined to a single organ, but rather systemic.

Barriers to Understanding: Why We Still Don’t Know Enough

Despite the concerning evidence, the study highlights major limitations in the existing body of research:

• Most studies rely on pristine polystyrene particles, not reflective of real-world plastic pollution.
• Many experiments use doses far higher than typical human exposure.
• Lack of methodological standardization makes comparison across studies difficult.
• There's a shortage of long-term, human epidemiological data.

As the authors emphasize, "the absence of clinical trials and population-level studies creates a critical blind spot in our understanding of chronic microplastic exposure."

Policy Implications: What Needs to Happen Now

This review doesn’t just raise scientific concerns—it also makes concrete recommendations for policy and research:

1. Standardize detection methods for MNPs in food, water, and air.
2. Develop human-relevant plastic models, using degraded mixtures and real-world exposure levels.
3. Launch longitudinal human studies with biomarkers to assess cumulative effects.
4. Create interdisciplinary frameworks involving toxicologists, epidemiologists, and the plastics industry.

“We need to move beyond lab rats and into real-world human health assessments,” the authors argue.

Why This Matters Globally—and Locally

The review is globally relevant, but its findings hold particular urgency for regions like Latin America, where plastic pollution is high and environmental regulations vary. Cities like Lima and Mexico City face mounting challenges in controlling plastic waste in water systems, food chains, and urban air.

Local health agencies could take the lead in regional monitoring programs, public awareness campaigns, and stricter control of plastic additives such as BPA in consumer products.

Conclusion: A Call to Action for Research and Regulation

Micro- and nanoplastics are no longer invisible. They are now part of our environment, our homes, and potentially—our bodies. The evidence presented in this review serves as a wake-up call for both the scientific community and policymakers.

With targeted research and proactive regulations, it’s still possible to mitigate the health risks posed by MNPs. But the window for effective intervention is closing fast. We must act before these tiny particles become a major public health crisis.

Topics of interest

Pollution Health