What Are Microplastics? Their Potential Harm to Human Health

Microplastics refer to plastic fragments and particles smaller than 5 millimeters in diameter. In reality, their size ranges from micrometers to millimeters, forming heterogeneous mixtures of irregularly shaped plastic particles—often indistinguishable to the naked eye and colloquially termed "the PM2.5 of the sea." Compared to conventional "white pollution" plastics, microplastics pose heightened environmental risks due to their minuscule size, which intensifies their ecological impact. Globally, emerging contaminants of concern fall into four major categories: persistent organic pollutants (POPs), endocrine-disrupting chemicals (EDCs), antibiotics, and microplastics. Once released into the environment, these are classified as emerging pollutants.

Primary Sources of Microplastics:

1. Single-use plastic bags: When discarded, they take decades to degrade, fragmenting into microplastic particles that infiltrate oceans and ecosystems.
2. Disposable utensils: Takeout containers, paper cups, and similar items release copious microplastics when exposed to heat or friction, some entering the food chain.
3. Wear and tear of other plastic products.

Microplastics enter the human body via ingestion, inhalation, and other pathways, potentially triggering inflammatory responses, organ damage, endocrine disruption, and long-term risks to immune and reproductive systems. While research is ongoing, minimizing plastic exposure remains key to mitigating harm.

Potential Health Risks of Microplastics

1. Physical Damage and Inflammation

Microplastics may mechanically irritate digestive or respiratory tissues due to their sharp edges or microscopic size, provoking localized inflammation. Chronic intestinal exposure, for instance, could compromise the gut barrier, elevating permeability to toxins and potentially linking to conditions like irritable bowel syndrome (IBS).

2. Chemical Toxicity

Plastics often contain additives like phthalates (plasticizers) and flame retardants, which may leach from microplastics and disrupt endocrine function. Some compounds exhibit estrogen-mimicking effects, threatening reproductive health and child development. Moreover, microplastics readily adsorb environmental pollutants (e.g., heavy metals, polycyclic aromatic hydrocarbons), amplifying toxic co-exposure.

3. Organ and Cellular Accumulation

Animal studies reveal microplastics crossing the blood-brain and placental barriers, accumulating in organs like the liver and kidneys, and inducing oxidative stress and cellular dysfunction. Human studies have detected microplastics in blood, placenta, and even breast milk—though long-term health implications remain unclear, chronic accumulation may elevate disease risks.

4. Immune System Disruption

Microplastics can be flagged as foreign bodies, triggering excessive immune responses that fuel chronic inflammation or autoimmune disorders. Nanoparticles might further disrupt immune cell signaling, impairing pathogen defense.

5. Other Potential Risks

Some research hypothesizes links between microplastics and neurodegenerative diseases (e.g., Alzheimer’s) via neuroinflammation, while other studies suggest they may alter gut microbiota, indirectly affecting metabolism and immunity.