Microplastics are plastic particles smaller than five millimeters, while nanoplastics are even tinier, measuring under one micrometer. These synthetic fragments originate from the breakdown of larger plastic debris and are now a pervasive form of global pollution. They are ubiquitous, detected everywhere from the deepest oceans to high mountain ranges. Scientific investigation has confirmed their presence throughout the human body, including in blood, lung tissue, and the placenta. Research is now focused on understanding the effects these particles have on human physiology following their entry into the body.
Routes of Human Exposure
The primary pathways for microplastic entry into the human body are through ingestion and inhalation from contaminated environmental sources. Ingestion is a significant route, largely due to water and food products that act as vectors for the particles. Bottled water contains substantially higher levels of plastic particles than tap water, leading to significantly higher annual intake for consumers who rely on it.
Food items are also major contributors, particularly seafood like bivalves and shellfish that are consumed whole. Furthermore, over 90% of globally sampled table salt brands contain microplastics, with sea salt showing the highest concentrations, potentially contributing hundreds of particles to the diet each year.
Inhalation presents a distinct concern, especially within indoor environments where people spend the majority of their time. Synthetic textiles, such as polyester and nylon, are the main source of airborne microplastic fibers, which shed from clothing, carpets, and upholstery. Indoor air levels of microplastics are often two to eight times higher than outdoor air levels. These microscopic fibers are easily inhaled and can lodge deep within the respiratory tract.
Internal Journey and Organ Accumulation
Once ingested or inhaled, the fate of the plastic particles depends heavily on their size. Larger microplastic particles are mostly eliminated, passing through the digestive tract and being excreted via feces. However, particles smaller than \(10 \mu m\), and especially nanoplastics, can cross the intestinal barrier and enter the circulatory system. This translocation across the gut lining is thought to occur through cellular processes like endocytosis or phagocytosis.
Upon entering the bloodstream, these particles are distributed throughout the body. Animal studies have demonstrated their accumulation in multiple metabolic and barrier organs, including the liver, kidneys, spleen, and brain. The liver and kidneys are major sites of accumulation due to their roles in detoxification and filtration.
Nanoplastics pose a specific concern because their minute size allows them to potentially cross the blood-brain barrier, which typically protects the central nervous system. The accumulation of these particles in various human tissues has been confirmed through postmortem analysis. While the body does attempt to excrete some of the internalized particles through the kidneys (urine) and the liver (biliary excretion), the smallest plastic fragments can persist in tissues.
Documented Health Impacts
The presence of microplastics and nanoplastics within the body exerts toxic effects through both physical interaction and chemical exposure. One primary mechanism is the induction of cellular stress, particularly oxidative stress. This occurs when the production of reactive oxygen species (ROS) overwhelms the cell’s antioxidant defenses. Uncontrolled ROS production can damage fundamental cellular components like DNA, lipids, and proteins, potentially leading to cell death or premature cellular aging, known as senescence.
At a systemic level, microplastics in the gastrointestinal tract can disrupt the balance of the gut microbiome, leading to a condition called dysbiosis. This microbial imbalance and physical irritation can compromise the intestinal barrier, causing a “leaky gut” effect. The resulting chronic, low-grade inflammation can then extend beyond the digestive tract, potentially contributing to systemic health issues.
Another element is the harm from chemical additives bound to the plastic. Microplastics act as carriers for toxic substances, notably Bisphenol A (BPA) and phthalates, which are classified as endocrine-disrupting chemicals (EDCs). Since these chemicals are not permanently bonded to the plastic polymer, they can leach out once inside the body.
These leached EDCs interfere with the body’s hormonal signaling pathways, even at very low concentrations. They can mimic or block natural hormones, which can disrupt reproductive health, alter metabolism, and impair thyroid function. The presence of plastic particles within atherosclerotic plaque removed from human carotid arteries was associated with a greater than fourfold increased risk of subsequent heart attack, stroke, or death.
Strategies for Reducing Intake
Individuals can take several practical steps to reduce their personal exposure to microplastics, particularly regarding water and food consumption. Since bottled water contains high concentrations of plastic particles, switching to filtered tap water is an immediate improvement. Highly effective home water filtration systems, such as Reverse Osmosis (RO) or Ultrafiltration (UF), can remove up to 99% of microplastics due to their extremely fine membranes, which filter particles down to \(0.0001\) microns.
Regarding food, it is beneficial to avoid storing or heating food in plastic containers, as heat significantly increases the leaching of plasticizers and microparticles. Switching to containers made of glass, ceramic, or stainless steel for food storage and microwaving minimizes this chemical transfer. Additionally, reducing consumption of highly processed and pre-packaged foods can lower intake, as they often have higher plastic contamination from manufacturing and packaging processes.
To address the inhalation route, particularly from synthetic textiles, simple changes in laundry habits can make a difference. Further reduction can be achieved by managing household dust.
Reducing Exposure from Textiles and Dust
Washing synthetic garments less frequently, using cold water, and selecting shorter wash cycles reduces the amount of fiber shedding. Further reduction can be achieved by installing an external washing machine filter or using an in-drum microplastic-catching device, which can capture a substantial percentage of fibers before they enter the wastewater. Lastly, frequent dusting with a damp cloth and vacuuming with a HEPA filter helps to remove airborne microplastic fibers that accumulate in household dust.