Author: Preethika Arunkumar

As defined by the National Oceanic and Atmospheric Administration, microplastics are “small plastic pieces less than five millimeters long.” They are created from plastic debris that eventually degrades through physical and chemical weathering into smaller pieces. Common sources of microplastics include plastic bags, bottles, packaging, and other everyday usable items. However, they may also originate from plastic-based clothing (such as polyester and nylon) and, surprisingly, cosmetics (where they are often added to provide texture). 35% of the world’s microplastics come from synthetic textiles, 28% from car tires, 24% from city dust, 7% from road dust, 3.7% from marine coatings, 2% from personal care products, and 0.3% from plastic pellets. (Armstrong 2022) For clarification, city dust refers to the abrasion of household objects, plastic materials, and infrastructure. The microplastics from road dust consist of polymer tape and paint used for road markings, and the primary plastic coatings for marine use include polyurethane and epoxy. From this data, it is surprising that a relatively small amount of microplastics arise from actual plastic pieces (like plastic beads), which we would expect most of the microplastics to come from. However, it is revealed that the main source of microplastics are our own daily used products.

This being said, how do microplastics enter commonplace human materials and the environment? As mentioned above, microplastics may be broken down by environmental factors such as the sun’s radiation and washed into bodies of water. At the same time, plastic fibers in clothing are shed each time we wash synthetic fabric, and water from washing machines containing these plastics is eventually discharged into the environment or to a wastewater treatment plant. Another major method of microplastic distribution is sewage. According to the UN Environment Programme, between “80 per cent and 90 per cent of the plastic particles contained in sewage … persist in the sludge.” Once sewage sludge is sprayed onto fields as fertilizer, it can persist in the soil and be absorbed by plants. As can be expected of objects of this size, microplastics can make their way through an ecosystem effortlessly, causing large amounts of harm along the way.

Microplastics are much more dangerous than large plastic primarily because of their size and other physical properties, including elasticity and shear strength. Along with this, microplastics have several chemical properties that determine how much pollution they can cause. Plastic has additives (including antioxidants, dyes, flame retardants, and UV stabilizers) to determine its physical properties and the performance of plastic products. Various polymers combined with additives can result in a large amount of contaminants that can leach into the environment. There are several additives of concern in plastic products that are commonly used every day by the average consumer. Bisphenol A (BPA) is a common additive. It is a primary component of safety equipment and food packaging as they are resistant to high temperatures. It has been found to be disruptive of hormones in the human body and is associated with obesity, cardiovascular disease, reproductive disorder, and breast cancer. Other dangerous additives include phthalates and heavy metals, which serve to increase the properties of plastics. (Campanale et al., 2020) Moreover, various chemicals already present in the environment can be absorbed by plastic, further increasing its toxicity.

The way microplastics are absorbed into the environment all starts with the smallest of organisms. Mollusks and zooplankton easily accumulate microplastics because they are primarily biofiltering organisms. For example, microplastic content in blue mussels is approximately 36 + 7 particles per 100 g. (Van Cauwenberghe & Jansen, 2014) According to Haegerbaeumer et al. (2019), the presence of microplastics within small aquatic organisms decreased food activity and fertility, along with decreasing larval growth and development. Fish and other consumers absorb microplastics and concentrate it within their organs once they have ingested an organism that contains microplastic. 49% of the examined fish in the North East Atlantic Ocean contained microplastics. Most of the particles consisted of 151–1,500 µm fibers and 100–1,500 µm shreds of polyethylene and polyester, which reveals the dangers of small microplastics. Here are the effects of microplastics on various organs in the fish’s body. The brain may be affected, causing changes in motor and feeding activity, and behavioral changes. A concentration of microplastics in the gills can cause structural damage. Microplastics can cause exceptional amounts of damage in the reproductive system, decreasing the production of caviar and penetrating into the eggs, slowing growth and decreasing the chance of survival in fry after hatching. (Zolotova et al., 2022) Ingested microplastics “can block the gastrointestinal (GI) tract of … fish and can also cause physical damage internally such as lacerations or irritations to sensitive GI tissues.” (Canadian Wildlife Health Cooperative) Similarly to the fish that ingest small aquatic organisms, predators of fish will concentrate microplastics within their bodies. Organisms such as seabirds, larger fish, and marine mammals begin to feel the physical effects of microplastics in their bodily functions. The passage of microplastics finally ends at the top of the food chain, with the organism most in danger from the effects of microplastics.

Similarly to other organisms, microplastics pose several health risks to humans. Digestive systems are impacted through physical irritation of gastrointestinal systems, eventually causing inflammation. Gastrointestinal issues occur once the balance between beneficial and harmful bacteria is disrupted by microplastics. (Yuanxiang et al., 2019) Environmental toxins present in microplastics such as heavy metals and polycyclic aromatic hydrocarbons are absorbed by the body once microplastics are ingested. This can affect the gastrointestinal system by causing nausea, vomiting, and abdominal pain. (Abbasi et al., 2021) Along with this, microplastics affect the human body’s hormonal system. This may lead to metabolic disorders, developmental disorders, and reproductive disorders. (Vandenburg et al., 2017) Even though it is generally accepted that ingestion of microplastics is harmful for humans, there is limited evidence on our exposure levels to microplastics. Now, we have found out that microplastics are present in our food, but the most horrifying fact is that microplastics are even present in the air we breathe. A study conducted by Wright et al. (2020) of the air quality in central London determined that microplastics were contained in each of their deposition samples. Fibrous microplastics were most prevalent, compared to non-fibrous microplastics, and the average total deposition rate of microplastics was 771 + 167 particles/m2/d. The diameter of the observed fibrous microplastics ranged from 5 to 75 µm, and most prevalent lengths were between 400 - 500 µm. As stated by the authors of the study, smaller microplastics were observed by the microscope, but were not included in the results because of analytical limitations of the instrument used. This means there may potentially be even smaller particles present in our air. As you have probably already guessed, microplastics have harmful effects on our respiratory system. Small microplastics are associated with mitochondrial damage in respiratory cells. (Lin et al., 2022) Inflammation and damage of the lungs causes shortness of breath and a low concentration of oxygen in the blood leads to fatigue and dizziness. (Lee et al., 2023)