Imagine something so small that it has attached itself to almost everything around you yet, you can never see it with the naked eye. Imagine blindly consuming toxins that circulate throughout almost every part of your body day in and day out, never conscious of the significant bodily damage taking place inside of you. What I am describing is the unfortunate reality for humans in today’s plastic-obsessed world. Microplastics exist in almost all corners of the environment, and their potential harm to human health and the environment has received increasing attention from the public and the scientific community. Through explaining characteristics of microplastics, effect of exposure to humans, society’s stance on the issue, and analyzing the production of plastic, I am striving to furnish an answer to an immense and somewhat perturbing question: how do microplastics interact with biological systems, influence environmental sustainability, and are they a significant and long-term threat to human health? By investigating this difficult question, we must first answer some more specific, preliminary questions.   

Microplastics are tiny particles of plastics that are created either in a targeted manner, by an industrial process, or due to a natural continuous processes of chemical breakdown and degradation into the environment.¹ The original creation process of the microplastic separates the particles into two subsections: primary and secondary. Primary microplastics are those whose size is purposefully manufactured at sizes under five millimeters. Some examples of primary microplastics are microbeads in exfoliating facial cleansers and scrubs, body wash gels for the shower, scrubbing pads used for dishwashing, as well as microfibers that come off objects like towels or other textiles. Secondary microplastics can be described as microplastics that are created from plastic polymers through normal weathering processes. These secondary processes include erosion, UV radiation, oxidants, abrasion, photo-oxidation (occurs under the influence of radiant energy, such as light), and biological transformation over long periods of time.²

Microplastics are also classified based on their physicochemical properties: microfibers, the most common form of microplastics from sources like laundry and clothing made from materials like polyester and acrylic; fragments, the larger microplastic particles from sources like plastic cutlery and lids; nurdles which can be characterized as miniscule plastic pellets; microbeads, characterized as plastics under 1 millimeter in diameter from sources like exfoliated soap and toothpaste products; and nanoplastics, the smallest classification of plastics, 1-100 nanometers in diameter, sourced from the disintegration of microplastics.²

Society’s proficient understanding of microplastics and their danger is extremely important to the ability to tackle this issue before it becomes something too far gone for us to control. In order to gauge where society stands in terms of microplastic knowledge, we can turn to a study done in Shanghai, where researchers analyzed the public’s awareness and behavior towards plastics and their willingness to reduce emissions of microplastics. Rapid economic development in Shanghai has not only promoted consumption growth but also led to a surge in domestic waste; in fact, in 2017 Shanghai ranked second among cities in China for most household waste, producing more than 9 million tons of household garbage.³ With a waste statistic like that, one could assume that the people of Shanghai are aware of what their waste of plastic goods is doing to their environment and their own physical health respectively, yet we are shown this may not be the case. The study consisted of random face-to-face interviews to complete a total of 437 valid questionnaires. The “survey results show[ed] that only 26% of the respondents had heard of microplastics before the survey, and the majority were relatively unfamiliar with microplastics.” … “When informed with the possibility that microplastics may affect human health, 75% of respondents became worried or even overly worried.”³ Using this study as a representation of the general public, it shows that the majority of the public does not know about the physical and chemical properties of microplastics, proving that even in one of the top waste producing cities people are still ignorant to the harm being done. Although the public may realize that plastics have a negative impact on the ecological environment, it is very important that we do not let them underestimate this impact. The only way we are going to begin to see large strides in the development of new technologies put in place to mitigate microplastic exposure, is if we get the public outraged about the issue. In some cases, bringing something like this to the forefront of the general public may cause many people to become scared and worried for what is coming next, but in this case I believe that is exactly the type of reaction that is going to be necessary to lead us into a world with less microplastics. We need people alarmed and willing to do something about this problem so measures can be taken to lessen the plastic production of large corporations who aren’t concerned with anything other than making a profit.

Humans are exposed to microplastics in three main ways: ingestion (consuming contaminated food or drinking water), inhalation (breathing in airborne microplastic particles), or dermal contact (skin exposure to particles). “Wastewater treatment plants, large plastic fragmentation, solid waste management, aquaculture, runoff, agriculture, fishing, or industrial factories (among others) are sources of  pollution.”¹  Overall, oral intake (ingestion and inhalation) is the main route of human exposure to microplastics and the “potential risks for human health are centered on its gastrointestinal, hepatic, and reproductive toxicity; neurotoxicity, and combined toxicity of its adsorbed contaminants, whose mechanisms might be involved in oxidative stress, inflammatory reaction, and metabolism disorders.”⁴

While microplastics themselves can be detrimental to different bodily functions, they may also act as carriers of other toxic substances to the tissues, like the substances they were elaborated from: phthalates, UV stabilizers, Bisphenol-A, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, persistent organic compounds, colorants, flammable retardants, just to name some of the most plausible toxins carried by microplastics.⁴ By focusing in on Bisphenol-A and phthalates, two compounds that interfere with hormone functions even at very low doses, we are able to identify how endocrine-disrupting chemicals (EDCs) like these have numerous disruptive effects in the human body. These compounds “can alter fetal development at the epigenetic level, with effects that may be passed down through generations.”⁴ More specifically, maternal transfer of microplastics to the developing fetus has been demonstrated through the analysis of human placenta. EDCs are implicated in the later-life development of chronic conditions, including metabolic, reproductive, and degenerative diseases, as well as certain cancers.

“Declines in male reproductive health, such as increasing rates of cryptorchidism (undescended testes), poor semen quality, low testosterone levels, and testicular cancer, have also been linked to EDC exposure. Specifically, exposure to anti-androgenic EDCs during a critical phase of fetal testicular development, known as the ‘masculinization programming window’ (MPW), can disrupt testicular development and function. Reduced androgen activity during the MPW can lead to both immediate and long-term reproductive disorders.”⁴

As stated earlier, oral intake is the main route of exposure, but how are these microplastics sneaking their way into our food, water, and air? In terms of food, a lot of the time microplastics and other hazardous substances may be released from food containers because of the food’s heat effect on the packaging; more specifically ready-to-eat food products or products you cook/defrost while still in the packaging.⁴ Beyond plastic packaging exposure, crops watered with contaminated water can also expose humans to microplastics during consumption. There is also an abundance of microplastics in aquatic environments that can easily enter the food web by trophic transfer through seafood in the human diet.

To put some numbers next to this data, we can look at, on average, how many microplastic particles humans ingest through food in a year. “A mean amount of 132,740 p/g (particles/gram) [microplastics] were determined in five frequently consumed fruits and vegetables (apples, pears, broccoli, lettuce, and carrots) supplied by different grocery shops. Taking these data as a representative for this food group, and following the WHO recommendation to include at least a daily intake of 400 g of fruit and vegetables, humans would be ingesting 53.096 × 10⁶ p/day.” … “Accordingly, a mean content of 0.98 p/g of seafood was determined. Assuming the annual global seafood consumption of 22.41 kg per capita, the global per capita [microplastics] consumption linked to seafood is 22.04 × 10³ p/year.”¹ In terms of drinking water, microplastics may be exposed to bottled water from its plastic packaging, but it has been determined that the most relevant source of water contamination are wastewater treatment plants.¹ To be more specific, in the municipal wastewater treatment plants of US states: California, New York, Wisconsin, and Ohio, an estimated average daily 4 million fibers of microplastic is discharged by each single plant respectively.⁵ Different researchers have assessed the amount of microplastics in bottled as well as in tap water, reporting high variability in the data by averaging the data, we can identify “humans would ingest an average of 13,552,977.57 p/L of water packaged in single-use plastic bottles, which translates into 27,105,955.14 p/day assuming a total consumption of 2L of bottled water per day.”¹  Inhaling microplastics residing in the air is another way humans are exposed and many people do not even know about them. Actions such as opening a plastic package, microfiber detachment from textiles in clothing, or the wear of vehicle tires, all contribute to microplastic particles in ambient air. Through atmospheric deposition (the process in which particles move from the atmosphere to earth’s surface), these particles arrive at land, aquatic environments, or even to remote locations where microplastics have been found in snow from varying locations on earth. When analyzing quantitative data associated with airborne microplastics, there is “estimated an airborne [microplastic] concentration of 0.685 p/m3. Considering a respiration frequency of 12 breaths/min and a tidal volume of 0.5 L, the breathing rate is 8.64 m³/day; so, humans would inhale about 6 (5.918) p/day. However, airborne MNPLs estimation depends on the sampling methodologies, air renovation rates, and other factors such as human activity, furniture, or cleaning habits,”¹ meaning this figure is not going to be applicable to everyone, nor the same person who might have switched up their routine from the previous week.

It is very scary to think about the amount of toxins and pollutants we are being exposed to daily, without even acknowledging or understanding the health risks involved. In fact, estimated from recent data available, the total burden of human exposure to microplastics is 2.93 × 10¹⁰ p/year. The science around microplastics is still very young, with new developments and studies coming to light daily. The subsequent steps should consist of solidifying the public’s understanding of microplastics, making people aware of what they are putting into their bodies, and rallying society to come together and combat the different leaders of exposure. Additionally, continuing to strengthen biomonitoring studies in humans is very important to the future of our health because it would allow us to accurately establish the exposure levels and the induced effects of microplastics. 

In light of all the negative environmental and health risks that come as an accessory to the production of plastic, the question: why are we continuing to produce plastic in the first place, becomes something worth investigating. Durability and longevity are two similar positive characteristics of plastic that are significant factors in keeping the production of plastics going. The long-lasting quality of plastic allows for plastic to often be used in homes, bridges and as infrastructure in buildings.⁶ The durability of plastic is one of the main reasons for its ever increasing longevity. The durability of plastic stems from its molecular structure and means of production. Plastic is a polymer, meaning it is a chemically-based material made of long chains of molecular units. These chains are made up of carbon, hydrogen, nitrogen, oxygen, and sometimes fluorine and chlorine for specific types of plastics. The long chains of molecules that make up plastic allows for it to be flexible enough to absorb wear and tear while strong enough to resist things like water, decay, rust, and corrosion. Longevity also transitions attention to another positive characteristic of plastic which is that less plastic goods need to be thrown away due to consumer usage. The durability and long lasting nature of plastic means there is going to be less plastic in your garbage bin, therefore less plastic waste in our landfills and less need for production of replacement plastic-made goods.⁶ When you have used the plastic good to the maximum of its utility, you recycle the plastic, throwing it into a separate garbage bin to be sent off to a plastic recycling facility, melted down, and repurposed into an entirely new product. This allows for there to be less plastic waste if recycling is used proficiently by the members of a community.

A larger, more specific reason to continue the production of plastic is the positives linked to the application of plastic in the medical field. “The development of plastics in the 1930s, 1940s, and 1950s enabled the development of medical devices that overtook and eventually replaced the foundation materials with newer and better materials such as polyvinyl chloride for IV bags and tubing, silicone tubing for catheters and balloons, polyolefins for trays and bottles, and fluoropolymers for IV catheters.”⁷ Before the use of plastic, medical devices were made of glass, ceramics, or metals depending on the intended use of the device. Even though these devices were sterilized between uses, they regularly caused cross-contamination between patients and caused a high patient mortality rate. The majority of products nowadays that are made for the device industry are made from commodity polymers or readily available, inexpensive polymeric materials. “The primary materials in use continue to be the four mainstay polymers: polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), and polystyrene (PS).”⁷ The use of plastic allows for a more sterile procedure by offering one-time-use devices and eliminating the need to sterilize and reuse tools; in this way, the problem of health risks due to device-bred cross-contamination between patients is eliminated. By looking at the result from different medical procedures before and after plastic was introduced into the industry, we are able to identify how the change in devices affected the outcome on the patient and the procedure itself.

Not many years ago, when a heart patient presented with blocked or restricted arteries, the only course of treatment was to do open heart surgery or coronary artery bypass graft surgery.⁷ As you can imagine, undergoing this procedure is very complicated for the surgeon and very traumatic and expensive for the patient. With the development of the heart catheter, a device made of plastic that is able to deliver a vascular stent or scaffold, the landscape for treatment of blocked and restricted arteries was changed forever. Use of the heart catheter is much less invasive than open-heart surgery, with it reducing recovery times, lowering risks to the patient, and lowering expenses, making treatment accessible to more patients. Products such as multiple instrument access ports, a device made from plastic, allows for minimally invasive surgeries to be performed within the peritoneal cavity through a single incision in the abdomen. With use of this plastic device, “the surgeon could then perform procedures such as biopsies, appendectomies, gallbladder procedures, hernia repair, and hysterectomies without the need to open the abdomen beyond the one small incision.”⁷ This development allowed for the surgeon to have enhanced precision and control while using minimally invasive techniques to complete the procedure. The device also produced a much shorter recovery time for the patient, while lowering the complication rates as a whole. Multifunctional devices such as the Pill Cam, a video recording device made of primarily plastic, rely on extremely tiny components but improves the diagnosis accuracy, helps eliminate false positives/the need for investigatory biopsies, is more cost effective, and from a patient perspective, far more comfortable than the substitute option, a colonoscopy.⁷ In some cases plastic is used not to produce a medical device, but to serve as a medical device itself. An example of this could be using the PEEK polymer as an implant stem. Comparing the use of peek polymer versus its substitute Titanium, the polymer has close to the same flexibility as the bone and there is a reduced tendency for the implant to loosen over time.⁷ Overall, it seems that the use of plastic in the medical device industry has greatly reduced recovery times, blood loss, the risk of infections and other complications from open procedures, and has benefited society by way of a drop in the cost of healthcare.

During 2018 alone, 359 million tons of different plastic materials were produced globally, many of them single-use goods, becoming waste after its short lifespan. Most of, if not all of, the plastics manufactured for different applications were not biodegradable, resulting in an excess of plastic waste accumulated in both landfills and natural habitats found in the environment. In fact, disregarding the amount of untraceable plastics that were littered throughout the year, 25% of the plastic post-consumer waste ended up in landfills in 2018.¹ One sub argument in the counter argument stating production of plastic should continue at its current rate is that plastic is a very durable material and is extremely long lasting, even when its application is intended to be single-use. In a way, this ‘strength’ of plastic functions as a weakness in the big picture. This is because extremely long lasting plastic produces extremely long lived microplastics; for example, microplastics from plastic water bottles made from PET (polyethylene terephthalate) have a lifespan of 450 years in the environment.² These plastic goods that are being praised for their long lasting durability are the same plastics that are filling our environments with long lasting microplastic pollution and filling our air with toxins that will outlive all of us. Speaking on the affordability of plastic goods, we must acknowledge the negative externalities that are associated with the consumption of plastic goods. Sure, it might be more expensive to buy the more sustainable option when at the store, but by making the conscious choice to stay away from products made from plastic material, you are not only bettering the environment, but you are actively reducing health risks linked to microplastic exposure. One can argue that plastic is recyclable, therefore waste should be mitigated and we should be getting more out of one good that is plastic when compared to a good that is made of metal or glass based on our ability to recycle the plastic good. While this is true in theory, this is not a realistic truth in our society; in fact, a report put out by the environmental groups Beyond Plastics and The Last Beach Clean Up in 2022 showed that the recycling rate in the United States is around 6% with the possibility of even less.⁸ Using research done by Scottish researchers at recycling facilities in the United Kingdom to represent the processes of the United State recycling industry, we are able to perceive just how much microplastic pollution is created by processes of recycling. The research shows, “perhaps as much as 400,000 tons [of microplastics] in the United States alone, or the equivalent of about 29,000 dump trucks of microplastics.”⁷ Though recycling is generally good for the environment when it is done effectively, it is important that society does not view recycling as the answer to all of our problems in terms of pollution and plastic waste, and begin to search for alternative methods.

The concept of alternative methods can be used to transition us into the more central counter argument to reducing the production of plastic, which is the positive benefits of the application of plastics in the medical field. A recent study involving the investigation of microplastics released from medical devices showed some concerning data. The study analyzed eight medical devices which are mainly made of polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC). These medical devices consist of: the disposal infusion set, disposable plastic blood bags, disposable blood collection device, disposable sterile injection needle, disposable sterile syringe, disposable burette infusion set, and two other devices made up of similar material that were not included in the online report. disposable medical devices, more specifically these mentioned devices, generally require high-temperature steam disinfection before disposal.⁹ This process, which is shown to release large amounts of microplastics, makes these devices a non-negligible source of secondary microplastics from the beginning; the information found by researchers through physicochemical characterization (study of a substance’s physical and chemical properties) further proves that plastic medical devices need to be replaced. Researchers found that “the amount of [Microplastic particles] released from PP-prepared disposable medical devices [1.27 ± 0.34 × 10⁶] was greater than that from PVC-prepared disposable medical devices [1.08 ± 0.14 × 10⁵]”.⁹ This is a very concerning statistic, acknowledging that though Polypropylene is a very prevalent polymer used to create medical devices, it can cause inflammation, oxidative stress and gut damage.⁴ By contrast, the study also found that “the particle size of the released [microplastics] was the opposite, PVC-prepared disposable medical devices [11.45 ± 1.79 μm] > PP-prepared disposable medical devices [P4: 7.18 ± 0.52 μm].”¹¹ This difference in surface morphology is based almost fully on the type of polymer, still, this data represents that the microplastics from the PP-prepared disposable devices are going to more easily pass throughout one’s body parts. The same study also analyzed the toxicity of disposable medical devices-derived microplastics in Caenorhabditis elegans. Casenorhabditis elegans, often referred to as C. elegans, is a miniscule (about 1 mm long) transparent nematode or roundworm that is one of the most abundant environmental organisms and is popularly used model organism for research in molecular and cell biology because of its transparent body, easy culture, and short life cycle. Another important thing about C. elegans worth noting is that they share significant genetic similarity with humans, allowing researchers to study fundamental biological processes like cell division, aging, and disease pathways using the model organism.

Keeping the genetic similarity in mind, we look at the effect exposure to different microplastics affect the nematode. The study found that “exposure to 10 and 100 mg/L low-density polyethylene and polylactide reduced the brood size of worms,” … “exposure to 100 mg/L [polystyrene] beads reduced the brood size and egg ejection rate of worms, and polystyrene exposure disrupted worm development by shortening body length and width.”¹¹ This study reflects a significant decrease in the brood size of the organism when exposed to polyethylene, polylactide, and polystyrene beads, meaning that the reproductive health of the nematode is being damaged. A decrease in brood size represents a decrease in the number of eggs produced by the nematode. The polystyrene beads also reduced the egg ejection rates showing how significant of an impact that microplastic has on the reproductive health of an organism that’s genome’s counterparts correspond to a large portion of human genes. The toxicity assessment expressed that medical device-derived microplastics also significantly affected the nematode’s longevity, significantly increasing germ cell apoptosis in C. elegans and disrupting the intestinal barrier of worms, decreasing their lifespan.¹¹ This is alarmingly representative of the negative effects of exposure in humans. The intestine is one of the main areas of microplastic accumulation and intestinal damage and digestive tract obstruction are two of the foremost risks associated with ingestion of microplastics. There is still a lot of research that needs to be done involving more sustainable alternatives to replace some of these important disposable medical devices. It would serve the medical device community well to understand the materials available from companies such as NatureWorks, Metabolix, and Braskem as new products are developed.⁷

Microplastics are a significant and pressing threat to human and environmental health with exposure to toxic contaminants increasing with the continued production and usage of plastic-made materials across so many aspects of our living in society. The widespread production and use of plastics, particularly for single-use products and even certain medical devices, pose a pressing threat to both environmental and human health by means of microplastics and measures need to be taken in order to both decrease plastic production, decrease human exposure, and increase the public’s knowledge on these important issues. In our current situation ignorance is not bliss and society needs to be informed in order to make major strides in the right direction. Spreading awareness of all risks brought about by the proliferation of microplastics in our water, air, food system and environment is going to enable society to consciously decide how they are going to get involved in beginning to fix this problem and shine light on the plastic-producing corporations that are hurting us the most.

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