Banner by Daniel Huffman
Is There Plastic in My Body?
by Daniel Huffman
Of all the materials known to humanity, perhaps the most versatile is one we created ourselves: plastic. With applications ranging from medical equipment, to electric insulators, to automobile parts, plastics are a critical component of our modern lifestyles. At the same time, once these objects enter ecosystems, they can inflict great harm on the native species and environment. The tragic effects of plastic pollution on various forms of marine life have been often publicized, and as a result, public sentiment has driven some progress toward reducing plastic pollution. Nevertheless, the amount of plastic in the oceans and throughout the Earth’s ecosystems continues to multiply. According to an estimate from the journal Current Biology, there are now approximately 5 trillion pieces of plastic in the ocean visible to the naked eye. However, this figure does not include an entire class of plastics that are often too small to see. With the discovery of microplastics in places as remote as the Arctic, it is even more urgent to curtail plastic pollution for the sake of the environment and ourselves.
Microplastics are small pieces of plastic less than 5 millimeters in length. These particles are typically formed either directly though the production of miniature plastic beads and similar items or gradually though the breakdown of larger plastic objects. Those that are intentionally produced at this size are classified as primary microplastics, whereas those that result from degradation are known as secondary microplastics. Although scientists are now aware of the abundance of microplastics in our environment, relatively little research has been directed towards them. While scientists have made predictions, there is not enough data to have a concrete understanding of how microplastics impact forms of life.
Given the countless sources of microplastic pollution in our daily lives, environmental exposure to microplastics was inevitable. The ocean is the largest domain in which microplastics are abundant. As a result, marine life is at high risk of exposure. Since microplastics are around the same size as the morsels that filter-feeders consume, these creatures readily ingest microplastics. When these filter-feeders are preyed upon by other marine life, the microplastics pass up the food chain. Ingestion of microplastics may detrimentally impact the organism, potentially reducing reproductive output, feeding activity and energy reserve levels. Additionally, once ingested, microplastics may release toxins absorbed during manufacture or subsequent exposure, such as bisphenol A, putting marine organisms at further risk. With a 2014 study revealing that individual mussels often ingest tens of plastic fibers and the extent of plastic pollution increasing year by year, it is clear that our planet’s ocean life is not safe from the reach of microplastics.
Marine organisms are not alone in their exposure to microplastics. In fact, humans are directly exposed to microplastics across all venues of daily life. Microplastics have been found in a variety of food items such as fish, sugar and table salt and are commonly present in unfiltered tap water or bottled drinking water. Considering the consumption of food alone, one study has estimated the average human intake of microplastics to be 39,000 to 52,000 particles per year. However, it is likely that the microplastics that settle on one’s plate as dust or contaminate food in plastic packaging or containers outnumber those already present in the food. Although it is known that microplastics are abundant in our everyday environment, there is yet limited consensus on the effects that exposure has on the human body.
A recent study by Prata et al. seeks to provide some answers. In their report, the researchers describe how microplastics may impact bodily systems depending on their method of exposure. The principle method of microplastic exposure for humans, along with other animals, is through ingestion, either by consumption of food or inhalation. Once ingested, Prata et al. predict that microplastics may make their way to various organs, including the intestines and liver. After entering a gastric adenocarcinoma cell, polystyrene, a hard plastic found in consumer products such as food packaging, has been observed to be capable of reducing the cell’s viability and prompting its pro-inflammatory responses, though these results may not generalize to other microplastics or cell types.
Unlike with food, there is not much one can do to limit their exposure to microplastics present in the air around them. One study conducted by Vianello et al. in 2019 estimates that the average adult male inhales 272 microplastics in a day, though the actual number likely varies depending on the cleanliness of the environment, materials of surrounding objects and season of the year. The smaller and less dense the microplastics, the deeper they will penetrate the lungs, and once there, the particles may cause inflammation. In vivo testing involving the use of live organisms and human lung biopsies have indicated that inhaled microplastics in high concentrations could also cause lesions to the respiratory system. Further, the presence of microplastics in biopsies of lung cancer patients indicates a possible correlation, though there is insufficient evidence to suggest causation.
In additional to ingestion and inhalation, microplastics could potentially enter the human body dermally through contact with one’s skin. Scientists have speculated that particles of length smaller than 100 nanometers, formally classified as nanoplastics, may be capable of penetrating skin. Although dermal contact is a less prevalent method of microplastic exposure, particles that cross the dermal barrier may cause detrimental effects, such as causing epithelial cells to suffer oxidative stress, an imbalance in the cells’ oxidative reactions. As with all forms of exposure, however, more research must be done to determine the full effects microplastics have on the human body when internalized dermally.
After entering the body through one of these methods, microplastics may impact body systems in a variety of ways. For one, microplastics may disrupt one’s energy balance by increasing the body’s intake of energy. Scientists predict that microplastic exposure may disrupt the metabolic and immune systems as well. Another area in which microplastics have been theorized to impact the human body is neurotoxicity. In vivo testing has demonstrated that exposure to microplastics precedes findings of neurotoxicity, and traffic pollution containing microplastics has been found to increase the risk of dementia and Alzheimer’s disease. Once again, additional research must be conducted before reaching firm conclusions, though these findings may reveal a connection between microplastic exposure and neurological impairment.
While it is just one of several ecological crises currently plaguing our planet, microplastic pollution is a pressing problem. With the production of plastic set to increase fourfold over the next three decades, human exposure to microplastics is bound to increase substantially. Not enough research has been done yet to ascertain the effects this increase in microplastic exposure will have on human health. However, laboratory experiments and observations on other forms of life indicate that exposure may be harmful in several ways. Fortunately, one can limit their exposure to microplastics and reduce their own contribution to plastic and microplastic pollution by being mindful when purchasing, eating and drinking. Given the scale and impact of the crisis, individual actions such as these, as well as systemic change in our production and use of plastics, will be necessary in protecting our planet’s ecosystems and its inhabitants.