Nowadays, it seems impossible to avoid plastic products. From containers to clothing, plastic’s cost-effectiveness, versatility, and durability have led to it becoming an integral part of our lives. However, its ubiquitous presence and lasting environmental impact have brought about an unavoidable problem: polystyrene microplastics.
What are polystyrene microplastics?
Microplastics are tiny plastic particles that are less than 5mm in diameter, or the size of a sesame seed. They can either be produced directly from normal wear and tear of synthetic fabrics and personal care products or as a result of the natural weathering of larger plastic items over time. Microplastics, specifically polystyrene microplastics, have raised environmental and health concerns due to their widespread presence in both aquatic and terrestrial ecosystems and their common usage in food packaging (1). Therefore, polystyrene microplastics pose a concern to human health as they could be unintentionally consumed in our diets through contaminated food and water sources. Recent research highlights the impacts of polystyrene microplastic ingestion on human health, specifically its effect on our gut health.
What is gut health?
Gut health is a term used in both medical and commercial contexts to describe a condition where there is no physical or psychological gastrointestinal (GI) distress or disease. A common theme that often arises when referring to ‘gut health’ is the state of the GI microbiome. The GI microbiome is a composition of various bacteria that are responsible for intestinal metabolism, defense, and regulation. Additionally, it is responsible for maintaining the GI barrier, which needs to be healthy to protect against the development of serious GI diseases and inflammation (2).
How is polystyrene microplastics affecting our gut health?
Within the last 50 years, the presence of polystyrene microplastics in the ocean has increased by two orders of magnitude. Their potential to detrimentally affect the GI microbiome and weaken the integrity of the GI barrier has become a concerning issue. Recent research has shown that the GI microbiome can be affected after exposure to concentrations of polystyrene microplastics that are currently present in the environment (100 and 1000 μg/L). It can cause a decrease in the abundance of the bacterium responsible for the breakdown and absorption of food, digestion, and maintenance of the immune system (3). Exposure to polystyrene microplastics can also decrease the diversity and richness of the bacterial community similarly to patients who have GI conditions such as inflammatory bowel disease (4). These alterations to the GI microbiome also have the potential to impact brain function. Ingestion of polystyrene particles can disrupt the intricate connection between the brain and intestines, implying that polystyrene microplastics can interfere with the coordination and communication of these components (5).
Ingestion of polystyrene particles has also been found to disrupt the gut barrier. The gut barrier is comparable to a multi-layered fortress, with the first line of defense represented by the fluid barrier of the mucosal layer that regulates the transport of external molecules. The walls consist of a layer of cells that make up the epithelial lining and act as the final physical defense against foreign invaders. Disruption of any of these layers would compromise the gut’s ability to defend against pathogens and harmful bacteria. However, recent studies have shown that microplastics can successfully infiltrate the gut barrier and bioaccumulate in the small intestines and other organs (6). Though mechanisms by which microplastics are transported across the gut barrier remain unclear, it has been reported that microplastics can disrupt gut barrier function by discouraging mucosal secretion (3), weakening the gut’s defense. With a weakened fluid barrier and a permeable wall, gut health can become vulnerable to diseases and toxication by chemicals that are commonly associated with microplastics (7,8,9).
How to reduce your intake of polystyrene microplastics?
On average, Northern Americans consume 39,000-52,000 microplastic particles annually, roughly equal to 5g of plastic or an entire credit card (1). These estimates only considered six well-studied food sources and their average microplastic particle content, likely underestimating actual consumption rates.
So, what measures can we take to give us peace of mind? To minimize unintentional microplastic consumption, it is important to be informed about common sources where microplastics are most abundant. Studies have reported consumable products with the highest amount of microplastics can be found in drinking water, with global annual ingestion ranging from 9,000 to 175,000 microplastic particles per person (7). However, these ingestion rates vary depending on the source of the drinking water. On average, individuals who drink tap water are estimated to consume 16,000-68,000 microplastic particles a year, while those who drink bottled water are estimated to consume 346-292,000 microplastic particles (7). An effective strategy to reduce the unintentional consumption of microplastics therefore may be to minimize drinking bottled water and by being cautious of tap water quality.
While addressing steps to reduce our microplastic intake is crucial, it is also important to focus on measures to prevent microplastic accumulation in our environment. Starting with small changes, like reducing disposable plastic consumption and choosing reusable or biodegradable products, can have a long-term impact. For those who prefer a proactive approach, advocating for reduced plastic usage by companies and for improved government water management policies would also help transform how we care for our environment and ourselves.
Overall, the impact of polystyrene microplastics on gut health is growing due to their widespread abundance in our environment and everyday products, making them unavoidable. While there is still much to learn about the effects of polystyrene microplastics on human health, recognizing its impact on gut health can help us be better informed on how to make healthier lifestyle choices. By doing so, we can take precautions to minimize our intake of polystyrene microplastics.
As we journey towards a clearer understanding of the interplay between polystyrene microplastics and our well-being, let's harness this knowledge to empower ourselves to make wiser choices and safeguard our guts from unnecessary plastic invaders.
Written by Rosalia Mendieta, BS and Aishwarya Bhusal, BS
Edited by Aldrin V. Gomes, PhD and Stephanie Palacio, PhD
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Jin, Y., Lu, L., Tu, W., Luo, T. & Fu, Z. Impacts of polystyrene microplastic on the gut barrier, microbiota and metabolism of mice. Sci Total Environ 649, 308–317 (2019).
Usman, S. et al. Polystyrene microplastics induce gut microbiome and metabolome changes in Javanese medaka fish (Oryzias javanicus Bleeker, 1854). Toxicology Reports 9, 1369–1379 (2022).
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