BY DAYA BAUM
Microplastics (MPs), defined as plastic particles measuring less than 5 mm, have emerged as a pervasive environmental contaminant, raising significant concerns about their impact on human health. These particles originate from industrial processes that produce microplastics by the unintentional release of by-products, deterioration of everyday consumer products, and degradation of larger plastic waste. Over time, MPs have infiltrated the food chain, contaminating seafood, drinking water, and agricultural products, which find their way into humans. In the body, MPs serve as vectors for toxic chemicals and pathogenic microorganisms. MPs have been seen to exist in various food chain components: meat, milk, and seafood. Aquatic organisms and livestock may act as exposure routes due to their consumption of water-containing MPs. Primary routes of exposure include ingestion, inhalation, and dermal absorption. MPs have been detected in human feces, blood, and the placenta. MPs present numerous potential health dangers, including digestive, hormonal, and neurological disturbances. The disruption of everything from the microbial equilibrium to impairment of nutrient absorption highlights the necessity of further public health interventions to reduce MPs exposure.
Disruption of Gut Microbiota Homeostasis
The gut microbiota, a diverse community of microorganisms residing within the gastrointestinal tract, plays a pivotal role in metabolic regulation, immune function, and homeostasis (maintaining a stable internal environment). Emerging research suggests that MPs may disrupt this microbial balance, contributing to dysbiosis, a disproportion in the gut microbiome composition and function. Studies have demonstrated a decline in beneficial microbes, such as Lactobacillus and Bifidobacterium, along with an expansion of pathogenic species, including Escherichia coli and Clostridium difficile. This microbial imbalance, dysbiosis, has been implicated in a range of gastrointestinal disorders, such as inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS). Additionally, the plastisphere, the microbiota associated with MPs, serves as a hub for pathogenic bacteria and antimicrobial resistance gene (ARG) transfer.
Additionally, MPs absorb and transport endocrine-disrupting chemicals, such as bisphenol A (BPA) and phthalates, which further worsen microbial imbalances. These chemicals interfere with gut microbial metabolism, leading to chronic inflammation and impaired mucosal immunity. These disruptions not only compromise intestinal function but also have systemic consequences, including neuroinflammatory responses and metabolic syndrome, a group of biochemical and physiological abnormalities that increase the risk of chronic diseases, including strokes and type 2 diabetes. Moreover, MPs serve as breeding grounds for biofilms —microbial communities embedded in an extracellular matrix, a surrounding network of molecules that support and give structure to body cells and tissues. This allows them to facilitate cell-to-cell communication and the exchange of ARGs. The co-selection of ARGs in MP-associated pathogens worsens global spread of antimicrobial resistance.
Microbial Degradation of Microplastics
Recent research has explored whether gut microbiota possess the capability to degrade MPs. Some bacterial and fungal species exhibit enzymatic activity that can partially metabolize plastic polymers under specific conditions. However, the extent and efficiency of this degradation remain unclear, as studies have not provided definitive quantification of the percentage of MPs broken down by gut microbiota, nor have they determined whether this degradation process is complete. Investigations into MP digestion and gastrointestinal interactions employ both in vitro and in vivo methodologies, with dynamic simulators such as the simgi® system (in vitro), a gastrointestinal model designed to simulate the physiological and biochemical processes that occur in the GI tract. While in vivo animal models offer physiological relevance, they present ethical and logistical challenges, necessitating the refinement of in vitro approaches that can more accurately simulate human digestion.
The significant variation in the structure of MPs further complicates degradation. The diversity in polymer composition suggests that not all MPs are susceptible to microbial breakdown, and the conditions within the human gut —including pH, oxygen levels, and microbial diversity— may not support efficient MP degradation. Even if partial breakdown occurs, the byproducts of this process and their effects on gut health remain largely unknown. Potential metabolic intermediates could introduce additional toxicity or contribute to oxidative stress, further compromising gastrointestinal integrity. While microbial degradation of MPs is a promising avenue for reducing plastic pollution, its role in mitigating MP accumulation in the human gut has yet to be solidified. More comprehensive research is needed to determine whether engineered microbial consortia — a group of organisms that synergize — could enhance degradation efficiency and whether such interventions could be safely applied to human health.
Potential Avenues to Mitigate Microplastic Exposure at Yale:
Given the negative effects of MPs on gut health, educational institutions such as Yale University can have meaningful effects on the implementation of measures that reduce student exposure and further innovation. While Yale Hospitality has already done well with reusable cutlery, it is worth investigating the packaging of its food, sourcing, and the materials used to cook food. Partnering with suppliers who prioritize sustainable agricultural and aquacultural practices can help reduce MP presence. Transitioning to glass, ceramic, or new non-plastic alternatives can decrease the contamination of prepared meals. Finally, continuing to allocate funds to environmental research efforts aimed at developing novel MP detection, filtration, and elimination methodologies can foster greater human health.
Daya Baum is a sophomore in Branford College.
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References
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