Although a 2019 World Health Organization (WHO) report concluded that microplastics in drinking water posed no risk to human health, accumulating evidence is beginning to challenge these findings.
Since plastics became widely used in the mid-20th century, they have evolved from a novel substance to an essential component in countless applications, with global production reaching 368 million tons in 2019 and expected to double by 2039. The production and degradation of plastics involve physical, chemical, and biological processes, leading to the formation of tiny fragments known as microplastics (MPs) and nanoplastics (NPs), which accumulate in the environment. Beyond the well-documented environmental harms of MPs and NPs, growing evidence of their presence within the human body raises concerns about their potential to trigger various harmful biological processes. Their detection in the urinary tract and their potential links to kidney and bladder diseases, as shown in animal studies, are particularly alarming.
Impacts Becoming Apparent
As the impact of plastic pollution becomes increasingly apparent, the need for standardized international definitions of MPs and NPs is pressing. Government publications reveal notable discrepancies between organizations in defining these fragmented plastics. The lack of consensus among regulatory bodies highlights the challenges in mitigating the environmental and health impacts of MPs and NPs. The International Organization for Standardization offers the most precise classification, defining MPs as solid, insoluble plastic particles ranging from 1 µm to 1 mm and NPs as particles smaller than 1 µm.
The intrusion of MPs and NPs into the human body, whether through inhalation, ingestion, or skin exposure (via wounds, hair follicles, or sweat glands), has been linked to harmful biological effects, including inflammation, alterations in cellular metabolism, physical cellular damage, and reduced cell viability.
Urinary Tract Plastics
The detection of MPs and NPs in the human urinary tract, combined with limited understanding of their effects, is a growing concern. An exploratory study published earlier this year aimed to systematically summarize the existing literature regarding the presence of MPs and NPs in the urinary tract and their potential consequences, guided by these research questions:
- What are the characteristics of the plastics detected in the human urinary tract?
- How are MPs and NPs defined in the current literature?
- What methodologies are used to explore the presence and effects of MPs and NPs?
- What are the pathophysiologic consequences of the presence of MPs and NPs in the human urinary tract?
For this study, the “urinary tract” included the kidneys, bladder, ureter, urethra, and urine. By focusing on the urinary tract, the study aimed to consolidate current understanding of MPs and NPs, raise awareness of this emerging issue, and lay the groundwork for further research that could contribute to public health policies and clinical practice guidelines.
The researchers conducted a scoping literature review following the recommendations of the JBI [formerly known as the Joanna Briggs Institute). They systematically searched five databases — PubMed, Scopus, CINAHL, Web of Science, and Embase — as well as gray literature sources.