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The Potential Threat of Plastic Pipe Aging:
Leaching Microplastics and Nanoplastics into Drinking Water Networks
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by PPN Editor | 19th June 2023
Introduction
The security of drinking water networks is a critical concern for human health worldwide. Plastic plumbing has become increasingly popular in water distribution systems due to its numerous advantages over traditional metal plumbing. However, there is growing research indicating that contaminants, including microplastics (MPs) and/or nanoplastics (NPs), may leach from plastic pipes, raising concerns about their potential impact on human health. This article explores the issue of leaching MPs and NPs from aging plastic pipes and emphasizes the need for further investigation.
The Ubiquity of Plastic Pipes
Over the past few decades, plastic piping, such as polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP-R), and cross-linked polyethylene (PEX), has been widely utilized in various applications globally.
Plastic pipes offer advantages such as portability, corrosion resistance, cost-effectiveness, and long service life. Plastic pipes are extensively employed in municipal and building water supply systems as well as agricultural irrigation.
In general, plastic pipes constitute around 80% of urban water supply pipes and 85% of building water supply and hot water supply pipes. Given the absence of a suitable alternative material, plastic pipes are expected to continue dominating water supply systems in the foreseeable future.
Disinfectants and Aging of Plastic Pipes
Disinfectants, such as chlorine, chloramine, and chlorine dioxide, are commonly used in drinking water treatment plants and secondary disinfection networks. However, free chlorine produced by these disinfectants can create a highly oxidative environment that ages and oxidatively embrittles plastic pipes.
Long-term exposure to water containing free chlorine can lead to changes in the mechanical, surface, and morphological characteristics of plastic pipes. The aging process can result in decreased antioxidant contents, increased crystallinity, chain rupture, and visible cracks in pipe walls. These changes raise concerns about the potential leaching of MPs and NPs into the drinking water network.
Potential Leaching of MPs and NPs from Aging Pipes
Based on aging mechanisms and material performance characteristics, it is plausible that MPs and/or NPs can be leached from aging plastic pipes. However, further research is required to ascertain the extent and nature of such leaching. The long-term accumulation of MPs and NPs in drinking water networks poses a potential threat to human health.
Although studies on the potential toxicity of MPs and NPs to aquatic organisms have been widely reported, research on the effects of MPs and NPs on human health remains limited. Understanding the potential risks and mechanisms of leaching, as well as the uptake and toxicity of MPs and NPs in humans, is crucial to ensure the safety of drinking water.
Potential Toxcity for MPs and NPs from Plastic Pipes
After prolonged exposure, these plastics can undergo photochemical, thermal, or biological degradation, resulting in the formation of degradation products. While the toxic effects of microplastics/nanoplastics (MPs/NPs) on aquatic organisms, such as the production of reactive oxygen species and reproductive dysfunction, have been extensively documented, studies investigating the potential risks of MPs/NPs to human health are still scarce. MPs/NPs can enter the human body through the food chain, dermal exposure, and inhalation. Several reviews have summarized the potential uptake and toxicity of MPs/NPs in humans.
Phagocytosis, macropinocytosis, clathrin-and caveolin-mediated endocytosis are potential pathways through which human cells can uptake MPs/NPs, depending on the particle size. In vitro studies have shown that exposure to polystyrene MPs (10 mm) or NPs (40 and 250 nm) at a concentration of 10 mg/L can induce oxidative stress and toxicity in cerebral and epithelial human cells, attributed to the generation of reactive oxygen species.
Additionally, MPs/NPs present in the gut lumen can interact with proteins due to their large surface area and charge, potentially leading to immune system alterations and local inflammation. Furthermore, due to their high surface area-to-volume ratio and hydrophobic nature, MPs/NPs may act as vectors, transporting other environmental contaminants into the body. Consequently, it is crucial to investigate the potential risks of MPs/NPs to human health, even though no clinical manifestations have been reported so far.
A few studies have reported the presence of low amounts of MPs in tap water. However, it remains unclear whether MPs leach from pipes due to potential chemistry of groundwater sources such as the hardness or softness of the water. Future research should focus on the potential release of MPs or NPs from aging plastic pipes used in drinking water distribution systems and their toxic effects on humans.
The current sampling and detection techniques mostly cover the micrometer range, posing limitations in detecting NPs or MPs leaching from pipes. Therefore, there is an urgent need for new methods to detect and quantify NPs or MPs, as well as to investigate the influence of disinfectant type, temperature, and the presence of biofilms on pipe walls on the release kinetics and mechanisms of MPs/NPs.
Challenges and Future Research Directions
Detecting and quantifying MPs and NPs leaching from plastic pipes present analytical challenges. Existing sampling and detection techniques are mainly limited to the micrometer range, necessitating the development of new methods to detect NPs or MPs.
Additionally, the influence of disinfectant type, temperature, and the presence of biofilms on pipe walls on the release kinetics and mechanisms of MPs and NPs requires further investigation.
Strategies to mitigate MP and NP release or uptake by humans need to be developed. Identification of potential exposure pathways and implementation of effective mitigation measures are crucial to safeguard public health.
Moreover, strategies should be developed to reduce the release or uptake of MPs/NPs by humans. While many aspects regarding the potential release of MPs and NPs from aging pipes, as well as their potential toxicity to humans, remain to be determined, it is crucial to identify and mitigate possible exposure pathways before severe effects are observed.
Conclusions
The potential leaching of MPs and NPs from aging plastic pipes in drinking water networks raises concerns about human health. Although research in this area is still in its early stages, the presence of plastic litter in the environment, along with evidence of biotoxic effects on aquatic organisms, highlights the urgency of investigating the risks to human health.
The development of reliable detection methods, further research on release kinetics and mechanisms, and the implementation of strategies to reduce MP and NP exposure are essential for ensuring the safety of drinking water networks and protecting public health.
ExcelPlas Polymer Labs have developed detection and analysis techniques for both quantification and identification of microplastics from plastic pipes.
