Microplastics in Drinking Water: Unraveling the Key Questions and Potential Threats
Microplastics have emerged as a major environmental concern, contaminating various ecosystems, including marine water, freshwater, food, air, and even drinking water. Understanding the risks associated with microplastics in drinking water is critical for public health and environmental protection. In this article, we delve into the key questions surrounding microplastics, their sources, potential hazards, and available data on their presence in drinking water.
We also explore the risks associated with ingesting microplastic particles and biofilms and discuss the efficacy of current water treatment processes in removing these pollutants. Additionally, we highlight the need for further research and offer recommendations for water suppliers, regulators, policy-makers, and the public to address this global challenge.
What are Microplastics?
Microplastics are a diverse category of tiny plastic particles characterized by various shapes, sizes, densities, and chemical compositions. Although no universally agreed-upon definition exists, microplastics are often described as plastic particles less than 5 mm in length.
However, this definition is somewhat arbitrary and limited for assessing their presence in drinking water, as larger particles are unlikely to be found in treated water. Nanoplastics, a subset of microplastics measuring less than 1 µm in length, are also of concern due to their potential impact on human health.
Did you know?
“Microplastics can come from a variety of sources including larger plastic pieces that have broken apart, resin pellets used for plastic manufacturing, or in the form of microbeads, which are small, manufactured plastic beads used in health and beauty products.” [FROM – noaa.gov/microplastics]
How do Microplastics Enter Drinking Water?
Microplastics can find their way into drinking water sources through multiple pathways, including surface run-off after rainfall, wastewater effluent (both treated and untreated), industrial effluent, degraded plastic waste, atmospheric deposition, and even plastic bottles and caps used in bottled water.
Surface run-off and wastewater effluent are considered the primary sources of microplastics, although a deeper understanding of their specific origins is necessary to develop targeted interventions.
Microplastic Concentrations in Drinking Water
Studies on microplastics in freshwater have reported particle counts ranging from 0 to 1000 particles per liter (particles/L). However, data on microplastic concentrations in drinking water are limited, with only nine identified studies reporting particle counts from 0 to 10,000 particles/L and mean values from 10^-3 to 1000 particles/L.
Comparisons between freshwater and drinking water studies should be made cautiously, considering the differences in filter sizes used for sampling.
Potential Threats Posed by Microplastics in Drinking Water
Microplastics present three potential hazards: physical particles, chemicals, and microbial pathogens as part of biofilms. The health risks associated with each hazard depend on the dose and route of exposure. Current evidence suggests low concern for chemicals and biofilms in drinking water.
However, research on the physical hazard of plastic particles, especially nano-sized ones, is limited, and more studies are needed to draw definitive conclusions.
Human Health Risk of Ingesting Microplastic Particles
While data on the toxicity of plastic particles, particularly nanoscale ones, are insufficient, studies indicate that microplastics larger than 150 µm are likely to be excreted through feces, limiting their uptake.
Toxicology studies in rodents have shown some liver inflammation, but the relevance of these findings to human health remains uncertain due to the high exposure levels used in the studies.
Human Health Risk Associated with Biofilms on Microplastics
Biofilms that attach to microplastics in drinking water are considered a low health concern due to their relatively low concentration compared to other particles in freshwater. Drinking-water treatment processes, including disinfection, can effectively control biofilm-associated pathogens.
Kinds of Microplastics Found in Drinking Water
Various particle shapes have been observed in freshwater studies, with the most detected polymers roughly corresponding to plastic production volumes. In drinking water, fragments and fibers are the predominant particle shapes, and polyethylene terephthalate and polypropylene are the most commonly detected polymers.
Reliability of Studies
The reliability of microplastic studies is questionable, with many lacking sufficient quality control in sample treatment, polymer identification, laboratory preparation, clean air conditions, and positive controls. While some improvements in quality control have been noted in recent studies, interpretation of results should be cautious.
Human Health Risk from Chemicals Associated with Microplastics in Drinking-Water
Chemicals associated with microplastics have been assessed using the margin of exposure (MOE) method. The MOE assessment suggests that chemicals associated with microplastics in drinking water are of low concern, given the large difference between estimated intakes and toxicological points of departure.
MOE Method:
“The Nash and Moe method of determining vertebral rotation clinically. The apical vertebral body is divided into six equal segments longitudinally. When both pedicles are in view, there is no vertebral rotation. It is graded as “0”. When the pedicle in the concave side (the right side) starts disappearing, it is graded as “1”. When the pedicle disappears, it is graded as “2”. When the contralateral pedicle (pedicle in the convex side) is in the midline of the vertebra, it is graded as “3”. When it crosses the midline of the vertebra, it is graded as “4”. Source: researchgate.net/The-Nash-and-Moe-method-of-determining-vertebral-rotation-clinically
Microplastic Removal from Drinking-Water
Wastewater and drinking-water treatment systems, when optimized, are highly effective in removing particles similar in size and characteristics to microplastics. Advanced treatments like nanofiltration and ultrafiltration can effectively remove even smaller particles.
What is Reverse Osmosis?
Reverse osmosis is a water purification process that removes contaminants, impurities, and dissolved solids from water by forcing it through a semipermeable membrane. The process relies on the principle of osmosis, where water naturally moves from an area of lower solute concentration to an area of higher solute concentration through a membrane until equilibrium is reached.
However, in reverse osmosis, this natural flow is reversed by applying pressure to the water, causing it to move from the more concentrated side to the less concentrated side, effectively filtering out impurities and leaving behind purified water.
The semipermeable membrane used in reverse osmosis is designed to allow water molecules to pass through while blocking the passage of larger particles, ions, and contaminants. This membrane has extremely small pores that can effectively filter out substances like bacteria, viruses, dissolved salts, heavy metals, and other pollutants, resulting in high-quality, clean drinking water.
Reverse osmosis is widely used in various applications, including residential, commercial, and industrial settings. In homes, it is a popular method for producing clean drinking water, as it can effectively remove harmful substances and improve the taste and odor of tap water. Many modern water filtration systems for homes utilize reverse osmosis technology to ensure the provision of safe and purified water for household use.
Source: safewater.org/ultrafiltrationnanoandro
In addition to its residential applications, reverse osmosis plays a vital role in industrial processes, such as desalination, where it is used to convert seawater into freshwater by removing the salt and other impurities.
It is also used in the production of ultrapure water for various industries, including pharmaceuticals, electronics, and power generation, where water quality is critical for manufacturing processes.
Overall, reverse osmosis is a highly effective and versatile water purification method that has become increasingly popular due to its ability to provide clean, safe, and great-tasting water for various purposes, benefiting both individuals and industries alike.
How to Avoid Microplastics
Avoiding microplastics is essential for protecting both the environment and human health. While microplastics have become pervasive in various ecosystems, there are several practical steps individuals can take to minimize their contribution to microplastic pollution. Here are some effective ways to avoid microplastics:
Reduce Single-Use Plastics: One of the most significant sources of microplastics is single-use plastic items like bottles, bags, utensils, and straws. By reducing the consumption of these items and opting for reusable alternatives, individuals can significantly reduce their plastic footprint.
Choose Natural Fabrics: Synthetic fabrics, such as polyester and nylon, shed microfibers when washed, contributing to microplastic contamination in water sources. Opt for natural fiber clothing, like cotton, linen, or wool, which sheds fewer microfibers and is biodegradable.
Support Sustainable Brands: When purchasing products, support brands that actively take steps to reduce plastic packaging and incorporate eco-friendly materials in their products.
Properly Dispose of Waste: Ensure proper waste disposal by recycling plastic items instead of littering. Proper recycling prevents plastics from ending up in water bodies and breaking down into microplastics.
Use Microfiber Catching Laundry Bags: Special laundry bags equipped with filters can trap microfibers released during washing, preventing them from entering wastewater.
Avoid Personal Care Products with Microbeads: Check product labels for microbeads, tiny plastic particles used in some personal care products like exfoliating scrubs. Opt for products with natural exfoliants instead.
Be Mindful of Cosmetic Glitters: Avoid using cosmetic glitters made from plastic, as they can contribute to microplastic pollution when washed down the drain.
Support Ocean Cleanup Initiatives: Participate in or support initiatives aimed at cleaning up plastic waste from beaches and water bodies to prevent further microplastic contamination.
Educate and Raise Awareness: Spread awareness about the impact of microplastics and educate others about ways to minimize their plastic use.
Promote Local Policy Changes: Advocate for local policy changes to reduce plastic pollution, such as banning single-use plastics or promoting plastic-free alternatives.
By adopting these practices and encouraging others to do the same, individuals can play an active role in mitigating microplastic pollution and creating a cleaner and healthier environment for current and future generations.
Recommended Actions
Policy-makers and the public should take action to minimize plastic pollution in the environment, recognizing the multiple benefits it confers. Water suppliers and regulators should prioritize the removal of microorganisms and chemicals known to pose health risks and optimize water treatment processes to incidentally remove microplastics. Routine monitoring of microplastics in drinking water is not necessary at this time.
Future Research Needs
Filling research gaps is essential to better assess the risks of microplastics in drinking water and inform management actions. Targeted and quality-controlled studies should explore microplastic occurrence, sources, composition, fate, and potential health effects under relevant exposure scenarios. Toxicological data on common plastic particles are needed, and understanding total microplastic exposure from various environmental media is crucial for comprehensive risk assessment.
Conclusion
Microplastics in drinking water are a growing concern that demands comprehensive research, effective water treatment processes, and responsible environmental practices. While the health risks associated with microplastics are currently considered low, proactive measures should be taken to minimize plastic pollution for the benefit of both human health and the environment. Through concerted efforts, we can address the challenges posed by microplastics and safeguard the purity of our drinking water sources.