[Reading Science] ① "Invisible Fragments" in Tap Water

The Truth About Ultrafine and Nanoplastics That Are Not Filtered at Purification Plants

The fact that invisible microplastics and nanoplastics may be present in tap water has already been established through investigations and research conducted in various countries. However, to what extent are these particles present in Korea's tap water, and what gaps remain unaddressed?

Domestic researchers and environmental experts advise that the current status and limitations of microplastics in Korean tap water should be considered within the bounds of what is "measurable."

First Investigation in 2017-2018: "Results Reflect Only What Is Measurable"

The discussion of microplastics in Korean tap water began in earnest with a 2017-2018 investigation by the Ministry of Environment and the National Institute of Environmental Research. At that time, microplastics were detected at levels of 0.2 to 0.6 particles per liter (ℓ) in 3 out of 24 water purification plants nationwide. In a 2024 analysis of 120 plants, the concentration was found to be 0.1 to 0.2 particles per liter. Numerically, this is relatively low compared to advanced countries.

Regarding this, Choi Incheol, a researcher at the Water Utilization Research Division of the National Institute of Environmental Research, stated, "On average, very few particles are detected per liter, but since there is no internationally standardized analytical method, it is difficult to definitively determine the concentration." Currently, domestic tap water studies generally focus on relatively large microplastics with a diameter of 20 micrometers (㎛) or more. Smaller particles-those under 20㎛, especially nanoplastics under 1㎛-are difficult to detect with current analytical technology, resulting in a lack of related data. He explained, "There are no national data on the nano scale, and the risks are not clearly defined," adding, "More research is needed."

Even If Filtered at the Plant, 'Inside the Home' Can Become a New Source of Contamination

Even if water quality is good at the purification plant, there is a possibility that new sources of contamination may arise as tap water travels to households. Overseas studies have shown significant differences in detected amounts depending on sampling points, with the material of the pipe lining cited as a cause. Linings, such as those made from polyvinyl chloride (PVC), polyethylene (PE), and fiberglass-reinforced polyethylene terephthalate (FRP-PET), are plastic-based coatings that can shed microfragments into the water over time.

Sedimentation basin of Arisu Water Purification Center, Ttukdo, Seongdong-gu, Seoul. Photo by Moon Honam munonam@

Park Saerom, principal researcher at the Korea Institute of Civil Engineering and Building Technology, said, "Systematic data on secondary occurrence during the supply process is lacking in Korea, but Japanese cases suggest that the material and structure of pipes can affect detection levels," adding, "Investigations are also needed for domestic water supply pipes."

Water purifier filters, though discussed mainly at the research level, are also mentioned as potential sources of contamination. Park advised, "If filters are used for too long or replaced too late, microplastics may be generated due to filter wear," recommending adherence to replacement cycles.

Potential Risks Increase at the Nano Scale... But Data Remain 'Missing'

The scientific community classifies plastic fragments by size: microplastics (approximately 1㎛ to 5mm) and nanoplastics (approximately 1 nanometer (nm) to less than 1㎛). Nanoplastics are much smaller than microplastics and have such high physical penetrability that they may pass through cell membranes, placing them at the center of discussions about human health risks. There are also reports that toxicity may be heightened when combined with fine dust.

However, the World Health Organization (WHO) states that "human health risks cannot yet be conclusively determined," emphasizing the need for further research. Researcher Choi also noted, "In the absence of international standard analytical methods, both exaggeration and premature conclusions should be avoided." Principal researcher Park added, "There are ongoing concerns that the nano scale poses greater ecological and human health risks," emphasizing, "Ultimately, the key issues are measurement capability and management standards."

Based on the data released so far, Korean tap water is at a relatively good level. However, this only reflects what is measurable; for ultrafine and nano-sized particles under 20㎛, the data are essentially nonexistent.

Principal researcher Park stated, "There is far less data on the actual state of microplastics in Korea compared to other countries, and almost no information on the nano scale," adding, "This gap signifies uncertainty." Researcher Choi explained, "The filtration process has been identified as the most effective removal stage, but since microplastics can enter through various routes, long-term monitoring and source management are required."

Technology Development Has Begun, but Institutional Foundations Are Lacking

Last month, Professor Kim Hyejeong's research team at Korea University reported a "mini hydrocyclone" technology using fine air bubbles in the international journal Water Research. By combining microbubbles, the team significantly improved the separation efficiency of microplastics. Professor Kim stated, "It is possible to enhance separation efficiency without chemicals, so there is great potential for developing this into a high-efficiency, low-cost water purification technology." This is significant as it shows that measurement and removal technologies are also being developed domestically.

However, technology alone is not enough. Micro- and nanoplastics are not yet included as statutory water quality standards, and there is insufficient institutional basis to support risk assessment and management standards.

To address this, the "Special Act on the Reduction and Management of Microplastics" was proposed in September 2024. The bill, introduced by Assemblywoman Lee Sujin (Democratic Party, proportional representation) and 12 other lawmakers, aims to regulate the entire flow of plastic pollution by mandating surveys, standardizing analytical methods, encouraging reduction technologies, and establishing management plans, as well as prohibiting the sale and manufacture of products containing high concentrations of microplastics and setting discharge standards.

Experts stress that a system of investigation, monitoring infrastructure, and management standards must be established based on this law. Principal researcher Park Saerom pointed out, "The microplastics issue cannot be solved by the efforts of a single organization. A legal and institutional framework for national-level investigation and research must be established first." Researcher Choi Incheol added, "We are proactively developing analytical methods, conducting surveys, and researching health risks, and are preparing to ensure that the results lead to discussions on setting standards."

According to current investigations and research, Korean tap water is considered sufficiently safe by existing standards. However, the smallest nano-scale particles remain outside the scope of measurement, and as long as this gap exists, it is difficult to say that health risk assessments are complete.

Resolving the controversy with accurate data and scientific evidence depends on research, technology, and the institutions and policies that support them. There seems to be no reason to further delay the "Special Act on Microplastics," which could serve as the starting point.