Toxic organic solvents such as toluene, ethylbenzene, and xylene have been detected in dissolution tests of water supply materials and products, including water pipes and valves. However, the current sanitary and safety standards for water supply materials lack criteria to limit the leaching amounts of these three substances.

According to the final report of the "2025 Research on Monitoring and Management Plans for Unregulated Harmful Substances under Sanitary and Safety Standards" secured by the office of lawmaker Lee Yong-woo (National Assembly's Climate, Energy, Environment, and Labor Committee), toluene was detected in 174 (29.6%), ethylbenzene in 102 (17.4%), and xylene in 120 (20.4%) out of 587 water supply materials and products such as valves investigated between 2022 and 2025. The report was submitted to the Korea Water and Wastewater Certification Corporation last December after being conducted by institutions including the Korea Conformity Laboratories (KCL).

Researchers investigated products that included materials subject to volatile organic compound (VOC) analysis among those that requested certification, ad-hoc inspections, and quality tests from testing institutions.

Organic solvents were detected across multiple product categories. The detection rate for toluene was highest in metal pipes at 46%, followed by valves at 36%, pumps at 34%, and paints at 30%. Non-metal pipes and faucets also showed detection rates of 29% and 26%, respectively.

Particularly, out of 45 steel water pipes coated with epoxy resin to prevent corrosion, toluene was detected in 33 (73.3%), ethylbenzene in 41 (91.1%), and xylene in 44 (97.8%).

Researchers analyzed that solvents used in manufacturing or applying paint remain trapped inside the coating layer and leach out into water. They explained that a "solvent entrapment" phenomenon can occur if the outer surface of the coating layer hardens faster than the inside, preventing solvents from escaping sufficiently. They noted that solvents can also remain when the coating layer is too thick or insufficiently cured.

These results are based on dissolution tests where materials are brought into contact with water under specified test conditions, and do not represent direct measurements of tap water supplied to households. In actual usage environments, variations in water flow and contact concentration mean the concentrations found in tests do not directly translate to tap water concentrations or residents' exposure levels.

However, citing foreign toxicity evaluation data, researchers explained that these substances can affect the liver, kidneys, and nervous system depending on the exposure pathway and level. Considering the repeated detections and high-concentration leaching in some products, they determined that management at the material stage is necessary.

Nevertheless, sanitary and safety standards for water supply materials do not have criteria to restrict them. The necessity of establishing standards was previously pointed out in a 2022 Board of Audit and Inspection audit. The Ministry of Environment (currently the Ministry of Climate, Energy, and Environment) explicitly stated in its "2025 Performance Management Implementation Plan" that there are no sanitary and safety standards for toluene, ethylbenzene, and xylene in water supply materials, and following the audit findings, it has been promoting revisions to the Enforcement Decree of the Water Supply Act since February 2024 to incorporate these substances into the standards.

Researchers proposed newly applying dissolution standards for epoxy resin water supply materials: 0.07 mg/L for toluene, 0.03 mg/L for ethylbenzene, and 0.05 mg/L for xylene. Each is one-tenth the level of drinking water quality standards.

They also stated that it is necessary to manage epoxy-coated water pipes—where high-concentration leaching was confirmed—on a phased basis, and to support companies in transitioning to paints that use fewer or no solvents.

Lawmaker Lee emphasized, "Although hazardous substances were detected in products coming into contact with tap water, criteria to test them are yet to be established. The Ministry of Climate and Environment must thoroughly investigate the causes of detection, include these substances in sanitary and safety standards for the safety of citizens' tap water, and promptly establish related official test methods."

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