vol.63-3 (2025/9/30)

Basic information on PFAS and recent issues

Per- and polyfluoroalkyl substances (PFAS) are synthetic organic compounds characterized by strong carbon-fluorine bonds, conferring them with exceptional resistance to heat, chemicals, and degradation, as well as water- and oil-repellent properties. Due to these features, PFAS have been widely applied in various industrial and consumer products, including textiles, firefighting foams, and semiconductor manufacturing processes. Among them, perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) have drawn particular attention due to their environmental persistence and bioaccumulative nature. Since the early 2000s, manufacturers such as 3M and DuPont initiated voluntary phase-outs, and regulatory frameworks, including the U.S. EPA’s stewardship programs, have driven reductions in emissions. Short-chain alternatives such as PFBS and GenX have been introduced, although their toxicological and environmental profiles remain insufficiently characterized. Environmental contamination from PFAS has been documented globally, including in Japan, where elevated concentrations have been reported in groundwater and surface water near industrial facilities, military bases, and urban wastewater treatment plants. Indoor environments have also been identified as potential sources of human exposure, with PFAS detected in house dust and air, likely originating from treated textiles, personal care products, and building materials. In response to growing concerns, a number of companies–such as Uniqlo, KEEN, and IKEA–have transitioned to PFAS-free product lines. In Japan, regulatory measures are being strengthened, with drinking water standards set to be incorporated into the Water Supply Act in 2026. However, comprehensive monitoring and health risk assessments, particularly for emerging and unregulated PFAS compounds, remain pressing challenges.

Analytical methods for Per-and Polyfluoroalkyl Substances (PFAS) in air samples

Per- and Polyfluoroalkyl Substances (PFAS) have been widely used in various industrial and commercial applications since their unique physicochemical properties. However, their environmental contamination has been a social concern. The development of liquid chromatography-tandem mass spectrometry (LC-MS/MS) has provided opportunities for analyzing polar compounds and proven the occurrence of highly water soluble compounds such as PFAS in the environment. Recent studies have indicated PFAS-related water quality contamination across various regions in Japan, increasing social concern regarding to health risks. In 2024, the tolerable daily intake (TDI) for both PFOS and PFOA was suggested at 20 ng/kg body weight per day, as outlined in the “Assessment of the Health Effects of PFAS in Food”. Consequently, this assessment has prompted a decision to undertake a review of water quality standards starting in 2026. The main sources of human exposure are water, food and breathing. Sampling techniques such as active air sampling (AAS) and passive air sampling (PAS) are used to collect the PFAS sample in air. The pre-treatment process involves ultrasonic extraction, shaking extraction and solid phase extraction. Quantitative analysis is performed using LC-MS/MS and/or gas chromatography-tandem mass spectrometry (GC-MS/MS). Accurate quality control, including operational blank management, is also essential for ensuring the reliability and accuracy of analytical results.

Analysis of PFAS in the air using new air sampler of PFAS

Per- and polyfluoroalkyl substances (PFAS) represent one of the most critical concerns under the Stockholm Convention on Persistent Organic Pollutants, and numerous research have reported their detection in the environment. To understand the pollution levels, it is required to analyze PFAS in various media, such as water, air, and soil. With regard to air, PFAS in the atmosphere plays an important role in long-range transport and their transformation, and it is considered to need comprehensive analysis of PFAS in the air. The air sampler named “FM 4” has been developed in order to enable simultaneous collection of PFAS in particle phase and gas phase. FM 4 is composed of quartz fiber filters (QFF), polyurethane foam (PUF) and activated carbon fiber disk (GAIAC®). GAIAC® has been developed newly to achieve satisfactory recoveries of neutral PFAS (e.g. fluorotelomer alcohols). A new method using FM 4 and GAIAC® enables multiple analysis of ionic PFAS and neutral PFAS. If the regulation of PFAS in the air is established in the future, analysis and removal would likely be required more. FM 4 and GAIAC® are expected to contribute to development of removal technology of PFAS in the air as it needs analytical technology.

Development of PFAS-free air filter media

Per- and polyfluoroalkyl substances (PFAS) are defined as fluorinated substances that contain at least one fully fluorinated methyl or methylene carbon atom. In air filtration applications, PFAS are commonly used to impart water and oil repellency to filter media. However, the carbon and fluorine in PFAS are strongly bonded, so they are not easily decomposed, and furthermore, there are concerns about adverse health effects. In this study, PFAS-free air filter media are developed using a water repellent composed of fluorine-free hydrocarbon polymer. The newly developed filter media have the equivalent basic media properties to the conventional filter media containing fluorinated repellent. On the other hand, their behaviors toward oil droplets are different.

Demonstration and mechanistic study of PFAS removal using a microfiltration membrane with an adhered functional powder (PAC) layer:
Applications to aqueous phase and industrial exhaust gas

In recent years, regulations on PFAS (per- and polyfluoroalkyl substances) have been rapidly strengthened. PFOS and PFOA will be added to drinking-water quality standards in 2026, with eight additional substances expected to be designated for monitoring. As a result, the management focus is expanding beyond water purification plants to industrial wastewater and emission sources. Despite growing concern, effective and low-cost treatment technologies for airborne PFAS remain underdeveloped. This study introduces a novel “MF membrane-functional powder adhered layer method,” in which powdered activated carbon (PAC) is densely adhered to the surface of a microfiltration (MF) membrane to form an approximately 1 mm thick layer. Initially developed for gas-phase applications such as VOC removal, the technology has since been expanded to water treatment and demonstrated excellent PFAS removal performance at a demonstration site in Okinawa, Japan. This paper reports the purification performance, engineering characteristics, and removal mechanisms in water, followed by kinetic predictions and interim results of gas-phase applications, with prospects for future deployment.

Control of pressure differences between rooms in biological clean rooms

This paper reports on the significance, set points, means of pressurization with air-conditioning equipment and measurement methods related to pressure difference between rooms in biological cleanrooms. The pressurization is important for contamination control. The room pressure can be visualized by using pressure setting dampers. Note that there are many factors that can disturb room pressure.