About organic fluorine compounds (PFAS) in tap water

Organic fluorine compounds are organic compounds that have a bond between carbon and fluorine, and their collective term is PFAS (perfluoroalkyl compounds and polyfluoroalkyl compounds). Typical organic fluorine compounds include PFOS (perfluoroctan sulfoneic acid) and PFOA (perfluorooctanic acid). PFOS and PFOA are used in water repellents, fire extinguishers, coatings, etc., and are difficult to decompose in the environment and have high accumulation properties. In addition, there is PFHxS (perfluorohexanesulfoneic acid), which is the same organic fluorine compound and has the same properties as PFOS and PFOA, and is used as an alternative to it.
In addition, "fluorine and its compounds" in the water quality standard items are substances that combine inorganic substances such as fluorine and sodium, and are different from organic fluorine compounds that combine fluorine and carbon (organic substances).

According to reports, detection has been reported in Japan around airfields that used and used foam disinfectants containing organic fluorine compounds in the past, and around factories that have a track record of producing and using organic fluorine compounds. I am.

From April 1, 2020, PFOS and PFOA in tap water have been set to the national water quality management target setting items (provisional target value: 50 ng / L or less in total of PFOS and PFOA). In addition, PFHxS, an organic fluorine compound, was designated by the government as an item to be considered on April 1, 2021. The target value is not set.

• Water quality management target setting items are items that should be noted in water quality management, such as the possibility of detection in tap water. Target values have been set from the viewpoint of ensuring the safety of tap water in the future.
• Items requiring consideration are items that cannot be classified into water quality standard items and water quality management target setting items because toxicity evaluation is not determined or the amount of water in purified water is unknown.

50 ng/L is a value in which a person weighing 50 kg does not expect to have a harmful effect on health if a person consumes 2 L of water per day for a lifetime.

For PFOS and PFOA, the daily intake (TDI: 20ng / kg / day), which is considered appropriate from the risk assessments conducted over the past few years, is calculated on the condition that 50 kg of people weighing 2L of tap water per day. The evaluation value of PFOS and PFOA is 50 ng / L, respectively. In addition, the allocation rate, which indicates the contribution from tap water to the total intake, is calculated as 10%.

Furthermore, from the viewpoint of safety, we have set a provisional target of 50 ng/L as the total value of PFOS and PFOA.

Manufacture, import, use, etc. are restricted under the Act on the Examination and Regulations on the Manufacturing and Manufacturing of Chemical Substances (Chemical Review Law). PFOS was designated as a Class 1 Specific Chemical Substance in April 2010, and its production, import, and use were prohibited. In addition, the same measures were taken for PFOA from October 22, 2021. In addition, PFHxS was approved by the Cabinet on November 28, 2023, and was designated in February 2024.

The production, use, import and export of PFOS and PFOA is internationally regulated by the Stockholm Convention on Residual Organic Contaminants (POPs Convention).
In addition, we have set target values for PFOS and PFOA in drinking water in each country.
In U.K. and Germany, PFOS is set at 100 ng / L and PFOA is set at 100 ng / L. In the United States, the total value of PFOS and PFOA was set at 70 ng/L, and in March 2023, PFOS and PFOA were set at 4ng/L each as new regulatory values, but the final regulation value has not been determined.
The World Health Organization (WHO) has set provisional guideline values for PFOS and PFOA in drinking water to 100 ng / L, respectively, for the revision of the "Drinking Water Quality Guidelines", and the total of PFAS including these (all organic fluorine compounds) It states that the provisional guideline value is set to 500 ng / L. However, the official guideline values cannot be calculated at present because there are no certain indicators to be used for toxicity evaluation.

According to a national survey, animal experiments and overseas cases have reported that continuous intake of large amounts of organic fluorine compounds may have health effects such as carcinogenicity and thyroid abnormalities, but internationally scientific knowledge is insufficient. The government will continue to collect information on toxicity assessments and monitor the detection status.
According to the “Q & A on PFOS and PFOA (July 2023)” prepared by the Ministry of the Environment, there have been no cases of individual health hazards, which are thought to be mainly caused by the intake of organic fluorine compounds in Japan.

Since 2011, Yokohama City has been measuring tap water and tap water (water before water purification treatment) at three water purification plants in the city for PFOS and PFOA of organic fluorine compounds. Until now, both tap water and tap water have never exceeded the provisional target values.
In addition, there are reports that were detected in groundwater in Japan, but in Yokohama City, water from rivers and dam lakes is used as water sources.
As for the test result, please see page about test result of organic fluorine compound in tap water.

Treatment with powdered activated carbon, granular activated carbon, ion exchange resin, NF membranes and RO membranes is common as a method of removing organic fluorine compounds from water.
In addition to conducting periodic water quality inspections four times a year in Yokohama City, we also exchange information on detection status in cooperation with neighboring entities. Until now, the water treatment plant in Yokohama City has never exceeded the provisional target value, but if a high concentration is detected, we will strengthen monitoring of intake points and raw water at the water treatment plant, and inject activated carbon as necessary to reduce organic fluorine compounds.
In addition, in preparation for the risk of organic fluorine compounds in the lower Sagami River basin, we conducted a feasibility study on the removal of organic fluorine compounds in raw water using powdered activated carbon, and confirmed that if the total of PFOS and PFOA is about 300 ng/L or below the provisional target value of the water quality management target setting items is 50 ng/L by injection in Kosuzume Purifiction Plant.