Photo/Illutration The central government building that houses the Ministry of Health, Labor and Welfare and the Environment Ministry in Tokyo’s Chiyoda Ward (Asahi Shimbun file photo)

Tap water quality in homes and businesses across the nation seems to be fine, the first in-depth survey on the issue suggests.

The finding follows a joint survey by the Environment Ministry and land ministry to assess the presence of perfluoroalkyl and polyfluoroalkyl substances, collectively known as PFAS, which are regarded as hazardous to human health.

The two entities released their findings Nov. 29 after inspecting 3,755 water utilities and other businesses.

In past sampling, 14 projects emerged where PFAS concentrations exceeded the government’s provisional target values.

But as of the end of September this year, tap water quality got the all-clear in the samplings for fiscal 2024 ending in March.

The results were for projects that supply more than 5,000 people as well as community waterworks that supply at least 101 people and no more than 5,000.

The survey was carried out from the end of May to the end of September.

The ministries then summarized the status of inspection and detection in tap water surveys from fiscal 2020 to fiscal 2024 for the 3,595 waterworks projects that responded to the survey.

Currently, the government’s “provisional target value” is 50 nanograms per liter for the combined levels of PFOS and PFOA, two of the most common types of PFAS. One nanogram is one-billionth of a gram.

In fiscal 2020, when the provisional target was established, 11 of the 466 projects showed levels exceeding the provisional target values.

But this number has been decreasing each year.

As of the end of September 2024, no instances occurred in 1,745 projects where levels exceeded the provisional target values.

In total, 2,227 projects have been tested at least once during the period from fiscal 2020 to fiscal 2024.

The highest value for each fiscal year confirmed by inspection is the one reported in the survey.

The ministries said they do not know precise details about the locations of the facilities that exceeded the provisional target values.

“We believe that appropriate measures have been taken by the companies,” said an Environment Ministry official, referring to the decrease in the number of projects that exceeded provisional target values.

Measures as simple as switching water sources proved to be successful, the official added.

The waterworks covered by the latest inspections showed that 98.2 percent of population was receiving tap water that falls below the government’s provisional target value in terms of PFAS.

On the other hand, 14 percent of waterworks projects, or 178 in total, and 50 percent of community waterworks projects, or 1,185 in total, had not been inspected to date, even though they were subject to the latest survey.

The reasons given were that “the possibility of PFOS and PFOA being present is low considering the surrounding environment,” “the cost of testing is burdensome” and “there is no obligation to conduct measurements.”

Currently, the provisional target values are not required by law to be inspected.

The two ministries said they will continue to call on businesses that have not been inspected or have not responded to the survey to do so.

The ministries are also compiling data on 8,000 or so projects that are relatively small, dedicated waterworks, and will release the data at a later date.

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