Japan's Environment Ministry plans to legally mandate regular testing of tap water for PFAS chemicals, with mitigation steps offered for some small water suppliers that could be overburdened by the requirement.

PFAS is a group of organic fluorine compounds. They include PFOS and PFOA, which are considered potentially harmful.

The ministry decided on Tuesday to establish a legal standard for the amount of the two chemicals.

It will stand at 50 nanograms per liter of tap water, which is same as the current provisional target. The government says no adverse health effects are believed to occur at this level.

The ministry plans to require local governments and water providers to test tap water once every three months in principle, and take remedial measures if the results fail to meet the legal standard.

At the same time, officials plan to allow small water suppliers to carry out testing once every six months or a year, if PFAS levels in their water stay at one-fifth of the standard or lower, or up to 10 nanograms per liter.

Officials believe small suppliers need relief measures, as they could be weighed down by the cost of testing, including the price of necessary equipment.

The ministry will seek public opinion on the overall plan, and hopes to enforce the new legal steps from April 2026.