The Japanese government has launched a nationwide survey on the levels of potentially harmful chemicals known as PFAS in tap water.

The Environment Ministry and the infrastructure ministry have asked local governments and water service providers to report the results of water quality tests since fiscal 2020. The deadline is the end of September.

Survey recipients are asked whether or not they have conducted tests for PFAS. If the organic fluorine compounds were detected, they are asked to report the highest concentrations found.

If they have not carried out such tests, they are asked to explain why, and whether they plan to do so in the future.

Experts believe some of the compounds could be harmful. In October last year, tap water tests in Okayama Prefecture's Kibichuo Town found levels 28 times higher than the government's provisional target.

The nationwide situation is unknown because tests for PFAS are voluntary.

Local governments and water service providers that have never carried out such tests are asked to conduct at least one by September 30 and report the outcome.

The ministries say they will use the data from the survey when they consider reviewing the preliminary target.