In a major policy change, the Ministry of Health and Welfare plans to support local government efforts to introduce fluorine to public water supplies in order to prevent tooth decay, ministry officials said Saturday.

In a major policy change, the Ministry of Health and Welfare plans to support local government efforts to introduce fluorine to public water supplies in order to prevent tooth decay, ministry officials said Saturday.

The officials said the ministry will provide technical support for local governments adding fluorine to public water supplies within the ministry's standard, 0.8 ppm or less in density of fluorine. The technical support includes setting and maintaining the appropriate density of fluorine in water, they said.

Fluorine is considered effective in preventing tooth decay. Currently 38 countries such as the United States, Canada and Australia add fluorine to public water supplies, according to the ministry.

In Japan, public water currently contains 0.1 ppm or less of fluorine. The government used oppose adding fluorine to public water supplies, as high densities of natural fluorine in public water had caused mottled teeth among residents who later filed lawsuits against local authorities.

However, the government reversed its stance because the effectiveness of fluorine in strengthening teeth and repairing tooth decay has been scientifically proven.

Dentists and local government officials support adding fluorine to public water supplies as the best method for preventing cavities, on the grounds that it is easy, effective and inexpensive.

The village of Gushikawa in Okinawa Prefecture considered introducing fluorine to public water in August as the first model project in Japan, and local officials asked the ministry for financial support.