wo weeks after it resumed adding fluoride to New Orleans’ drinking water for the first time since Hurricane Katrina, the Sewerage & Water Board said Wednesday it has run out of the compound and, starting today, will not be able to add any to the water until a new supply is found.

Most U.S. cities add fluoride to their water with the goal of reducing tooth decay among users.

The water board resumed adding fluoride to the water at both the east bank and Algiers treatment plants on Aug. 1.

With no public announcement, it had stopped the practice after Katrina because it was no longer able to obtain the chemical used. For several years there has been a national shortage of fluoride, the board said.

Dental and medical studies have shown that the addition of fluoride contributes to the dental health of those drinking the water, and the S&WB had been adding it since June 1974.

Water plant personnel monitored the level of fluoride in the water to ensure that it remained in the recommended range of 0.7 to 1.0 parts per million. Fluoride occurs naturally in Mississippi River water at concentrations of 0.2 to 0.5 parts per million.

Katrina did not damage the storage tanks or pipes associated with the fluoride system at either of the city’s water plants. But because the storm interrupted the water system’s operation for many weeks, the board’s fluoride supplier, Lucier Chemical Industries of Jacksonville Beach, Fla., redirected its supply to other customers.

Although a supplier was eventually found, the board’s agreement with it was on a shipment-to-shipment basis, based upon availability on the spot market.

The 3,908 gallons of fluoride the board bought last month has been exhausted and no more will be added to the water until a new supply can be obtained.

The 3,908 gallons cost $9,673. The pre-Katrina cost for the same volume was $2,693, the board said.

Marvin Russell, the S&WB’s water purification superintendent, has said he hopes to be able to secure a regular supply by year’s end, when the expiration of annual contracts may allow the board to get back into the supply loop.