The Department of Health announced that polychlorinated biphenyls are contained in the interior and exterior walls of a Princeville drinking water system tank on Kauai, but recent intense and regular tests show the drinking water is safe and contains no PCBs.

The source of the PCBs remains unclear, the department said Saturday.

The EPA says PCBs have been shown to cause cancer in animals and serious non-cancer health effects.

Scrapings of the tank’s inner wall were confirmed March 14 to contain PCBs, as well as the exterior wall. And caulking used on the tank’s exterior wall may also contain PCBs and could be a possible source, the Health Department said. 

The Environmental Protection Agency banned use of PCBs in 1979, but they may be present in many products manufactured before the ban. The tank was built in 1971.

In December, the Health Department found during routine testing trace amounts of a PCB, and discovered an oily sheen containing PCBs on the surface of the water in the tank that serves a population of 2,200 people on Kauai’s North Shore.

Owner Princeville Utilities Co. Inc. (PUCI) is taking the tank out of service, while it cleans it and will use three temporary tanks.

PUCI collected samples, but PCBs were not detected where water exits at the bottom of the tank, nor at two wellheads that supply the tank, the Health Department said.

PUCI is testing once a week at several different points and the Health Department monitors the water twice a month.