Contaminants found in a Kauai drinking water tank and water samples that serve South Kona residents are causing concerns, but state officials say neither finding poses a risk to human health.
On Monday, officials said that PCBs — a banned contaminant in the United States — were found in a water reservoir tank used to deliver drinking water to nearly 6,000 Kauai residents, the state Health Department announced Monday.
Drinking water from the tank was determined to be safe, however, "because samples collected from the water distribution system just after the tank did not contain PCBs," the Health Department said in a news release.
The tank serves Kekaha and Waimea, and was taken out of commission after the discovery. Officials said samples were collected in September after an oily sheen was found on the water's surface.
Water leaves the tank from the bottom, the Health Department said, and PCBs do not dissolve well in water.
The water samples were taken as part of a tank maintenance project undertaken by the Kauai Department of Water, and officials have launched an investigation to determine the source of the PCBs.
The Health Department said the concentration of total PCBs in an October sample from the surface of the tank was 13 parts per billion. Water tested from the pipe exiting the tank and leading to the distribution system and did not contain PCBs, though.
The federal and state maximum contaminant level for PCBs is 0.5 parts per billon at the compliance sampling point, or where water exits the tank.
PCBs were banned in 1979, and previously were found in plastics, caulking, oil-based paint and other products. They have been shown to have adverse health effects in humans and are considered probable human carcinogens.
Meanwhile, the state also said Monday that small amounts of dalapon were found in South Kona drinking water samples.
The dalapon was in the Hawaii County Water Supply's Keei wells A and B.
Dalapon was found in drinking water and well below federal and state maximum contaminant levels, the state said.
"These findings do not represent a health threat," said Keith Kawaoka, deputy director for environmental health.
Dalapon is a herbicide used to control grasses. It is not classified as a human carcinogen, but has been shown to have some adverse health effects in significant amounts.