FAIRBANKS — Both wells that feed North Pole’s city water system have come up positive for trace amounts of the industrial chemical sulfolane, but a top water quality official for the state says there is no public health emergency.

The state has not recommended that people stop drinking the water.

“The treatment of the city water (in North Pole) appears to be taking the sulfolane out of the city water,” Alaska drinking water program manager Cindy Christian said.

“Obviously, we would like to have none of this in the water. I don’t think it’s a public health emergency.”

The amount of sulfolane found in the North Pole tests is so slight — less than 10 parts per billion — that some tests have come up negative, officials said.

The city’s wells are deeper than most private wells, which have detected sulfolane amounts in the low hundreds of parts per billion. Only one of the city’s wells is in use, normal for the city at this time of year.

Sulfolane is a chemical used in fuel production. The spill that caused the contamination happened before 2000, according to state officials. Flint Hills bought the refinery in 2004.

The number of contaminated private wells in North Pole is believed to be about 55, according to Ann Farris, project manager for the Alaska Department of Environmental Conservation. Eighty-five have been tested.

The amounts detected in wells throughout North Pole vary, starting in the teens and in one case surpassing 400 parts per billion. Most wells are below 200 parts per billion, Farris said. One part per billion is on par with a drop of water in an Olympic-sized swimming pool.

Testing on public wells in Fairbanks, meanwhile, showed no sulfolane, Christian said.

Samples in Fairbanks were taken from the well supplying Golden Heart Utilities and College Utilities Corp. as well as the drinking water well at the University of Alaska Fairbanks, according to Christian. All of them came back “non-detect.” Testing of the drinking water well on Eielson Air Force Base is pending.

“We expected that they would be non-detect but we just wanted to make sure,” Christian said.

Officials believe the water table contamination, which originated at the Flint Hills Resources refinery in North Pole, stops where the Old Richardson Highway joins the Richardson Highway near Hawks Greenhouse. Wells were dug there on Monday and water samples taken Wednesday to confirm the northern boundary of the contamination, according to Flint Hills spokesman Jeff Cook.

State officials are working on determining an acceptable level of sulfolane for drinking water and expect to have that number next month. They are dealing with a lot of unknowns, namely a lack of information on the health effects of long-term exposure to small amounts of sulfolane.

In California, a water quality control board deemed 57 parts per billion of sulfolane acceptable in drinking water. The state of Alaska’s groundwater cleanup standard for sulfolane is 350 parts per billion.

Laboratory animals exposed to very high levels of the chemical have shown changes to organs, the nervous system and the immune system, according to state officials.