FAIRBANKS — How much sulfolane is safe to drink remains an open question despite a recently released report on the chemical by a panel of scientists.

The industrial chemical was discovered in groundwater in North Pole five years ago after leaking from an oil refinery. At least 300 water wells are tainted in an area covering about five square miles.

The owner of the refinery wants the state to relax rules for how much sulfolane is allowed in drinking water. A lack of research has made the task of setting sulfolane policy difficult.

A new two-year study by the National Toxicology Program, a government agency, could shed light on the question of sulfolane and public health, but the results are years out, a state regulator said.

Flint Hills Alaska Resources owns the oil refinery where the chemical spill took place. It halted production in May and has been downgraded to a distribution facility.

The company is pressing the state to relax its standard for sulfolane in drinking water from 14 parts per billion to 362 parts per billion. The number is known among regulators as a “cleanup level.”

“I wouldn’t want to drink that knowing there is 300 and something parts per billion of sulfolane in there,” Fairbanks North Star Borough Mayor Luke Hopkins said.

He is among several local leaders concerned about the standard being relaxed.

A North Pole legislator is preparing to do battle with the state over the matter.

Rep. Tammie Wilson, R-North Pole, said she is exploring what legislative action could be taken if the Alaska Department of Environmental Conservation relaxes the cleanup level.

“I am very concerned,” Wilson said. “The property owners had nothing to do with that contamination. Those who are responsible should get them back to where they started.”

Flint Hills has provided people with tainted wells alternate water sources, including bottled water, water tanks, filtration systems and water truck deliveries. The company has also spent millions improving North Pole’s municipal water system.

“Flint Hills has done an excellent job of making sure people have a filtration system or bottled water or water delivered,” Wilson said.

But the state lawmaker fears that Flint Hills would halt its assistance to homeowners if the state adopts the cleanup level the company wants. Adopting a cleanup level of 362 parts per billion is tantamount to declaring that most of the tainted wells in North Pole are fine to drink from.

Jeff Cook, refinery spokesman, declined to comment on the matter.

He said the company is reserving comment for when the state issues a revised cleanup level.

It’s not clear when that will happen.

“I think it’s safe to say that once people get back in the office, there will be an effort to get the whole team together and discuss what the most appropriate path forward is,” said Bill O’Connell, environmental program manager for the Alaska Department of Environmental Conservation.

A new report, analyzing the few studies on sulfolane conducted to date, offers no strong conclusions about how much sulfolane is safe for humans.

High doses of sulfolane have made laboratory animals sick. The amount of sulfolane in the wells in North Pole is much lower.

The new report is by the organization Toxicology Excellence for Risk Assessment and summarizes a meeting of a panel of scientists. They met in Fairbanks last fall.

The scientists discussed how much sulfolane is safe for humans. The scientists picked apart sulfolane studies and found that a study funded by Flint Hills is the strongest of the available sulfolane research but that more work must be done.

“The TERA report was pretty clear that there are some gaps in the data and this needs to be researched further,” said North Pole Mayor Bryce Ward, who spent hours reviewing the report.

Ward said he wouldn’t drink water containing 362 parts per billion of sulfolane.

“We need to make sure we are doing all that we can to protect human health,” he said. “If you have the choice, are you going to be more conservative or less conservative?”

Regulators will need to discuss how much weight to give the TERA report, which was paid for with state funding, said O’Connell, the state regulator.

“A cleanup level calculation takes into account a large number of variables,” O’Connell said. “There are just a lot of things that the ADEC is going to have to take into account when designing a cleanup level for sulfolane.”

The new study by the National Toxicology Program is scheduled to begin next spring, according to O’Connell. The toxicology program is an arm of the U.S. Department of Health and Human Services.

The study will be conducted for two years using laboratory animals and could be a game changer for the sulfolane issue, which has spurred multiple lawsuits involving the state, the city of North Pole, Flint Hills Alaska Resources and Williams Alaska Petroleum, which owned the refinery when the chemical spill took place.

O’Connell said the ADEC regularly changes policy. The agency would review the findings if new information about sulfolane came to light in a few years.

He sympathizes with the residents in North Pole impacted by the groundwater pollution. The sulfolane leaked into the water for years before it was reported.

“If I were living there, I would really want an answer,” O’Connell said. “Those answers are not available right now.”

Contact staff writer Amanda Bohman at 459-7587.