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Human Health and Toxicology - Sulfolane

Updated: November 28, 2018

Overview of Sulfolane

Currently the public is not exposed to sulfolane. Alternative water supplies are provided to all properties with any detection of sulfolane in the water, an estimated 1,500 people, along with additional "buffer zone" properties, to protect against plume expansion.

Flint Hills Resources Alaska (FHRA) and the State of Alaska are working with the City of North Pole to significantly expand their piped public water system to provide sulfolane-free drinking water to residents impacted by the sulfolane groundwater plume. More on the Piped Water Expansion.

In 2009, when sulfolane was first discovered in drinking water wells, DEC asked the Alaska Department of Health and Social Services (DHSS) as well as the Agency for Toxics Substances and Disease Registry (ATSDR) for assistance in establishing a safe drinking water level. As a result, both agencies conducted health consultations:

Summary of SULFOLANE health recommendations From the Alaska department of health and social services

Residents who have wells with sulfolane detections should continue using an alternative water supply for drinking and for growing edible plants. Edible garden plants can take up sulfolane from water, therefore people can be exposed to sulfolane by consuming produce that has been watered with sulfolane-contaminated water.

Given the concentrations of sulfolane reported to date, residents can still use wells with positive sulfolane detections for most household activities such as bathing, washing clothes and dishes, rinsing foods, and making foods where the water is discarded, such as boiling eggs. Based on currently available information, using well water to shower does not pose a health risk for North Pole residents, although inhaling sulfolane in water droplets during showering needs further evaluation.

Other exposure routes such as breathing vapors or direct skin contact are unlikely to pose a risk because the chemical has low volatility and is not absorbed through the skin.

Residents on the city’s public water system are encouraged to use city water for gardening.

Residents who raise chickens or other animals do not have to worry about sulfolane in their meat or other products (milk, cheese, eggs, etc.) as long as the animals are not drinking water that contains sulfolane.

Contact Information for the Alaska Department of Health and Social Services:

National Toxicology Program

The National Toxicology Program Initiates Long-Term Toxicity Studies

In 2011, the State of Alaska nominated sulfolane into the National Toxicology Program. The NTP is a federal interagency effort of the National Institutes of Health, the Center for Disease Control and Prevention, and the Food and Drug Administration, to safeguard public health by conducting cutting-edge toxicity research on chemicals.

In early 2012, sulfolane was officially accepted into the program. In December 2014, after a preliminary study was nearly completed, the NTP informed DEC that studies to evaluate the long-term health effects of exposure to sulfolane on animals would begin shortly. The long-term (2-year) study was initiated in May 2015.

The NTP has embarked on toxicology studies for sulfolane that address questions regarding long-term exposure to the solvent, as well as other research gaps. Specifically, the NTP is conducting a two-year study on rats and mice to evaluate the effects of long-term exposure to sulfolane in drinking water and the effects on pregnancy, development and the immune system. DEC is waiting for results of the NTP studies before setting a final cleanup level. (Download Fact sheet on the NTP studies, June 2015, revised November 2018 (PDF)

The status of the NTP studies, as of November 2018:

  1. 28-Day Toxicity Study – Awaiting Report
    • Mice, rats and guinea pigs were given a range of doses of sulfolane. A number of toxicity endpoints were assessed, including the amount of sulfolane in the animals. Histology of multiple tissues and immunology were also evaluated. Goals of this study were to:
  2. Determine if any of the animal species studied is more sensitive to sulfolane toxicity than the other species, and
  3. Identify appropriate dosing levels for longer duration studies.
  4. ADME Study – Awaiting Report
    • Studies measured the absorption, distribution, metabolism, and excretion (ADME) of a chemical in male and female mice and rats. ADME studies help understand how a chemical moves around within the body, including whether there are any differences between sexes or rodent species.
  5. Subchronic Toxicity Study – Awaiting Report
    • Mice and rats from the 2-year study were assessed after 3 months of exposure. The study looked at effects on a number of toxicity endpoints including markers of development in the rats. In a separate study, the immune system of rats and mice exposed to sulfolane for 3 months will be evaluated.
  6. Two-year, Chronic Toxicity Study – Awaiting Report
    • Rats and mice were given sulfolane in their drinking water for 2 years, consistent with how people would most likely come in contact with sulfolane. The purpose of this study is to determine the effects of long-term exposure to sulfolane including any potential carcinogenic effects. The NTP will do a limited assessment of pregnancy outcomes in rats.