Sulfolane

New findings published June 2026: The National Toxicology Program (NTP) peer-reviewed report titled “NTP Technical Report on the Toxicology and Carcinogenesis Studies of Sulfolane (CASRN 126-33-0) Administered in Drinking Water to Sprague Dawley (Hsd:Sprague Dawley SD) Rats and B6C3F1/N Mice” is now available.

Research Overview

Status: Completed
Substances: Sulfolane
Nominated: September 2011

Background Information

Sulfolane is an industrial solvent used in petroleum refining and natural gas processing. It was found in contaminated groundwater and drinking water wells near a refinery in North Pole, Alaska, prompting comprehensive studies by the National Toxicology Program to address key knowledge gaps about the potential toxicologic, carcinogenic, and developmental effects of exposure.

Sulfolane contamination has raised concern because the substance can move into groundwater and lead to human exposure through drinking water. Exposure may also occur through inhalation or skin contact for those who work in industries using sulfolane.

NTP Studies & Findings

What did the studies find?

See the table below for more information on NTP research related to sulfolane.

List of sulfolane studies
Study	Description	Status	Findings & Supporting Files
Two-year toxicity and carcinogenicity studies	Studies to determine effects of long-term exposure on rats and mice, including any potential carcinogenic effects. Studies also include an assessment of developmental effects in rats and a three-month interim study in rats and mice to identify effects after subchronic exposure.	Completed	Findings: Blystone et al. 2026: Full report, summary, and data
Immunotoxicity study	Rat and mouse studies to determine the potential of sulfolane to effect immune system function.	Completed	Supporting files: Watson et al. 2021 Data tables
28-day toxicity study	Studies in multiple animal species to determine species sensitivity.	Completed	Supporting files: Shipkowski et al. 2021 Data tables
Absorption, distribution, metabolism, and excretion	Animal studies to investigate how well sulfolane was absorbed into the body, where it circulated in the body, and how it was cleared following oral administration and skin application.	Completed	Findings: In male and female rats and mice, sulfolane was well absorbed when given orally; the dose showed up in high amounts in the circulatory system when a high dose was administered orally Sulfolane applied to the skin was absorbed more readily in mice than in rats Sulfolane was eliminated rapidly, with urine as the main excretion route in both rats and mice of both sexes Supporting files: Waidyanatha et al. 2019a Waidyanatha et al. 2020 Silinski et al. 2019

Research at Other Agencies

United States

Alaska (AK)
- Health Consultation: Sulfolane Plume in Groundwater: Evaluation of Community Concerns About Sulfolane in Private Water Wells
- North Pole Refinery Project Documents – This website contains many resources on sulfolane, including fact sheets, newsletters, press releases, FAQs, and reports regarding drinking water, site characterization and remediation, and human health and toxicology.
- North Pole Refinery | AK Dept. of Environmental Conservation
- Human Health and Toxicology - Sulfolane and PFAS | AK Dept. of Environmental Conservation
US Environmental Protection Agency: National Center for Environmental Assessment
- Provisional Peer-Reviewed Toxicity Values for Sulfolane
US Centers for Disease Control and Prevention: Agency for Toxic Substances and Disease Registry
- Health Consultation - Sulfolane, 2010
- Health Consultation - Sulfolane, 2011

Informational Resources

Nominations

Presentations

NTP Board of Scientific Counselors Meeting, Research Triangle Park, NC, December 2011
- Research Concept: Sulfolane
- Slides: Sulfolane

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