• Sources Cited
  • Subject Specialist
Sources Cited As a news piece, this article cites verifiable, third-party sources which have all been thoroughly fact-checked and deemed credible by the Newsroom in accordance with the Civil Constitution.
Subject Specialist This Newsmaker has been deemed by this Newsroom as having a specialized knowledge of the subject covered in this article.
Suncor Energy’s Commerce City plant is seen Feb. 17, 2023. (Olivia Sun, The Colorado Sun via Report for America)

The Suncor refinery in Commerce City again released potentially dangerous sulfur dioxide and hydrogen sulfide into the surrounding neighborhood late Friday night, the second time in April, and state health officials warned the emissions could exceed permitted levels throughout Saturday. 

The incident was the second this month involving excess air pollution at Suncor, which is increasingly the target of neighbors, local officials and environmental advocates who believe plant emissions are an ongoing violation of environmental justice provisions in federal and state rules. 

Suncor sent out a message on its text and phone alert system at 11:40 p.m. Friday saying “refinery personnel responding to the incident. No immediate action needed by the community.”

But Saturday afternoon, the Colorado Department of Public Health and Environment said multiple levels of monitors at the Suncor fence line and in the neighborhood detected potentially hazardous emissions that would remain above state permit levels for Saturday, and the neighbors should consider safety measures. 

“Exposure to air pollutants like sulfur dioxide and hydrogen sulfide can impact your health depending on how much, how long, and how often you are exposed,” the state’s release said. “These pollutants can also cause difficulty breathing, especially for people with asthma. Hydrogen sulfide may irritate the skin, eyes, and throat and can cause headaches, poor memory, tiredness, and balance problems.”

While emissions levels at Suncor were dropping Saturday, the state advised neighbors that they could take actions such as limiting outdoor activity, closing windows and doors, using air conditioners and home air purifiers. 

The Daily Sun-Up podcast | More episodes

“These suggestions do not replace the department’s ongoing actions to limit air pollution,” the state’s release said. “We recognize that not everyone is able to change their daily activities or afford all these recommendations. However, we want to ensure everyone is informed about options they can use to protect themselves and their families.”

The state said the latest Suncor incident happened in the sulfur recovery equipment in Plant 1, and put sulfur dioxide emissions over Suncor’s permit limits 250 parts per million for a 12-hour rolling average, and 15.68 pounds an hour for a 1-hour average.

“We believe that Suncor will continue to exceed its 12-hour rolling average limit throughout the day today,” the state said Saturday. “As of 9 a.m., Suncor was no longer exceeding its 1-hour average limit.”

Suncor said in a Saturday afternoon release that the emissions did not reach the level of threatening acute health problems.

The state said its various monitoring resources also found “concentrations of hydrogen sulfide in gases combusted in the Plant 1 flare and in the Plant 1 heaters and boilers were above the permit limit of 162 parts per million for a 3-hour average.”

The state’s Air Pollution Control Division contacted Suncor when it got the company’s alert, and continues to monitor information from the sensing equipment. The state said it is continuing to investigate the incident, as well as one on April 12, with possible penalties or other enforcement. 

In the first April incident, the state said the refinery sent potentially dangerous spikes of sulfur dioxide into the surrounding neighborhood early on a Wednesday after an equipment failure, though the state health department’s notice didn’t go out until Wednesday evening.


Environmental groups have also recently targeted Suncor’s ongoing problems with releases of PFAS “forever chemicals” into Sand Creek, which runs by the refinery and empties nearby into the South Platte River, a drinking water source for multiple suburbs north and east of Denver. 

Discharges of toxic “forever chemical” PFAS into Sand Creek and the South Platte River by Suncor’s refinery spiked to thousands of times the EPA’s revised drinking water guidelines for three months starting in November, according to filings with state regulators. 

Michael Booth

Michael Booth is a Colorado Sun reporter covering health, health policy and the environment. Email: Twitter: @MBoothDenver