WDEQ meets new, lower sulfur dioxide standard

Air Quality Division
Published: July 9, 2021


Photo credit: Genesis Alkali

By Kristine Galloway

CHEYENNE – Wyoming’s air continues a decades-long trend of low levels of sulfur dioxide (SO2).

SO2 is a pollutant that can be a bi-product of combustion with fuels that contain sulfur, such as coal. The U.S. Environmental Protection Agency (EPA) classifies it as possibly hazardous to people’s health.

The level of SO2 in Wyoming’s air has always fallen below the allowable level set by the EPA in 1971 as part of the Clean Air Act. After the EPA lowered the standard in 2010, staff members in the Wyoming Department of Environmental Quality (WDEQ) Air Quality Division (AQD) set out to prove the state’s levels still were at or lower than the standard.

Those staff members recently found this to be true.

Cara Keslar, WDEQ’s air quality monitoring section supervisor, said, “It’s an affirmation of great air quality.”

She added that the new SO2 standards is much more stringent than the previous standard.

In particular, the AQD staff has shown that people living around facilities that might emit SO2 can still be confident they aren’t breathing in high concentrations of the pollutant.

Amber Potts, WDEQ’s State Implementation Plan and rules section supervisor, said SO2 can irritate the skin and mucous membranes of the eyes, nose, throat and lungs. High concentrations of SO2 can contribute to breathing difficulties.

She said, “I work, volunteer and raise my kids in Wyoming. It's nice to know that I have had a hand in walking Wyoming through this favorable designation process.”

Potts added that proving this attainment is important for Wyoming’s economy, as well.

Industrial organizations may be more likely to come to the state because they would need to jump through fewer hoops to operate.

“If we were in nonattainment, there would be a whole slew of air quality requirements that would need to happen,” Potts explained. “With this designation, the economy is not being hampered by air quality restrictions.”

Keslar said the AQD permitting rules require new sources to prove they will not contribute to a violation of air quality standards. With Wyoming meeting SO2 standards statewide, it’s easier for companies considering a move to the state to prove they won’t contribute to such a violation.

Potts said working with existing facilities to prove attainment was a pleasure because facility staff cared about the effort and worked hard to support a good outcome.

She explained that the EPA split up the national effort to verify SO2 levels into four rounds, starting with facilities that released the highest concentrations of SO2.

No Wyoming facilities were recommended to participate until the third and fourth rounds. The work for WDEQ and identified facilities started in round three, which began about six years ago.

Potts said, “They had to monitor the SO2 concentrations, which was quite a lot of work and resources.”

Facilities chose whether they wanted to prove they met the SO2 standards through either a monitoring or a modeling process.

Keslar explained that the monitoring process took four years and required the facilities to physically monitor their ambient air.

The less extensive modeling process took two years. She said it involved facilities generating a simulated computer model that calculated emissions using meteorology.

Keslar said many facilities in the state no longer need to monitor for SO2 unless the EPA should lower the standard again. They can choose to self-monitor, however.

She added that EPA reviews the standards every five years.