DEQ tells committee wildfire smoke dwarfs other sources; EPA tightened PM2.5 standard to 9 µg/m3

Bo Wilkins, Air Quality Bureau Chief at the Department of Environmental Quality, briefed the House Natural Resources Committee on the state’s approach to smoke and PM2.5.

Wilkins said the Air Quality Bureau focuses on PM2.5—particles smaller than 2.5 microns that can penetrate deep into lungs and the bloodstream—and that wildfire smoke is the dominant source of PM2.5 statewide. He cited multi‑year averages and slide examples showing large year‑to‑year variation (the transcript references roughly 30,000 tons in 2020 and about 300,000 tons in 2021), and said an average of roughly 120,000 tons of PM2.5 over the last three years puts wildfire emissions orders of magnitude higher than the state's largest regulated industrial emitter (cited in the presentation as about 1,250 tons per year).

DEQ described expansion of the regulatory monitoring network with a federal grant (new permanent monitors in Dillon, Cut Bank, Glendive, Glasgow and other sites) and deployment of lower‑cost non‑regulatory sensors (PurpleAir) including a PurpleAir in Schools program (the presentation cited roughly 100 sensors deployed and about 60 operating). Wilkins said an individual permanent regulatory monitor costs roughly $20,000–$25,000 plus monthly QA/QC; PurpleAir units cited in the presentation cost about $280 and provide useful, lower‑quality data for public information.

Wilkins reviewed emissions factors that show wildfire per‑ton emissions are the highest, followed by prescribed fire and pile burning, with residential wood and pellet stoves lower per ton. He described biochar production as a developing use for biomass with potential co‑benefits (carbon sequestration, soil improvements) and said the Air Quality Bureau is reviewing a biochar facility application.

Prescribed burning seasons and permitting differ by season: spring/summer open burning is largely unrestricted (county permits), fall burning uses burn zones with county‑by‑county rules in the West, and winter burning requires local and DEQ approval to minimize impacts. Wilkins explained the distinction between major burners (annual permitting for entities that burn >5,000 acres, including federal agencies and large timber companies, often managed through interagency airshed groups) and minor burners (managed through DEQ’s online minor burning program with new data collection on pile sizes and emissions).

Wilkins also addressed the regulatory implications of EPA's February 2024 revision of the PM2.5 National Ambient Air Quality Standard from 12 µg/m3 to 9 µg/m3. DEQ is completing area designations and will submit them to EPA; areas that do not meet the new standard could become nonattainment and require state plans to reduce PM2.5. He noted the exceptional‑events rule allows DEQ to exclude certain wildfire impacts from attainment calculations if EPA concurs, but the rule is complex and EPA concurrence is required; DEQ is in discussion with EPA on some events (Wilkins cited Libby as an example where exceptional events debate may affect whether the area is ultimately designated nonattainment). Wilkins emphasized that exceptional events do not remove data from the historical record.

Committee members asked about greenhouse‑gas quantification from smoke (DEQ said it does not itself categorize greenhouse gases but works with partners who do) and about whether federal wildfire management choices can be regulated by the state (DEQ said planned prescribed burns are subject to permitting but unplanned wildfire decisions by federal land managers are not regulated by the DEQ under the Clean Air Act except via the exceptional‑events framework). Wilkins concluded by offering to circulate the presentation to the committee.

The committee adjourned after thanking Wilkins and requesting staff circulate the slides.