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Sulfur Dioxide (SO2) emissions at Intalco

Apr. 26, 2019

The Northwest Clean Air Agency is working with the Washington Department of Ecology, the U.S. Environmental Protection Agency’s Region 10 based in Seattle, and various stakeholders to bring sulfur dioxide (SO2) emissions from Alcoa’s Intalco aluminum smelter in Whatcom County in line with national air quality standards.

On Dec. 21, 2020, EPA designated a small portion of Whatcom County that includes the Intalco smelter as being in nonattainment of the federal standard.

UPDATE: In early 2021, the Intalco nonattainment area was put on hold because of the recent change in the Federal Administration. Specifically, a hold was placed, pending review, on recent activities that occurred in the 90-day period prior to the change in administrations. That hold has now been lifted and the nonattainment area work is proceeding on its original schedule. Check Ecology’s Alcoa Intalco webpage for more information.

BACKGROUND: Two air quality monitors near the Intalco smelter have, at times, shown SO2 emissions above the National Ambient Air Quality Standard (NAAQS) of 75 parts per billion. Evidence suggests that the area where periodic exceedances occur is relatively small. But when this occurs a specified number of times within three consecutive years, EPA can designate the area as a nonattainment area, meaning it exceeds the federal standard.

Ecology and the Northwest Clean Air Agency prepared a technical report on their findings and submitted the report to EPA:

On Aug. 21, 2020, EPA proposed a nonattainment area that includes the Intalco facility.  EPA held a public comment period that ended Sept. 21, 2020. EPA had to finalize the designation by Dec. 31, 2020.

(Courtesy image.)

The federal Clean Air Act requires that a nonattainment area include not only the area that is violating the federal pollution standard but also nearby areas that contribute to the violation.

Criteria that factor into determining the boundaries for the nonattainment area include air quality data, emissions information, population density, traffic and commuting patterns, expected growth, weather, topography, jurisdictional boundaries, and control of emissions.

Ecology’s Industrial section has jurisdiction over the Intalco facility, including air emissions. But the proposed nonattainment area’s boundary also includes the Petrogas West facility and some private properties.

Intalco and Ecology (in coordination with other parties, including NWCAA) are required to put together a plan to bring the area back into attainment within a designated time period.

See Ecology’s web pages about SO2 air quality designations and SO2 in general for more information.

About Sulfur Dioxide (SO2) and health

Excess SO2 emissions are a concern because they can impact human health and the environment.

Short-term exposures to SO2 can harm the human respiratory system and make breathing difficult. Children, the elderly, and those who suffer from asthma are particularly sensitive to the effects of SO2.

SO2 and other sulfur oxides can react with other compounds in the atmosphere to form small particles, which may penetrate deeply into sensitive parts of the lungs and cause additional health problems.

SO2 and other sulfur oxides also could contribute to acid rain and to visibility-reducing haze on public lands like national parks and wilderness areas.

If you have questions about possible health impacts, call Whatcom County Health at 360-778-6000.