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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.

Ecology is taking public comment on a proposed agreed order with Intalco that is designed to help the facility meet those standards. The comment period will run May 8 through June 10.

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.

Image of a north-oriented map labeling two sulfur dioxide monitoring sites on Kickerville Road and Mountain View Road in Ferndale and the nearby Intalco Aluminum plant

(Image courtesy of the Washington Department of Ecology.)

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 depending on a nonattainment area’s boundaries, some nearby industrial operations, businesses and homes under NWCAA’s jurisdiction could be included within that nonattainment area.

Intalco and Ecology (in coordination with other parties, including NWCAA) would be 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 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.