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Study pinpoints magnesium refinery as major source of northern Utah's 'brown clouds'

Posted at 10:42 AM, Jan 27, 2023

SALT LAKE CITY — A new federal report pinpoints a magnesium plant as a major contributor to the winter "brown clouds," or inversion, often seen over northern Utah, and Salt Lake City, in particular.

The study from the Cooperative Institute for Research in Environmental Sciences came from a period of winter air pollution in 2017 and showed that the plume from the US Magnesium refinery along the Great Salt Lake produced "emissions of chlorine and bromine, known as halogenated compounds, [and] were significant contributors to the persistent winter brown clouds."

According to the report, models showed that chlorine and bromine emitted by the refinery was responsible for 10-25% of the area's particulate matter 2.5 (PM 2.5) during pollution episodes.

"Particulate matter contains microscopic solids or liquid droplets that are so small that they can be inhaled and cause serious health problems. Particles less than 2.5 microns in diameter, also known as fine particles or PM 2.5, pose the greatest risk to health, affecting both lungs and your heart," the study says.

The refinery extracts metal from the brine of the lake.

While the study was conducted using data from 2017, its lead author, Carrie Womack, said the emissions of chlorine have not shown any significant decline in the last five years.

During research flights around the plant, the air scientists found was unlike anything they had previously sampled due to the high chlorine emissions.

"Close to the plant, we didn't even need to check the instruments to know we were flying through the plume,” Womack wrote. “We could smell it. It smelled like bleach!"

Winter pollution levels of PM 2.5 in the Salt Lake Valley exceed national air quality standards an average of 18 days per year. Those instances have been associated with poor health effects, and during a time period between 2003-08, another study showed they accounted for a 42% higher rate of emergency room visits for asthma.