Adapted from Utah State Today.

Shrinking water levels at the Great Salt Lake are not just about Utah’s water supply—they may pose a serious risk to public health. New research from a team at Utah State University and the University of Utah documents the ways metal-laden dust from the drying lakebed may find its way into human bodies—directly through ingestion and indirectly through food systems.

The work was carried out by former USU graduate student Molly Blakowski, who was supervised by Janice Brahney, an associate professor of watershed sciences, with key support from U geochemist Diego Fernandez, who oversees a mass-spectrometry facility at the U’s Salt Lake City campus.

The team found that leafy vegetables exposed to Great Salt Lake dust contained elevated levels of elements like arsenic and uranium, even after thorough washing. The research documented how metals in dust could adhere to crops and evaluated whether they could be absorbed by roots.

“Dust is an acute health hazard, but rarely measured for composition or bioavailability of potentially toxic components,” said Brahney, who runs a dust-monitoring network across the Western U.S. “This new research takes our understanding one step further, measuring how toxic-laden dust could infiltrate Utahns’ lives in pervasive ways.”

Toxins can be taken into the body directly through ingestion, as well as through inhalation and through the skin. More than one-third of the modeled exposure scenarios showed that exposure to toxic metals surpassed levels of concern for children. Dust carrying heavy metals can also be deposited onto crops, where it can be incorporated into plant tissues through leaves or roots.

What happens when dust is applied to leaves vs. soils

To demonstrate whether dust-borne toxins can be absorbed by food crops, the team exposed cabbage growing in an experimental setting to dust collected from Farmington Bay’s playa. For some of the test plants, the dust was applied directly to the leaves with a brush, and for others, the dust was applied to the soil. A third group of plants was untreated for use as a control.

The plant material was analyzed by an inductively coupled plasma mass spectrometer (ICP-MS) at Fernandez’s lab, where they tested the leaves for various heavy metals.

“We report what happens in the leaves when you apply dust straight to the leaves and through the soil,” said Fernandez, a research professor in the U Department of Geology & Geophysics. “When you do it through the soil, it doesn’t seem to do much. But yes—when you apply to the leaves—for uranium, lithium, beryllium, arsenic and antimony.”

Dust-exposed cabbage leaves exhibited elevated levels for those elements, but that wasn’t the case for selenium, strontium, thallium and molybdenum, whose levels were in line with the control group.

Lakebed dust would be difficult, if not impossible, to avoid. Within the three most highly populated counties bordering the lake—Salt Lake, Weber and Davis—there are approximately 40 community gardens, countless backyard gardens and small farms, and around a dozen farmers’ markets where locally grown vegetables are distributed.

“Growing food and home gardening is an important part of Utah culture,” Brahney said. “We like to get our hands in the dirt. So we need to make sure the atmosphere isn’t adding contaminants to our local soils and water that we depend upon.”

Sediments on the dry playa around Great Salt Lake have been contaminated by a century of mining, waste disposal, oil refining and other human activities, said Blakowski, now a senior scientist with the Great Basin Unified Air Pollution Control District monitoring California’s Owens and Mono lakes.

Some metals are more bioavailable than others

“The dropping levels of the lake have exacerbated the problem,” she said. “And the lake’s dust is just one part of a complex mixture of atmospheric metal deposition on the Wasatch Front, which includes active and legacy pollution from mining, smelting and vehicle exhaust.”

The chemistry of these interactions is complex, according to the research. Some of the metals identified in the dust dissolve easily in the natural environment, allowing them to be transported or taken up by plants. While others were soluble in stomach acid, raising concerns about ingestion.

“If it gets to your stomach, you’re going to get more,” Fernandez said. But bioaccessibility and health risks vary across the elements and exposure pathways.

Take cadmium. When inhaled, about 20% of the cadmium borne on dust becomes soluble, but that portion reaches 80% if it’s ingested into the stomach, which is awash in acidic fluids, according to Fernandez. For lead, that share is 65%.

The health effects of exposure to these metals can also be additive, the researchers said. It’s not just exposure to arsenic that’s a concern, but also lead and antimony, as well as other toxic metals, Blakowski said.

Brahney’s overarching work also seeks to evaluate the concentrations of other types of toxins in the playa sediments, including cyanotoxins (poisons produced by bacteria) and organic contaminants, the latter in collaboration with faculty in the USU’s Department of Chemistry. The additive effects of all these potentially harmful components are yet to be evaluated, Brahney said.

“The next step is for expanded dust monitoring around the lake to reduce uncertainties and help researchers refine health risk assessments,” Blakowski said. “And efforts to restore water levels and reduce industrial pollution are complementary strategies that should be pursued.”

The authors call for expanded dust monitoring, improved exposure modeling and additional field and lab-based studies on crops grown near the Great Salt Lake.

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This study is to be published in the May edition of Atmospheric Environment and is available online now under the title, “Metal mobility and bioaccessibility in Great Salt Lake dust and exposure risks for humans and food crops.” The research is supported by My Good Fund, a Salt Lake City nonprofit, the National Science Foundation, the Geological Society of America and FRIENDS of Great Salt Lake and the Utah Department of Natural Resources.

• Brian Maffly Science writer, University of Utah Communications
  801-573-2382 brian.maffly@utah.edu