Study finds microplastics falling with Sierra Nevada snow, raising drinking water concerns

Tiny pieces of plastic are falling with snow across the Sierra Nevada, including in remote areas, and researchers and local water officials say the findings raise new questions about what snowmelt could be carrying downstream into the Truckee River, Reno’s main water source.

Researchers collected snow from seven locations in the Sierra, melted it and used special lights to distinguish plastic from dirt and plant material. During storms, some sites recorded as many as 3,200 plastic pieces per square meter each day. At one site near Mammoth Mountain, researchers found as many as 7,500.

Study leader Aleksandra Karapetrova said she did not expect the results to be so widespread.

“I was pretty shocked, honestly. ... We were able to consistently detect them across all sites,” Karapetrova said.

The study found that plastic can travel through the air, and snowflakes can capture some of it as they fall.

“When a storm occurs, the snowfall scavenges out these particles from the atmosphere,” Karapetrova said.

Researchers traced some storm air back over Fresno and Madera counties but could not determine exactly where the plastic originated.

The findings are drawing attention locally because Sierra snowmelt flows into the Truckee River, which supplies water to the Truckee Meadows. Monica Arienzo, a researcher at the Desert Research Institute, said a separate study found some of the same kinds of plastic in the Truckee River.

“We actually find a lot of the same plastics that this study found,” Arienzo said.

Will Raymond, director of operations and water quality for the Truckee Meadows Water Authority, said the river is the region’s primary water source.

“Our primary source of supply for the Truckee Meadows is the Truckee River,” Raymond said.

TMWA has not tested its reservoirs or treatment plant for microplastics, and Raymond said there is not yet a standard way to test for them. He said conventional treatment can remove microplastics, but not completely.

“Our conventional water treatment processes are very effective at removing microplastics but it’s not 100% removal,” Raymond said.

The study did not test drinking water or examine health effects. TMWA said local tap water is safe to drink.

Desert Research Institute researchers are also testing snow in the Tahoe Basin and plan to compare those results with the Sierra study.

Study finds microplastics falling with Sierra Nevada snow, raising drinking water concerns

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