While nearly $3 billion has been spent on Lake Tahoe’s clarity in the past quarter century, what’s actually in the water was never a concern until the last handful of years.

Water isn’t the only thing in the lake and that’s a problem because most people who live in Tahoe are consuming water from the lake or from well water. Multiple studies have shown an abundance of microplastics are in Lake Tahoe.

Tahoe was the third worst lake for microplastics in a study published in the journal Nature last year.

Tahoe Water Suppliers Association (TWSA) is working with scientists at Tahoe Environmental Research Center in Incline Village and Desert Research Institute in Reno to combat the problem.

“(We) have done independent sampling of four in-takes. A very small amount of contamination was found on a scale of hardly anything compared to what is being found in other surface waters and what they are finding in bottled water,” said Madonna Dunbar, TWSA executive director.

A petri dish shows the microplastics found in Lake Tahoe. (Image: Katie Senft)

TWSA member are: Cave Rock Water System, Edgewood Water Company, Glenbrook Water Cooperative, Incline Village GID, Kingsbury GID, Lakeside Park Association, North Tahoe PUD, Round Hill GID, Skyland Water Company, South Tahoe PUD, Tahoe City PUD, and Zephyr Water Utility.

Dunbar said the basin has more than 50 water purveyors, mostly small ones that include individual neighborhoods.

Because microplastics are anything smaller than 5mm, which is the size of a grain of rice, they aren’t easy to see. Nor are they something to be picked up on a beach cleanup or by divers scouring the lake’s floor.

“Particles of greatest concern to human health are smaller than 20 microns,” explained Katie Senft, a staff research associate with TERC. For perspective, a human hair is 20 to 120 microns.

Senft in 2018 started studying microplastics at the beaches in the basin. A year’s worth of water samples were taken starting in August 2020. Her group took more samples than the Journal study did, but the results were similar.

When money surfaces Senft hopes to do more studies.

“I’d like to look at atmospheric depositions of plastics,” she said.

What wildfires blow in is a concern. When Senft and her cohorts took a sample of Lake Tahoe on Aug. 4, 2021, the Caldor Fire had not started, but the Dixie Fire was raging. They recorded a spike in microplastics that day. Just think of all those plastics burning, then floating in the air and eventually landing in your lungs, in the soil, in bodies of water.

“The year we did our monitoring work on Tahoe we got higher levels in the spring and summer. I think (this was because of) the spring run-off over roads and bringing everything that had settled on snow over winter with it,” Senft said.

One reason Tahoe has a microplastic problem is that once the particle gets into the lake it will take on average 650 years to leave, according to Senft. This is because of the “residence time”—or how long it takes a single drop of water to pass through the system. The size of Lake Tahoe is what makes for its long residence time.

“The longer residence time of a lake, the more likely it is to have a high abundance of plastics because it doesn’t have the flush,” Senft said. “That is one of the big pieces. We can’t really change that. That is why it’s important to think about what we can do to minimize the number of plastics entering the lake in the first place.”

DRI is working on a study in conjunction with the League to Save Lake Tahoe about how dryer lint is polluting the air with microplastics. So much of our clothing—fleece, rayon, polyester, acrylic, and spandexcontains plastic.

Monica Arienzo, an associate research professor with DRI, later this year expects to release findings from eight South Lake Tahoe citizen scientists who collected the output from their dryers by putting mesh over the outlet.

“We found a lot more material than we thought we would,” Arienzo said. “We wanted to look at dryers because it’s a possible source of microplastics into the environment. It can be in the air, travel longer distances, and get into streams. One reason to study it is it’s something that could be regulated by putting mesh at the end of a dryer or some other technology.”

Microplastics are essentially ground up trash.

“If you are worried about microplastics in the water, the best thing you can do is use less plastic. It has multiple benefits to each person and the planet,” Senft said. “Plastic bag bans and water bottle bans all help.”

Starting on Earth Day this year South Lake Tahoe banned all bottled water less than 1 gallon. Truckee approved a similar ordinance in January. Multiple jurisdictions in the area ban plastic bags, though Nevada is woefully lacking on these types of regulations.

Note: A version of this story first appeared in the Tahoe Mountain News.

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