Scientists search for source of microplastics in the Lake Tahoe Basin and nearby Sierra

Desert Research Institute and League to Save Lake Tahoe citizen scientists team up to evaluate the output of clothing dryers

Comet C/2020 F3 (NEOWISE) reflected in Emerald Bay - photo: Bob Tregilus CC BY-NC-SA 4.0 (7/10/2020)

Monica Arienzo is an assistant professor of hydrology at the Desert Research Institute (DRI) in Reno. Last year, Dr Arienzo discovered microplastics in the water of Lake Tahoe and snow of the nearby Sierra. The problem with microplastics she learned, they’re everywhere.

“Everywhere we’ve looked, we’ve identified microplastics. Microplastics are tiny pieces of plastic that are about the size of a pencil eraser and smaller. So we look down to a size of about a bacteria cell size,” Arienzo said in a phone interview. “And we’ve been finding these pretty much everywhere we look.”

Decades of global, single-use plastic production have deposited an all but insoluble legacy of microplastic particles across the planet, to say nothing of plastic litter. Much is unknown. Last August the World Health Organization called for further study to assess the potential impacts of microplastics on human health.

Methods to identify the composition of bacteria-sized particles of nylon or polyethylene in water are rare in the world. Scientists at DRI’s Microplastics Laboratory in Reno begin by carefully filtering the sample water.

“What we do, for example, for water samples or for snow – in the case of snow, we melt the water – then what we do is we stick that water through a series of filters of a known size, and what happens is that any of those particles, if they’re plastic or other particles, they get stuck in the filter. And then we can look at those filters under our microscope. We can use some visual methods to say if that looks like a micro plastic or if it looks like something else, like an algae, or sediment.”

But visual assessment alone cannot conclusively identify the composition of the tiny particles. This fall, Arienzo and team will begin using a specialized microscope to identify what captured particles are made of.

Infrared spectroscopy is a method by which infrared light of known frequency is directed at a material. The frequency of the light that is absorbed is a highly accurate indication of the material’s composition.  A library of these spectra, as they are known, is used to identify the material. Traditionally, infrared spectroscopy has been used to evaluate larger samples of material. Using the technique through a microscope is groundbreaking.

“We can actually look at the particle and say, ‘is it a nylon, microplastic, or is it a polyethylene microplastic?’ That’s really important for saying something about where they came from. So for example, if it was nylon, that indicates that it probably came from clothing,” Arienzo said.

The Clothing Dryer Study

Over the next 3 weeks a group of League to Save Lake Tahoe citizen scientists will outfit their clothes driers with special filters to capture particles from dryer vent emissions. Dr. Arienzo explained that unexpected results from a remote snow sample led to a curiosity in dryer emissions.

“We collected some snow north of Truckee in what we thought was a fairly remote location, and when we looked at it under the microscope, I was shocked at how many fibers I was finding in this sample. And these fibers, they’re really thin, they’re thinner than a hair width and they tend to be quite long. And that really was interesting to see so many of them in the snow from a place where we didn’t really expect to see much.

“And when we looked at it under this infrared microscope, we saw that some of those fibers were in fact nylon and rayon. And that made me start to think where these are coming from, and it led to me thinking about dryers and dryer vents as a source of microplastics.”

League to Save Lake Tahoe has developed and maintains a robust citizen science program. Eyes on the Lake, for instance, is a program that enlists beachgoers, paddlers, SCUBA divers, and boaters to help identify invasive plant species to better prevent their spread.

Citizens scientists also monitor water quality and litter and other environmental parameters in and around the lake. For the next 3 weeks, they will use a special mesh screen to capture particles from their dryer vents for analysis.

“Then after three weeks,” Arienzo said. “(They) take that mesh screen and send it back to us at DRI. And what we’re going to do is we’re going to then take that mesh screen, we’re going to compare what we find to learn how much of what is deposited is plastic versus other things.

“So in the case of my dryer vent, there’s a lot of dog hair that ends up in it because I’ve got a dog that likes to shed a lot. So we’re going to try to figure out what percentage of what’s emitted in our dryer vents is plastic versus other things like cotton, wool, or hair or other things like that.”

Jesse Patterson is the chief strategy officer for League to Save Lake Tahoe. Patterson recalled his thoughts after Monica Arienzo announced the discovery of microplastics in the Tahoe Basin last summer.

“My reaction was like, ‘are you serious?’ But at the same time, not totally surprised. They’re (plastics are) so prevalent in our world right now. And I think it only makes sense they’d show up here. I was optimistic, perhaps naively optimistic, that we had enough environmental protections up here to make sure it didn’t happen, but the reality is they’re here. We’ve got to figure out where they’re coming from and what to do about it,” Patterson said by phone.

Millions of people visit Lake Tahoe every year, and some 50,000 year-around residents call the basin home. Citizen science harnesses the vast observational power of visitors and locals to more carefully monitor the environment.

“We’ve long believed at Keep Tahoe Blue that citizen science is the solution to what ails us,” Patterson said. “And that essentially means anybody that comes up here should have it easily accessible for them to learn the skills and provide the input we need as land managers and caretakers of Tahoe to do the right thing, and we think we built a program that could do it, and this partnership with DRI exemplifies that.”

Knowledge informs policy, and for Patterson and the many citizen scientists of League to Save Lake Tahoe, if dryer emissions are spreading microplastics, they need to know and take corrective action.

“Is the way we do our laundry actually contributing plastics to the lake that we love? And if so, what do we do? What do we do about it? Right? Doing laundry is kind of part of life. I have two little kids and so I do a lot of laundry. So how do we do it in a way that doesn’t damage the very reason we’re here?”

For Dr. Arienzo, identifying the problem is a central part of finding a solution, but the knowledge that microplastics are so ubiquitous is disheartening for someone concerned with the environment.

Monica Arienzo is practical and acknowledges the utility of plastics and what they mean for our collective quality of life. Along with potentially adding filters to dryer vents, Arienzo says individuals can make better choices regarding the use of plastics.

“One of the interesting things about studying plastics is that we do use them every day in our lives but we don’t necessarily have to, and that’s the part I think is really interesting. Personally, I’ve been thinking a lot about little things I can do in my daily life, like using a reusable mug, trying to use nice stainless steel or bamboo straws that they make these days, trying to use shampoo bars instead of shampoo bottles.

“So I think that we can, as a society, move towards more reusable items, and increasing the amount that we recycle. Because currently, we actually don’t recycle a lot of the stuff we make. So if we can work towards recycling, and just reusing things or using things that don’t have so much plastic in them, I think that’s the potential upshot of all this research.”

Want to know what to do about the microplastics problem? Here are 7 simple, evidence-based solutions to target your efforts.


Brian Bahouth is the editor of the Sierra Nevada Ally and has been a public media journalist since 1996. Support his work.