Microplastics in Our Streams: The Tiny Particles That Have a Big Impact

UC Riverside scientists are taking a novel approach to studying an enigmatic topic—the amount, quality, and sources of microplastics in Los Angeles County’s urban streams.

Microplastics are particles with a maximum diameter of 5 millimeters, which is about the size of a pencil eraser. This category could include nanoplastics, which are much smaller than the width of a normal human hair.

Scientists have been aware that these particles have been leaching through the environment for decades, but concern about them has only recently begun to grow.

“There is increasing evidence that these materials are toxic,” said Andrew Gray, UCLA associate professor of watershed hydrology.

Recent studies indicate that microplastics can have negative effects on reproductive health, especially for males.

Microplastics and nanoplastics can also cross organ boundaries and infiltrate cell walls. As they do so, they may be carrying other compounds added during manufacturing or picked up as they travel through the environment, such as heavy metals or perfluorooctane sulfonate, chemicals used in products such as fire-fighting foams, stain-resistant fabrics, and food packaging.

In addition, microplastics cause problems for animals whose airways and digestive tracts can become clogged with them when they are mixed with food.

In order to manage these substances in our water, scientists need to understand what types of plastic are present and where they come from. Gray’s group at UCR got nearly $1 million from the Los Angeles County Clean Water Program to learn this information.

“Microplastics are a complex group of pollutants with a wide range of particle sizes and shapes, and different ramifications for human and water health,” said Gray.

“We want not only a baseline of what is there at a given time, but an understanding of how it got there, where it is drained, and how it is transported through our urban waterways,” he said. “We expect storm water to transport most of the microplastics through rivers and streams to the coastal ocean.”

The three-year microplastics project will focus on the Lower Los Angeles River, Lower San Gabriel River, Ballona Creek, and the Dominguez Canal. In collaboration with LA County Public Works, UCR will collect rainwater samples from stations already set up for other types of water quality measurements. The samples will then be analyzed in Gray’s lab.

Gray’s group intends to use what they’ve learned about these four streams to help standardize methods for observing microplastics in stream flow, especially under storm conditions. They also want to develop models of the ways plastic travels through waterways. They will then apply these models to direct monitoring efforts at additional streams where monitoring stations do not already exist, and where it is expensive to establish.

Ultimately, more advanced monitoring systems can provide information on a variety of management strategies that can be used for specific compounds. For example, one type of plastic frequently found in water samples analyzed in Gray’s lab comes from tires and streets.

“We tend to think of emissions from combustion, but there are also a lot more emissions associated with vehicles than combustion. Brakes, fluids, tires, roads—all of those things have plastics that leak, decompose, and wash away,” Gray said. It is no longer so. Today’s tires are mixed with a lot of plastics and petroleum-based additives.”

Tire and road particles have toxic effects on commercial species of fish, including salmon and trout, as well as other aquatic animals. If researchers can identify entry points into waterways, they can create strategies at those locations to help reduce runoff and clean it up before it travels into municipal drains and moves downstream.

There are many strategies to reduce plastic waste that can be implemented daily by consumers. People can start to reject single-use plastic containers and items in favor of safer and more sustainable materials. Gray also hopes that in the future there will be more pressure on the parts of the economy that produce plastic goods.

Since a lot of microplastics are produced by breaking down larger plastic particles that have already entered the environment, the problem is likely to persist.

“Even if we stopped producing all plastics today, the legacy of pollution will continue for decades. But not all microplastics may be toxic, and for those plastics, we have the opportunity to reduce their manufacture and impact,” Gray said. “Improved surveillance will certainly help guide those efforts.”