New study reveals extreme levels of microplastics in San Francisco Bay

A study published in early October by two Bay Area environmental research institutes has raised alarm among local environmentalists after it found that the San Francisco Bay is highly polluted with microplastics, tiny plastic particles that pose a threat to the health of marine ecosystems, and potentially human health.

The study was published by researchers from the San Francisco Estuary Institute (SFEI) and Five Gyres Institute, based in Richmond and Los Angeles, respectively. Both research institutes study aquatic and ecosystem health, and jointly embarked on a three-year study to collect data on the sources and pathways of microplastic pollution in the San Francisco Bay.

Microplastics are tiny plastic particles that can range in size and material, but are smaller than five millimeters in diameter, which is the regulatory cutoff for materials that are considered “trash” and are supposed to be disposed of by city waste management services.

For the study, scientists collected samples from treated wastewater, surface water, stormwater, and sediment at different sites across the Bay Area to assess what these particles are made of and how they’re getting into the bay. The researchers found that the bay has some of the highest recorded levels of microplastic pollution in the world. Report co-author Rebecca Sutton, a senior scientist at SFEI, thinks the bay’s pollution is particularly high because of the dense urban population and narrow outlet from the bay to the Pacific Ocean.

“For me the concern is while it is an open question, exactly how much is too much, we for sure know that we’re making more and more plastic every year, and more is getting into the environment,” said Sutton. “And the stuff is persistent; it is not breaking down. It’s merely fragmenting into smaller pieces and so for me that means the problem is only going to grow unless we address it.”

How much worse is pollution in the Bay Area compared to the rest of the world? It’s hard to compare levels between different environments because collection data is limited and methodology can vary across studies, but the San Francisco Bay figures are roughly three times higher than those detected in a 2016 study of Lake Ontario, the body of water with the second-highest recorded level of microplastic pollutants. Importantly, researchers for the study in Lake Ontario used a much smaller sieve to collect samples. If researchers in the Bay Area had used a comparable sieve, levels would have likely been even higher.

The Bay Area researchers found that one of the predominant microplastics in stormwater and sediment are black, rubbery fragments that resemble car tires and the recycled tire pellets used in artificial turf. They make up nearly half of all microplastics found in stormwater runoff—nearly seven trillion particles every year. This suggests a new source of pollution that scientists were previously unaware of: the erosion of tires into small fragments that get washed straight into storm drains and enter the bay without any filtration.

Sutton said she was surprised by just how high the microplastic levels in stormwater were. She said she expected similar levels to those found in treated wastewater. But, she said, “Turns out, they were 300 times higher.”

“In retrospect, it does actually make sense, because wastewater goes to the wastewater treatment facility which can remove quite a bit of the microplastics, whereas stormwater in the Bay Area is generally untreated,” she said. “It rushes right from the street, to the creek, to the bay, so there’s no chance for the microplastics to settle out from the water. They go right to the bay.”

Sejal Choksi Chugh, executive director of Baykeeper, a nonprofit that works to monitor and improve the health of the San Francisco Bay, said she was surprised, too, that so many microparticles were coming from runoff and possibly from tires. “That’s a new source that I hadn’t considered,” she said.

Even worse, she added, other pollutants might be entering bay waters the same way. “When you have water running directly onto the roof and into the streets, you have the potential for higher levels of pollutants, not just microplastics, but oil and pesticides and other chemicals,” she said.

Choksi-Chugh said these findings will be important for guiding Baykeeper’s advocacy strategy as they work with cities to find effective technologies to prevent pollutants from reaching the bay. “Right now, for example,” she said, “the stormwater runoff problem is addressed by trash capture devices. When you have trash entering this device in a storm drain, it captures it before it gets in the bay. Most of the microparticles won’t be able to be captured.”

Baykeeper has been advocating for advanced treatment facilities that filter smaller pollutants for years, which Choksi Chugh said could help filter out microplastics, as well as pharmaceuticals and chemicals from cosmetic products. But the 40 Bay Area wastewater treatment facilities have been hesitant to upgrade because the advanced technology is expensive, she said.

Paula White, community programs manager of The Watershed Project, a Bay Area nonprofit whose mission is to protect and educate people about local streams, rivers, and tributaries that lead to the bay, suggested solutions that can be found in landscaping and green infrastructure. “A whole lot of these materials are coming from car tires. If we are able to capture stormwater runoff before it enters creeks and bays, it wouldn’t be a problem,” said White.

Their projects include bioswales,which provide flood abatement and filtration of stormwater. White describes a bioswale as an excavated channel with a perforated layer with gravel and sand and plants on top. The plants take up nutrients and metals, improving soil quality. An overflow drain helps protect against floods, and the bioswale also creates habitat for wildlife.

Still, although Choksi Chugh agrees that green infrastructure offers solutions, it’s still only a short-term fix. “Anything that intercedes the water before it enters into a storm drain could be helpful,” she said. But, she added, if you capture the plastics in a bioswale, “Does that mean that microplastics are now contaminating the soil? That would be a big concern.”

The SFEI and Five Gyres study’s researchers also found that the second most common type of microplastic in the bay is fibers from synthetic textiles like polyester and acrylic. These are the two most commonly-used fibers in the apparel industry, according to Sutton. High-performance clothing, such as raincoats, cycling shorts, and fleece, are typically made from synthetic fabrics, and they shed microplastics when washed. These fibers were the most dominant particle the researchers found in treated wastewater, sediment, and surface water, although there were also high levels in stormwater.

“It makes perfect sense that if you are making clothes out of recycled plastic, they will shed little bits of plastic,” said White.

The Five Gyres Institute has suggested that filters installed on washing machines could be a solution, according to Sutton. But once again,Choksi Chugh pointed out that filtering isn’t a complete solution.  “We don’t want to create another problem by having the fibers from the filter going to the landfill and then enter the water stream that way, or we don’t want soil to become contaminated with microparticles,” she said.

Natural fabrics like cotton and wool shed fibers, too—and the researchers found them in the water, as well. But scientists suspect the cotton will biodegrade over time, while plastic persists in the environment.

Research about microplastics is still a new field, and so far there is not conclusive evidence about how these plastics will affect the environment and human health. The SFEI and Five Gyres report notes that microplastics can expose organisms to potentially harmful chemicals, especially plastic additives like flame retardants, plasticizers, and dyes. A study published in 2015 by the Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP) notes that microplastics can have adverse physical effects on marine life, such as obstructing feeding appendages or damaging digestive tracts. This study also suggested that microplastics absorbed by marine life might allow toxic chemicals to travel farther than they normally could.

The SFEI and Five Gyres study particularly noted that “Microplastics have been shown to transfer up food chains and cause adverse effects in fish.” The researchers found these fibers in the digestive tracts of two prey fish species—topsmelt and Northern anchovy—which they collected in Tomales Bay. And, the study’s authors noted, the concentration of these particles increases towards the top of the food chain. While the health implications for humans are still not fully known, the GESAMP report researchers state that these particles can enter human gastrointestinal, lymph and circulatory systems, and may be connected to allergic reactions, asthma, cancer, and heart disease.

“We don’t have a clear toxicity threshold to work with,” said Sutton. “And so there’s a lot of uncertainty as to how much is too much for us. That goes for wildlife and even more for people.”

On a recent weekday afternoon, most shoppers at the REI in Berkeley, a store that specializes in outdoor-wear and environmentally-friendly products, said they hadn’t heard of the study before, but were aware that microplastics are a problem.

“I have to have a jacket, so I’d have to figure out what can you wear that’s not plastic. Because everything has synthetics in it, for the most part,” said Clare Woakes, who was wearing a knit fleece zip-up from Patagonia’s “Worn Wear” collection, which accepts gently worn garments and gives them a new life. Shopper Will Skyrud said he felt similarly at a loss for alternatives. “I don’t know if there’s a brand I could choose that would get around the issue,” he said.

Both expressed support for other actions people could take: For example, customers could wash their outerwear very infrequently, and reduce buying by making sure they wear their clothes until they are no longer useable. Companies could make apparel from recycled plastic sources like water bottles, which at least cuts down on the need for new plastic. Both Patagonia and the North Face have apparel lines that make fleece and other polyester outerwear from recycled plastic.

Patagonia and the North Face could not be reached for comment.

The researchers also found a third source of microplastics: microbeads, which are used in some cosmetic and cleaning products like soap and face wash. California Assembly Bill 888 recently banned the use of microbeads in rinse-off products, which took effect on July 1, 2018. However, fabric softener and some biomedical products that use microbeads are not included in the ban.

The report indicates that it is possible to filter microbeads from water using facilities that have tertiary treatment, which removes inorganic compounds and bacteria. However, the report also states that it is likely much more cost effective to prevent pollution from microbeads in the first place.

In their conclusion, Sutton and the other authors call for more research into the risks of microplastics, as well as into potential ways to reduce pollution.

To environmental advocates who have read the report, the study is a landmark because it provides new evidence that both stormwater and tire debris are huge pollutant sources. It also establishes a baseline for plastic pollution levels in the bay, and strengthens the methodology to be used for microplastic research.

“Plastic is just cheap, so it just gets put in everything,” said White. And changing that is hard, she said, because “business as usual in this country is organized around plastic.”

“The fundamental lesson is that our human urban impact is having a bigger impact than we even realized,” said Choksi Chugh. “Any new plastic is contributing to problem.”