SOURCE: The Guardian

DATE: October 4, 2019

SNIP: The most comprehensive study to date of microplastics in California has turned up a mind-boggling amount of plastic particles in the San Francisco bay.

An estimated 7tn pieces of microplastics flow into the San Francisco bay via stormwater drains alone, researchers discovered. Nearly half of the microscopic particles found in stormwater looked suspiciously like tiny fragments of car tires, which rainfall washes off the streets and into the ocean.

Treated wastewater contributed an additional 17bn particles of plastic, according to the study. Researchers also found plastic in sediment collected from the bay and its many tributaries and inside the digestive tracts of fish.

“It was basically everywhere we looked,” said Rebecca Sutton, an environmental scientist at the San Francisco Estuary Institute, a local institution that led the three-year, $1.1m research effort.

[R]esearchers accounted for two types of debris: microplastics, which are particles identified by a laser as fragments of plastic, and microparticles, which are particles the researchers suspect to be plastic, but couldn’t identify as such with the laser.

The fragments and fibers they analyzed included the remnants of plastic packaging and bottles, microscopic shreds of cigarette butts and fibers from clothing. Nearly half the particles found in stormwater were “these squishy black particles that we think might be from tires”, Sutton said. “But it’s really hard to get a definitive sense of where exactly it’s all coming from because there are so many sources of plastic pollution.”

The study is “extremely comprehensive”, said Stefan Krause, a microplastics researcher at the University of Birmingham. Even as scientists and engineers strive to clean up the hundreds of thousands of metric tonnes of the plastic debris floating on the ocean’s surface, it is becoming increasingly clear that “we have thousands and thousands and thousands of times more plastics that we can’t see”, Krause said.