SF Chronicle: Huge amounts of plastic, much of it from car tires, washing into SF Bay, SFEI study finds

The San Francisco Chronicle highlighted some of the surprising and alarming findings produced by the Microplastics project:

More than 7 trillion tiny pieces of plastic wash from city streets into San Francisco Bay each year, a new study finds, a staggering amount of pollution that researchers weren’t entirely aware of and aren’t prepared to stop.

The microplastic, defined as plastic particles smaller than 5 millimeters, are the remnants of bottles, cigarettes, clothing fibers and a seemingly endless list of plastic products. They’re pushed by rain into storm drains and carried through rivers and creeks into the bay.

Nearly half of this pollution, according to the report, consists of black rubbery fragments that the study’s authors believe are from worn tires.

“These urban stormwater findings really surprised us,” said Rebecca Sutton, lead author of the study and senior scientist for the San Francisco Estuary Institute, a research center in Richmond. “We were not anticipating such high levels.”

The study represents the most comprehensive look at microplastics in California. The work is unique in quantifying just how much plastic pollution comes from stormwater runoff. The researchers estimate that rain is washing 300 times more plastic into the water than what enters through sewers and sewage treatment plants.