Workshop convened to develop expert consensus on microplastics health effects

SCCWRP and its partners have convened a multi-part science workshop to build international expert consensus on the health-based thresholds at which microplastics of different sizes, shapes and compositions can be expected to trigger adverse effects in wildlife and humans.

The Microplastics Health Effects Workshop, which began meeting in October, is intended to inform development of a comprehensive, statewide strategy for assessing exposure risks from this ubiquitous form of plastics pollution. The workshop is a response to recently enacted State legislation that calls on California to boost capacity to manage microplastics in drinking water and aquatic ecosystems.

The health effects workshop kicked off in mid-October with a weekly, five-part webinar series to share the latest science on microplastics toxicity and management options; the first webinar attracted more than 450 attendees worldwide. The workshop is hosted by SCCWRP, the San Francisco Estuary Institute and the University of Toronto in coordination with the California State Water Resources Control Board and the California Ocean Protection Council.

In a parallel effort, an international team of researchers that includes SCCWRP has been working for the past year to standardize measurement methods for microplastics.

Microplastic particles, which are widespread in aquatic environments, have the potential to bioaccumulate through food webs, to serve as an exposure pathway as chemical contaminants leach from them, and to translocate into tissues and organs.

After the workshop’s webinar series concludes in mid-November, a group of about 20 international microplastics experts will begin working to identify the key health effects of microplastics on humans and aquatic life, including prioritizing which characteristics of microplastics (e.g., size, shape, polymer) are of greatest biological concern. Microplastics are typically defined as any plastic particle up to 5 millimeters in diameter, with many of these particles too small to be seen with the naked eye.

The experts’ deliberations, which will be facilitated by SCCWRP, will result in a preliminary set of recommended toxicity thresholds for microplastics that can be linked to specific actions California managers can take. The work is expected to be completed by summer 2021.

To support the upcoming deliberations, SCCWRP is developing a database of existing toxicity data from microplastics studies around the globe. The database will help the experts quickly query and visualize toxicity data, as well as identify data gaps.

For the past year, California also has been working on a parallel study to develop international standardization of microplastics measurement techniques. This intercalibration study, which will pave the way to comprehensively monitor microplastics in aquatic environments, was an outgrowth of a spring 2019 workshop at SCCWRP to discuss how to standardize microplastics measurement methods.

Both workshops were spurred by passage of two 2018 State laws:

» Senate Bill 1422 requires the State Water Board to develop plans for measuring microplastic particles in drinking water by 2021.

» Senate Bill 1263 requires the California Ocean Protection Council to adopt and implement a statewide strategy for lessening the ecological risks of microplastics to coastal marine ecosystems, especially through research and policy changes.

For more information, contact Dr. Leah Thornton Hampton.