Study illustrates power of non-targeted analysis to help identify toxic chemicals

A team of researchers that includes SCCWRP has completed a high-profile, first-of-its-kind case study demonstrating how to use an analytical method known as non-targeted chemical analysis to help identify specific chemicals in complex environmental mixtures as the cause of observed toxicity.

The multi-year investigation, which focused on mass seasonal deaths of coho salmon in the Pacific Northwest, illustrates the power and potential of using non-targeted chemical analysis to help solve some of the most vexing management challenges in environmental toxicology.

During the study, which was published in December by the journal Science, researchers used non-targeted chemical analysis to zero in on a specific, previously unknown chemical responsible for the coho salmon toxicity in the Pacific Northwest. SCCWRP has been working to advance non-targeted chemical analysis for the past decade.

The chemical responsible for the Pacific Northwest salmon die-offs – 6PPD-quinone, a derivative of a ubiquitous preservative used in tire manufacturing – was not on researchers’ radar at the beginning of the study, underscoring the value of using non-targeted chemical analysis in tandem with more established chemistry and toxicology methods to identify specific toxicity culprits.

Pinpointing a precise cause of observed toxicity can be a significant management  challenge in urban aquatic environments, which are commonly home to thousands of individual chemical contaminants. When environmental managers observe toxicity, such as during sudden fish die-offs or via standard toxicity testing in a laboratory, their options for intervening are limited until they can identify the specific chemical responsible.

Non-targeted chemical analysis uses high-resolution mass spectrometry technology to identify specific chemicals in complex mixtures by their physical and chemical properties, enabling researchers to cast a much wider net when investigating the cause of observed toxicity.

In addition to exploring the potential of non-targeted chemical analysis for novel chemical identification, SCCWRP also is investigating the potential to use the technology as a management strategy for pinpointing the origins of widespread fecal contamination in Southern California waterways during wet weather.

The ongoing effort involves using non-targeted chemical analysis to produce overall patterns in the chemical makeup of contaminants in wastewater and roadway runoff. Known as “fingerprints,” these highly visual readouts have the potential to distinguish wastewater from roadway runoff, which could pave the way for water samples to be chemically fingerprinted as a management strategy for investigating the origins of fecal contamination. Initial findings were published in October by the journal Environmental Science & Technology Letters.

California managers already have taken action in response to the Pacific Northwest salmon study. California’s Department of Toxic Substances Control announced in January that it will begin engaging with tire manufacturers on the 6PPD-quinone issue as part of a broader investigation targeting zinc, which is another chemical used in tire manufacturing that also is toxic to aquatic life.

6PPD-quinone is an oxidation product of 6PPD, a chemical additive in tires that prevents the rubber from being damaged by ozone. As tire wear particles containing 6-PPD are shed onto roadways,  6PPD-quinone can end up in nearby waterways. Even very small concentrations of about 1 microgram per liter can be lethal to salmon.

For more information, contact Dr. Bowen Du.