Research in Seattle-area creeks has discovered tire bits shedding lethal amounts of a little-known, salmon-killing chemical called 6PPD-quinone. … In December 2020, 27 coauthors published an article in the journal Science identifying 6PPD-quinone as the coho killer. Within weeks, the U.S Tire Manufacturers Association asked California officials to treat tires with 6PPD as a priority under the state’s toxic-chemical laws. Coho salmon is an endangered species in California. The California rule, once finalized, would give manufacturers of tires sold there 180 days to assess any known or potential alternatives to 6PPD in tire rubber.