Salmon have been dying mysteriously on the West Coast for years.

December 3, 2020

https://www.cnn.com/2020/12/03/us/microplastics-tire-rubber-chemicals-killing-coho-salmon-scn/index.html

"Roughly 3.1 billion tires for the planet's more than 1.4 billion vehicles are produced annually".  That's lots of tires!  Thanks for the link Howard.

Thanks for the article.  From the linked article, I was asking myself how this relatively complex molecule could be distributed widely enough and at what concentrations.  I pulled this from the science paper abstract:

 "Retrospective analysis of representative roadway runoff and stormwater-impacted creeks of the U.S. West Coast indicated widespread occurrence of 6PPD-quinone (<0.3-19 μg/L) at toxic concentrations (LC50 of 0.8 ± 0.16 μg/L)."

Considering it is not the direct bi-product from the tire and microplastic sources (still requires oxidation - papers implicate ozone, however many oxidants are capable of hydroquinone to quinone oxidation) it is surprising to me that concentrations are this high and distributed as consistently as they seem to be.  If they are toxic to Coho, they should be toxic to many other species as well, and the paper indicates this is true, and is a bigger problem in used tires vs new tires (old tires = more time for the oxidation to occur):

"It is unlikely that coho salmon are uniquely sensitive, and the toxicology of 6PPD transformation products in other aquatic species should be assessed. For example, used tires were more toxic to rainbow trout (4-fold lower 96-hours LC50) relative to new tires (29), an observation consistent with adverse outcomes mediated by transformation products."

Very interesting article, especially for a process chemist interested in both fishing and green chemistry.