A few years ago, scientists started identifying a potentially major culprit in the dramatic decline of the coho salmon fishery — a chemical known as “6PPD-quinone,” a byproduct of a chemical used in automotive tires. Throughout the course of their life, tires deposit the precursor of this chemical everywhere they travel. This precursor degrades into 6PPD-q and enters the water system, killing coho in particular — a protected species under the Endangered Species Act — with great efficiency. Now, a new study from Humboldt Waterkeeper, conducted in Eureka and Arcata throughout the last few months, shows that you don’t need a huge, dense car population to generate potentially lethal concentrations of 6PPD-q — regular old parking lots seem to do it just fine. … The study comes at a time when the California Assembly is considering legislation — Assembly Bill 1313 — that would require owners of large parking lots to acquire stormwater discharge permits and mitigate their runoff.