The 13 largest U.S. tire manufacturers are facing a lawsuit from a pair of California commercial fishing organizations that could force the companies to stop using a chemical added to almost every tire because it kills migrating salmon. Also found in footwear, synthetic turf and playground equipment, the rubber preservative 6PPD has been used in tires for 60 years. As tires wear, tiny particles of rubber are left behind on roads and parking lots, breaking down into a byproduct, 6PPD-quinone, that is deadly to salmon, steelhead trout and other aquatic wildlife when rains wash it into rivers. “This is the...