A US judge will decide if, as research suggests, a chemical tyre additive is harming endangered fish species A US judge will decide if, as research suggests, a chemical tyre additive is harming endangered fish species Last week, a district judge in San Francisco, California, presided over a three-day trial brought by west coast fishers and conservationists against US tyre companies. The fishers allege that a chemical additive used in tyres is polluting rivers and waterways, killing coho salmon