Washington and California recently adopted laws that ban all but traces of copper in automotive brake pads by the year 2021. The two states say the metal gets into watersheds and hurts endangered salmon. The decision could change the way brakes are made around the world.
Copper is a great material for brakes. It's durable, and it absorbs heat and noise. But it comes with an environmental price.
"Each time a driver uses their brakes, a small amount of the material gets worn off, and when it rains, that can be washed into streams and rivers," said Ian Wesley, who's with the Washington State Department of Ecology.
About a third of the copper in some watersheds in California and Washington State comes from brakes. And copper is not good for salmon, because it wreaks havoc with their ability to smell.
Salmon release a pheromone when they perceive a threat. Other salmon react to the scent by dropping to the bottom of the water and staying there, very still.
"When they do that, it helps them avoid the predators, but if there's even very low levels of copper in the water, they can't smell this pheromone, and they continue to swim around kind of oblivious to the danger that's nearby," said Wesley.
The phased-in ban by the two states will likely affect everyone. That's partly because it's just too expensive to develop a product for one or two states.
Terry Heffelfinger is head of product engineering for Affinia Global Brake. He says European car companies still use an older style of brake that doesn't use copper. But many Americans don't like them, because they're noisy.
"They also make your wheels dust more than ceramic materials," he said.
Heffelfinger says it will take time to develop a copper-free brake as quiet and dust-free as the kind that's being phased out.
By the way, while they were banning copper in brakes, California and Washington also banned asbestos in brakes. A few non-domestic car companies still use asbestos brakes here. That ban will take effect in just three years.