Starting in 2021, Washington state and California laws would require that brake pads have less than 5% copper by weight. The laws are meant to make brake pads safer for salmon. Similar legislation was passed in 2010 in both states. Since it’s not a financially viable solution to sell vehicles with one type of brakes in just two states, it is likely that the Washington and California laws will change what makes up the brake pads sold in the rest of North America.
Last month, the regulators in Washington completed the rulemaking process to set up the regulations and enforcement mechanisms. Washington actually passed its law before California.
The rules were shaped by automakers, brake manufacturers and retailers. These two laws have provisions that forbid the use of asbestos, lead, hexavalent chromium and other toxic chemicals in brake pads beginning in 2014. The copper in brake pads function as a friction material so that the vehicle will be brought to an efficient stop. Each time that a driver hits the brakes, a small portion of the copper-laden material is left on the road.
The copper would later end up in waterways where marine wildlife, including salmon, is affected. According to a Washington Department of Ecology report in 2011, about 21% of the copper (37 metric tons) that's deposited into Puget Sound each year is the result of the brake discharge.
David Baldwin, a research zoologist at the federally funded Northwest Fisheries Science Center, said that salmon will be prevented from finding food or evading predators when there’s at least 5-10 micrograms of copper per liter of water. [source: Automotive News - sub. required]