An article in the New York Times (Feb 3, 2012) describes a proposal that requires that automobile brake pads decrease the copper content to less than 5 % by 2021 in Washington and less than 0.5 % by 2025 in California.  The copper releases during braking is said to release metal dust that harms aquatic life.   But if individual states create product standards, how will manufacturers guarantee compliance for products produced and sold across the US ? Will the toughest standards become national standards to preserve supply chain flexibility ? How should similar concerns about mercury (in automobile switches) and lead (used in automobile wheel balancing) be converted into regulatory changes ?