How do you know the copper in runoff is from brake pads? What about other sources like pipes, or pesticides, or naturally occurring copper?
• A: Our studies of San Francisco Bay included estimates of copper releases from a comprehensive inventory of non-brake pad sources, including architectural copper, copper in pesticides applied to land in urban areas, copper in agricultural land applications of pesticides, copper in algaecide treatment of surface waters, copper from pressure-treated wood preservatives, copper in marine antifouling paint, copper in pool, spa, and fountain algaecides, copper in fertilizers, copper releases from industrial facilities, copper in industrial runoff and industrial releases to surface waters, copper in industrial air emissions, and copper in domestic water discharged to storm drains. We also took naturally occurring copper into account. These sources were not as important as brake pads in highly urbanized watersheds. Our studies indicated that copper from brake pads accounted for, in some cases, more than half of the human generated copper coming off of highly urbanized watersheds.
