Copper

Copper has been used by humans for over 10,000 years — it is one of the first metals smelted — and its conductivity and corrosion resistance made it the standard plumbing material throughout the 20th century [1]. Before widespread adoption of PVC and CPVC pipes, virtually all US plumbing was copper, and a significant fraction still is today. The problem is water chemistry: corrosive water — water that is soft (low mineral content), slightly acidic, warm, or stagnant — eats copper from the inside of pipes, releasing dissolved copper ions into your drinking water [2]. Lead-free solder introduced after 1986 to replace lead-tin solder sometimes uses copper-silver alloys that can also contribute. Water utilities add corrosion inhibitors (usually orthophosphate) to minimize this leaching, but the effectiveness depends on proper application [3].

Drinking water from copper plumbing is the primary exposure source above dietary levels for most Americans [1]. The first water drawn from a tap after several hours of stagnation — such as first thing in the morning — has the highest copper concentrations because water has been sitting in contact with copper pipes overnight. Corrosive water from acidic well water, soft water regions, or water that lacks adequate corrosion inhibitor treatment can leach copper at significant levels [2]. Dietary copper is essential and widely distributed in food (liver, shellfish, nuts, legumes, chocolate), and most Americans get adequate copper from food without any excess. Infant formula prepared with copper-rich water can deliver excess copper to infants [3].

Copper at low essential intakes is required for multiple enzymes, iron metabolism, and neurological function [1]. At excess concentrations from drinking water, copper causes GI effects acutely (nausea, vomiting, diarrhea — the classic symptom of copper toxicity) and liver damage with chronic high intake. Wilson's disease — a genetic disorder where copper metabolism is impaired — demonstrates the severe hepatic and neurological damage that occurs when copper accumulates unchecked [2]. Infants are particularly sensitive: their livers are less capable of regulating copper accumulation, and Indian childhood cirrhosis — a severe liver disease in infants — has been linked to copper-contaminated formula in several historical outbreaks. The EPA action level for copper in drinking water is 1.3 mg/L [3].

Infants fed formula prepared with tap water from copper plumbing in corrosive-water regions are at highest risk [1]. People with Wilson's disease or other conditions impairing copper metabolism are sensitive to dietary copper at normal or above-normal intakes. Residents in soft-water regions (much of the Northeast and Northwest) with copper plumbing and corrosive water have the highest household tap water copper concentrations [2]. People who drink the first draw of water in the morning before flushing their pipes receive the highest copper concentrations [3].

Flush your tap for 30–60 seconds in the morning before drinking or using water for cooking — running the tap until the water is cool displaces copper-rich standing water from pipes [1]. Use cold water (never hot) for drinking and cooking — hot water leaches more copper from pipes. If you have infants drinking formula, use a certified NSF/ANSI Standard 53 filter certified for copper reduction on your kitchen tap, or use filtered or bottled water for formula preparation [2]. Test your water for copper if you have well water or if you live in a soft-water region with older copper plumbing. Corrosion inhibitors added by utilities reduce leaching; if your utility reports high copper, contact your health department [3].