Copper compounds

Copper is one of humanity's oldest metals, with archaeological evidence of copper use stretching back 10,000 years — it was the first metal smelted and the basis of the Bronze Age when alloyed with tin. [1] Today copper compounds are produced from copper ore mining and smelting operations worldwide (global production exceeds 20 million tons per year of refined copper), and a wide range of inorganic copper salts (copper sulfate, copper chloride, copper oxide, copper nitrate, copper arsenate) and organic copper compounds (copper naphthenate, copper 8-hydroxyquinolate) are manufactured for diverse applications. Industrial uses include copper sulfate as a fungicide and algicide for swimming pools, ponds, and agriculture; copper oxide as a pigment and wood preservative; and copper naphthenate as a wood treatment. Copper's biocidal properties arise from the same mechanism that makes it toxic at high doses to organisms — redox cycling of Cu(I)/Cu(II) generates hydroxyl radicals (Fenton-like chemistry) that damage cell membranes, proteins, and DNA. [2] The EPA's N100 HAP category includes all copper compounds except copper phthalocyanine dyes. Emissions come primarily from copper smelters, refining operations, chemical manufacturing, wood treatment facilities, and agricultural use. Mining operations that generate acid mine drainage can mobilize copper into streams at concentrations acutely lethal to fish and macroinvertebrates. [3] Copper is also released from household plumbing in soft, acidic water systems, and lead-copper rule requirements reflect this.

Occupational exposure occurs for copper smelter workers (inhalation of copper fumes and dusts causing metal fume fever), mining workers, agricultural applicators of copper-based fungicides, and wood treatment workers. General population copper intake is primarily dietary (seafood, nuts, seeds, organ meats are copper-rich foods; recommended daily intake is about 900 µg/day). Drinking water from copper pipes in acidic water systems can contribute meaningful copper intake, particularly in infants. Swimmers in copper sulfate-treated pools or ponds have dermal and incidental ingestion exposure.

While copper deficiency causes serious health problems (anemia, neurological dysfunction, connective tissue disorders), excess copper — particularly from industrial exposures — causes liver damage, hemolytic anemia, and kidney failure. [2] Copper sulfate ingestion causes severe gastric irritation and can be lethal at doses above 1 g. Copper fume fever in smelter workers is an acute inflammatory lung condition similar to metal fume fever. Wilson's disease is a genetic disorder of copper overload that illustrates the consequences of chronic copper accumulation in liver and brain. Aquatic toxicity is a major concern: copper is extraordinarily toxic to algae, fish, and invertebrates at concentrations in the low µg/L range.

Copper smelter workers, copper mining workers, brass foundry workers, and workers in copper chemical manufacturing have the highest occupational exposures. Agricultural workers applying copper sulfate fungicides face dermal and inhalation risk. Infants fed formula made with copper-rich tap water (acidic water conditions) are a sensitive population for dietary overexposure. People with Wilson's disease or other conditions of impaired copper excretion are at risk from normal exposure levels.

1. In homes with copper plumbing and acidic water, run cold water for 30–60 seconds before drawing water for drinking or formula preparation — especially in the morning after water has sat in pipes overnight. 2. Test tap water if you have copper pipes, soft water, or an older home. 3. Agricultural workers using copper sulfate should wear appropriate PPE (gloves, eye protection, respirator) and observe buffer zones near waterways. 4. Industrial workers in copper smelting should use respiratory protection against copper fumes and dusts. 5. Do not use copper sulfate in garden water features with fish — even low concentrations are lethal to fish.