Chapter 92: Copper

INTRODUCTION

HISTORY AND EPIDEMIOLOGY

Copper is available in available in nature as elemental copper or as one of its sulfide or oxide ores. Important ores include malachite (CuCO₃⋅(OH)₂), chalcocite (Cu₂S), cuprite (Cu₂O), and chalcopyrite (CuFeS₂ or Cu₂S⋅Fe₂S₃). Chalcopyrite, a yellow sulfide ore, is the source of 80% of the world’s copper production. The smelting, or separation, of copper ores began about 7,000 years ago; copper gradually assumed its current level of importance at the start of the Bronze Age, around 3000 B.C. Smelting begins with roasting to dry the ore concentrate, which, in more modern times, is further purified by electrolysis to a 99.5% level of purity. The sulfide ores have naturally high arsenic content, which is released during the extraction process, posing a risk to those who smelt copper.

Although acute copper poisoning is uncommon in the United States, the historical role of copper as a therapeutic remains noteworthy. Copper sulfate was used in burn wound debridement until cases of systemic copper poisoning including hemolysis were reported.⁵⁰ In one report, each wound debridement procedure was associated with an 8% to 10% fall in the hematocrit. In the 1960s, copper sulfate (250-mg dose, containing 100 mg copper ion) ironically was recommended as an emetic, typically for use in children following potentially toxic exposures.⁵⁹ It was recognized for its speed of onset and effectiveness, and it compared favorably with syrup of ipecac. However, copper-induced emesis was rapidly identified to be extremely dangerous, and this practice was generally discontinued,⁶⁷ although fatal cases still occur. Copper salts are administered in religious rituals as a blue-green-colored “spiritual water,” containing 100–150 g/L of copper sulfate as an emetic to “expel one’s sins.”¹⁰⁹

Copper sulfate is used as a fungicide and algicide, and to eradicate tree roots that invade septic, sewage, and drinking water systems. Copper oxide, in combination with salts of chromium and arsenic (chromated cupric arsenate {CCA}), was used as an outdoor wood preservative, despite concerns over environmental arsenic contamination and has since been removed from the market.²⁰ Copper sulfate is the most readily available compound and is the form involved in the majority of nonindustrial copper exposures. Copper sulfate was a favorite ingredient in many home chemistry sets because of its brilliant blue color when dissolved in water. Although serious poisoning, particularly in children, led regulatory agencies in the United States to restrict its use, it accounts for the most consequential chemistry set–related toxic exposures reported in other countries.⁷⁸ Similarly, homegrown copper sulfate crystals from kits are occasionally responsible for fatal poisonings.⁴²

Acute or chronic copper poisoning occurs when the metal is leached from copper pipes or copper containers. This occurs when carbon dioxide gas, used for postmix soft drink carbonation, backflows into the tubing transporting ...