SAFETY OF COPPER

Copper is one of a few metallic minerals which are essential for normal functions of several processes in the human body. It is estimated that humans digest about 1 mg of copper per kg of body weight daily. Depending on the copper content and form of copper, 15 to 97% of the copper is absorbed in the stomach and small intestine. Various copper transporters move the ingested copper through cell membranes, after which copper binds to albumin, glutathione, and amino acids. The primary site of copper uptake is the liver, where it is incorporated into copper-dependent proteins. The liver controls copper release and thereby maintains copper homeostasis. Copper is excreted through feces, and the majority of fecal copper comes from biliary excretion. The human body utilizes copper for the innate immune response by increasing the phagocytic and bactericidal activities of neutrophils and the antimicrobial function of macrophages. Signs and symptoms of copper deficiency include anemia, neutropenia, myelopathy, and peripheral and optic neuropathy. Copper toxicity due to excess ingestion of copper is rare; however, it can lead to nausea, vomiting, hematemesis, hypotension, melena, jaundice, and diarrhea. Chronic copper excess can damage the liver and kidneys. High internal copper concentrations can result from a genetic disorder, Wilson’s disease is a rare autosomal recessive disease affecting between 1 in 30,000 and 1 in 100,000 of the population. Wilson’s disease affects the proper metabolism of copper and is associated with a reduced rate of copper excretion through bile, resulting in a toxic accumulation of the element within the liver. Clinical manifestations include hepatic (elevated serum aminotransferase levels, chronic hepatitis, cirrhosis, and hepatic failure), neurological (tremor, choreiform movements, Parkinsonism, gait disturbances, dysarthria, seizures, and migraine), ophthalmic (K-F rings and sunflower cataracts), psychiatric (depression, neuroses, and psychosis), and renal abnormalities.

Even though a high internal concentration of copper is toxic, the exogenous application of copper is considered safe to humans. Such a claim is supported by the fact that, for almost 50 years, copper intrauterine devices (IUDs) have been safely used for up to 10 years of single placements, with no reported adverse effects. Globally, copper pipes are widely used for the distribution of water because of their ability to resist corrosion. Copper is also safely used in health care for the control of Legionella and other waterborne bacteria through a copper-silver ionization water filter, in dentistry for the reduction of carries by using high copper concentrations in dental amalgam alloys, and for the prevention of foodborne diseases on copper alloy surfaces. Furthermore, the use of copper as a biocide has become indispensable and is frequently used in antifouling paints; for wood preservation; for the control of green algae in lakes, rice fields, canals, rivers, and swimming pools; and for the prevention of the fungal disease of grapes (downy mildew).

The safety of copper-impregnated textiles is studied through extensive animal studies, which all demonstrate no skin irritation or sensitization or any other adverse reaction to copper oxide-impregnated textiles. Subsequently, its safety in humans was demonstrated in various clinical trials. Contrary to microbes, human skin cells are able to metabolize and utilize copper, and consequently, the risk of adverse reactions is negligible. In contrast to human cells, microorganisms are exceedingly sensitive to excess concentrations of copper, as they cannot control their extracellular environment to allow for excretion. Other metals commonly used in health care, such as aluminum, nickel, and silver, cause harm to the environment, and even though human cells are also able to utilize aluminum and other trace metals, significant health issues have been documented. Apart from the obvious adverse effects on the respiratory tract for aluminum industry employees, aluminum drinking levels in potable water are also positively associated with the risk of cognitive impairment, dementia, or Alzheimer’s disease. The use of nickel-containing products is increasing, which led to an increased environmental burden of nickel compounds, a serious health risk for humans, as nickel is not an essential element for humans. Nickel can result in skin sensitization, lung fibrosis, poisoning of the kidneys and the cardiovascular system, and tumor formation.

Silver is applied in hygiene, personal care, and health care as silver coatings on hard surfaces, spray for prevention of sore throats, and silver-impregnated dressings for treatment of chronic wounds. The production and usage of silver nanoparticles pose a threat for the environment and humans. Environmental toxicity is caused by soluble free silver ions that are released from industrial wastes. Adverse effects on humans include permanent discoloration of the skin (argyria) or the eyes (argyrosis); liver and kidney damage; irritations of the eyes, skin, respiratory system, and intestinal tract; and strong toxic effects on the proliferation of and cytokine expression by peripheral blood mononuclear cells. As silver ions are soluble, silver-impregnated products will leach silver ions during washing or recycling. In contrast, copper oxide is nonsoluble, and copper oxide-impregnated products will therefore not pollute the environment and, as such, will have permanent antimicrobial properties.

（To be continued）

Copy from cmr.asm.org

--------------------------------------------------------------------