<P> In case reports of humans intentionally or accidentally ingesting high concentrations of copper salts (doses usually not known but reported to be 20--70 grams of copper), a progression of symptoms was observed including abdominal pain, headache, nausea, dizziness, vomiting and diarrhea, tachycardia, respiratory difficulty, hemolytic anemia, hematuria, massive gastrointestinal bleeding, liver and kidney failure, and death . </P> <P> Episodes of acute gastrointestinal upset following single or repeated ingestion of drinking water containing elevated levels of copper (generally above 3--6 mg / L) are characterized by nausea, vomiting, and stomach irritation . These symptoms resolve when copper in the drinking water source is reduced . </P> <P> Three experimental studies were conducted that demonstrate a threshold for acute gastrointestinal upset of approximately 4--5 mg / L in healthy adults, although it is not clear from these findings whether symptoms are due to acutely irritant effects of copper and / or to metallic, bitter, salty taste . In an experimental study with healthy adults, the average taste threshold for copper sulfate and chloride in tap water, deionized water, or mineral water was 2.5--3.5 mg / L . This is just below the experimental threshold for acute gastrointestinal upset . </P> <P> The long - term toxicity of copper has not been well studied in humans, but it is infrequent in normal populations that do not have a hereditary defect in copper homeostasis . </P>

Select the primary functions of copper in the human body