Copper is an essential trace element for most plant and animal species, including man. Its deficiency is characterized by specific biochemical and pathological lesions. The customary adult daily diet provides adequate copper to prevent signs of deficiency. Both copper deficiency and chronic copper intoxication are relatively rare.
The absortion of copper is limited to about one third to one half of that ingested under usual circumstances. When large amounts of copper are ingested, the absorptive mechanism becomes saturated and much of the copper remains unabsorbed. Further limitations are imposed by competition for absortion with cadmium and zinc, by organic complexing with ascorbic acid, and by the alkalinity of intestinal contents. Much of the copper that is absorbed is later excreted in the bile so that more than 90 percent of ingested copper is found in feces.
Cupric gluconate, cupric sulfate and cuprous iodode are GRAS in foods for specified purposes: cupric gluconate as a nutrient and/or dietary supplement; cupric sulfate in paper and paperboard products used in food packaging; and cuprous iodide as a source of dietary iodine in table salt.
About 2mg copper per day is required by the average adult with an acceptable daily intake of 0.5mg per kg body weight or about 30mg recommended by international authorities. About 2 to 4mg copper per day are supplied as natural ingredients in the normal diet. Copper added to food in the form of cupric gluconate is estimated to be about 0.005mg per capita daily. The amounts added as cupric sulfate or cuprous iodide are unknown but are believed to be less than that from cupric gluconate. Thus, the normal diet supplies several hundred times the amount of copper added to foods. The amount of anions ingested form copper salts added to foods is negligible compared with that produced physiologically or found in normal diets.
Animal toxicity with copper salts was observed only with quantities several orders of magnitude greater than that used as food supplements.
Cupric gluconate, cupric sulfate and cuprous iodide were all nonmutagenic in various microbial tests.
Cupric gluconate and sulfate, as well as other copper salts tested, were noncarcinogenic when given by mouth or parenterally. No reports of carcinogenicity studies on cuprous iodide were available to the Select Committee.
Cupric gluconate produced teratogenic effects in the chick embryo, but not in mice or rats. Cupric sulfate was embryotoxic and teratogenic when injected in large amounts into pregnant hamsters.
In light of these considerations, the Select Committee concludes that: There is no evidence in the available information on copper (cupric) gluconate or copper (cupric) sulfate that demonstrates or suggests reasonable grounds to suspect a hazard to the public when they are used at levels that are now current or that might reasonably be expected in the future.
There is no evidence in the available information on cuprous iodide that demonstrates or suggests reasonable grounds to suspect a hazard to the public should it be used at the level and in the manner now authorized.
There is no evidence in the available information on copper (cupric) sulfate that demonstrates or suggests reasonable grounds to suspect a hazard when it is used as an ingredient of paper and paperboard materials in food packaging at levels that are now current or that might reasonably be expected in the future.