Copper is a necessary trace element for human health. However, in its free, unbound and oxidized state, copper can act as a pro-oxidant and toxic element. Copper fungicides are an "allowable" chemical that can be used on organic food crops. Organically grown produce may contain copper residues from copper fungicide usage. The presence of copper fungicides may partially account for elevated hair, urine and blood copper levels in some people, as well as associated problems related to copper toxicity.
Copper toxicity is a well established health challenge. There are many people who would argue that copper toxicity is a major health concern that goes virtually unnoticed. For industrial uses, copper is used as a fungicide, in water pipes (which can and do eventually corrode, especially with acidic tap water), in swimming pools, in jewelry and in some cookware.
Copper exists in various forms. Copper fungicides such as copper sulfate contain oxidized copper. Oxidized copper cannot be used by the mitochondria. It is toxic. Theoretically, oxidized copper in the soil can be reduced and converted to Copper 1 by plant chemistry. However, topical copper fungicides, which consist of oxidized copper may be present on fruits and vegetables that you buy in stores or at your local farmer's markets. Do plant cells contain oxidized copper? This is not currently known.
Washing vegetables (even if organic) is a good idea, especially if copper fungicides have been used. However in instances like olive oil (which may contain copper fungicide residue), or other oils, there is no way to remove the residual copper.
The concern of copper toxicity from industrial sources is valid. Understanding the role of agricultural copper fungicides on human health necessitates further research.