Copper in Wines and Vineyards: Taste and Comparative Toxicity to Pesticides

Vines are among the crop plants that are most heavily treated with pesticides. Two of the authors have previously characterized the taste of pesticides in water and wines. In light of a current debate, in this paper we have summarized data on the taste and potential toxicity of Copper (Cu) in wines, as well as on the necessity of its use in vineyards, and in organisms in general. Copper has been considered as an organic pesticide. We underline here that it is protective of life and only toxic by saturation of the capacity of physiological processes. It is found at an average dose of 0.15 mg/l in organic wines, and at up to 1.5 mg/l or more in non-organic ones, probably because of its presence in the composition of synthetic pesticides. It is detectable in water by taste from 0.075 mg/l. Its taste is characterized in the present work. Tasters were able to detect the taste of copper in a wine spiked in a blinded manner to a level of 0.15 mg/l. When added at 1 or 1.5 mg/l it was found to clearly modify the taste of wine. At a level of 0.15 mg/l, it would be necessary for a human of 80 kg to drink 80 l of organic wine per day to reach the threshold of acute toxicity of copper. On the other hand, a medical prescription of copper can stimulate the immune system of an adult at a level of 1 mg/day. For comparison, we found that a favourably judged (awarded 100/100 in the Parker Guide) non-organic bottle of wine contained 146 ppb of boscalid, a widely used synthetic pesticide. If we consider the formulants and residues present in numerous pesticides, such as petroleum and arsenic or other heavy metals, the threshold of chronic toxicity will be reached from the consumption of 22 ml of this wine. Similar results are obtained for fenhexamid and glyphosate in Roundup, which have a considerably higher toxicity than an excess of copper. Copper cannot therefore be considered as being comparable with the synthetic pesticides derived from petroleum that are present in non-organic wines, in contrast with the recently published views of regulatory bodies. Moreover, the environmental impact of copper in organic vineyards under normal treatment appears to be positive, in that it improves biodiversity, in contrast with the impact of synthetic pesticides.