My literature search has returned with several articles re the toxicity of copper salts used in agriculture, mostly spraying grapes, cucurbits and tomatoes. A few cases of 'vine-sprayers lung' have been reported. Copper is present in all foods and we each consume on average 1.2mg/day. It is excreted in the faeces. When copper is sprayed on to foliage it is not absorbed by the plant so won't appear in your spuds. When used as a varroa treatment it did not harm the bees! High levels in the soil can harm earthworms - but the foliage on my spuds is so dense that I doubt if much reaches the soil and the foliage is removed from the plot after harvesting.
I found the articles very difficult to understand despite having a degree in Natural Sciences! Try this one if you have an hour to spare.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7009614/