I zest the peels often and enjoy a gin and tonic with lime, would buying organic or from a specific producer help avoid it? The cost should be minimal for these items.
It appears that the highest amount of Tiabendazole found is 0.79mg/kg so I would guess on an individual rind it would be roughly 0.1mg if that. Given dosage amounts seem to be about 25mg/kg/day I would guess it would take an obscene amount of it to cause any sort of bodily reaction. Wouldn't this concern be on par with consuming things that contain deadly things but in ppb or ppt quantities?
"Wouldn't this concern be on par with consuming things that contain deadly things but in ppb or ppt quantities?"
It's not going to be enough to be toxic to humans. The issue is whether it's either introducing antifungal resistant fungi into your body, or causing fungi already in your body to become antifungal resistant.
http://en.wikipedia.org/wiki/Enilconazole
http://en.wikipedia.org/wiki/Tiabendazole