I think some people are particularly susceptible and for others repeated exposure has an additive effect. Along with every sheep farmer I know I've fallen into a sheep bath and come to no harm as far as I know. Quite bizarrely at one time they used to add Abate to drinking water in some parts of the world. https://europepmc.org/article/med/5302335 My researched failed because I couldn't find a level of dilution of the stuff that didn't kill Daphnia Magna Strauss. Or at least I gave in and got a job because of that reason.