We haven’t pinned down the masses of any individual neutrino, and we don’t even know which ones are heavier than the others. When it comes to our ability to collect raw data, neutrinos present a triple threat: they’re incredibly lightweight (even the electron weighs over 5 million times more than all the neutrinos combined), they shift their identity as they travel (and their rate of flavor oscillation changes as they travel through different substances, so there’s no one-size-fits-all solution), and they barely interact with anything in the first place…
Bear in mind that the ultrapure water used in these things behave like an acid. There is a story of a dropped wrench, the remains of which were later found to have been completely dissolved.
I don’t think humans will suffer the same type of ion exchange that a wrench might from ultrapure water. Don’t drink from the pool and I bet you’d be perfectly safe. Someone has to have an MSDS we can check to see if it’s safe.