Is there any reason to expect there would be "toxins", given that it's just water? I can imagine how there might be accumulated toxins it's a pack of chicken breasts left in a hot car for 8 hours, but if it's water it should be fine? After all, boiling water is a tried and true way of making water safe to drink.
Yes, there are substances that slip through, but it works well enough for most cases that it's probably fine. Otherwise you get into weird edge cases like "what if there are prions in the water?!?" or whatever.
Heavy metals are a big problem, especially from cheap brass fittings common in outdoor water hoses.
Indoor plumbing, by contrast, uses copper and/or plex tubing and so there’s near zero risk of metal poisoning (caveat on cheap plex fittings- don’t do that.)
