How freaked out should I be?
The town is recommending that everyone switch to bottled water for all their drinking and ice for a while. I am honestly freaking the heck out about the water we have already consumed. More realistically, do I need to totally avoid all of the water from the tap for the foreseeable future? Should I be cooking with bottled water? Making ice with bottled water? Etc?
Factually. What am I looking at?
All I can go off is Erin Brockovich, so I would say use bottled water at the very least for drinking and cooking.
The US has no national maximum level for hexavalent chromium though the EPA is trying to get one.
You can take a look at this Health Canada paper which seems to be proposing a maximum amount of 0.1mg/L.
Inhalation seems to be the most dangerous way to be exposed.
I’m not an expert, but I did some research because there is also Chr6 in my town’s water supply. Your stomach acid pretty much takes care of it, though you can absorb some through mucus membranes. Inhalation is the real danger so showers (steam/mist) might be a bad idea–if you google you’ll see a lot of safety information for workers in places where it’s present as vapor. I spoke to the woman in charge of water quality where the Erin Brockovich thing happened, and based on the levels in our water she said adults should be fine, for infants you might want to use bottled water for formula.
The danger level depends on the amounts, obviously. Telling people to use bottled water might be a CYA move, or it might not.
If it were me, I would assume that the Cr levels would be harmful over a period of years, but exposure for a few days would not be. There are a lot of places in the world (like Hong Kong) where people drink bottled water because of heavy metal content, but it is perfectly fine for a tourist to drink it for a few days. Daily exposure over a lifetime would be be cumulative, but your body can deal with a few days of low levels.