The Environmental Working Group just released a report saying that tap water in many U.S. cities has high levels of the carcinogen hexavalent chromium
on the list of cities with the highest concentrations? San Jose, CA, the city whose tap water I consume every freakin' day. California has proposed, but not yet enacted, a safe limit for hexavalent chromium of 0.06 ppb. San Jose's water has slightly more than 22 times that amount.
We do filter our tap water in various ways, but I don't think any of them involve reverse osmosis, which appears to be the reliable method for removing hexavalent chromium.
I'm not entirely clear yet on how much I should be worried about this. I'm not certain that drinking tap water contaminated at this level exposes me to more risk than any number of other things I routinely do each day. But I'm not pleased.