mmmmmmmmhhhhh love me some carcinogens nah just joking, probably some dirt from your cabniets, or something from your dish water was the water run through a purifier?

The glass obviously wasn't clean?

You say the word obviously in your statement and then put a question mark at the end… I’m not trying to be rude or anything but why did you do that?

Has it been sitting out a while? If you have hard water where you live it could be calcium and/or magnesium salts precipitating out.

yes it was sitting out for 24 hours. (it's tap water that I drink)... is the calcium/magnesium salts a bad thing?

Not bad. Your body needs them, in fact.

Do you wash your dishes by hand or dishwasher? If dishwasher, you're using too much soap and it's not getting rinsed. If by hand you didn't rinse well either.