I have a plastic water bottle I've been using for a year, and even though I wash it regularly in the dishwasher, it gives off this weird moldy smell. I've tried white vinegar but it always comes back. What's happening chemically? Is it dangerous to keep using it?
Plastic, especially in the dishwasher, creates micro-scratches where bacteria and mold settle in comfortably and you can't reach them with normal washing. It's not really some complicated chemical thing, it's just that you've got a little ecosystem that's developed in there and white vinegar kills the bugs but not deep enough. You're not in immediate danger, but honestly after a year with this persistent smell, it might be time to replace it - a stainless steel or glass water bottle would probably give you less headaches in the long run.
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