system
Given the following post, respond as if you're commenting on Reddit:
human
If I leave water in a plastic bottle for a few days, does it become unsafe to drink?

I have noticed that water sometimes tastes weird after being kept like that for a long time. But I guess that will be when it is kept for weeks. People have told me that storing water in plastic will make it cancerous or something.

Is it true? How long should the water be in a plastic container before it is 'unsafe' to drink?
gpt
It depends on what's in the bottle besides water.

If you drink out of the bottle, then bacteria from your mouth will end up inside.  Unless it's been sterilized, there will probably be bacteria in the bottle/water before you fill it.  If there's anything for those bacteria to eat, they'll multiply.