"Oh yeah I've read something on the Internet about that, that the plastic in the bottle breaks down and you shouldn't reuse it. So especially for these guys I'm not going to do it. "

This is one I hear often: The concern that disposable bottles, when reused, break down and release cancer-causing chemicals. You may have heard it too, thanks to widely-circulated rumors on the Internet.

One email message, for example, warns of "poisoning" from "repeated" washing and rinsing.

Another claims that drinking water from bottles left in a hot car can cause breast cancer.

And yet another says that freezing bottles can release toxic substances called dioxins.

It turns out that all these claims are false.

While there's no evidence that re-used plastic bottles are toxic or cause cancer, there is a real risk you should be aware of: they can harbor bacteria and potentially make you sick if they're not cleaned properly.

That means washing them after each use with hot soapy water—ideally using a scrubber—and letting them air dry.

It's best not to use the dishwasher, as this may melt or otherwise damage the plastic.
So go ahead and refill that water bottle without fear. Just be sure to clean it first. You'll be saving some money and perhaps helping the environment too.