Helo All. Is it safe to re-use plastic bottles?!

Helo All. Is it safe to re-use plastic bottles?

Many beverages are sold in plastic bottles. In the country that i live in where the tap water is safe to drink, people use these plastic bottles repeatedly over long periods of time to store and drink water from. I suppose that it's very convenient and inexpensive to use these plastic bottles. Please explain to me if these plastic bottles are safe to store and drink water from especially over long periods of time. ~¤~ Th?nkìng ~¤~ Y?u ~¤~ F?r ~¤~ Y?ur ~¤~ ?nswèrs ~¤~

Hehe...if you lived in Australia, which I'm guessing you don't, you would have seen a documentary on tv just a few weeks or a month or so ago from "Whats Good For You" or something and they were testing people's plastic bottles that they had drunk out of for ages.
Some of these people were getting all these strange symptoms like headaches and getting sick more easily, and little symptoms, I can't quite recall in detail now though but they were things that were affecting their work. The reason was that these people had bacteria and nasty stuff in their water bottles, and a few had this disgusting green mouldy stuff growing at the bottom of their drink bottles, because they weren't washing them out, simply filling them up again and again. Mind you, these bottles were something like 6 months old, or older...
With the germs that exist in the mouth, it's a pretty bad idea to not wash them out at all.
You need to wash them out every time you use them, and just to be safe, I would not use a water bottle for more than a month. Even not that, I would go as far as not using it for more than two weeks, if I were to use it every day.
I don't understand why people don't wash plastic bottles anyway. You always wash cups at home, it's considered gross not to wash cups, even if all you drunk was water. So it's best to wash the plastic bottles and not to use them for longer than a month.