There are different kinds of plastic and accordingly they discharge dangerous chemicals. On every plastic bottle there are special signs printed on bottom that shows whether the bottle is dangerous or not.
1 or PET or PETE - safe for a single use only
3 or 7 or PVC and PC - release toxic chemicals
2 or 4 or 5 and PP - safe for multiple uses
Plastic bottles are a rich source for bacteria
According to scientists, drinking water from a used plastic bottle is almost the same as drinking from a dog’s water bowl. It is said that the bacteria regularly grows in the plastic bottles. It is better to not drink from them or regularly washing them with warm soapy water.
Check the bottles neck regularly
The most bacteria on a plastic bottle is found on its neck. We swallow the germs present in there by sipping from the neck. It’s better to sip from a straw then by its neck.