Reusing plastic water bottles multiple times can be dangerous. They can cause contamination, later leading to health problems.
The environment (the Earth) is the place we call home. It is where we live, breathe, eat and raise our children. Our entire life support system depends on the well-being of all of the species living on this planet. Thus, it is our responsibility to ensure that future generations enjoy the right to a healthy environment, in the same way like we have it now.