How does water become toxic?
Our body is made up of about 60% water. Needless to say, water is essential for our survival. But what if the water you are drinking isn’t exactly good for you? Water, itself, doesn’t spoil or expire. It only becomes bad due to external factors.
Is your water contained in glass, metal or plastic? Generally, the best container is non-toxic glass because there are less chances of chemicals leeching into the water. If your water container is plastic, then you have to worry about chemicals leeching into the water you are drinking due to prolonged storage in less than ideal conditions. Chemicals such as maleates and fumarates, which are known potent endocrine disruptors (hormonally active chemicals) which are harmful for children, pregnant women and women of child-bearing age.
The storage conditions:
Was your water stored under direct sunlight or in the ref? A water bottle that has been opened and drank from would have some sort of bacteria from saliva. Thus, if you leave that bottled water under direct sunlight, then I wouldn’t recommend you drinking from that bottle after 24 hours since heat helps bacteria multiply.
To sum it up, you can go ahead and drink the water that has been left in a bottle for 24 hours, but consider the conditions mentioned above. Better safe than sorry.