As you know chemical released by plastic water bottles can cause cancer (It is not the water that affects you a but the chemical released from the bottle) How to avoid: Check the bottom of the bottle there should be a triangle sign and there will be a number on it. If the number is higher than or equal to 5 --> then this bottle is safe to use. Numbers under 5 will release the chemical. For most bottled water, the number is 1. Remember to check and stop reusing those bottles. Please pass on this information to your friends.
