In late 2007, stores began to pull Nalgene bottles that produced a chemical called bisphenol A (BP-A), which can cause behavioral, neural, and hormonal changes in fetuses, infants, and children. I know I have also heard this chemical may cause breast cancer, prostate cancer, and other undesirable conditions and cancers. Studies have shown that old-school nalgene bottles, and many other popularized forms of them labeled 7 on the bottom, secret BPA, which mimicks estrogen. Either way, for all of you wishing to be green and using the same bottle of water everyday to take with you to work or school, here is a chart to explain what is safe and what you should avoid.
(Basically, avoid bottles or containers numbered 3, 6, and 7). Click on the image to see it in its entirety. Notice that in addition to being unsafe, number 7 bottles also are not recyclable or healthy for our environment. Again, most Nalgene bottles or those similar to them are a 7.
Nalgene also now produces a line of BP-A free bottles, and there are many other options out there for those wishing to keep using their water bottle. After finding out about this, I went home and got rid of all of my Nalgene bottles (all were 7s), and I have bought a cheap $4 bottle (32 oz.) from Target made by Rubbermaid that fits the bill perfectly (number 5). So on your way to saving the planet by reducing the amount of bottled water you use, make sure your health is safe too.
Note: My friend over at Green and Cheap blog did a follow up post on this with some more great research, so if you are interested, check out her post