I agree wholeheartedly with Sarah. To me, the biggest threats to our health are:
-over-eating/eating the wrong foods,
-lack of exercise (for your average American, not us ULers...).
Life expectancy has increased at an astronomical pace, due to better hygeine, 'better' nutrition (hey, over-nutrition is better than under-nutrition after all), and of course better medicine (which happens to include a lot of drugs/chemicals which also hurt a lot of folks as well as help many). A large part of these advances is due to having better storage of food, water and drugs. It seems clear to me that the pros outweigh the cons by a large margin. This doesn't mean I am complacent, and if there is a consumer based push for better packaging, I'm all for it.
I put stress at the top of my list, but it's just my personal opinion. When you're chronically stressed, you don't sleep as well, you don't eat as well, you are less inclined to exercise, plus all those stress hormones floating around HAVE to be worse for you than trace amounts of estrogenic chemicals in your water bottle or tin can.
I have a friend who was stressing over this issue, and wanted to know what was safe to drink out of. I looked at her dumbstruck, and said "You are taking HRT! I think you have better things to stress about" This is true even more for women taking, eg estrogenic contraceptives. Drinking alcohol will have more impact on your estrogen levels than drinking water out of a plastic bottle. So will obesity, and the list goes on...