Guest post by Jason Pollens
The Nalgene bottle is a ubiquitous accessory among members of the progressive Jewish community. Nalgene bottles branded with institutional logos are also commonly offered as promotional items by Jewish organizations. However, there is a dirty little secret about the safety of this bottle. It turns out that most Nalgenes (the ones which claim they are indestructible) can actually do a lot of harm to you. If you look on the bottom of your Nalgene and see it has a number 7 in the triangle that means that it is made with polycarbonate plastics which are suspected to leach endocrine disruptors. (For info on other types of plastics click here.) The most worrisome chemical is bisphenol-A, a known hormone disruptor.
As Sierra Club magazine reports:

For years, scientists have been finding that endocrine disrupters like BPA can impair the reproductive organs of rats and mice, reduce sperm counts in rats, and bring about changes in tissue that resemble early-stage breast cancer, among other effects. But Nunc International, maker of Nalgene bottles, maintains that its products are “safe for use with human consumables”; cites other research that found no dangerous leaching; and points to a 2002 study in which rats fed a diet containing BPA at levels higher than those in Hunt’s laboratory suffered no apparent reproductive or developmental effects. Hunt counters that the rat study did not look at eggs or embryos. “The [plastics] industry says this is just rodent studies,” she says, “but we know that the human egg is more fragile than the mouse egg. If we wait for really hard evidence in humans, it will be too late.”

If you are using a number 7 plastic you are more at risk of birth miscarriages and defects along with breast cancer. For men the plastic can affect levels of testosterone in a negative way. The danger is most apparent when the bottle is showing signs of wear or has been exposed to heat.
There is an alternative which isn’t expensive (in some cases cheaper) and much safer. Of course there is an option of buying a water bottle with a number 2, 4, or 5 on the bottom; however the safest way to go is with a light weight stainless steel bottle. An example is the Kleen Kanteen which has served me well. In a world where we often don’t know what is best for us there is at least an easy solution for what type of water bottle we should use.