Rumors have been surfacing for a while about the ill health effects of lexan plastic bottles, such as the popular blue-topped Nalgene.
In the past month alone I've heard two people off-handedly remark that the plastic breaks down into toxins.
It sounded like an urban myth, like the old razor in the apple story or the alligators in the sewer.
So I checked into it.
It seems there is some evidence that normal wear and tear can break the plastic down, releasing bisphenol-A (BPA), a chemical that mimics the hormone estrogen that could cause genetic abnormalities in developing fetuses.

An informative piece in Sierra magazine details how Patricia Hunt, a professor and researcher at Case Western Reserve University in Cleveland, found out about the plastics during an unrelated study. A lab tech at Hunt's lab was cleaning the lexan trays in mouse cages with a harsh detergent. Shortly after, Hunt's lab suddenly noticed an alarming defect in the mice. The defect, called aneuploidy, is an abnormal loss or gain of chromosomes.The lab did tests and traced the defects to the effect of the harsh detergent on the Lexan.

Lexan's maker, Nunc International, has said the plastic is perfectly safe. Obviously, since many people use them and still lead healthy lives, they fall somewhere short of cyanide on the safe/unsafe spectrum.
Still, if you value your alleles (those little pairs of chromosomes that hold all our genetic goodies) it might be a good idea to hand-wash plastic bottles with a mild soap.

Theo Colborn, author of a book about how chemicals affect our genes called Our Stolen Future, said people with developing endocrine systems (i.e. unborn babies and their mothers) should be especially careful.

-Dave