What's BPA, and do I really need a new water bottle?

Bisphenol-a Background

BPA disrupts the normal fetal development of mice; does that mean we can expect the same effects in humans?
BPA disrupts the normal fetal development of mice; does that mean we can expect the same effects in humans?
Joel Sartore/Getty Images

If it weren't for a laboratory mishap roughly 10 years ago, it's possible you wouldn't be reading this article. But in August 1998, the geneticist Dr. Patricia Hunt was studying the ovaries of mice and noticed her data behaving strangely. For some reason, chromosomal errors leaped from 2 percent to 40 percent in the mice making up her control group. These abnormalities eventually would lead to miscarriage and birth defects. The determined cause: BPA [source: Neimark].

After running more tests, Hunt learned that all of the mice cages and water bottles were contaminated with BPA that had leached out of the polycarbonate plastic. When she replaced the plastics, the mice cells returned to normal. Her work revealed that exposure to BPA disrupts fetal development, as well as the eggs of the fetus that will be responsible for the next generation.

Since her discovery, Hunt and other researchers have become convinced that BPA is a cause for concern in humans, as well as mice. Critics of the studies linking BPA to cell damage, however, argue that the research isn't conclusive. Some point to a 2002 study showing that humans process BPA differently than mice, so we won't necessarily experience the same health effects. Others say that the BPA that finds its way into the food supply is safely below the limits set by the U.S. Environmental Protection Agency.

A plastics industry Web site called Bisphenol-A.org says BPA is completely safe unless you regularly eat 1,300 pounds (590 kilograms) of canned or bottled food a day [source: Zandonella]. The American Chemistry Council and the U.S. Food and Drug Administration seem to agree. Although the agency is reviewing its stance, it continues to downplay concerns about using products made with BPA [source: Dunham].

Other government bodies, such as the U.S. Department of Health and Human Services and the U.S. Centers for Disease Control and Prevention say that there is some concern about risks to humans who consume BPA. The differences of opinion among these factions arise partly because the ill effects of BPA are linked primarily with mice and partly because of the nature of the chemical itself.

BPA is a difficult substance to nail down; it doesn't behave like a typical toxin. While other chemicals labeled as toxic have clear-cut impacts (asbestos exposure leads to cancer, lead poisoning causes reduced mental capacity), BPA is sneakier. Rather than harm the body outright, BPA is an endocrine disruptor. It changes the way our body's hormones function, mimicking our own natural hormones -- in this case, estrogen.

Estrogen can alter the behavior of more than 200 genes, which control the growth and repair of nearly every organ and tissue in the body [source: Environmental Working Group]. Among other things, estrogen affects fetal development, cell structure and the onset of puberty, and your body's cells are highly sensitive to even tiny changes in estrogen levels.

Studies show that doses of BPA between 2 and 20 micrograms per kilogram of body weight alter the reproductive system of male mice. Babies fed canned formula heated in a polycarbonate bottle may consume that amount in just one day [source: Neimark]. So while some early toxicity studies done on BPA determined that high doses were safe, it's important to remember that BPA doesn't behave like your average toxin. Scientists aren't sure why, but high amounts of BPA don't always seem to affect genes the same way low doses do. It sounds counterintuitive, but with BPA, it turns out that less is actually more [source: Zandonella].

Should you, the consumer, swear off all plastics? Probably not. Learn some more sensible recommendations next.