Bisphenol-A (BPA), a chemical found in some plastic bottles has been shown to affect egg development. Researchers at Brigham and Womens Hospital/Harvard Medical School showed that the left over eggs from IVF were less likely to develop properly if there were exposed to high levels of BPA. Click here from the story from the Boston Globe. Click here for the original article from the journal Human Reproduction. It is not clear whether the low levels seen in most plastic bottles is enough to cause any problems though.