According to a recent study conducted at Tufts University (story here)…Bisphenol A exposure to unborn baby mice was seen to cause more weight gain in adulthood eating the same amount as other mice not exposed to the chemical.

Bisphenol A (BPA or 4,4'-dihydroxy-2,2-diphenylpropane) has also been known to cause the following in mice at low exposure (wiki):

• Decreased maternal behaviors
• Insulin resistance develops in 2 days, chronic hyperinsulinemia at day 4
  Prostate cells more sensitive to hormones and cancer
• Breast cells predisposed to cancer
• Decline in testicular testosterone
• Lower bodyweight, increase of anogenital distance in both genders, signs of early puberty and longer estrus.
• Increased prostate weight 30%
• Changes in breast tissue that predispose cells to hormones and carcinogens
• Permanent changes to genital tract

All I can say is WOW!!! This does not sound very good to me but it is good to note: DO NOT use polycarbonate for your hot liquids – BPA will leach out of the plastic and into your liquid!