Getting It Right: BPA and the Difficulty Proving Environmental Cancer Risks

S cience still has no answer on whether bisphenol A (BPA) has carcinogenic effects in humans, even as the U.S. government and retailers have banned products containing it. BPA has become the unofficial poster child for several compounds found in products that some researchers claim may be health hazards, including cancer. But critics of the BPA – cancer link say that most studies have used only animals, making extrapolating findings to humans difficult. And too often, studies that find BPA safe have been ignored. First appearing in products in the 1950s, BPA is a common chemical in homes today. It is the chemical building block for clear polycarbonate plastic, which is used in bottles, in the linings of metal food cans — including cans containing infant formula, and in other food storage containers. It is also found in paper receipts. And it ' s getting into our bodies. The 2003 – 2004 National Health and Nutrition Examination Survey (NHANES III) conducted by the Centers for Disease Control and Prevention (CDC) found detectable levels of BPA in 93% of 2,517 urine samples from people aged 6 years and older. Although the practical implications of such a mechanism remain unknown and may be speculative at best, some experts say that the effects of environmental exposures have been widely underestimated. To date, more than 150 studies have shown that BPA disrupts the hormone system and causes changes that mirror properties of cancer cells. One recent example is a study in the Sept. 1, 2011, issue of Carcinogenesis , which found that breast cells exposed in vitro to BPA undergo structural changes that enable them to proliferate like cancer cells. Exposure to BPA affects the mTOR pathway, which regulates cell growth, proliferation, motility, survival, protein synthesis, and transcription. When the mTOR signal is turned off, cancer cells do not survive, but once mTOR is activated, cells can proliferate. " It is a sort of switch that turns things off and on at the cellular level, " said lead adding that although cells exposed to BPA won ' t necessarily become cancer, any chemical that can prompt healthy cells to act like cancer cells is wor-risome. However, Goodson admits that it ' s impossible to say yet whether the same effect occurs in humans. Many researchers believe the dearth of studies on humans complicates interpretation of the fi ndings. In general, researchers understand that animal …