07.apr.07
Globe and Mail
Martin Mittlestaedt
http://www.theglobeandmail.com/servlet/story/RTGAM.20070406.wbisphenolA0407/BNStory/Front/home/?pageRequested=all
Bisphenol A is, according to this story, ingested by practically everyone in Canada who eats canned foods or drinks from a can or hard plastic water bottles.
Now a controversy is raging over the safety of widespread public exposure to the chemical, which is known to act like a synthetic female sex hormone.
At the heart of the intense debate over bisphenol A is that it challenges the main tenet of modern toxicology, the idea that the dose makes the poison, a principle credited to the 15th-century Swiss alchemist Theophrastus Paracelsus.
Under this principle, a two-pack-a-day smoker is more at risk of cancer than a one-pack-a-day user, and the belief that rising doses make a substance more dangerous is the basis of all government regulations that seek to set safe exposures for harmful chemicals.
It seems obvious that a high dose of a poison would be more dangerous than a lower one, but bisphenol A is creating a stir because it doesn't follow this seemingly common-sense rule. Researchers say this oddity results from the fact that bisphenol A isn't a conventional harmful agent, such as cigarette smoke, but behaves in the unconventional way typical of hormones, where even vanishingly small exposures can be harmful.
This is why some environmentalists and scientists contend that bisphenol A, which leaches in trace amounts from food and beverage packaging, is among the scariest manufactured substances in use, an eerie modern version of the vaunted lead water pipes by which ancient Romans were unknowingly poisoned.
Extrapolating from the results of animal experiments, they suspect bisphenol A has its fingerprints all over the unexplained human health trends emerging in recent decades hinting at something going haywire with sex hormones, including the early onset of puberty, declining sperm counts, and the huge increase in breast and prostate cancer, among other ailments.
But manufacturers — which include some of the world's biggest chemical companies — insist bisphenol A is harmless and say those claiming otherwise have it wrong.