Canada First to Label ‘Bisphenol A’ As Officially Dangerous

[depakid]

One of the things these articles usually leave out is the reason why endocrine disrupters (and in the case of BPA -and estrogen mimic) show effects at very low exposure levels (and can be much less harmful at higher levels).

The usual "rule of thumb" in toxicology, passed down from the middle ages is that "the dose equals the poison." The more one is exposed to, the greater the effects. Not so with hormones- they often follow a non-monotonic dose response curve- not a linear one. The inverted "U" shape of the dose response is due to the fact that after a certain level, the body's feedback mechanisms come into play, neutralizing the hormone's impact.

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Health Canada is calling bisphenol A a dangerous substance, making it the first regulatory body in the world to reach such a determination and taking the initial step toward measures to control exposures to it.

Bisphenol A, or BPA, is one of the most widely used synthetic chemicals in modern industry. It is the basic building block for polycarbonate, the see-through, shatter-proof plastic that resembles glass, and is also used to make the epoxy resins lining the insides of most tin cans, along with some dental sealants, sports helmets, and compact discs.

“Bisphenol A is in every Canadian home. It threatens the health of every Canadian. Moving against it would be a hugely significant victory for public health and the environment,” said Rick Smith, executive director of Environmental Defence, a group that has been campaigning for a ban on the chemical from food containers.



U.S. tests have found that more than 90 per cent of the population carries in their bodies trace residues of the chemical, whose molecular shape allows it to mimic the female hormone estrogen. Small amounts of BPA can leach from food and beverage containers during use, such as when they are heated, exposed to harsh dishwashing chemicals, or contain acidic substances. Health Canada is testing Canadians’ BPA levels, but the results will not be available for several years.

In response to concerns over the safety of BPA, many specialty retailers, including Mountain Equipment Co-op, have pulled polycarbonate plastic containers from their stores, and BPA-free bottles are been flying off shelves, creating shortages. Hudson’s Bay Co. announced last month that it had “secured large quantities” BPA-free baby products, a sign of how quickly even the mass market has moved against the chemical.

Independent researchers in dozens of studies have linked trace BPA exposures in animal and test-tube experiments to conditions involving hormone imbalances, including breast and prostate cancer, early puberty and changes in brain structure, particularly for exposures during key points of fetal or early neonatal development.

More: http://www.commondreams.org/archive/2008/04/16/8330/