N&Q4 - Bisphenol A (as at May 30, 2008)
What does current research suggest about exposure to the chemical?
Studies in peer-reviewed journals have indicated that even at low doses, BPA can increase breast and ovarian cancer cell growth and the growth of some prostate cancer cells in animals. Yale researchers found that when BPA was administered to pregnant mice, it altered a gene responsible for normal uterine development. The study, published in the Journal of the Federation of American Societies for Experimental Biology in January 2007, theorized that, "If pregnant women are exposed to the estrogen-like properties found in BPA, it may impact female reproductive tract development and the future fertility of female fetuses the mother is carrying."
A study published in the journal Chemistry & Biology in 2006 showed that "modified versions of bisphenol A likely to be formed in the body do stimulate breast tumour cell growth in vitro," according to a statement by Theodore Widlanski, the study’s lead researcher and a biochemistry professor at Indiana University. "Enzymes present on the surface of breast tumour cells appear to convert the modified BPA back into BPA."
He cautioned that the study, by researchers at Indiana University and University of California at Berkeley, did not indicate products such as bottled water aren’t safe. "We have only demonstrated a possible mechanism that explains what people have been speculating about for years." he said. "It doesn’t mean that your bottled water is any less safe today than it was yesterday. It just means that if it isn’t safe, we might be able to explain why."
A University of Cincinnati research team published a study in the journal Endocrinology in 2005 showing bisphenol A may disrupt important effects of estrogen in the developing brains of rodents. They worked with rats at a period in their development equivalent to the third trimester of human fetal development, through to the first few years of childhood. At low doses, bisphenol A appeared to affect the normal activity of estrogen.
"We have now shown that environmental estrogens like BPA appear to alter, in a very complicated fashion, the normal way estrogen communicates with immature nerve cells," said lead researcher Jay Belcher in a statement. "The developmental effects that we studied are known to be important for brain development and also for normal function of the adult brain."
In 2003, researchers at Case Western Reserve University in Cleveland published in the journal Current Biology the results of studies of low levels of exposure of the chemical on the reproductive systems of mice. They found that the mice’s eggs showed increased rates of two chromosome abnormalities. In normal mouse or human eggs, the chromosomes line up, ready for the egg to split in two when fertilized. But in many of the eggs of the exposed mice, the chromosomes were not aligned. In addition, the egg cells of the exposed mice often had too few or too many chromosomes.
These kinds of chromosomal abnormalities are the leading cause of birth defects and mental retardation in humans, according to Patricia Hunt, the study’s lead researcher and a professor of genetics.
What is Health Canada’s take on the chemical?
Health Canada’s evaluation of bisphenol A, launched in Nov. 2007, included a review of human and animal studies around the world and research into how much of the chemical is leaching from consumer products.
The study is part of a more comprehensive review of about 200 chemicals the federal government has singled out for more careful study.
Health Canada’s assessment primarily focused on BPA’s effect on newborns and infants up to 18 months of age. The ministry determined the main source of exposure for newborns and infants is through the use of polycarbonate baby bottles when they are exposed to high temperatures, and the migration of bisphenol A from cans into infant formula.
While Health Canada says newborns and infants are exposed to bisphenol A at levels below what is considered to pose a risk, it said in April 2008 that it plans to ban baby bottles containing BPA. Health Canada also intends to work with industry to reduce the use of BPA in cans containing infant formula.
"We’ve concluded it’s better to be safe than sorry," Health Minister Tony Clement told reporters when he announced the ban on polycarbonate baby bottles containing bisphenol A in April 2008.
In May, Health Canada assured consumers cans of tomato sauce and tins of apple juice are safe to eat and drink, after testing detected low levels of the chemical bisphenol A in the products.
The federal agency issued a statement saying trace amounts of the chemical were not cause for concern.
"A preliminary examination of the results show that levels of BPA reported as migrating from canned food sources are very low, in the range of parts per billion [one billionth gram in a gram of food] and are consistent with levels of BPA reported in canned foods sold worldwide."
An average Canadian would need to eat several hundred cans of food daily to be at risk, Health Canada said.
(CBC, June 2, 2008)
