The buzz on bisphenol A — the controversial chemical used to make many hard plastic toys, bottles and food containers — is proving perplexing for many consumers and retailers. As the growing debate about the potential health effects of BPA rages on, consumers are left puzzled as to whether they should keep or clear their cupboards of polycarbonate products.
On the one hand, recent animal studies theorize the chemical may be linked to obesity, infertility and insulin-resistance in rodents. The federal government added BPA to Canada's toxic substances list in October 2010.
Conversely, the plastics industry vigorously defends the chemical, noting it has been used widely for 50 years.
Statistics Canada data released in August 2010 found about 91 per cent of Canadians have detectable levels of BPA in their bodies, with those between ages 12 and 19 most likely to have the chemical in them. The findings are consistent with results from international studies — BPA has been detected in 93 per cent of Americans aged six or older, and 99 per cent of Germans aged three to 14.
Health Canada had long held the chemical was not a risk to human health, but in October 2008 Canada became the first country in the world to ban the import and sale of polycarbonate baby bottles containing bisphenol A. The federal government also announced it would devote $1.7 million over three years to study the chemical.
The announcement followed an April 2008 statement by federal Health Minister Tony Clement. Clement said his department had studied the effects of the chemical and found that in most instances, negative health effects only occur at levels of bisphenol A exposure much greater than normal. But Clement expressed concern about exposing infants to the chemical.
"We have concluded that early development is sensitive to the effects of bisphenol A. Although our science tells us that exposure levels to newborns and infants are below levels that cause effects, we believe the current safety margin needs to be higher."
Clement also said Canadians can continue to use hard plastic reusable water bottles and plastic tableware, and that Health Canada "will be providing some advice on how to use them properly."
Meanwhile, the U.S. Food and Drug Administration (FDA) has said it does not consider normal exposure to BPA to be a hazard. However, on Apr. 14, 2008, the U.S. National Institutes of Health released a report that concludes that there is some concern that fetuses, infants and children exposed to BPA may be at increased risk for early-onset puberty and prostate and breast cancer.
The report also concluded there is no direct evidence that exposure to bisphenol A adversely affects reproduction or development in humans. But because of a lack of data on the effects of BPA on humans, "the possibility that bisphenol A may impact human development cannot be dismissed."
A Chinese study in 2009 found that men who were exposed to extremely high levels of BPA were far more likely to report some sort of sexual dysfunction. The study examined 164 factory workers who were exposed to 50 times more BPA than the typical North American male would come into contact with.
Although the results were described as "dramatic," researchers were quick to point out that it was unclear what the effect of lower exposure would be.
What is bisphenol A?
Bisphenol A is a chemical compound found in some hard, clear, lightweight plastics and resins. It's used in the production of various types of food and drink containers, compact discs, electronics and automobile parts, and as a liner in some metal cans. Animal studies suggest that, once ingested, BPA may imitate estrogen and other hormones, according to the National Institutes of Health.
How do I know if my container contains bisphenol A?
Some polycarbonate containers — especially water bottles — are marked with the code number 7 on the bottom, but this doesn't necessarily mean that the item contains BPA. If unsure, call the manufacturer and ask about the BPA content in the product.
Metal food cans are not labelled, making it harder for consumers to avoid those made with linings containing BPA. And since food cans are often heated during the canning process, "there's almost a guarantee some BPA has leaked into the food," says Cassandra Polyzou, program co-ordinator for toxics at Toronto-based Environmental Defence.
Polyzou said some studies have also shown tin can liners containing BPA break down more readily when they come into contact with fatty food such as fish, and acidic food such as tomatoes and apple juice. It also breaks down more readily in the presence of alcohol.
What does current research suggest about exposure to the chemical?
In January 2008, researchers at the University of Rochester released a study suggesting BPA remains in the body for longer than was previous thought. The study was published in the journal Environmental Health Perspectives.
"BPA levels appear to drop about eight times more slowly than expected — so slowly, in fact, that race and sex together have as big an influence on BPA levels as fasting time," said researcher Richard W. Stahlhut.
Another study published in September 2008, also examined BPA exposure in humans. The study, which included 1,455 American adults, found that 90 per cent of participants had detectable levels of BPA in their urine. Researchers said those with the highest levels of BPA concentrations in their urine had nearly three times the odds of cardiovascular disease, compared with participants with the lowest levels of BPA. The study also found people with high BPA levels had 2.4 times the odds of Type 2 diabetes in comparison with those with the lowest levels.
In response to the study, the trade group the American Chemistry Council said the researchers had not proven a causal link between BPA and adverse health effects.
"As the authors themselves note, they do not conclude that the presence of BPA is causing adverse health effects — they merely noted a statistical association," the group said.
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."
On Oct. 6, 2009, the journal Environmental Health Perspectives published a study which found that pregnant women exposed to BPA were more likely to have daughters with aggressive and hyperactive behaviours. No significant effect was found among the boys the women gave birth to.
The researchers studied a group of 249 women from Cincinnati. The findings are the first linking BPA exposure in the womb to changes in a child's behaviour. Other research involving much larger groups of women is planned to see whether the results hold up.
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 Scott 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.
How did Health Canada draw its conclusions?
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.
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.
In July 2009, a Health Canada analysis of 122 baby foods kept in glass and metal jars found BPA had leached into most tested items. But the exposure levels were very low — from 0.19 parts per billion to a high of 7.22 parts per billion. A similar study of bottled water at the same time found exposure levels between 0.5 and 8.82 parts per billion.
At a level of 1.5 parts per billion, an adult weighing 60 kilograms would have to consume about 1,000 litres of bottled water in one day to approach Health Canada's provisional tolerable daily intake.
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.
How have Canadian retailers responded?
Lululemon Athletica Inc., also Vancouver-based, announced plans later the same month to stop selling plastic water bottles that contain bisphenol A. The company did not pull bottles already in stores. Lululemon said it had followed the issue for more than a year before deciding it would switch to new water bottles made of acrylic.
In anticipation of Health Canada's announcement, a number of retail giants announced in the spring of 2008 that they would rid their stores of products containing bisphenol A. Those include Wal-Mart Canada, Canadian Tire, Hudson's Bay Co. and Forzani Group, Canada's largest sporting goods retailer. Sears Canada, Rexall Pharmacies, London Drugs and Home Depot Canada also said they had removed products with bisphenol A from their stores.
Nalgene Outdoor Products — a U.S. manufacturer of popular water bottles made from hard, clear polycarbonate — announced in April it will stop making the containers because they are manufactured with BPA.
What alternatives can I use?
Use glass, stainless steel or porcelain containers, especially for hot food or liquids.
For baby bottles, choose glass or look for hard plastic bottles without bisphenol A. They can be found at health food stores and some baby stores.
For preserved goods, opt for glass jars or canned goods that do not have liners containing BPA.