Bisphenol A is a chemical used to make different kinds of plastics. It has been used since the 1940s to make epoxy resins. These are found in products like paints, protective coatings in food cans, adhesives, and electronics.
In 1957, scientists discovered that linking BPA molecules together in large chains created a hard plastic substance called polycarbonate. This is currently used in many different products, including impact-resistant windows, compact discs, medical equipment, and reusable food and drink containers.
BPA production has increased dramatically since the early 1960s. Billions of kilograms are now produced worldwide. BPA is all around us, and inside most of us. One study from the US showed that bisphenol A can be found in almost all adults and children.
Since so much BPA was being produced, scientists tested it for safety in the 1980s. They gave rats and mice various levels of BPA and watched them for health effects. At very high doses, exposed mice had lower fertility and weight loss.
Scientists also experimented with lower doses to find the level at which no effects were seen. An even lower level was then set as a maximum for human exposure. It was believed that this would protect humans from harm. BPA does not build up in the body, and the levels to which people were actually exposed were much lower than this limit.
As the normal exposure level was low, there was little concern about human health effects until the late 1990s. Scientists then began to worry about similarities between BPA and the female hormone estrogen. They experimented using doses similar to the levels of known human exposure. These levels were much lower than those used in previous studies. Scientists found that exposed male mice had heavier prostates. This suggested that very low doses of BPA, acting like estrogen, could affect health. As well, the health effects were different from the high-dose health effects found in earlier studies.
After this, many scientists began doing research using very low doses of BPA. Some studies showed effects in mice and rats. Others showed no difference between animals that were given BPA and those who were not. As there are differences between studies, scientists do not agree on whether or not very low doses of bisphenol A cause health effects in humans.
The fact that the studies use animals, and there are differences between animals and people, causes more disagreement. An animal’s body may process chemicals differently than the human body. As well, animals in studies are exposed to chemicals in different ways than humans would be exposed. For instance, although most human exposure is through food and drink, many studies injected BPA into mice rather than putting it in food. Finally, it is hard to know how cell changes or other small effects in an animal might represent human disease.
For these reasons, no one is sure of what kinds of health effects BPA might cause in humans, since it is not ethical to experiment on people.
While federal scientists do not believe adults are at risk from current exposure levels, declaring the synthetic chemical toxic opens the way for regulatory action. The government wants to ban plastic baby bottles made from the chemical and work with food and packing companies to reduce the amounts leaching out of tin cans into infant formula.
It is natural to want to know if a product is clearly good or bad. However, this lack of agreement between scientists makes it difficult to know whether we should worry about BPA.
The reality is that every choice we make has some risk and some benefit. The way we look at risk does not just depend on research. For instance, most of us know that traffic collisions are the number one cause of death in children under 14. However, because driving is a part of our lifestyle, we do not stop driving.
On the other hand, we have not heard much about bisphenol A until now. It is unfamiliar, and we do not have a lot of control over how much there is in our environment. This affects how we think about our exposure to it.
So, should we worry about our exposure to BPA? There is no simple answer to that question. Recent expert reviews of all the published evidence suggest that the development of unborn babies, infants and young children may be affected by exposure to BPA. This is based on studies showing that mice and rats exposed to BPA at a very young age showed behaviour changes. There is much less evidence that BPA causes cancer, obesity, or other health effects. There is also less evidence that exposure to low doses affects the health of adult mice and rats.
Scientists are continuing to work on answering the many questions we all have about bisphenol A. Their recommendations may change as more is learned.
At present, Health Canada recommends that we limit the exposure of infants and young children by avoiding using baby bottles with BPA. As well, the levels in infant formula cans are to be reduced. Parents currently using polycarbonate baby bottles should not fill them directly with boiling liquid, but instead wait for the liquid to cool before filling the bottle. Alternately, glass or non-BPA plastic baby bottles can be used to reduce exposure.
There is no good evidence that exposure to BPA at levels currently seen in the general population is affecting the health of adults. As a result, Health Canada’s recommendations focus on newborns to children 18 months of age.
This advice is based on the fact that almost all of the BPA in our bodies comes from food and drink. Sports equipment, electronics and CDs are not a health risk.
Those who wish to choose food and drink containers without BPA can look at the recycling symbol on the container for information. Typically, this symbol has a number from one to seven inside it. The number indicates the type of plastic in the product. BPA-based polycarbonate is one kind of plastic in the number seven group. If the number seven container is also marked ‘PC,’ this identifies it as polycarbonate. If it does not show the letters ‘PC,’ the container may or may not contain BPA.
If no recycling symbol is present, there is no easy way to know what makes up the plastic. BPA can also be found inside the container lining of canned food. Remember, we do not yet have good information on all of the ways that BPA can get into our food and drink. More research is needed.
As you make choices about what products to use, think about the safety of materials that could replace bisphenol A. A great deal of attention has been placed on this material. Still, we do not know the extent of the problem. Avoid replacing BPA-based packaging materials with another untested or unknown substance about which we know even less.
Health Canada will be funding more research on bisphenol A and on possible replacement products. We need to keep looking for answers to the many questions around BPA. This way, we will be able to make informed decisions about our health and our environment.