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25 July 2012
Over recent years you will have heard of a substance called bisphenol A (BPA). It is used in many plastics and concerns over its health effects have become so widespread that many companies have been removing it from their products. Now two new research papers have reignited the BPA issue. One has highlighted the effect of BPA on the environment and another raising concerns about the substance used to replace BPA in many products.
BPA is used to stabilise plastics and it is estimated that around three billion kilograms of it are produced annually. As a component of polycarbonate it is used to make food and drink containers. Many baby bottles did contain BPA although around the world companies have been removing BPA from their baby products. BPA is also used in the plastic resin that lines cans containing foods and drink. It is also present in some dental sealants.
The concern around BPA is that since it acts as a hormone it may have a range of health implications. We know that it binds to the receptors that oestrogen attaches to but it also attaches to other related receptors as well. The concerns are that BPA could be linked to infertility, obesity, breast and prostate cancer, diabetes, cardiovascular disease, thyroid malfunction and attention deficit disorder.
In a new study significant concerns have been raised around the environmental impact of BPA.
In the study researchers exposed two species of fish to BPA in their tank water. The fish used were Blacktail Shiners (Cyprinella venusta) and Red Shiners (Cyprinella lutrensis), two species found in rivers across the United States. After fourteen days of exposure the researchers put some of the fish together and found that BPA had changed the mating behaviour and appearance of the fish. The BPA altered male fish appearance and changed female fish behaviour. The net result is that after being exposed to BPA the fish were more likely to mate across species. If BPA extensively contaminates waterways and this kind of thing happened in the wild then biodiversity would be threatened and there could be a blurring of the boundaries between species. This is all due to the hormonal effects of BPA.
Against this background there have been widespread attempts to reduce the use of BPA. Many products will loudly proclaim that they are now “BPA-free”. The question of course becomes what are they replacing BPA with?
in 2010 a report in the journal Chemosphere looked at BPA use in the paper used in cash registers to generate receipts. For their study researchers looked at urine samples of almost 400 women and compared BPA levels to the women’s occupations. Those with the highest concentrations were cashiers, who had 2.8 mcg of BPA per gram. Teachers had 1.8 mcg per gram and industrial workers had 1.2 mcg per gram. So this study was suggesting that BPA used in the cash register receipts could leach out of the paper and through the skin of the cashiers. As a result of this kind of research BPA has been replaced on many occasions in receipt paper by its chemical cousin bisphenol S (BPS). Now a new study has raised concerns about BPS itself.
In the new report published in Environmental Science & Technology note that BPS has been used to replace BPA in a lot of thermal and recycled paper but there are questions about whether it is actually any safer. These researchers also observed that BPS is absorbed through the skin at about nineteen times the rate of BPA. So how bad might BPS be?
An article to be published in the August issue of the journal Toxicology In Vitro , found that analysis using two highly standardised transactivation assays showed that the oestrogenic activity of Bisphenol A and Bisphenol S is of a comparable potency. Other research has shown that BPS has slightly less biological activity than BPA, but not much. So BPS appears to have at best slightly less hormone-mimicking characteristics than BPA but it still has an effect, but research also suggests that it might also be less biodegradable than BPA.
It goes to prove the old adage that you just have to be careful that the cure is not worse than the disease.