3D chemical structure of bisphenol A (Photo credit: Wikipedia)
Bisphenol A or BPA is it is known to its chums is used in polycarbonate plastics. These include
- that hard plastic which look like glass but doesn’t break as dramatically,
- the white plastic liners found in many cans, microwave oven ware, eating utensils and bottles (including baby bottles).
- Plastics labelled with the number “7” identification code. HOWEVER not all plastics labelled with the number “7” contain BPA. The number “7” code is assigned to the “Other” category, which includes all plastics not otherwise assigned to categories 1-6.
The chemical was invented in the 1930s during the search for synthetic estrogens. Diethylstilbestrol was found to be a more powerful estrogen, so bisphenol A was put to other uses. It was polymerized to form polycarbonate plastic and used to make a wide range of products including those listed above.
Over the years there have been an increasing number of claims that the polymer is not stable. That, over time, BPA breaks down over time and releases hormones into whatever product it comes into contact with. Research has indeed proved that BPA can leach into food from the epoxy linings in cans or from polycarbonate bottles, and that the rate increases if the containers are heated i.e. babies bottle being sterilised or a tin being heated.
However additional studies are now suggesting that the ingestion of leached BPA could be harmful. In March 1998 for example a study in Environmental Health Perspectives (EHP) found that BPA simulates the action of estrogen when tested in human breast cancer cells. A more recent study published in EHP shows a significant decrease of testosterone in male rats exposed to low levels of BPA. The study concludes that the new data is significant enough to evaluate the risk of human exposure to BPA.
BPA is now considered by many to be a hormone disruptor, a chemical that alters the body’s normal hormonal activity.
In the last 10-15 years that concerns have been raised over its safety, particularly during pregnancy and for young babies.
In April 2008, the United States Department of Health and Human Services expressed concerns about it.
The Canadian government have just banned listed it a toxic substance and banned it from being used in baby bottles.
The following chart was taken from the very informative and interesting Wikkipedia article but you can find the same information all over the internet
Low dose exposure in animals
| Dose (µg/kg/day) | Effects (measured in studies of mice or rats,descriptions (in quotes) are from Environmental Working Group)[104][105] | Study Year |
| 0.025 | “Permanent changes to genital tract” | 2005[106] |
| 0.025 | “Changes in breast tissue that predispose cells to hormones and carcinogens” | 2005[107] |
| 1 | long-term adverse reproductive and carcinogenic effects | 2009[76] |
| 2 | “increased prostate weight 30%” | 1997[108] |
| 2 | “lower bodyweight, increase of anogenital distance in both genders, signs of early puberty and longer estrus.” | 2002[109] |
| 2.4 | “Decline in testicular testosterone” | 2004[110] |
| 2.5 | “Breast cells predisposed to cancer” | 2007[111] |
| 10 | “Prostate cells more sensitive to hormones and cancer” | 2006[112] |
| 10 | “Decreased maternal behaviors” | 2002[113] |
| 30 | “Reversed the normal sex differences in brain structure and behavior” | 2003[114] |
| 50 | Adverse neurological effects occur in non-human primates | 2008[44] |
| 50 | Disrupts ovarian development | 2009[77] |
So why the hell is BPA still being used you might ask- while checking your pants nervously and belting the kids.
Because the science is by no means conclusive. It has become something of a cause with consumer and green groups who are vociferous in their opposition. Media reporting tends to concentrate on the negative aspects of any new reports. Yet several scientific panels, including the European Union’s Scientific Committee on Food, the National Toxicology Program and the Harvard Center for Risk Analysis, have all concluded that the claims that low doses of BPA affect human health have not (yet ), been substantiated. While accepting that animal testing has produced adverse results they can find no concrete evidence that humans will react the same way.
And even if they do, the amounts of BPA we ingest are so minimal as to be negligible.
The current U.S. human exposure limit set by the EPA is 50 µg/kg/day.
Which means, as the BPA industry’s voice over at to bishenol-a.org, puts it
“Based on the results of the SPI study, the estimated dietary intake of BPA from can coatings is less than 0.00011 milligrams per kilogram body weight per day. This level is more than 450 times lower than the maximum acceptable or “reference” dose for BPA of 0.05 milligrams per kilogram body weight per day established by the U.S. Environmental Protection Agency.”
Which means an adult would have to eat 230 kilograms of canned food and beverages every day of their life to exceed the safe level of BPA set by the U.S. Environmental Protection Agency.
As the toxicologists love to say – it’s not the poison but the dose…..
However, what is certain is that BPA is a $6 billion plus global industry. According to the National Institute of Health, approximately 940,000 tons of BPA are produced in the U.S. per year. About 21% is used in epoxy resins and most of the rest goes to polycarbonate. You can find out more here
You can find our most recent BPA related posts here and this is another good read.
Whatever the final conclusions, I feel I have quite enough of my own, home-made estrogen to be going on with. I choose avoid BPA where ever possible.
I limit food from tins, drink from cans and don’t use plastic food containers.
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