What is BPA ?

What is BPA ?

Bisphenol A or BPA is it is known to its chums is used in polycarbonate plastics.  These include

  • CDs, cell phones, car parts, medical devices, safety goggles
  • some thermal paper products such as till receipts.
  • hard clear plastic
  • the epoxy plastic liners found in many cans and tins,
  • Plastic 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.

馬口鐵罐頭食品涼粉 Category:Canned food Category:Grass ...

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 – between  nervously checking your genital tract and belting the kids.

‘BPA is such an easy chemical to make and it’s so useful,’ explains Tamara Galloway, a professor in ecotoxicology at the University of Exeter, UK.  ‘It is made from very cheap ingredients – acetone and phenol – and it makes a nice, clear, rigid polycarbonate and is really useful for making epoxy resins. “ Via Chemistry World .

According toPlasticsEurope, an association representing European plastic manufacturers, polycarbonate technology contributed €37 billion to the EU in 2007. And they state that more than 550,000 jobs in the EU depend – either directly or indirectly – on the production and use of polycarbonate. Via Chemistry World .

Also 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.

In Europe, the tolerable daily intake for BPA is set at 0.05 milligrams per kilogram of body weight. This value is an estimate of the amount of a substance that can be ingested daily over a lifetime without appreciable risk. The figure was calculated in 2006 by the European Food Safety Authority (EFSA), who at the same time stated that intakes of BPA through food and drink, for adults and children, were well below this value.Via Chemistry World .

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.

want to know more – this is another good read.

You can find reports, studies and media scares on BPA here

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1 comment

  1. Pingback: Why does my tin can have a plastic liner and is it bad for me? | plastic is rubbish

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