Home
Health
concerns
Suspect
chemicals
The
endocrine system
Issues
Policy
responses
Take Action!
(chemical reaction)
(chemical reaction)
About
this site
Bisphenol A
Uses
- Bisphenol A is used in the production of epoxy resins and polycarbonate plastics. These plastics are used in many food and drink packaging applications, whilst the resins are commonly used as lacquers to coat metal products such as food cans, bottle tops and water supply pipes (ENDS, 1995).
- Some polymers used in dental treatment contain Bisphenol-A.
Hormone disrupting effects
- Bisphenol A was first shown to be oestrogenic in 1938, using ovariectomized rats (Dodds and Lawson, 1938)
- More recently, it was found to be oestrogenic in the MCF-7 human breast cancer cell culture assay in 1993 (Krishnan et al., 1993). The hormonal effects could be measured at concentrations as low as 2-5 ppb (2-5 µg/l).
- Bisphenol a can also act as an antiandrogen, blocking the action of dihydrotestosterone in a yeast screen containing a human androgen receptor (Sohoni and Sumpter, 1998). In this screen bisphenol a was approximately as potent as flutamide, a well known anti-androgenic chemical.
- Liquor containing bisphenol-A obtained from tinned vegetables has been found to be oestrogenic to human breast cancer cells (see below).
- Bisphenol a produces identical effects to those produced by oestradiol on rat uterus and vagina; the vagina was particularly sensitive to the chemical (Steinmetz, 1998).
- Exposure of developing male mice in the womb has been shown to enlarge their prostate glands (Nagel et al, 1997). This research has however be disputed by two controversial chemical-industry backed studies, see the low dose page for more details.
- It has been claimed that bisphenol acts in the same way as female hormones in the area of the developing rat brain which regulates fertility and sexual behaviour (Anon, 1998).
- Administration of bisphenol a to male rats just after birth led to slight changes in the structure of the efferent ducts, though these changes seemed to only be transient (Fisher et al., 1999).
- New research shows that female mice exposed in the womb to low doses of bisphenol a (2.4 micro-g per kg per day to the mother) had a significantly reduced delay between vaginal opening and first vaginal oestrus (Howdeshell et al., 1999). This research also used information on litter position in the womb, which showed that those females positioned between female litter mates were most affected by bisphenol a, those between males were least affected. Research is suggesting that girls are reaching puberty earlier, see human health page for details.
Human Exposure
Cans
- The liquid in some cans of tinned vegetables have been found to contain both bisphenol A, and the related chemical dimethyl bisphenol-A. The highest levels of bisphenol A were found in cans of peas, with an average of 23 µg per can. Other liquors containing bisphenol A were from cans of artichokes, beans, mixed vegetables, corn and mushrooms. There was no detectable bisphenol A in cans of palm hearts, asparagus, peppers and tomatoes (Brotons et al., 1995).
- All liquors which contained bisphenol A were oestrogenic to a human breast cancer cell assay. Those liquors without detectable bisphenol A were not oestrogenic. The liquor from the most contaminated vegetables, the peas, produced 58% of the oestrogenic response generated by oestradiol (Brotons et al., 1995).
- The vegetables themselves were not tested for oestrogenicity or Bisphenol A content , though since they probably contain more fat than their liquor, they are likely to contain at least as much Bisphenol A as the liquor.
- This research also included an examination of cans of other, more fatty, products, including condensed milk, pork and beans and concentrated milk-based infant formula. Unfortunately, the products themselves were not analysed. Instead, the cans were emptied, cleaned, then filled with distilled water and autoclaved at 125 °C for 30 minutes, then the water was analysed. Some of these water samples, including those from condensed milk cans, were found to contain bisphenol A and were oestrogenic. All canned foods are autoclaved after canning; the fact that bisphenol A is leached into water during autoclaving in these experiments suggests that any product packed in similar cans will contain bisphenol A. It is also likely that substantially more bisphenol A will leach into fatty products.
- NB: Which canned products do or do not contain bisphenol A cannot be determined from this study, since it will depend on the particular brand of product tested. The cans were purchased in Spain and the USA, but came from a variety of countries.
- US Food and Drug administration research has found that bisphenol a leaches from infant formula cans into infant formulae (Biles et al, 1997). The levels of bisphenol found in the formula varied between 0.1 ppb and 13.2 ppb, from one to six times lower than the Brotons study, above.
- EC rules limit migration of bisphenol A into food to 3 mg/kg, compared with a maximum liquor concentration in this research of 80 µg/kg (ENDS, 1995). The EC limit does not allow for oestrogenic toxicity.
- In 2001 the UK Food Standards Agency published a study on the leaching of bisphenol a from food cans.
Polycarbonate bottles
Many transparent 'plastic' bottles are made from polycarbonate, usually a polymer of bisphenol a. Several studies have been done on leaching of bisphenol a from these bottles. The US campaign group the National Environmental Trust has done their own research on this issues and also have background information on their site.
Dental exposure
Some (but not all) dental resins contain bisphenol A. Olea et al. (1996) found that a sealant containing bisphenol A diglycidylether methacrylate (bis-GMA) was oestrogenic to MCF7 breast cancer cells. Samples of the saliva from 11 patients taken 1 hour after dental treatment contained bisphenol a and bis-GMA. There is some dispute about the deatils of this research (Ashby, 1997; Imai, 1999;Olea, 1999).
Alternatives
Bisphenol -A is not used in all can lacquers, but the Metal Packaging Manufacturers Association considers that the industry might have problems switching to new formulations (ENDS, 1995). The general secrecy surrounding the chemicals used in can linings makes it very hard for any external observer to evaluate what alternatives are available.
For more information
WWF published a detailed report on the hormone disrupting effects of bisphenol A in May 2000; it is available free on the web: "Bisphenol A - A known endocrine disrupter".