Regulatory authorities insist the dosages from such exposure are nothing to worry about, yet the mounting evidence shows that the chemical is toxic at disturbingly low levels-especially to unborn babies.
If you're a consumer of canned food-such as baked beans and chicken soup-then you may be swallowing harmful residues of a toxic, oestrogen-mimicking chemical that is linked to cancer and damaged sexual development.
A comprehensive report by the US public-health and environmental watch-dog Environmental Working Group (EWG) discovered that bisphenol A (BPA), a chemical commonly used to line the inside of food cans, is leaching into the food product inside, exposing the public to dangerous levels of the noxious compound.
Although the research was carried out in the US-where laboratory tests found BPA in over half of nearly 100 cans of food purchased from major supermarket chains-the EWG points out that BPA contamination of food is a global concern. Indeed, in studies conducted over the past two decades, scientists have detected BPA in breast milk, serum, saliva, urine, amniotic fluid and cord blood from at least 2200 people across Europe, North America and Asia.
According to the EWG, these wide-spread exposures are a serious public-health concern, as even low levels of BPA have been associated with a diverse range of toxic effects. The chemical may also be contributing to "the litany of human health problems" that are on the rise among the world's popula-tions, including breast cancer, diabetes, obesity, infertility and polycystic ovarian syndrome.
What's bad in canned goods?
BPA is produced in large amounts across the globe. As well as being an ingredient in the epoxy resins that line food cans, BPA can also be found in polycarbonate plastics such as water bottles, baby bottles, children's toys, adhesives, electronics, and even tooth fillings and sealants. Nevertheless, canned foods are thought to be the predominant route of BPA exposure.
In recent years, various environ-mental groups have been warning us that exposure to BPA from food-can linings and other sources poses a potential human health risk. And now, this latest report from the EWG shows just how real that risk is.
Independent laboratory tests con-ducted by the EWG found BPA in 55of the 97 cans of food analyzed-including chicken soup, ravioli and infant formula-purchased from three major supermarket chains in various locations in the US. In one out of every 10 cans of all foods tested, and in one of every three cans of baby formula, a single serving contained enough BPA to expose a woman orchild to BPA levels that were more than 200 times the US government's traditional safe level of exposure for industrial chemicals.
A survey conducted by the Food Standards Agency in the UK had similar findings. The group tested 62 samples from canned goods sold in UK super-markets and detected BPA in almost 40 products. The compound was found at levels up to 0.07 mg/kg in 37 samples and at 0.35-0.42 mg/kg in one further can (www.food.gov.uk/science/ surveillance/fsis2001/bisphenols).
Although these levels were all within safety limits, there is growing concern over the damage that the chemical might cause to health at even miniscule concentrations.
The evidence so far
According to the EWG, there is now "near irrefutable evidence" that BPA has toxic effects at low levels of exposure. In its report, which summar-izes the extensive data in the scientific literature so far on the adverse effects of BPA, the group states that, "Few chemicals have been found to consistently display such a diverse range of harm at such low doses."
Indeed, in a review published in 2005, researchers Dr Frederick vom Saal, from the University of Missouri, and Dr Claude Hughes, from East Carolina University in North Carolina, found over 90 studies-albeit in animals, so the findings may not necessarily apply to humans-confirm-ing BPA toxicity at surprisingly low doses. In 31 of these studies, "sig-nificant effects" were even seen with exposures below the supposedly 'safe' or reference dose of 50 mcg/kg/day.
At some of the lowest doses, they found that BPA caused permanent alterations in breast and prostate cells that can lead to cancer, insulin resistance [a hallmark trait of type 2 (non-insulin-dependent) diabetes], chromosomal damage linked to re-current miscarriage and a wide range of birth defects, including Down's syndrome.
The two scientists also noted that "rate of growth and sexual maturation, hormone levels in blood, reproductive organ function, fertility, immune function, enzyme activity, brain structure, brain chemistry, and behaviour are all affected by exposure to low doses of BPA". These effects have all been demonstrated in a wide range of laboratory animals (Environ Health Perspect, 2005; 113: 926-33).
Interestingly, where traditional toxicology asserts that the higher the dose, the greater the harm, BPA tests show that low doses can be the most toxic of all. In one laboratory test, a low dose of BPA produced a 70-per-cent higher growth rate in human prostate cancer cells in cell cultures than did higher doses (Molec Cancer Ther, 2002; 1: 515-24).
In another investigation using mice, it was discovered that lower doses of BPA not only altered the mammary glands, but also induced changes in the female genital tract (Biol Reprod, 2005;
72: 1344-51). A possible explanation is that minute doses of BPA fall belowthe 'radar' of the body's own natural detoxifying mechanisms, thus allowing them to do more damage.
Nevertheless, despite these sugges-tive findings, a review by the European Food Safety Authority (EFSA) earlier this year concluded that BPA poses no immediate health risks, dismissing much of the animal data on BPA toxicity because humans are able to metabolize the chemical much more quickly than animals do (www.efsa.europa. eu/EFSA/efsa_locale-1178620753812_ 1178620772817.htm).
However, Dr vom Saal, who along with 37 other researchers has reviewed more than 700 scientific papers on BPA, insists that the animal data are highly relevant. "At the cellular level, there is essentially no difference bet-ween the way the mouse cells respond to BPA and humans do," he says. And because BPA affects the hormonal system, it can have an effect at "staggeringly small concentrations" (New Scientist, 2007; issue 2616).
What's more, there is a handful of human studies that add to the concern over the potential hazards posed by BPA. Japanese scientists discovered that women with polycystic ovarian syndrome had higher blood levels of BPA compared with women who have normal ovarian function. They also found positive correlations between BPA concentrations and androgen levels (Endocr J, 2004; 51: 165-9). And polycystic ovarian syndrome, notes the EWG, is the most common form of female infertility in the US, affecting 5-10 per cent of American women.
Blood levels of BPA in women have also been linked to recurrent mis-carriage and complex endometrial hyperplasia, where the lining of the womb becomes thickened-a condition generally considered to be a precursor of endometrial cancer (Hum Reprod, 2005;20: 2325-9; Endocr J, 2004; 51: 595-600).
In men, researchers found that those who are occupationally exposed to epoxy resins had higher urine concen-trations of BPA than the controls. Theyalso had lower amounts of follicle-stimulating hormone, which is critical to sperm formation. Diminished secre-tion of this hormone in men can result in reduced sperm concentrations and infertility (Occup Environ Med, 2002; 59: 625-8).
Given these human findings as well as the animal and laboratory data, and the fact that human exposure to BPA is so widespread, to so cavalierly dismiss the possibility that BPA can be a serious human health risk seems to be totally irresponsible.
Cans as health hazards
BPA is not the only chemical to leach out of food-can linings. European tests on just three different can coatings revealed at least 23 BPA-related chemicals that leach into food (Food Addit Contam, 2004; 21: 390-405). According to the EWG, ". . . these contaminants occur at levels that can dwarf better-known environmental pollutants that can accumulate in food, like PCBs [polychlorinated biphenyls] and DDT [dichloro-diphenyl-trichloroethane]."
Indeed, one scientist states, "Con-centrations of [migrant chemicals like BPA] commonly exceed . . . pesticides by orders of magnitude; most of the migrating compounds are not even identified; and only a few have been tested for toxicity . . ." (Food Addit Contam, 1999; 16: 579-90).
So, every time we eat food from a tin, we just don't know what dangerous concoction of chemicals we may be exposing ourselves to. It's just one more reason to avoid processed foods.
How to minimize your risk
- addition to food-can linings, bisphenol A (BPA) can also be found in a
wide range of other consumer products. To limit your exposure:
- consume fresh, unprocessed foods and avoid canned foods as much
- avoid number 7 plastics. Polycarbonate plastic food containers marked with a number '7' in the recycling logo usually contain BPA. In general, these are rigid and transparent plastic containers. Plastics that are numbered 1, 2 and 4 are safer choices, as they don't contain BPA, says the EWG
- use glass baby-bottles, or those made of the safer polypropylene and polyethylene plastics. Pliable, cloudy-coloured plastic does not contain BPA. Medela-brand bottles used to store breast milk are also labelled
- choose glass rather than plastic water bottles, or get your water from the tap. See WDDTY vol 17 no 8 for advice on water filtration. Also, avoid metal water bottles as they may be lined with BPA-containing plastic
avoid using plastic containers in the microwave. Ceramic, glass and other microwaveable dishware are good alternatives
- avoid storing food and drink in plastic containers. Glass and stainless steel are better, safer choices.
BPA and pregnancy
Among the more alarming findings is that bisphenol A (BPA) can cross the placenta and affect the embryo or fetus during critical periods of development. A German study detected BPA in human fetuses in the womb at levels known to cause adverse effects in animals (Environ Health Perspect, 2002; 110: A703-7).
What's particularly worrying about prenatal exposure is the fact that, in both animal and human fetuses, the natural detox mechanisms that deactivate and filter BPA from the body are not yet fully developed (Neoplasia, 2002; 4: 98-102). The fetus, therefore, is especially vulnerable to the chemical's toxic effects.
In animals, exposure to BPA in the womb can cause deformities of the reproductive organs (Neoplasia, 2002; 4: 98-102; Environ Health Perspect, 2002; 110: A703-7) as well as breast and prostate cancers in later life (Reprod Toxicol, 2006; 146: 4138-47; Cancer Res, 2006; 66: 5624-32).
Moreover, the EWG's independent tests found unsafe levels of BPA in one out of every three cans (33 per cent) of infant formula.