Plastics, tin cans and……cancer!

By Dr Janey

The chemical Bisphenol A (BPA), has in recent years become a subject of much debate. While the scientists who raise the alarm of the potential health hazards of BPA and the growing numbers of self-educated, health-conscious members of the public express their concerns; the industries that utilise BPA, continue to utter their reassurances.

If you are reading this because you are interested in preventing or treating cancer, you may want to sit up and take note of some of the facts of this debate!


So just what is BPA and where do we find it?

Put simply, BPA is everywhere – in our homes and in many of the food and drinks we buy in our supermarkets! It is a chemical found in polycarbonate plastics that can generally be recognised as the hard, transparent and shatter-resistant plastics as used in water bottles, sports bottles, babies’ bottles etc. Apart from plastics, it is also used as a component of epoxy resins as found in the lining of most of our canned foods and canned drinks.

BPA at a glance

And it doesn’t end there! Dentists use it as a component of many dental fillings and sealants. Many of us handle thermal paper in the form of purchase receipts and event tickets on a regular basis – these have large quantities of free BPA. And then there’s our water pipes that may be repaired, especially in older buildings, with epoxy linings that contain, guess what…..BPA!

BPA was initially introduced as a chemical back in the 1930′s. However, it is only in more recent years with the exponential increases in the use of plastics and cans for holding our food and drinks, that the use of BPA has become increasingly more relevant.

As Tim Osswald, an expert in polymer engineering at the University of Wisconsin-Madison explains; during the manufacturing process not all BPA is locked into chemical bonds and thus the remaining BPA can work itself free and enter into the food or water contained within the bottle or can. This becomes exacerbated as the plastic ages, but importantly also when the structure is heated as would be the case when holding hot drinks, being heated in the microwave, left lying in the sun etc. In addition to that, the high heats used by autoclaves to sterilise all canned foods during the manufacturing process also induces leaching of BPA into the contents within them.

In fact, because of the omnipresence of BPA in our water bottles and tinned cans, as well as the other sources of BPA as mentioned above, a trial conducted by the Centre for Disease Control and Prevention in 2004 in the US, revealed that 93% of over 2500 people tested, showed levels of unmetabolised BPA in their urine. BPA has also been detected in the blood as well as in human breast milk.

BPA controversy

So just how relevant is it that most of us have BPA in our bodies?

The plastic industries and chemical associations would argue, not much! A predictable response of course, but let’s look a little closer…

The industries that stand in defence of BPA state that the trials that point to the risks that this chemical carries, are not reliably repeated, and therefore cannot be considered to carry much weight. However, Patricia Hunt Ph D, a prominent researcher in molecular biosciences states otherwise. When she worked together with a team of 36 other researchers led by Frederick vom Saal in analysing hundreds of studies on BPA, it was found that 90% of these studies confirmed the health risk of BPA. Notably, the only studies that failed to demonstrate a health risk with BPA were those that were funded by the plastics industry!

The American Chemical Association (supporter of dozens of companies involved in the production of plastics) states that the toxicology of BPA is “well understood” and that it “exhibits toxic effects only at very high levels of exposure”. These ‘toxic effects’ have been set at 50 micrograms per kg of body weight per day by the FDA.

However, Patricia Hunt reminds us that treating BPA as a toxin can lead to false conclusions. By following the rules of toxicology, if a chemical is bad then a higher dose must be worse. However BPA is a hormone disruptor and mimics the action of oestrogen, rather than being a straight forward toxin. At low levels such a chemical can wreak the most harm, while at high levels it can ‘overwhelm’ and serve to shut down the body’s response. In fact, during Hunt’s trials on rodents which originally brought the issue of BPA to the world’s attention, a level of 20 micrograms per kg body weight of BPA per day (ie less than half of the FDA’s ‘safe’ levels) was sufficient to cause significant adverse effects. In addition to this, it would appear that in reality, exposure to BPA is longstanding and the effects likely to be cumulative, while trials only demonstrated a relatively short term exposure to this chemical.

These above trials worked with concentrations of BPA in the range of parts per million. However, as noted in ‘Scientific American’, more recent trials dealing with concentrations of BPA as low as 1 part per trillion triggered a physiological response. This suggests that any exposure to BPA could have consequences!


So just what are these consequences?

  • Breast cancer: As per the article entitled, ‘The Crucial Role of Oestrogen on breast cancer’ (also available on this site), our risks of breast cancer increase proportionately with our life-time exposure to oestrogen. BPA is a synthetic oestrogen and therefore, as mentioned above, acts by mimicking the effects of oestrogen.

Therefore women who consume food or drinks from polycarbonate plastics and tinned cans are increasing their exposure to oestrogen, and with that their risk of breast cancer. This occurs not only through life, but is likely to begin as early as the foetal stage in the womb of the mother if the mother consumes these products. Due to this oestrogenic effect, BPA has also been shown to induce early-onset puberty in girls, thus increasing the length of exposure to oestrogen during those girls’ lifetimes.

  • Prostate cancerdue to increased exposure to this oestrogenic chemical with exposure beginning as early as in the womb
  • Various reproductive problems including reduced sperm counts, miscarriages, male sexual dysfunction (when working with BPA in the work place) and others
  • diabetes due to insulin resistance
  • Behavioural changes: Children and infants appear to be particularly susceptible to BPA and there are concerns about its affect on foetal and infant brain development as well as behavioural disorders such as attention deficit hyperactivity disorders (ADHD)
  • obesity by promoting adipogenesis (the tendency to form fat cells)
  • thyroid abnormalities by attaching to thyroid receptor cells and in doing so becoming a thyroid disruptor

Note: BPA has been demonstrated, in rodents at least, to have detrimental effects not just in the individual consuming it, but in 3 subsequent generations.


So how do we go about avoiding exposure to BPA?

  1. Avoid drinking from plastics that show the recycling symbol with the number 7 (or the letters PC – polycarbonate) that can usually be found on the bottom of the bottle. As mentioned earlier, these tend to be the hard, transparent plastics. Use glass bottles or stainless steel water holders instead.
  2. If you do have to use these plastics, take all precautions to avoid them becoming heated which will promote leaching of BPA into the contents. This includes avoiding the use of microwaves to heat the contents, avoiding washing these plastics in the dishwasher, manually washing them with hot water and not leaving them to get hot in the sun.
  3. Avoid washing these plastics with chemical detergents which can be abrasive, thus accelerate leakage of BPA.
  4. Avoid consuming food or liquids from tinned cans eg soft drinks, canned vegetables and fruit etc
  5. Choose natural and non-refined foods instead!
  6. Choose holistic dentists and question your dentist on the constituents of dental sealants and implants used (note: BPA is not the only toxic chemical used in dentist’s chairs)
  7. Many baby’s bottles and pacifiers (called dummies in some countries) are made from polycarbonate plastic. Use glass bottles instead and avoid pacifiers where possible.
  8. Free BPA can also be present in large amounts in carbonless copy paper and thermal paper such as is used in receipts, event tickets, airline tickets and some labels. The handling of these tickets can leave residues on the hands which may lead to inadvertent ingestion of BPA. Therefore take care when handling such items and wash hands thoroughly thereafter.

BPA in plastic bottles

Risk to the environment: Apart from the numerous adverse health effects on humans, BPA has also been shown to have detrimental effects on aquatic organisms through direct contamination as well as through degradation of plastic litter that reaches our oceans and inland waters. Fish appear to be the most vulnerable, but molluscs, crustaceans and amphibians are also affected both with regards to reproduction as well as in growth.


Governing health bodies around the world have been slow to act on the regulation of BPA use with a couple of exceptions: In Japan BPA was replaced with natural resin to line tin cans in 1997 after scientists demonstrated that BPA was leaching out of babies’ bottles. Subsequent studies in Japan have shown that levels of BPA in the urine have dropped dramatically. In addition, Canada’s federal health system, ‘Health Canada’, has instituted proposals to reduce BPA levels in the lining of infant formulas and to investigate industry alternatives.


If your health and those of your friends and family matters to you, don’t wait for health authorities and governments to tell you that BPA is a risk to your health……you may wait a long time!

Act now, and act by choosing alternatives to tin cans and plastics when it comes to your food and drinks…… your health and those of your loved ones will be better for it!

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