The safety of babies’ bottles made of polycarbonate plastic with the ingredient Bisphenol A (BPA) has been in the news again. This time it’s being widely, but not quite accurately, reported that the US food safety regulator (USFDA) has done an about face on its thinking on the safety of BPA.
The USFDA continues to stand by the current internationally-accepted safety levels for human exposure to BPA. But, like all food safety regulators including NZFSA, the USFDA is monitoring research findings on BPA. Its approach now is to encourage people to take reasonable steps to reduce exposure, especially for pregnant women, babies and infants.
Opponents of BPA point to Canada’s recent ban on babies’ bottles made with it as more evidence that BPA is dangerous. What they don’t acknowledge is that this decision differs from the conclusion by Health Canada’s experts that BPA is safe at the levels people are currently exposed to, and that their politicians decided to ban BPA in babies’ bottles despite the science. BPA critics are further encouraged by the latest moves in the US to encourage reduced use of polycarbonate bottles and feeding cups for babies and infants.
The recent Canadian and US actions highlight the difference between what the risk assessors (scientists) say, based on the available science, and what the risk managers do (which often brings in the political arm of governments) after considering not just the science, but probably also public opinion, costs, and politics. This mismatch between the conclusions of the risk assessors and the decisions of the risk managers is adding another dimension to the whole BPA debate.
BPA is an ingredient of polycarbonate plastics, which have been widely used for about 40 years in babies’ bottles, sports water bottles and food can linings. It can be identified by the number 7 in the recycling symbol on the product.
Used in these products, BPA can leach into food or water in very low concentrations, especially if repeatedly exposed to very high temperatures or harsh detergents such as in the microwave or dishwasher. For this reason the World Health Organization has set a conservative Tolerable Daily Intake (TDI) of 0.05 mg BPA/kg of body weight. This TDI applies a 100-fold safety margin to the maximum amount of the substance which can be consumed every day over a lifetime without showing any detectable health effect (the no-observed-adverse-effect-level, or NOAEL). To put it in perspective: a 5kg baby would need to drink from 80 polycarbonate plastic bottles a day for many years to reach the safety limit.
Studies in animals have linked BPA to a range of adverse health effects including heart disease and type 2 diabetes. In recent years, concerns around BPA have revolved around its ability to mimic the hormone oestrogen. Substances that have this characteristic are called ‘endocrine disruptors’ and some recent animal studies have raised theoretical questions around BPA’s possible effects at current human exposures on the brain, behaviour, and prostate gland in foetuses, infants and children. None of these studies is definitive. There are too many confounding factors, and so many other potential explanations for these observed health effects.
For example, if a study shows a link between urinary concentrations of BPA and heart disease can we attribute the disease to BPA? Or is it more likely that people with heart disease tend to eat more convenience foods? These are often packaged in polycarbonate plastic containers or plastic wrap containing BPA. But convenience foods also often contain higher levels of fat and salt which have proven links to heart disease. It may be the link between BPA and heart disease is correlation, not causation.
In terms of oestrogenic effects, by far the greatest contributor to oestrogen in the human body is phyto-estrogens found naturally in many plants we eat. The studies published so far have many gaps in them in terms of clarifying these connections.
Obviously, animal studies don’t reflect real world human experiences. That’s why results from animal studies include such high safety margins when applied to people. In the BPA studies to date, the USFDA notes inconsistent results between studies, doubts about the relevance of some animal models to human health, differences in the way and speed at which BPA is metabolised and detoxified at different ages and by different species, and in some studies there is a lack of information on whether toxicity increases with corresponding rises in BPA doses.
All regulators would like to see further research to address shortcomings in the existing studies and to provide more certainty. Otherwise the danger is that poor decisions may be made on the basis of public opinion and perception rather than real risk.
While decision-making that places a high value on public opinion and politics is a legitimate approach in a democracy, we all have to wear the outcome of the decision. A decision that gives more weight to public opinion than solid scientific evidence might not improve health outcomes but it may take useful products out of action or increase costs unnecessarily. Of most concern, it may open the way for another – potentially even greater – risk. We all know that one alternative to plastic babies’ bottles – glass – is not entirely risk free. But, the greatest risk by far with food is pathogenic bacteria. If we ban plastic wrap or polycarbonate containers because of perceived issues with BPA, we may expose ourselves to higher levels of bugs in our food. This is likely to be a far greater danger than the miniscule amounts of BPA we are currently ingesting.
When we take an action, we have to understand and live with the consequences.
NZFSA Chief Executive