Bisphenol A – or BPA – has been something of a controversial substance for some time in the United States (US) as well as overseas. In the past, it’s been widely used in everyday products such as water bottles, baby feeding bottles, the linings of food cans, and some cash register receipts. However, despite its arguably widespread use in commerce, there has been a dramatic decline in the use of BPA in the US over the past few years, especially in baby feeding bottles and sippy cups (where it is now banned), and in plastic water bottles. This has been driven by increasing public concern, and outcry, over the safety of the substance in such products.
To help make sense of what is known, and what is not, on the safety and risks of BPA, we’ve compiled a short set of questions and answers:
What is BPA, and where is it used?
BPA is one of the components of polycarbonate plastics, the hard, clear plastics used everywhere from glasses and DVDs to windows, headlamp lenses and water bottles. It’s also used in epoxy resins, which are extremely tough and heat resistant materials. Because these resins are so resistant to chemicals and heat, they are often used to line the inside of food cans to protect against corrosion and contamination. BPA can also be found in thermal cash register receipts – which use paper that darkens when heated.
Why is BPA used in food containers?
Materials like polycarbonate and epoxy are strong, versatile, and resistant to chemicals and heat, making them well-suited for use in products used to store food in.
Up until a few years ago, BPA was commonly found in polycarbonate water bottles, baby bottles and sippy cups. The material was used because it’s strong, light, and durable. However, in 2012, the US Food and Drug Administration (FDA) banned the use of BPA-containing polycarbonate in baby bottles and sippy cups because, based on a petition from the American Chemistry Council, these uses had been abandoned by manufacturers.
While the FDA still considers BPA to be safe for use in food products used by adults, there has also been an apparent sharp decline in its use in water bottles in recent years, resulting in few, if any, overtly BPA-containing water bottles being available for purchase in the US today.
BPA is still used in food can liners, as it continues to provide a highly effective barrier against corrosion and contamination. A major issue here is that the chemistry of some foods – especially acidic foods like tomatoes – can cause can liners, and the cans themselves, to degrade and corrode. This increases the chances of harmful bacteria like Clostridium botulinum – which produce the highly dangerous botulinum toxin – from getting into the food contents. BPA-containing epoxy resins are especially effective at maintaining the integrity of cans for a wide range of foods, and for a long time seemed a smart choice in terms of performance, versatility and safety.
However, given concerns over possible health impacts of BPA, a number of manufacturers have committed to reducing and/or eliminating the use of BPA in their food cans over the next few years. And a number of food retailers are preferentially stocking food cans that do not contain BPA, or exploring other forms of food containers.
What are the health concerns associated with BPA?
There are concerns that BPA behaves like the human hormone estrogen if it gets into the body (it was originally developed as a synthetic form of estrogen). Because of this, some researchers worry that, if exposed to significant levels, it might interfere with normal biological functions, and lead to a range of health impacts. Some are concerned that unborn children and infants may be especially vulnerable if exposed to BPA at certain times in their development.
In response to these concerns – both in the US and other regions – there has been intense research into the safety of BPA. Like much research, though, the findings cannot be said to be completely conclusive. What the research does do, however, is provide policy makers, regulators, industry and other key stakeholders – including the public – with a better understanding of where using BPA might be acceptably safe, and where caution may be warranted.
In 2014, the US FDA completed a four year review of over 300 scientific studies on BPA, and did not find any evidence that the substance is unsafe when used in food packaging.
And in 2015 the European Food Safety Agency (EFSA) – the FDA’s European counterpart – published a comprehensive assessment of the state of the science, and concluded that “there is no health concern for any age group from dietary exposure [to BPA] and low health concern from aggregated exposure”.
Both the FDA and the EFSA evaluations were comprehensive, and closely examined available data on evidence of BPA causing health effects at different exposure levels. However, despite both agencies concluding that BPA is acceptably safe under normal conditions, current research hasn’t completely ruled out possible health impacts within vulnerable populations including unborn and young children, and people who experience especially high exposures.
Underlining this, in 2008, the US National Toxicology program (NTP) – a US federal interagency program that evaluates substances of public health concern – published the results of an extensive evaluation of BPA. The report concluded that BPA poses “some concern for effects on the brain, behavior, and prostate gland in fetuses, infants, and children at current human exposures”. However, it went on to stress that there is negligible concern that pregnant women exposed to BPA will result in “fetal or neonatal mortality, birth defects, or reduced birth weight and growth in their offspring,” and negligible concern that exposure will cause reproductive effects in non-occupationally exposed adults.
Despite these evaluations, there remain numerous published studies in peer-reviewed journals that suggest BPA may be associated with a range of chronic health conditions, including cancer, type-2 diabetes, obesity, asthma, and behavioral changes.
Many of these studies are still inconclusive, and while they suggest areas we should be paying attention to, they are not mature enough yet to support informed safety decisions in many cases. In part this is because we are still learning how to understand the subtler effects of chemicals like BPA in the body.
One of the challenges being faced by researchers is that there is some evidence that low levels of BPA may turn out to be more harmful than higher levels. While it’s unclear how lab studies relate to actual health impacts in many cases, it appears that small amounts of BPA may trigger different types of responses – and lead to different health impacts – than higher levels, especially within certain periods in a foetus or child’s development.
This idea of small amounts of material being more harmful than large ones (technically, it’s called a non-monotonic response) may seem somewhat counterintuitive. It’s also quite controversial, and as yet there is only limited evidence to support it in the case of BPA. This is also a concept that is relatively new to how chemical risks are evaluated, and because of this there is sometimes disagreement amongst experts on how to interpret the data we do have on potential health impacts.
Because of uncertainties like this, the US National Institute of Environmental Health Sciences (NIEHS), in partnership with the FDA and academic researchers, is currently involved in multi-year study (the CLARITY-BPA research program) that’s looking at better understanding how BPA might present risks to health – especially at low levels – and how these might be avoided.
How risky is BPA?
The most comprehensive evidence-based analyses available indicate that, at typical exposure levels – i.e. those a normal person would experience who regularly eats canned food – there is negligible risk to an individual’s health from exposure to BPA.
In its latest review, EFSA concluded that being exposed to BPA is safe if you keep below 4 µg per kg of body weight per day. In other words, if you weigh 70 kg (~ 155 pounds), you should be OK if you are exposed to less than 280 µg each day. EFSA estimated that most people are typically exposed to less than 56 µg per day – five times less than the safe level.
The exact amount of BPA you might be exposed to each day depends a lot on what you do and what you eat. For instance, EFSA’s review indicated that food from cans may contain as little as ~2 µg of BPA per can, or as much as ~20 µg of BPA per can. An earlier, 2011 study measured the amount of BPA in the contents of 78 cans (representing different foods), and found that concentrations ranged from 2.6 to 730 ng/g – or between ~1 and 310 µg for a 15 oz can of food (although these were the extreme values measured – with most values being below this upper level.)
The bottom line here is that risk depends on both the potential for something to cause harm (its “hazard”), and how much of it is needed to cause a certain amount of harm (in other words, how much we are exposed to). We know from research that BPA certainly has the potential to cause harm, depending on how old you are. But then, so too, do many other things we expose ourselves to each day. To understand the actual risk, we need to know how much of the substance is dangerous.
Part of the challenge here is that our bodies quickly convert BPA into a much safer form (it’s a process called “conjugation”), and rapidly excrete the substance through normal physiological processes. And so while we know that unconjugated BPA can be harmful, most of this harm is rapidly neutralized by our bodies.
Because of this, even though BPA presents a hazard, current research indicates that the risks to adults are probably low under typical exposures.
Are any risks associated with BPA different if you’re pregnant?
There is research in animals that suggests being exposed to BPA while you are pregnant may possibly affect your unborn child. This research is still ongoing, and is by no means conclusive. But what we do know is that it might be possible for the unconjugated (i.e. the harmful) BPA to reach the fetus in utero, where an ability to effectively handle the substance has yet to develop.
Recent research, for instance, has shown that both conjugated and unconjugated BPA can be found in fetuses of exposed mothers. Research has also shown that, where pregnant mice are fed a diet that has high concentrations of BPA (far higher than people are typically exposed to), there is an increased likelihood of their young developing liver cancer.
These, and similar studies, need to be read with some caution as, while they raise important questions, they do not provide conclusive data that can be used to predict risk. This is especially the case where they involve excessively high exposures, there are uncertainties in how animal (and cell-based) studies relate to humans. Nevertheless, studies like this do indicate that there is more to learn about the safe use of BPA, especially in vulnerable populations. It is for these reasons that federal agencies like the National Institute for Environmental Health Sciences continue to commit large amounts of funding for research in this area.
Isn’t it safer to avoid BPA, just in case?
At the end of the day, the decision to use or avoid BPA-containing products is a personal choice. Certainly, the bulk of current research – and assessments by many leading experts – indicate that exposures such as eating food from cans containing BPA is acceptably safe, and not something to be concerned about. But this alone is unlikely to be reassuring to all consumers. And even if the science suggests that BPA is “safe” in relation to their personal circumstances, there are likely to be many consumers among us who wish to exercise their right to purchase BPA-free products and limit their potential exposure accordingly.
If, however, you do decide to go BPA-free, it is worth considering what it is replaced with. We know, for instance, that using unlined food cans is far riskier than using lined ones. Put simply, it is too easy for pathogens to get into the food as the can corrodes, potentially resulting in exposure to dangerously contaminated food.
In response to public concern over the use of BPA in consumer products, some companies are replacing BPA with alternative substances in their cans. While this responsiveness to concerns should be acknowledged, such action does, however, raise a myriad of other questions regarding potential health impacts of these alternatives. Many of them have not, for example, been the subject of the types of extensive research that has been conducted on BPA (which has been studied very extensively indeed). This opens the door to using alternatives that look good on paper, but may turn out to be potentially more harmful in practice.
These are what are called “regrettable substitutions”, because they turn out to be not as great as they initially seemed. And history is, unfortunately, full of them despite the best intentions of all involved.
So what’s the bottom line on BPA?
While most researchers and risk assessment agencies consider BPA to be acceptably safe when used appropriately, there’s still ongoing research to get a better handle on when and where it’s OK to use, and where maybe more caution is needed.
When used in products like food cans, BPA-containing materials help keep the contents safe. But as with most technologies, there are tradeoffs between the benefits and the potential risks. Because of this, perhaps the more important question is “how we ensure our food is as safe as possible – whatever approaches we use?”.
Manufacturers are already looking into BPA alternatives, and some of them have introduced BPA-free products, with more on the way. This certainly helps eliminate the question of whether BPA is safe, because the BPA isn’t there any more. But what is less clear is whether the alternatives are more, or less, safe.
This is where more research is needed, as well as better ways to ensure the overall safety of the food we eat.
In the meantime, the more we know about how the pros and cons of BPA and other materials, the better-able we’ll all be in making informed decisions on the safety of the food we eat.
You can read more CRIS Bits posts on BPA here.