Plastics have played an enormous role in increasing our quality of life. There is practically nothing that we do that hasn’t been improved or made possible by plastics… so the importance is not really up for debate. The concern, however, is whether it is safe to use plastics which come into contact with our food and our developing children.
As parents, one of our most important tasks is providing safety for our children so that they can grow into the best version of themselves. Unfortunately, in this age of social media, information (and misinformation) is spread at unprecedented speeds and it seems like a new “health risk” is discovered on a daily basis. Recently wifi, cell phones, processed meats, GMO’s and plastics have come under scrutiny and often it can be too time consuming to properly research these risks. Luckily, I’ve already done the research for you, so all you need is a few minutes to read this blog! I’ve spent the past 9 years doing research at renowned institutions in Boston and New York and throughout this time have acquired the skill of critically analyzing scientific works. Personally, none of my research has ever focused on anything remotely related to plastics, but lucky for you I do possess the expertise to provide you with relevant, published scientific data in an unbiased fashion.
In my approach, I used PubMed to search the literature for scientific articles to extract facts pertinent to the topic of the day. The core of what I do lies in attempting to disprove the commonly accepted hypothesis (in this case the hypothesis is that plastics are safe), while analyzing evidence both for and against this hypothesis and then deciding which side offers more compelling and credible evidence. To keep myself an unbiased reader, I try not to consider who funded and published the data and focus more on the strength of the study design and reproducibility.
Today the focus will be on all things plastic. To understand the issues facing plastic safety there are a few things you need know. First, there are 7 different categories of plastics: 1) Polyethylene Terephthalate (PET), 2) High Density Polyethylene (HDPE), 3) Polyvinyl Chloride (PVC), 4) Low Density Polyethylene (LDPE), 5) Polyproylene (PP), 6) Polystyrene (PS) and 7) Other. Technically you should find one of these numbers on everything that is plastic, but I’ve found many exceptions to that rule. Without getting into the specifics of each and every one I’ll just point out that PET is the most commonly used plastic for non-reusable water/soda bottles, etc. and polycarbonate, which falls under the “other” category, is a hard plastic which is commonly used for reusable water bottles. Epoxy resin, which is used to coat the inside of metal food containers, is also in this “other” category. Polycarbonate and epoxy resin have received a lot of negative attention because they both used to be made with bisphenol A (BPA; which will also be fondly referred to as phenols), which has become one of America’s most hated compounds.
During the production of plastics, compounds are added which give them certain characteristics, i.e. color, flexibility, or formability. These compounds are called additives or plasticizers and it is usually them, and not the actual plastic polymers, that are suspected of leaching into our food and causing issues. An important note is that BPA is actually reacted with phosgene to create polycarbonate, so it is necessary to make the plastic unlike most other additives.
THE LIFE AND TIMES OF BPA
I’d like to start by discussing BPA because there is extensive research and it provides the framework for what we can expect from future studies of others plastic compounds. BPA was invented in 1891 but wasn’t used commercially in plastics until 1957 where it served as a component of epoxy resins (which coat the inside of metal food cans, the back of receipts, and the outside of hospital furniture, among other things). Although the Federal Food Drug and Cosmetics Act of 1958 required the FDA to regulate chemicals in food, BPA was thought to have low toxicity because a study in the 1960’s showed only minor effects when it was applied to human skin1. Its carcinogenicity wouldn’t be studied for another 20 years so no regulations were put into place by the FDA at this time.
The first study on its carcinogenicity was published in 1981 in a toxicology report by the National Cancer Institute (NCI) which concluded that BPA was not carcinogenic to rats or mice2. This may seem like a rather innocuous start, however the conclusion that the authors came to doesn’t accurately reflect the data. In the experiment male and female rats and mice were treated with saline (salt water), “low-dose” phenols or “high-dose” phenols. A significant increase in leukemia or lymphoma in male rats given the low-dose phenols compared to saline was observed. Results also showed an increase in leukemia or lymphoma in the high-dose group compared to saline but the increase was not statistically significant. In all, 18/50 rats in control group developed leukemia or lymphoma compared to 31/50 in the low-dose group and 25/50 in the high-dose group. The authors dismissed this result as significant because the high-dose group had less cancer than the low-dose group. Basically, they didn’t trust the data (more on why this isn’t as abnormal as it sounds later).
However, clearly phenols had some effect on the rats in this study which is why it is very odd that the authors said in no uncertain terms that there was no carcinogenicity. A reasonable person might think at the very least I should repeat this experiment or perhaps use a larger sample size, but instead the NCI classified it as non-carcinogenic and the plastics industry breathed a sigh of relief. In 1988 the FDA would set a regulation of 50 ug/kg body weight per day of bisphenol A based in part on data from this initial study. It should be noted that according to the laws at that time if BPA had been classified as carcinogenic there would have been no allowable dose, i.e. it would not have been allowed to be used in plastics that contact food3.
As research in the 1980’s began to pick up BPA was linked to potential harmful reproductive effects in multiple studies4, 5. Later experiments showed that exposure to BPA caused neurological defects in mice6, hyperactivity in rats7 and aggressive behavior8. Along with neurological effects, BPA was also found to induce insulin resistance in mice9 and induce growth of breast cancer in cells10. Prior to 2008, over 100 research studies were performed by academic institutions with government funding and 90% of these studies showed at least some adverse effects from exposure to BPA at or below the FDA’s allowable level3. Comparatively, there were 11 studies which were funded by the plastics industry and miraculously showed no effects from these exposure levels3.
By 2009 it was clear that the scientific literature had reached the conclusion that BPA was harmful to animals at levels at or below the FDAs regulated limit and the FDA was facing a lot of pressure to explain this. In response, they did what any reasonable government agency would do under these circumstances: admit that there was concerning research regarding bisphenol A and began a program to help limit its exposure until they could definitively determine whether the amount of BPA that people were regularly exposed to was dangerous or not. Just kidding, what the FDA actually did was ask the Executive Director of the American Chemistry Council (a trade group that represents chemical manufacturers) to prepare a report showing that BPA is safe11. Then the FDA ignored the National Toxicology Program (another government agency) when concern was expressed about the effects of BPA.
Finally, an assessment was released in 2008 saying that BPA was shown to be safe despite evidence to the contrary. After the FDA released this assessment, the FDA Science Board Subcommittee wrote a response saying “The draft FDA report does not articulate reasonable and appropriate scientific support for the criteria applied to select data for use in the assessment12”. Basically, the scientific branch was telling the regulatory powers of the FDA that their assessment that BPA was safe was not supported by science. Apparently, this made no difference to the FDA as they still hold the position today that BPA is safe at the levels which humans are currently exposed to.
There were two major arguments being made by researchers who claimed that BPA was safe. The first was that humans were being exposed to very low levels of BPA and the second was that these very low levels of BPA were not harmful. While the first argument is still up for debate, the second has been repeatedly proven false over the years. While there is a handful of scientists who have published studies which show humans are exposed to very low levels of BPA with practically no chance of causing harm13, 14, most studies show that the current exposure levels are large enough to have adverse effects, and have actually linked BPA exposure to multiple diseases including breast cancer and type 2 diabetes15, 16, 17, 18, 19. It may seem odd how one group of researchers can conclude that BPA is completely safe, whileothers find the exact opposite result, but in this case the reason is fairly clear. Relatively recently, a phenomenon was discovered called non-monotonic dose response curves which explain why low levels of BPA and other estrogen disrupting chemicals are harmful at lower levels than expected. Basically, the theory is that sometimes a low dose of a compound can have a larger effect than a higher dose of the same compound (FYI: this explains the results of the very first carcinogenicity study on BPA that I discussed earlier). As you can imagine, some scientists are having avery difficult time accepting this new information since it is contrary to the way scientists have analyzed toxicology data for decades. However, that doesn’t mean that it isn’t the correct way to analyze the data as there are now hundreds of studies which support this new theory20. Ultimately, the groups who deny the health risks associated with BPA are just refusing to accept the new evidence because it’s new. They are kind of like your parents when they tell you that BPA is safe because they have used it their whole life and they are fine.
To summarize, BPA has been linked to multiple adverse effects at or around the levels which most scientists estimate we are being exposed to. Exposure is so widespread that 93% of people tested had detectable levels in their urine according to the National Institute of Environmental Health Sciences, and there is virtually no unbiased research that says it’s completely safe. After years of consumer outrage, many companies have removed BPA from their plastics and this felt like a big win for lots of people. Was this really a big win though? When plastic companies started to remove BPA, I thought it was very odd because hardly anyone was reporting on what they were replacing it with. Obviously whatever replaced BPA had to be structurally similar since it’s an integral part of the plastic.
I have joked with my wife that they were probably just replacing bisphenol A with bisphenol B. As it turns out I was pretty close because they are mostly using bisphenol S or bisphenol F! These compounds are very similar to BPA, and early studies have shown that they are as active as BPA AND have the same endocrine disrupting behavior as BPA. The only real difference is that there is much less research on these compounds so it will be a few more years before the scientific community can say with certainty that they are as dangerous as BPA. Once BPS and BPF are proven to be dangerous, the companies will switch to new compounds that haven’t been tested and the cycle will start all over again.
OK Enough about BPA! After all, there are 6 other plastic categories that don’t contain the stuff and they can’t all be bad, right? That’s not exactly true. The bottom line is that all commercially available plastics have additives that haven’t been studied nearly as much as BPA. Unfortunately, we have been operating under the premise that everything these noble plastic companies add to their plastics are safe, unless there is an overwhelming amount of evidence proving that they are unsafe. So, while you may not be able to decisively say that using plastics that contact food is harmful you similarly cannot assume that they are safe. Considering that it took almost 30 years of research to convince most people that BPA was dangerous, you may have to decide for yourself whether plastics are worth the risk before all the research is done on each and every plastic.
MORE THAN JUST BPA
Moving on to the other plastics we begin with polyvinyl chloride (PVC). PVC has also been researched fairly extensive because it leaches di-2-ethylhexyl phthalate (DEHP) which is known to have reproductive, neurological, respiratory and carcinogenic effects21. Research on this plastic started back in the 1970’s where a study found that phthalates migrated from haemodialysis tubing into patients’ blood22. At the time it was recommended that the tubing be made from a different plastic that had less harmful potential, but PVC is still common in medical devices today so that advice was not heeded. In addition to medical devices, PVC is often used for baby toys and studies have shown that phthalates do in fact leach from the PVC into the infants’ saliva when they put their mouths on the toys. Although there is no debate about whether these children are ingesting phthalates, scientists tend to disagree as to whether or not the amount of phthalates consumed by the children is harmful23, 24, 25, 26. Overall, PVC isn’t really used for plastics that contact food so it’s probably not something you have to worry about on a daily basis unless you have children. Even then, I’m not sure how much it’s even used for baby toys anymore because my toddler has A LOT of toys and the vast majority of them are made of polypropylene, not PVC.
Unlike polycarbonate and PVC, polyethylene terephthalate (PET) is the first plastic that we will discuss which at least some internet sites claim is safe. To be fair, however, there are mixed feelings amongst bloggers as some think you should exercise caution when using PET and others think you should not use it at all. Most commonly known for being used in water and soda bottle containers, this plastic is obviously used in extremely large quantities so it’s very important to determine its safety. A few things really popped out at me when I started researching PET, and the first was that antimony leaches from this plastic in relatively high amounts27, 28, 29. This is surprising because it seems like a bad idea to have a heavy metal leaching out of a plastic used by millions of people every day. Anyway, studies have shown that time and heat both increase the leaching rate of antimony30, 31 and one study found that under conditions described as a “worst case scenario” i.e. 75°C for 5 days, the levels of antimony exceed the allowable daily limits set by the EPA30. Additionally, studies have shown that antimony leaching is variable depending on bottle manufacturer. This is not good news for consumers since there is no way to determine when you’re buying a bottle whether or not that particular manufacturer uses plastic which leaches high or low amounts of antimony. Antimony isn’t the only compound of concern from PET bottles however, as multiple studies have also detailed endocrine disrupting activity32,33. One study in particular, tested 36 commercially available PET plastics and 26 of them had detectable estrogenic activity33.
Generally considered one of the safest plastics around, polypropylene is used for everything from baby toys to water bottles and “microwave safe” plates and bowls. For some reason most blogs that discuss plastics seem to think that because polypropylene is strong and resistant to heat that it will leach less than other plastics. Even www.lifewithoutplastic.com, which as you can imagine is about as anti-plastic as it gets, claims that PP is relatively safe. However, despite these claims PP does in fact leach compounds just like the other plastics. In fact, in 2008 researchers found that two additives were leaching into water from PP tubes, one of which was an anti-bacterial agent and the other was oleamide, a biologically active compound34. Additionally, an in-depth study tested PP and PS baby products including teethers and nipples and they found that relatively high amounts of endocrine disrupting compounds were readily leaching into artificial saliva35. The good news from this study was that leaching decreased over time as the products were exposed to the extraction medium so soaking your baby’s new plastic products before they use them should remove the majority of the potentially harmful additives35.
LDPE, and HDPE haven’t had an abundance of research done with regards to their food safety, however one comprehensive study was performed back in 2011 and tested many different types of plastics including these. What was found was that almost all plastics leached potentially harmful compounds including 70% of HDPE and 50% of PS tested33. The studies showed estrogenic activity in 98% of plastic bags, 44% of deli containers, and 100% of food wraps that they tested. The products that were analyzed came from both large retailers and organic retailers, with no difference between the two in terms of compounds leaching. Three years later in 2014, two similar studies specifically tested BPA-free plastics for estrogenic chemicals, and confirmed their presence after leaching into the medium being tested36,37. According to the authors there was a bright side to this study in that a small portion of the plastics tested showed no evidence of potentially harmful estrogenic activity meaning that it may be possible for companies to make these plastics safely 33.
THE PLASTIC RAT RACE
We’ve talked a lot about how most plastics leach compounds with estrogenic activity but what exactly does that mean and how relevant is it for us? Well firstly, for all of these studies when the products have been “tested” for estrogenic activity it means that the researchers have analyzed the compounds that leached from the plastics in cellular assays. Basically, the compounds (or liquids containing the compounds) were added to specific cell lines and determine if activity is present based on the cells response. While this can be a useful first step, it really does not correlate at all with how people will respond to eating or drinking food with these compounds. In order to properly evaluate the effect of these specific compounds on humans they would need to be identified, which mostly hasn’t been done yet. Then each would need to be tested in animals, followed by biomonitoring studies in humans just like they have done with BPA. Obtaining this type of information will take decades, which brings me to my next point… is it worth it? For half a century plastics were only monitored for a handful of known compounds including BPA, specific phthalates or heavy metals. Now, plastics are also being monitoring for groups of compounds, such as endocrine disruptors, and while this is an improvement it does not encompass all compounds that are potentially leaching from the plastic so we still have no idea what the hazards really are. Meanwhile, as scientists are trying to determine the safety of plasticizers, plastic manufacturers can easily change their additives at any moment, potentially changing what compounds will leach and making years of research irrelevant. Instead of trying to determine the safety of plastic additives, perhaps a more effective way to remove doubt would be to simply make plastics that don’t leach. Sadly, as far as I can tell there are no such products on the market or in development.
SHOULD YOU USE PLASTIC?
While there is not sufficient scientific evidence to say whether using plastics is harmful, there is enough evidence to say with certainty that plastics do in fact leach potentially harmful compounds into food and water. There is also evidence that low doses of these compounds can have adverse effects on humans, but that has not yet been conclusively demonstrated. Alternatively, there is virtually no reliable evidence that plastics are safe to use, as this is just an assumption that was made when they were introduced 60 years ago. There is a very big difference between something which has been proven to be safe and something which has been assumed to be safe and has not yet been proven to be harmful. Full disclosure, I’m not exactly “health conscious” (I used to eat 2 double quarter pounders with cheese every day for lunch and would drink soda pretty much every chance I had- my wife has since stopped this habit), but it concerns me that we know very little about what is in our plastic. So if you are someone like me, then you might want to start limiting the amount of plastics that you regularly use, especially since it is not a huge inconvenience. Buying a bottle of iced tea in a glass bottle instead of a plastic bottle or storing leftovers in glass bowls instead of plastic bowls is about as easy as a transition as you can make. If you (or your wife) are someone who is very concerned with everything that you are putting into your body, then maybe you want to make more of a concerted effort to stop using plastics altogether. While it may be impossible to limit plastic exposure completely because almost all prepared foods are exposed to them, it should be fairly easy to swap out plastic for many of the things you use on the regular.
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So where do you stand on the “Is Plastic Safe” debate? We’d love to hear your comments below!
References:
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