Concern in recent years about the health effects of bisphenol A (BPA) have driven the chemical out of many of the plastic goods we use on a daily basis. But while you might not find BPA in new plastic bottles, bowls, or cans, those products have often switched to a similar chemical with similar properties to get the job done. Many companies have turned to bisphenol S (BPS) to fill the hole left by BPA. New research out this week calls into question how different BPS is from BPA in terms of health effects and gives readers pause to think how meaningful that “BPA-free” label really is.
What is BPA and what is it used for?
BPA is a chemical used in the manufacture of plastics. In particular, it’s often used to harden plastics to make them rigid and durable. It’s also used to make things like paint, adhesives, home and paper products, receipt paper, and to line cans and water pipes. In essence, BPA is almost everywhere because it’s used for many, many different types of products. Almost all of us have low levels of BPA circulating in our body even if you’re the kind of person who tries to avoid BPA.
Is BPA dangerous?
The safety of BPA is still an ongoing conversation in the medical and scientific field. There are some studies, mostly in animals, that have indicated that BPA might interfere with the some of the hormones in the body, especially hormones like estrogen that are involved in growth and reproduction. As a result, some have hypothesized that BPA may be involved in a wide variety of diseases, even though it’s only in the blood at very low levels in most people. The problem is that these ideas haven’t held up under more intensive study in humans. While animals are very similar to humans in many ways, there are also many differences. On the whole, well-designed studies of BPA’s effects in humans haven’t shown there to be any consistent, dangerous health effects in any age groups.
The U.S. Food and Drug Administration (FDA), which regulates chemicals people ingest based on their safety and effects on human health, has done extensive studies and reviews of the research on BPA and hasn’t found there to be any apparent danger. While the FDA no longer lists baby bottle and other baby products as a use for BPA, this is solely because the industry decided not to use the chemical in these products any more, not because it was banned for being unsafe as some have claimed. The same has been the case in the European Union, who has also concluded based on extensive review that there is no danger to human health.
What is BPS?
In spite of the lack of evidence for human health dangers, many individuals are concerned about the possible health effects of the chemical and have decided to avoid products that contain BPA. Companies have responded by removing BPA and labeling their products as “BPA-free.” Unfortunately, these products need a replacement for BPA, which in many cases is BPS. While BPS is chemically different from BPA in some ways, it’s in the same family and less is known about the health effects of BPS. This is where the current study comes in. The research team had done studies on the effects of BPA in the past and wanted to know if the health effects of BPS might be similar in the animal models they use.
How did the researchers study BPS?
The researchers used the zebrafish as their model animal. While you might think that no animal could be more different from humans than the zebrafish, they actually have many commonalities that make them useful. In particular, the zebrafish have a nervous system that develops in a similar way to humans and also uses many of the same hormones for development that researchers think may be affected by BPA and BPS. That means that changes in these systems in zebrafish are likely to occur in similar ways in humans. The researchers took zebrafish embryos and exposed them to different levels of BPA in a petri dish. They also exposed one group to a low level of BPS for comparison. They followed embryo development for five days and watched how they matured. They then looked at the genetics of each population of embryos to see which genes might be affected by BPA or BPS exposure.
What did the researchers discover?
The researchers found that BPA significantly sped up how quickly the embryos hatched even at low levels, indicating that they were developing faster as a result exposure to the chemicals. This had been found in the past for another species of fish and is one reason why some researchers think BPA might lead to early puberty in children. When the researchers looked at the brains of these fish on a microscopic level, they found that both BPA and BPS led to changes in the parts of the brain that release hormones responsible for growth, development and maturity. When the team looked at the gene analysis, they found that both BPA and BPS were binding to the same receptor for the sex hormone estrogen, which can also play an important role in brain development and may explain the changes they saw in the brain. They also found that both BPA and BPS seem to bind to and interfere with receptors for hormones in the thyroid and acted on genes involved in sexual development and reproduction. In summary, while BPS didn’t act in exactly the same way in all cases, it disrupted hormonal signals in a very similar way to BPA. Of note, neither chemical affected the survival of any of the fish embryos and the researchers didn’t assess the long-term health of the fish exposed to either chemical.
How does this apply to me?
These results should be interpreted cautiously. We can’t say from this study that BPS is bad for human health because we don’t have anywhere near enough data on what the effects are on humans in the real world. While changes were seen, it’s not clear what these changes mean and whether they harm the fish in any way. This study is mainly a nudge for further research.
What this study does remind us is that the “BPA-free” label doesn’t mean a plastic is free of anything that you might be trying to avoid. Removing an important chemical from production means it will be replaced by something else that, as in this case, may be chemically similar and have similar effects on humans. That label is more about marketing than about a true health claim. If you’re concerned about BPA, you may be able to lower your exposure by using glass, wood or metal products instead of plastic. But remember, BPA and BPS are present in many of the items we use today and, until a good alternative is found or serious health dangers appear, that will likely continue to be the case for the foreseeable future.