By: Dana Sackett
Zebrafish are small freshwater fish that originated in rivers from India. These fish share important biological properties with all vertebrates that make them useful in understanding how contaminants may impact other vertebrates in the environment, including ourselves. Logistically they are also useful because they are easy to maintain in aquariums, and they have external fertilization and transparent embryos, making all stages of development easy to measure. In fact, zebrafish were recently instrumental in several studies demonstrating that ‘BPA-free’ products may not be any safer than products with BPA (aka bisphenol A).
BPA’s are found in plastics (water bottles, tableware), the inside lining of cans, food packaging, receipts, and many more everyday products. With more and more evidence showing the harmful effects of BPA to wildlife and human health (see Where is Captain Planet when you need him), industries began to search for alternatives to BPA to use in their products. In fact, the FDA banned the use of BPA in all baby bottles, sippy cups, and infant formula packaging because manufactures dropped BPA for ‘safer’ alternatives in 2012. Indeed, many of the products labeled ‘BPA-free’ replaced BPA with the alternatives bisphenol S (BPS) or bisphenol F (BPF). However, these alternatives have recently come under scrutiny.
BPS and BPF have similar properties to BPA, which is why they are so useful as replacements. However, it turns out they seem to have the same toxic effects and potency as well. Studies using zebrafish showed that BPS caused impaired reproduction and growth, lower testosterone, lower sperm counts, lower egg production, smaller gonads, higher estrogen levels, lower and slower hatching rates, higher embryo malformations, affects on the thyroid hormone system, which impacts brain development during gestation, and more.
Zebrafish embryo. Source: http://www.cnn.com/2016/02/01/health/bpa-free-alternatives-may-not-be-safe/
In fact, a recent article compiled several studies on BPS and BPF to review what all those studies found. They showed that in zebrafish, rats and human cells, BPS and BPF had similar hormonal effects. Even more, this study directly compared BPA with these replacements and found that their effects and potency were very similar to BPA, calling into question the safety of ‘BPA-free’ products.
It seems that ‘BPA-free’ can no longer be called ‘non-toxic’ or ‘worry free’ as the labels here would suggest. Source: http://loe.org/shows/segments.html?programID=14-P13-00011&segmentID=4
Our environment is awash in chemicals that we produce. It seems that we need to do a better job of distinguishing harmful contaminants before they make-it into our everyday products and ecosystems. For now the best way to avoid exposure to these particular chemicals and keep them out of our environment is to avoid plastic as much as possible (drink out of glass or stainless steel containers, do not microwave food in plastic containers, avoid single-use plastic products) and to avoid handling receipts.
References and other info:
Briggs JP. 2002. The zebrafish: a new model organism for integrative physiology. Am J Physiol Regulatory Integrative Comp Physiol 282:R3-R9.
Ji K, Hong S, Kho Y, Choi K. 2013. Effects of bisphenol S explosure on endocrine functions and reproduction of zebrafish. Environ Sci Technol 47:8793-8800.
Naderi M, Wong MYL, Gholami F. 2014. Developmental exposure of zebrafish (Danio rerio) to bisphenol-S impairs subsequent reproduction potential and hormonal balance in adults. Aquatic Toxicol 148:195-203.
Rochester JR, Bolden AL. 2015. Bisphenol S and F: a systematic review and comparison of the hormonal activity of bisphenol A substitutes. Environ Health Perspect 123:643-650.
Stegeman JJ, Goldstone JV, Hahn ME. 2010. Perspectives on zebrafish as a model in environmental toxicology. In: Perry, S.F., Farrell, A.P., Brauner, C.J. (Eds.), Fish Physiology, 28. Academic Press, New York, NY, pp. 367–439.
Qiu W, Zhao Y, Yang M, Farajzadeh M, Pan C, Wayne NL. 2015. Actions of Bisphenol A and Bisphenol S on the Reproductive Neuroendocrine System During Early Development in Zebrafish. Endocrinology: DOI: http://dx.doi.org/10.1210/en.2015-1785