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Why we don't know all the facts about EDCs and humans.
Why we don't know all the facts about EDCs and humans.
By Sophia Yu
What makes a chemical "bad?"
When we think of "bad" chemicals, we tend to think of disease; that somehow if these "bad" substances enter our bodies, they will alter, change, or disrupt our normal processes. "Bad" chemicals are toxic. "Bad" chemicals must be avoided. So the question then becomes, how do scientists know for sure that things like phthalates or BPA or parabens are "bad" and other chemicals are not? What about the dosages of certain chemicals, especially those which are not necessarily the same level of toxicity? Most would be surprised to learn that in the case of most chemicals the answer is debatable, at least from the inside...
"How do scientists know for sure that things like phthalates or BPA or parabens are 'bad' and other chemicals are not?"
"How do scientists know for sure that things like phthalates or BPA or parabens are 'bad' and other chemicals are not?"
Ironically, as Endocrine Disrupting Chemicals (EDCs) have become more prominent in scientific research, they have also grown more controversial. EDC research originated with a focus on environmental and animal concerns. Many scientists credit the beginning of the EDC revolution to Rachel Carson’s 1962 novel Silent Spring, which explored the environmental harm attributed to the wide-usage of pesticides, namely DDT.4 Gathering evidence of infertile animals and decimated ecosystems, Carson was able to ring the alarm that something was not right with chemical pesticides, even despite widespread criticism and pushback of her claims. Because of its disruptive effects on the reproductive system, DDT was titled an EDC. Naturally, this same EDC conversation spread from effects on the environment, to effects on our own bodies.
Rachel Carson alongside her book Silent Spring
"The present day controversy of EDCs circles on their effects on humans; many scientists remain unconvinced that our scientific methods have adequately shown that EDCs cause harm to humans."
"The present day controversy of EDCs circles on their effects on humans; many scientists remain unconvinced that our scientific methods have adequately shown that EDCs cause harm to humans."
Figure 3 from Lee, D. H. et.al's paper which illustrates some of the key methodological limitations of EDC research
The present day controversy of EDCs circles on their effects on humans; many scientists remain unconvinced that our scientific methods have adequately shown that EDCs cause harm to humans. I can validate some of the reasoning behind this conclusion based on my experience and training. There are some serious yet objective methodological limitations that prevent scientists from gathering evidence that EDCs present harm in humans, the most interesting including (1) a lack of an unexposed or control group, and (2) the low reliability of exposure assessment1. As Michelle Murphy gets at with her term Alterlife, it is undeniable that 21st century humans live in a transitional state, one where we are experiencing an unwilling yet totally encapsulating form of chemical exposure3. As such, it becomes nearly impossible to identify an unexposed group of humans that can serve as a genuine negative control for which to compare and draw conclusions from1. Furthermore, many EDCs have short half-lives which provide limitations for ensuring the accuracy of exposure, even within animal models. BPA, for example, exhibits a large variability in repeated experiments, to the extent where exposure levels can even vary daily.1
Considering the limitations of our methodology as 21st century scientists, it makes sense why controversies have arisen which debate the effects of EDCs on humans. However, in my opinion, I wonder if this issue can be solved by reconsidering what we establish as the framework for testing EDCs in humans. Rather than relying solely on epidemiological studies to prove harm, it makes more sense to integrate additional evidence even from in-vitro experiments or from animal models to craft the picture of EDCs. The omnipresence of chemicals will not go away, but as scientists we still have the power to adapt our model to accommodate these changes.
Lee, D. H., & Jacobs, D. R., Jr (2019). Firm human evidence on harms of endocrine-disrupting chemicals was unlikely to be obtainable for methodological reasons. Journal of clinical epidemiology, 107, 107–115. https://doi.org/10.1016/j.jclinepi.2018.12.005
Melmed, S., Polonsky, K. S., Larsen, P. R., & Kronenberg, H. M. (2011). Williams Textbook of Endocrinology E-Book. Elsevier Health Sciences. https://books.google.com/books?id=nbg1QOAObicC
Murphy, M. (2017). Alterlife and Decolonial Chemical Relations. Cultural Anthropology, 32(4), Article 4. https://doi.org/10.14506/ca32.4.02
Schug, T. T., Johnson, A. F., Birnbaum, L. S., Colborn, T., Guillette, L. J., Jr, Crews, D. P., Collins, T., Soto, A. M., Vom Saal, F. S., McLachlan, J. A., Sonnenschein, C., & Heindel, J. J. (2016). Minireview: Endocrine Disruptors: Past Lessons and Future Directions. Molecular endocrinology (Baltimore, Md.), 30(8), 833–847. https://doi.org/10.1210/me.2016-1096
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