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The credibility of scientific discoveries depends on their reproducibility. As a scientist, it is therefore disastrous not to be able to reproduce your own conclusions. Our laboratory has been in this situation many times; In each case, the involuntary environmental exposure distorted our data. Our first accidental foray into toxicology 20 years ago convinced us of the need to understand the reproductive effects of chemical contaminants in the environment. The last turn of our journey in this way adds a new dimension to an old concern, BPA.
Bisphenol A, or BPA, is a chemical of human origin that has become a household word. This is a plasticizer used in a wide range of consumer products that daily exposure is inevitable. People absorb BPA through our skin – recipes and contamination of personal care products and water. We ingest it through contamination of plastic food containers and food and beverage liners. We even inhale it as a contaminant in the dust. Studies of this chemical number by the thousands, but the dangerousness of BPA remains "controversial". Here's why: While conventional toxicology data provide little or no evidence of harm, independent researchers like us have reported very low effects. doses supposed to be in the field of human exposure.
The consequences of these low dose effects on human health and reproduction attracted media attention and increased consumer discomfort. In response, manufacturers introduced BPA alternatives by producing bisphenols of similar structure. As a result, BPA does not simply contaminate our environment, but an ever-growing range of bisphenols. Our recent studies on several substitutes suggest effects on egg and sperm production similar to those induced by BPA.
The substitutes for BPA … Already seen?
Twenty years ago, we entered the world of BPA when mouse cages hosted for our studies were damaged when they were inadvertently washed with soil detergent. Unbeknownst to us, the detergent caused leaching of BPA from the cages. We were studying the eggs of young females and we observed an immediate increase of eggs with scrambled chromosomes that would give rise to chromosomally abnormal embryos. In the next 20 years, our studies and those of colleagues described the effects of BPA exposure on the brain, heart, lungs, prostate, mammary gland, and other tissues. development. Our studies have described serious effects on sperm production. Together, these results ignited the debate about the safety of BPA and resulted in the rapid emergence of "BPA-free" products.
Remarkably, almost exactly 20 years after the exposure of our BPA mice, we found ourselves, once again, victims of an environmental contamination that stopped our research. We were working to identify critical BPA exposure windows when we noticed that something was interfering with our experiences. This time, it was more difficult to break the ground: again, it seemed to be due to damage to the cage, but the damage was less severe, limited to a subset of cages, and some
The main culprit this time was not BPA but the replacement of bisphenol, BPS, by leaching damaged polysulfone cages. Knowing what it was doing, it was not easy to eliminate it. We tried several less expensive methods to solve the problem, but we eventually had to replace all the cages and water bottles of the installation. When we were able to resume our studies, we experimentally tested four common replacement bisphenols and found effects on sperm and egg production in our mice, analogous to those resulting from exposure to BPA.
The possibility that the effects of exposure can spread over several generations is a growing concern. Our recent experience with accidental exposure has allowed us to ask if the effects of exposure to BPS persisted from one generation to the next, and if so, for how long. Our data suggest the persistence of effects over three generations, with complete recovery evident in great grandchildren.
Widespread use of BPA chemicals
Do we just have bad laboratory karma? No, we think we have supersensory powers. The process of making eggs and sperm is tightly controlled by complex hormonal signals. This makes it vulnerable to endocrine-disrupting chemicals such as bisphenols – chemicals that can interfere with the hormones in our body. Bisphenol-based contaminants cause a seismic shift in our data, but it's not that other people's research is not equally affected, but most remain completely ignorant.
Importantly, our laboratory knew what data should look like from unexposed animals. What if we did not? We would have misinterpreted our results. Had we asked whether BPA had an effect, contamination with Bisphenol would have decreased it, leading us to conclude that BPA had little or no effect.
It's not just a hypothesis. The use of BPA is so prevalent in consumer products and common laboratory equipment (such as mouse caging materials or culture flasks) that a low level contamination of non-control groups exposed is more and more difficult to avoid. Data and findings from CLARITY-BPA, a broad and ambitious collaborative study by three US agencies, are being published. CLARITY was launched to understand why the results of traditional toxicological studies of BPA and those of independent researchers differ. Animal contamination was evident in a pilot study, but the source could not be determined and the CLARITY initiative continued.
Given our experience, we are very keen to draw conclusions from CLARITY data, as there is no way to determine the impact of low-level contamination.
The history of bisphenol details the evolution of a single class of chemicals that disrupt the endocrine system that are common contaminants in our lives. The ability of manufacturers to rapidly change chemicals to produce structurally similar substitutes compromises the ability of consumers to protect themselves from hazardous chemicals and the federal government's efforts to regulate them.
As a canary whose research has been derailed twice by bisphenols, we feel the need to choke out strongly: these contaminants can not only affect our health, but also our ability to conduct meaningful studies on their health and impact. l & # 39; environment.
SOURCE: The conversation
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