Replacement bisphenols are also endocrine disruptors

According to a new study by researchers at Washington State University, "Bisphenol-free" products may not be as safe and may even produce the same disruptive effects on the endocrine system as the bisphenols themselves. The new discovery comes 20 years after the discovery – by the same team – that bisphenol-A (BPA) produces chromosomal abnormalities in mice that can be passed down from generation to generation.

"In 1998, mice in our lab, housed in polycarbonate cages, were inadvertently exposed to a series of experiments when a person used the wrong detergent in the washer," says Patricia Hunt, lead author of the 'study. in the state of Washington. "This detergent damaged the plastic and leached the BPA from the cages, which caused a sudden increase in the number of abnormal eggs in normal females. Our discovery was highly publicized at the time and BPA became a familiar term.

Since then, thousands of other studies have also reported the disruptive effects of the endocrine system of BPA, and "BPA-free" products, considered safer, have subsequently flooded the market. "Unfortunately, manufacturers have simply replaced BPA with structurally similar bisphenols, and preliminary studies suggest that these chemicals could have similar effects to BPA itself," says Hunt.

Strange experience of déjà vu

"Following our misunderstanding with BPA, we opted for a more stable caging polymer, polysulfone (a replacement bisphenol composed of BPA and diphenylsulfone), for our laboratory mice. We have been using these cages for years without incident, but our new study, published in the same journal as the last time, Current Biology 10.1016 / j.cub.2018.06.070, describes a remarkably strange déjà vu experience.

Hunt and his colleagues made their new discovery in studies on meiosis in male and female mice. Meiosis refers to the process of sexual reproduction by which germ cells divide to produce gametes (eggs and spermatozoa). It is a specialized form of cell division that halves the number of chromosomes, creating four haploid cells, each genetically distinct from the cell from which it originated.

In their experiments, researchers observed changes in "meiotic recombination" with levels in some controls reaching values ​​similar to those observed in animals exposed to BPA. "Low recombination rates can be deadly because spermatocytes with homologs that do not recombine face certain death from a mechanism that stops and destroys cells with non-metaphase chromosomes," says Hunt.

"Same kind of effects on the gamete manufacturing process"

"To our surprise, our data changes coincided with the occurrence of physical damage (resulting in white residue) on some of the cages used in the facility. We tested these cages and found that they were leaking bisphenols. Although not all the cages were damaged and we could not determine how the damage occurred, the observed data changes indicate the same types of effects on the gamete manufacturing process that we had seen previously in BPA studies.

Gamete formation is controlled by subtle changes in hormone levels, she says, which makes the process extremely sensitive to the effect of compounds such as BPA that can mimic or interfere with the hormones in our body. body. "We call these chemicals" endocrine-disrupting chemicals "and it's harder and harder to limit our exposure to these products, as an increasing number of EDCs contaminate our daily lives."

Germinal effects can affect several generations

"Our results reveal that exposure to common replacement bisphenols causes effects on the germ line in both sexes, which can impact generations." They also suggest that chemical contaminants can affect research results. "Reproducibility is essential in science and the confounding effects of these chemicals (which are generally not taken into account in biology experiments)" muddy waters ".

Researchers say dozens of replacement bisphenols are being used today and their safety will need to be tested. "In addition to this fast-growing family, we believe that other classes of EDC will also have adverse effects on reproductive health," says Hunt. World of Physics. "These include parabens, perfluorinated compounds (PFCs), phthalates, flame retardants, and quaternary ammonium compounds. All of these chemicals are not only increasingly used in our daily lives, they are also important environmental contaminants and therefore need to be studied.