AMHERST — A chemical found in cosmetics and many consumer products may lessen protection against breast cancer that pregnancy hormones normally convey, according to research conducted at the University of Massachusetts.
Considered an endocrine disruptor, propylparaben at low doses may interfere with hormones that comprise the body’s endocrine system, according to data submitted by researchers from UMass and Baystate Medical Center and published March 16 in the journal Endocrinology,
“We found that propylparaben disrupts the mammary gland of mice at exposure levels that have previously been considered safe based on results from industry-sponsored studies,” said Laura N. Vandenberg of UMass’ Department of Environmental Health Sciences and School of Public Health and Health Sciences. “We also saw effects of propylparaben after doses many times lower, which are more reflective of human intake.”
The man-made chemical is commonly used in cosmetics as a preservative, and its presence was found in the urine in the majority of some 2,548 participants aged six years and older who took part in a Centers for Disease Control and Prevention study in 2005.
The study measured exposure from such use in the general population to paraben compounds whose presence as harmful endocrine disruptors continues to be debated. Questions raised in the debate include whether studies in animals reflect levels of exposure and metabolism for humans, and the U.S. Food and Drug Administration is among government agencies to say its scientists “continue to review published studies on the safety of parabens.”
Propylparaben is among the paraben compounds that has been investigated for how exposure might inhibit or disrupt the functioning of estrogen, sometimes referred to as the female sex hormone.
The question investigated in Vandenberg’s study with mice was would exposure to propylparaben during pregnancy and lactation alter the mammary gland long-term and in a way that could interfere with normal hormonal changes seen to help prevent breast cancer in humans?
Vandenberg said it did and plans further follow-up studies.
Pregnancy results in the breast organ being subjected to many hormonal-induced changes in preparation for producing milk. In addition, these changes are increasingly being linked to lowering a woman’s risk for breast cancer.
“Although our study did not evaluate breast cancer risk, these changes in the mammary tissue are involved in mitigating cancer risk in women,” she said.
The European Union is seen by many as having a tougher approach to the regulation of chemicals in consumer products and Vandenberg likes an approach firmly rooted in safety data.
“For chemicals that are used in personal care products, the expectation really should be that they are guilty until proven innocent,” said Vandenberg who called her study one of only a few involving controlled exposures in rodents to propylparaben.
She said it also involved the ability to wait the “equivalent of many months in a mouse life and observe effects that were present” from these exposures.
“This concerns us because generally there is this assumption that has been made that with chemicals, they might have effects on adults but when you take the chemical away the adult should go back to normal,” Vandenberg said.
“This study suggests we should not treat pregnant women in the same category because pregnant mice when they were exposed appear to have effects that are at least long-term if not permanent.”
Vandenberg said those involved in the study are looking “at the pups who were exposed when they were in the womb because we don’t know enough about propylparaben.”
“There is just a wide-open world of questions to ask,” said Vandenberg who plans a follow-up study involving evaluation of cancer risk in mice exposed during pregnancy and lactation to the compound.
“There is a lot of controversy out there about whether parabens might be a cancer risk and that comes from data that is now 20 years old on humans where researchers found parabens in breast tissue and in breast tumor tissue and so the worry is if it is there, what is it doing? And the answer is that in the rodent we do not know.”
Propylparaben exposure in Vandenberg’s study appeared to resulted in fewer types of immune cells that generally increase in the breast during pregnancy. Other changes included less-dense epithelial structures that help form the ducts where milk is produced and thinner connective tissue in the mammary gland.
“Pregnancy is a period in which there is ‘maturation” of the breast tissue, said study participant D. Joseph Jerry of breast changes that occur in preparation for lactation.
“The arc of the results indicates that relatively modest levels of propylparaben during pregnancy can erode the process of maturation in breast tissue. Therefore, the data point to a potential for concern.”
A professor of veterinary and animal sciences at the University of Massachusetts-Amherst, Jerry is science director of the Pioneer Valley Life Sciences Institute, a research partnership between Springfield-based Baystate Medical Center and UMass, and co-director of the Rays of Hope Center for Breast Cancer Research.
His research has long investigated changes at the cellular level that could contributed to the risk for breast cancer and while he noted the current study had limitations in regard to diversity of population exposed, he said its results highlight the “need for regulation of the levels humans are exposed to.”
“This study used mice that are genetically uniform,” said Jerry whose doctorate is in nutrition. “In contrast, responses in humans would be expected to range from extreme sensitivity in some while a minimal affect in others. This reflects the beauty that exists in the diversity of populations. Nonetheless, this study in mice provides data that informs the need for regulation of the levels humans are exposed to.”
He added that in terms of “breast cancer risk, the length of study in mice did not allow us to directly test for tumors in the mice.”
“However, separate experiments published by our team demonstrated that propylparaben could damage DNA in breast cancer cells in culture raising concerns,” Jerry said.
“This work also showed that, in mice, another chemical common in personal care products, benzophenone-3, also known as oxybenzone, was more potent in damaging DNA. This highlights the need to consider the risks, not of a single chemical in isolation, but within the context of the mixtures of chemicals in our environment.”
Joshua Mogus, a doctoral student in Vandenberg’s lab who tested five weeks out from exposure to propylparaben for results in the mother mice, is scheduled to present those results at the March 20 to 23 virtual meeting of the Endocrine Society.
Other study co-authors included Charlotte LaPlante, Ruby Bansal, Klara Matouskova, Shannon Silva, Elizabeth Daniele, Mary Hagen and Karen Dunphy, all of UMass; Sallie Schneider, who holds a doctorate in immunology and is director of PVLSI’s Biospecimen Resource and Molecular Analysis Facility at Baystate Medical Center, and Benjamin Schneider, also with that facility.
Their research received funding from the University of Massachusetts Commonwealth Honors College Grant, the Endocrine Society’s Summer Research Fellowship and the National Institutes of Health.
This content was originally published here.