Endocrine-disrupting chemicals linked to altered hormone levels, ovarian development in mice
COLUMBIA, Mo. – More than 15 million Americans live within a one-mile radius of unconventional oil and gas (UOG) operations. UOGs combine directional drilling and hydraulic fracturing, or “fracking,” to release natural gas from underground rock. Scientific studies, while ongoing, are still inconclusive on the potential long-term effects fracturing has on human development.
On August 25, researchers at the University of Missouri released a study that is the first of its kind to link exposure to chemicals released during hydraulic fracturing to adverse reproductive and developmental outcomes in mice. Scientists exposed the mice to 23 chemicals commonly used in fracking, as well as oil and gas development, to study their effects on key hormones. Scientists believe that exposure to these chemicals also could pose a threat to human development.
Researchers have previously found that these chemicals are endocrine-disrupting chemicals (EDCs) that mimic or block the body’s hormones — the chemical messengers that regulate respiration, reproduction, metabolism, growth and other biological functions. More than 1,300 studies have found links between EDCs and serious health conditions such as infertility, diabetes, obesity, hormone-related cancers and neurological disorders, according to the Endocrine Society’s 2015 Scientific Statement.
“The evidence indicates that developmental exposure to fracking and drilling chemicals may pose a threat to fertility in animals and potentially people,” said the study’s senior author, Susan C. Nagel, PhD, an associate professor of obstetrics, gynecology and women’s health in the School of Medicine. “Negative outcomes were observed even in mice exposed to the lowest dose of chemicals, which was lower than the concentrations found in groundwater at some locations with past oil and gas wastewater spills.”
Researchers mixed 23 oil and gas chemicals in four different concentrations to reflect concentrations ranging from those found in drinking water and groundwater to concentrations found in industry wastewater. The mixtures were added to drinking water given to pregnant mice in the laboratory until they gave birth. The female offspring of the mice that drank the chemical mixtures were compared to female offspring of mice in a control group that were not exposed. Mice exposed to drilling chemicals had lower levels of key hormones related to reproductive health compared to the control group.
The mice exposed to the chemicals in utero also tended to weigh about 10 percent more at 21 days of age than mice that were not exposed to chemicals. The mice that were exposed to chemicals had increased heart weights and other indicators for abnormal thickening of the heart muscle, which were not seen in the control group.
“Female mice that were exposed to commonly used fracking chemicals in utero showed signs of reduced fertility, including alterations in the development of the ovarian follicles and pituitary and reproductive hormone concentrations,” Nagel said. “These findings build on our previous research, which found exposure to the same chemicals was tied to reduced sperm counts in male mice. Our studies suggest adverse developmental and reproductive health outcomes might be expected in humans and animals exposed to chemicals in regions with oil and gas drilling activity.”
The study, Adverse Reproductive and Developmental Health Outcomes Following Prenatal Exposure to a Hydraulic Fracturing Chemical Mixture in Female C57BI/6 Mice, was published in the journal Endocrinology. Authors of the study include: Christopher D. Kassotis of Duke University in Durham, N.C.; John J. Bromfield of the University of Florida in Gainesville, FL; Kara C. Klemp, Chun-Xia Meng, Victoria D. Balise and Chiamaka J. Isiguzo of the University of Missouri; Andrew Wolfe of the Johns Hopkins University School of Medicine in Baltimore, MD; R. Thomas Zoeller of the University of Massachusetts Amherst in Amherst, MA; and Donald E. Tillitt of the U.S. Geological Survey’s Columbia Environmental Research Center in Columbia, MO.
The research was funded by the University of Missouri Research Council and Mizzou Advantage, a crowd-funding campaign on Experiment.com, and the U.S. Environmental Protection Agency’s STAR Fellowship Assistance Agreement awarded to Christopher D. Kassotis. [The content is solely the responsibility of the authors and does not necessarily represent the official views of the funding agencies.]
Hear Dr. Nagel discuss her recent paper, Adverse Reproductive and Developmental Health Outcomes Following Prenatal Exposure to a Hydraulic Fracturing Chemical Mixture in Female C57BI/6 Mice
Building on previous research, Dr. Nagel will present new findings on the effects of exposing female mice in utero to a mixture of 23 chemicals commonly used in unconventional oil and gas operations via their mother’s drinking water. Effects included suppressed hormones, increased body weights, altered organ weights, and other adverse health outcomes. Effects were shown at several doses, including doses equivalent to concentrations reported in drinking water sources. Implications for humans and animals exposed to these chemicals will be discussed.
Susan Nagel, PhD, is an Associate Professor of Obstetrics, Gynecology, and Women’s Health at the University of Missouri School of Medicine. She specializes in the role of natural and synthetic hormones in development, reproduction, and disease. She has published research on hormone receptor activities of hydraulic fracturing chemicals and surface and ground water in areas heavily impacted by natural gas development.
For more on Dr. Nagel’s work, please see:
- Chemicals Released During Natural Gas Extraction May Harm Human Reproduction and Development
- Human Development Could be Harmed by Endocrine Disrupting Chemicals Release During Natural Gas Extraction
- Oil and Gas Wastewater Disposal May Increase Endocrine Disrupting Activity in Surface Water and Harm West Virginia Waterways