Exposure to the chemicals – even at very low doses — used in hydraulic fracturing, or fracking, may impair fertility, according to a study recently published in Endocrinology.
The researchers, led by Susan C. Nagel, PhD, of the University of Missouri in Columbia, followed up on their previous work, in which they showed that 23 of 24 commonly used fracking chemicals affected estrogen, androgen, glucocorticoid, progesterone, and/or thyroid receptors in a human endometrial cancer cell reporter gene assay. They also showed that mixtures of these chemicals can behave synergistically, additively, or antagonistically on these receptors. (Endocrine News reported in-depth on the Missouri team’s previous work in the April 2014 issue.)
“The evidence indicates that developmental exposure to fracking and drilling chemicals may pose a threat to fertility in animals and potentially people.”
For this study, Nagel and her team exposed pregnant female C57Bl/6 dams were exposed to a mixture of 23 commonly used unconventional oil and gas chemicals at approximately 3, 30, 300, and 3,000 μg/kg·d, flutamide at 50 mg/kg·d, or a 0.2% ethanol control vehicle via their drinking water from gestational day 11 through birth. These four different concentration mixtures were designed to reflect concentrations ranging from those found in drinking water and groundwater to concentrations found in industry wastewater. “This prenatal exposure to oil and gas operation chemicals suppressed pituitary hormone concentrations across experimental groups (prolactin, LH, FSH, and others), increased body weights, altered uterine and ovary weights, increased heart weights and collagen deposition, disrupted folliculogenesis, and other adverse health effects,” the authors write.
“The evidence indicates that developmental exposure to fracking and drilling chemicals may pose a threat to fertility in animals and potentially people,” Nagel says. “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.”
The mice exposed to the drilling chemicals had lower levels of key hormones related to reproductive health — prolactin, follicle stimulating hormone and luteinizing hormone — compared to the control group. Mice exposed to smaller doses of the chemicals had fewer ovarian follicles, which suggests they have a reduced number of eggs and may have a shorter fertile period than other mice. In contrast, the mice exposed to the highest chemical dose had an increase in the primary follicle number, which could signal inappropriate follicle activation and ultimate follicle death.
The mice exposed to the chemicals in utero also tended to weigh about 10% 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.
“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.”
This was the first study to describe the effects of fracking chemicals on development, identifying several adverse endpoints, and the researchers write that this work should lead to “future, more comprehensive research.” They conclude that prenatal exposure to fracking chemicals at “environmentally relevant concentrations” can adversely affect reproduction and development in mice. (Male mice also experienced many of the same effects.)
“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 says. “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.”