Hydraulic fracturing, or "fracking," continues to cause much debate. While some people claim the practice is beneficial for the energy industry, others are concerned about the damage it may be causing to environmental and human health. Now, a new study fuels the latter concern, suggesting that prenatal exposure to chemicals used in fracking may influence a man's reproductive health in adulthood.

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Prenatal exposure to chemicals used in fracking may have negative implications for a man's reproductive health.

Senior study author Susan C. Nagel, PhD, of the University of Missouri in Columbia, and colleagues publish their findings in the journal Endocrinology.

Fracking is a method used to recover gas and oil from shale rock. It involves drilling into the earth and injecting a high-pressurized mix of water, sand and chemicals to fracture the rock and release the gas contained within.

For their study, the team tested 24 chemicals commonly used in fracking and identified 23 of them to be endocrine-disrupting chemicals (EDCs). These chemicals are known to interfere with the body's endocrine system by mimicking, blocking or interrupting hormones, which can lead to developmental, reproductive and neurological problems.

The researchers found that more than 90% of the 23 EDCs they identified interfered with the function of estrogens and androgens - including the male sex hormone testosterone, which is important for sexual and reproductive development.

The function of another class of reproductive hormone called progestogens were at risk of interruption by more than 40% of the EDCs identified, as well as a class of steroid hormones called glucocorticoids, which play a role in metabolism and stress.

In addition, the researchers found that around 30% of the EDCs identified interfered with thyroid hormone signaling, while some combinations of EDCs exacerbated disruption of certain hormones.

Fracking chemicals led to larger testicles, lower sperm count in mice

According to Nagel and colleagues, oil and gas companies are not required to reveal all the chemicals they use for fracking, despite concerns that these chemicals may leak through the process and contaminate groundwater.

On testing the wastewater from a number of fracking sites in Garfield Country, CO, the researchers identified the presence of 16 of EDCs they had tested previously.

The team used the 16 chemicals to create a concoction of 23 chemicals that represented the different levels humans would likely be exposed to from wastewater and drinking water.

Four different concentrations of the chemical concoction were given to pregnant mice via drinking water from day 11 of pregnancy right up until birth. The male offspring of the mice were compared with the male offspring of mice that were not exposed to the chemical mixture during pregnancy.

The researchers found that the offspring that were exposed to the chemical mixture prenatally had a lower sperm count, higher testosterone levels in the blood and larger testicles in adulthood than mice that were not exposed to the mixture.

What is more, mice that were exposed to the highest concentration of the mixture prenatally had a higher weight and were more likely to have structural changes of the heart than mice that were not exposed to the mixture at all.

Based on their results, Nagel says it is clear that the EDCs used in fracking can interrupt hormone functioning in the body by acting alone or in combination with other chemicals. She adds:

"This study is the first to demonstrate that EDCs commonly used in fracking, at levels realistic for human and animal exposure in these regions, can have an adverse effect on the reproductive health of mice.

These findings may have implications for the fertility of men living in regions with dense oil and/or natural gas production."

Earlier this year, Medical News Today reported on another study citing a potential health implication of fracking. Published in PLOS ONE, the study found pregnant women who live close to fracking sites are more likely to have babies with low birth weights than those who live farther away from such sites.