In the last two decades, hydraulic fracturing or fracking has boomed, gone bust, and is in the midst of another boom, producing close to 6 million barrels of oil and gas per day in the United States. Drillers pump dozens of chemicals into the ground to crack open shale deposits, releasing the hydrocarbons trapped within them. Despite promises that fracking is safe, those chemicals have been shown to contaminate ground-and-surface water in some areas, and the long-term effects of exposure to these compounds are not well understood.  

One new study in the journal Science in the Total Environment shows that some of the most common chemicals used in fracking have a direct effect on fat cells, causing them to proliferate and hold more fat into each cell.  

Researchers for the study—led by Chris Kassotis, a postdoc at Duke University’s Nicholas School of the Environment—exposed living mouse cells in a dish to a cocktail containing 23 of the most commonly used chemicals in fracking. They also exposed cells to contaminated samples collected from fracking wells and surface water they believed were contaminated from Garfield County, Colorado, and Fayette County, West Virginia. Samples from the well were diluted 1,000 times while the surface water was diluted 25 times. They then exposed the cells for two weeks. The 23-chemical mix led to 60 percent as much fat accumulation as rosiglitazone, a drug known to cause weight gain in humans. The wastewater led to an 80 percent accumulation; cells exposed to the surface water gained 40 percent as much fat as cells exposed to rosiglitazone. In all three cases, the formation of pre-adipocytes, or the precursors to fat cells, were all much higher than cells exposed to rosiglitazone alone.

The study was not done in isolation. It’s part of eight years of research into the public health impacts of fracking chemicals, which has shown that some of the compounds used may have endocrine-disrupting properties, meaning they can mess with the way the body handles hormones. In a 2015 study in Endocrinology, Kassotis and his collaborators exposed pregnant mice to different concentrations of the 23-chemical cocktail, then assessed the health of their offspring. What they found was an assortment of endocrine effects, including reduced sperm and egg production, increased testosterone in males, and increased weight in the body and heart. Since then, the team has published studies on the effects of fracking chemicals on the immune system, mammary cell development, and disrupted fertility in mice. 

So can fracking contamination make people gain weight? Kassotis is careful to point out that this is just a lab study, which did not examine environmental contamination by fracking wells. It simply shows that some of the 1,000 chemicals used by the fracking industry could have endocrine effects if humans are exposed. 

Whether or not people are in fact being exposed to the chemicals is a point of contention between industry and scientists. Another study from the Nicholas School of the Environment published in 2017 in Environmental Science & Technology estimated that between 2 and 16 percent of fracking wells in four states spilled contaminated water or fracking fluids into the environment between 2005 and 2014. An EPA study released in 2016 concluded that in some circumstances, fracking contaminated drinking water, which other academic studies have found as well, though the extent and scope is not known.

The Independent Petroleum Producers of America refutes claims of widespread contamination and argues that marinating cells in fracking chemicals has little relevance to human health. 

But Kassotis thinks the experiment is significant. “There are definitely limitations to in vitro or cell studies. You could argue that there is a lack of relevance in terms of exposing cells constantly to 23 chemicals,” he says. “I think you can also make the argument that people living in these regions are probably exposed to these chemicals regularly. These chemicals could end up in people’s water, so there may be oral exposure through drinking the water. There could be dermal exposure by bathing and washing and cleaning, and there could be inhalation exposure since lots of these chemicals are volatile.” 

“There’s still a lot we don’t know,” Kassotis says. “We don’t know the levels people are being exposed to these chemicals; the biomonitoring studies have just not been done. And we don’t know enough about all the chemicals,” he says. “So it’s hard to draw a clear translation to whether we would expect effects in people.” 

Kassotis says he hopes those types of studies take place soon. He also plans to continue looking at the metabolic effects of these chemicals. He is working with chemists to figure out just which of the 1,000 compounds used by fracking companies in their wells act as endocrine disruptors. That research will become even more critical in the years ahead—as fracking continues to boom in the United States, energy companies are beginning to launch large-scale fracking projects in other parts of the world.