Think fracking spills pose little threat to fish and wildlife? Think again.

A new study conducted by the U.S. Fish and Wildlife Service and the U.S. Geological Survey is drawing attention to the devastating impacts of fracking wastewater spills, profiling a 2007 Kentucky incident that left in its wake a decrepit environment unsuitable for animal inhabitation.

The site of the study was located in Knox County, Ky., where four fracking wells owned by Nami Resources Company were responsible for a spill that sent contaminated water into Acorn Fork, a tributary of Stinking Creek and a designated state resource water. The fracking well waste was disposed of in an open retention pit — one that overflowed, resulting in the contamination.

When a well is fracked, a combination of water, chemicals and silica sand is shot deep into the earth, where the pressure and cocktail blend forces open areas where oil or gas is hidden, allowing the resource to be extracted. When the oil or gas is separated from the fluid mixture, the remaining water contains metals found below the earth’s surface, along with chemicals used in the fracking process.

Six years after the spill, researchers monitoring the area have discovered that populations of fish in the area were harmed and killed by heavy metals and hydrochloric acid, byproducts of fracking wastewater. Specifically, examined fish were discovered to have gill lesions, as well as liver and spleen damage.

According to the Fish and Wildlife Service, the fracking water “killed virtually all aquatic wildlife in a significant portion of the fork, including fish and invertebrates.”

“Our study is a precautionary tale of how entire populations could be put at risk even with small-scale fluid spills,” U.S. Geological Survey Scientist Diana Papoulias said in a press release. “This is especially the case if the species is threatened or is only found in limited areas, like the Blackside dace is in the Cumberland.”

The blackside dace is one type of fish impacted by the spill, which is now classified as “primarily threatened” after the fracking wastewater contamination. While highlighting the importance of protecting fish habitats from fracking contamination, authors of the report also drove home the message that such waters serve humans, too.

“This is an example of how the smallest creatures can act as a canary in a coal mine,” Fish and Wildlife Ecologist Tony Velasco said in a press release. “These species use the same water as we do, so it is just as important to keep our waters clean for people and for wildlife.”

The joint study comes on the heels of an information campaign by the oil and gas industry to downplay the potential impacts of fracking. Jay Ambrose of the Centennial Institute indicates the threat posed by fracking waste to be overblown, claiming “much-diluted chemicals used in tiny amounts would have to rise thousands of feet to pass through solid rock without benefit of fracking to reach aquifers above.”

Unless, of course, that water, which is extracted in the fracking process, happens to leak from the above-ground, open-air pits it’s stored in, resulting in cases like the one profiled by the U.S. Fish and Wildlife Service.

In Colorado alone, the state’s regulatory body (the Colorado Oil and Gas Conservation Commission) has recorded more than 5,100 spills. While spills vary in size and impact, the statistics illustrate the frequency of spills.

In February, a PDC Energy spill sent more than 80,000 gallons of fracking fluid into nearby land. While streams and ponds were not believed to be contaminated, it was not known at the time whether that fluid contaminated groundwater, according to the Denver Post.