Fracking's impact on animals is still largely unknown, which scientists see as a real problem given that business is booming.

Hydraulic fracturing, or fracking, shows no signs of stopping. Between 2005 and 2013, some 82,000 fracking wells were drilled into the shale deposits beneath 17 states, according to the environmental advocacy group Environment America.

But scientists are concerned about this method of accessing oil and gas beneath the soil - which involves injecting chemicals into the ground. Opponents point out the environmental impacts of hydraulic fracturing, such as potential contamination of ground water, the depletion of fresh water, possible reduction in air quality and triggering of earthquakes.

There are already more than 1,000 documented cases of water contamination from fracking operations - from toxic wastewater, well blowouts, chemical spills, and more, according to Environment America.

But some also argue that the technique is not only dangerous to humans but to wildlife as well.

"We know very little about how shale gas production is affecting plants and wildlife," Sarah Souther, a conservation biologist at the University of Wisconsin-Madison, said in a statement. Souther and her colleagues discovered critical gaps in the current body of knowledge surrounding shale production, which they reported in the journal Frontiers in Ecology and the Environment.

"There is a lack of accessible and reliable information on spills, wastewater disposal and the chemistry of fracturing fluids," Souther added. "Of the 24 US states with active shale gas reservoirs, only five maintain public records of spills and accidents."

About 200 different chemicals are injected into the ground during fracking, but about a third of them lack sufficient toxicity information according to a study presented at the American Chemical Society on Wednesday.

"There are a number of chemicals, like corrosion inhibitors and biocides in particular, that are being used in reasonably high concentrations that potentially could have adverse effects," William Stringfellow, an environmental engineer at the University of the Pacific and lead author of the study, said in a press release.

Stringfellow and his colleagues identified eight chemicals that are particularly toxic to mammals, but the impact on the rest of the commonly used chemicals during fracking has yet to be determined.

Souther and her colleagues told Inside Climate News that they are not "anti-shale development," just "anti-lack of knowledge."