Now, scientists say they may have found another side effect: declining sperm counts and enlarged testes.
In a study published in the journal Endocrinology, a group of researchers led by Christopher D. Kassotis of Duke recreated levels of exposure to 24 chemicals used in fracking and drilling operations in lab conditions, and then exposed mice to them.
They found that that under these conditions, the mice exhibited "increased testis weights" and decreased sperm count, indicating that the deformed testicular tissue was impacting sperm creation.
They also exposed the mice to increased levels of diesel exhaust, a common component of fracking operations, and found that under these conditions levels of testosterone surged. Interestingly, while this correlates with increased sex drive in males, it actually decreases sperm count.
Finally, they ran exposure tests on human cells, and found many common fracking chemicals could inhibit the body's natural hormones from binding.
"Our results suggest possible adverse developmental and reproductive health outcomes in humans and animals exposed to potential environmentally relevant levels of oil and gas operation chemicals," they conclude.
Somewhere 30,000 and 50,000 wells have been fracked across more than a dozen states since America's "shale revolution" began in the latter part of the previous decade, though new well creation has slowed considerably this year as oil prices have plummeted.
Rob covers business, economics and the environment for Fusion. He previously worked at Business Insider. He grew up in Chicago.