An article on NPR.org supports claims of adverse health effects, as residents of Pennsylvania in close proximity to fracking sites claim symptoms of metallic taste in the mouth, nausea, vomiting, headaches, rashes, wheezing and aches and pains.  One interview subject specifically said these symptoms come in "wafts" that stink like nail polish remover when the wind blows in air from near the site.

In "The Future of Fracking: New Rules Target Air Emissions for Cleaner Natural Gas Production," published in Environmental Health Perspectives, author Bob Weinhold cites the EPA in  identifying cancer, cardiovascular, respiratory, neurologic and developmental damage as being linked to the aforementioned pollutants.  He also states that fracking chemicals have been tied to "adverse outcomes such as premature mortality, emergency department visits, lost work and school days and/or restricted activity days." 

The American Lung Association, the American Public Health Association, American Thoracic Society, Trust for America's Health and the Asthma and Allergy Foundation of America wrote a joint letter to the EPA calling for the "strongest possible standards to reduce harmful emissions from the production wells, processing plants, transmission pipelines, and storage units within the oil and natural gas industry."  Further, this group identified "circulatory, respiratory, nervous, and other essential and vital life systems" as being linked to air pollutants associated with fracking. 

In defense of fracking, a joint report from the Royal Society and Royal Academy of Engineering (UK) have deemed the practice safe.  According to the chief scientist in the study, Sir John Beddington, the risks of "hydraulic fracturing for shale can be safely managed provided there is best practice observed and provided it's enforced through strong regulation."

Still, it appears that few comprehensive studies have been done to investigate the health effects of fracking.  In fact, according to the Pew Charitable Trusts' Health Impact Project, a comprehensive study can cost as much as $300,000 and can take over a year of work, which has limited the groups who could perform such research.  However, in April 2012, the Institute of Medicine took up the cause, declaring an interest in examining how fracking "poses potential health challenges," which may definitively determine the potential health risks of this practice.  

That level of research is a big move in the right direction, but the final word on the health impacts of fracking is still to come.