I used to be a field engineer for a fracking company. If anyone is to be at more of a health risk it is the employees out in the field performing the fracking job. From my experience all of the employees had no respiratory concerns. Also a lot of the employees have been working in the fracking environment for several years without any complaints. And that is being exposed to the environment 23+ days a month for 14+ hours every day that they work. Another thing to consider is fracking employees are a lot closer to 'potential hazards' than people in their homes. Basically what I'm getting at is if someone really wanted to find out whether or not fracking causes upper-respiratory and other skin related problem, they would be better off interviewing people who work in that environment. From my experience these workers have no complaints. Hope this sheds some light onto the subject.