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. 2016 Aug 25;125(2):189–197. doi: 10.1289/EHP281

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Locations of study participants in the fourth quartile of unconventional natural gas develpment (UNGD) activity (A) and all other UNGD quartiles (B). Blue crosses: participants with at least one primary outcome [current chronic rhinosinusitis (CRS), migraine headache, and/or higher levels of fatigue]. Black circles: reference group participants with no current or past CRS, no migraine headache symptoms, and lower levels of fatigue. Yellow circles: locations of all drilled unconventional natural gas wells in Pennsylvania as of 31 December 2014. Patient residential locations were from the Geisinger Clinic; county boundaries from the U.S. Census Bureau TIGER/line files (U.S. Census Bureau 2010); and UNGD well locations from the Pennsylvania Department of Environmental Protection (Pennsylvania Department of Environmental Protection 2016). Maps were made with ArcGIS Desktop (release 10, Esri, Redlands, CA).