The study, titled "Gas Patch Roulette," was produced by Earthworks, a Washington, D.C.-based environmental group.
The results come from a survey completed by 108 residents in 14 Pennsylvania counties affected by drilling. Respondents came from Earthworks' "existing contacts in the target counties," people recommended by those contacts and people recruited at public events. Researchers also took air and water samples.
More than 80 percent of respondents reported noxious odors, and many associated them with symptoms such as dizziness, headaches and eye and throat irritation. More than half the water samples found elevated levels of methane compared with 2010, and several air samples found elevated levels of toxic industrial chemicals, the report said.
"Sixty-eight percent of respondents at households where chemicals were detected reported symptoms known to be associated with those chemicals," it said.
The report calls for more widespread testing, tighter regulation and greater enforcement of air and water pollution laws.
Marcellus Shale Coalition spokesman Steve Forde called the survey "blatantly misleading" and its results cherry-picked.
"By the 'researchers' own admission, their so-called methodology clearly demonstrates that this is not a work of objective scientific research, given that they relied completely upon 'existing contacts' and others who attended their anti-natural gas 'public events' for their survey," he wrote in an email.