EnCanas recent air-quality study on Grass Mesa indicated no health risks in the area due to gas drilling, according to a company press release.EnCana Oil & Gas (USA) hired Cordilleran Compliance Services to collect two rounds of air-quality samples on Grass Mesa to provide data in response to odor complaints from area residents.The first set of samples, eight in all, were collected upwind and downwind from five natural-gas well pads from 1:45 p.m. on Aug. 25 through 9:30 a.m. on Aug. 26.The second set of samples, 10 in all, were collected at 10 Grass Mesa residents homesites from 11:57 a.m. on Sept. 4 through 2:45 p.m. on Sept. 5.All samples were analyzed for volatile organic compounds (VOCs) by using U.S. Environmental Protection Agency (EPA) method TO-15.The method looks for 61 markers of volatile organic compounds listed as hazardous air pollutants in the Clean Air Act, said EnCana spokesperson Kathy Friesen. The TO-15 method is specifically used to assess risks of pollutants to human health and the environment.A volatile organic compound is a low molecular weight hydrocarbon that quickly evaporates when introduced into the air, said Lon Hesla, environmental engineer for the federal Environmental Protection Agency.Of the 61 VOC constituents analyzed, seven were detected in samples.Friesen said VOC concentrations were compared to EPA odor threshold concentrations, and to No Observed Adverse Effect Level (NOAEL) concentrations. The VOC concentrations in the samples were observed to be significantly lower than the odor threshold or NOAEL concentrations, Friesen said.The seven detected VOCs are benzene, toluene, xylene, hexane, cyclohexane, heptane and acetone.Those are all common to gasoline, Hesla said.Rebecca Brocks Grass Mesa lot is one of the locations where EnCana took samples. Brock has complained to EnCana and to the Garfield County Commissioners of headaches and nausea due to what she says are fumes coming from drilling rigs and wells.Brock said she questions EnCanas air-quality study results. Im still getting sick.