People living within a half-mile of oil- and gas-well fracking operations were exposed to air pollutants five times above a federal hazard standard, according to a new Colorado study.
The University of Colorado Denver School of Public Health analysis is one of a string of studies in Wyoming, Utah and Colorado that highlight the air-quality impacts of drilling and hydraulic fracturing, or fracking.
"Our data show that it is important to include air pollution in the national dialogue on natural-gas development that has focused largely on water," said Lisa McKenzie, the study's lead author.
The analysis found volatile organic chemicals at five times the level below which the emissions are considered unlikely to cause health problems, according to the federal Environmental Protection Agency's Hazard Index.
The chemicals can have neurological or respiratory effects that include eye irritation, headaches, sore throat and difficulty breathing, the study said.
"We are seeing indications that oil and gas operations can release chemicals that can be harmful to residents,"
The study used three years of data around Battlement Mesacollected by Garfield County.
The findings add fuel to the debate in Colorado over how far wells must be set back from residential areas — an issue being reviewed by the Colorado Oil and Gas Conservation Commission. The state requires a 150-foot setback in rural areas and 350 feet in developed areas.
"This study raises questions about those setback standards," said Frank Smith, director of organizing for the nonprofit Western Colorado Congress.
A bill in the state legislature that would have raised setbacks to 1,000 feet died in committee in February.
There are about 47,000 active wells in Colorado. Drilling began on nearly 3,000 more last year, most of them in Weld and Garfield counties, according to the oil and gas commission. In a study of nearly 5,000 well sites from 2009 to 2012, the commission found that 74 percent were at least 1,000 feet from any buildings. But 8 percent were within 500 feet of structures, some of which were residences.
Among the chemicals detected at elevated concentrations in the new study were trimethylbenzenes, aliphatic hydrocarbons and xylenes.
"The greatest health impact corresponds to the relatively short-term, but high emission, well completion period," the study said.