Exposures and Health Risks from Volatile Organic Compounds in Communities Located near Oil and Gas Exploration and Production Activities in Colorado (U.S.A.)

The study objective was to use a preliminary risk based framework to evaluate the sufficiency of existing air data to answer an important public health question in Colorado: Do volatile organic compounds (VOCs) emitted into the air from oil and gas (OG) operations result in exposures to Coloradoans living at or greater than current state setback distances (500 feet) from OG operations at levels that may be harmful to their health? We identified 56 VOCs emitted from OG operations in Colorado and compiled 47 existing air monitoring datasets that measured these VOCs in 34 locations across OG regions. From these data, we estimated acute and chronic exposures and compared these exposures to health guideline levels using maximum and mean air concentrations. Acute and chronic non-cancer hazard quotients were below one for all individual VOCs. Hazard indices combining exposures for all VOCs were slightly above one. Lifetime excess cancer risk estimates for benzene were between 1.0 × 10^-5⁻3.6 × 10^-5 and ethylbenzene was 7.3 × 10^-6. This evaluation identified a small sub-set of VOCs, including benzene and n-nonane, which should be prioritized for additional exposure characterization in site-specific studies that collect comprehensive time-series measurements of community scale exposures to better assess community exposures.