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Environ Sci Technol. 2016 Jul 19;50(14):7921-9. doi: 10.1021/acs.est.6b02762. Epub 2016 Jul 11.

Emissions of Polycyclic Aromatic Hydrocarbons from Natural Gas Extraction into Air.

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Department of Environmental and Molecular Toxicology, Oregon State University , Corvallis, Oregon 97331, United States.
College of Public Health and Human Sciences, Oregon State University , Corvallis, Oregon 97331, United States.
Department of Environmental Health, University of Cincinnati , Cincinnati, Ohio 45267, United States.


Natural gas extraction, often referred to as "fracking", has increased rapidly in the United States in recent years. To address potential health impacts, passive air samplers were deployed in a rural community heavily affected by the natural gas boom. Samplers were analyzed for 62 polycyclic aromatic hydrocarbons (PAHs). Results were grouped based on distance from each sampler to the nearest active well. Levels of benzo[a]pyrene, phenanthrene, and carcinogenic potency of PAH mixtures were highest when samplers were closest to active wells. PAH levels closest to natural gas activity were comparable to levels previously reported in rural areas in winter. Sourcing ratios indicated that PAHs were predominantly petrogenic, suggesting that PAH levels were influenced by direct releases from the earth. Quantitative human health risk assessment estimated the excess lifetime cancer risks associated with exposure to the measured PAHs. At sites closest to active wells, the risk estimated for maximum residential exposure was 0.04 in a million, which is below the U.S. Environmental Protection Agency's acceptable risk level. Overall, risk estimates decreased 30% when comparing results from samplers closest to active wells to those farthest from them. This work suggests that natural gas extraction is contributing PAHs to the air, at levels that would not be expected to increase cancer risk.

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