Human health risk assessment of air emissions from development of unconventional natural gas resources

Technological advances (e.g., directional drilling, hydraulic fracturing), have led to increases in unconventional natural gas development (NGD), raising questions about health impacts. This study estimated health risks for exposure to air emissions from a NGD project in Garfield County, Colorado, to support risk prevention recommendations in a health impact assessment (HIA). The authors used USEPA guidance to estimate chronic and sub-chronic, non-cancer hazard indexes and cancer risks from exposure to hydrocarbons for 2 populations: residents living >1/2 mile from wells; and residents living e1/2 mile from wells. Residents living e1/2 mile from wells were at greater risk for health effects from NGD than residents living >1/2 mile from wells. Sub-chronic exposure to air pollutants during well completion activities presented the greatest potential health effects. The sub-chronic, non-cancer hazard index (HI) of 5 for residents e1/2 mile from wells was driven primarily by exposure to trimethylbenzenes, xylenes, and aliphatic hydrocarbons. Chronic HI were 1 and 0.4. for residents e1/2 mi from wells and >1/2 mile from wells, respectively. Cumulative cancer risks were 10 in 1 million and 6 in 1 million for residents living e1/2 mile and >1/2 mile from wells, respectively; benzene was the major contributor to the risk. The authors concluded that based on the results from this study, risk assessment can be used in HIA to direct health risk prevention strategies. Risk management approaches should focus on reducing exposure to emissions during well completion. These preliminary results indicated health effects resulting from air emissions during unconventional NGD warrant further study. Prospective studies should focus on air pollution-associated health effects.

Authors: McKenzie, Lisa M.; Witter, Roxana Z.; Newman, Lee S.; Adgate, John L. ;Full Source: Science of the Total Environment [online computer ;