Human Health Risk Assessment of Air Emissions
1 from Development of Unconventional
Natural Gas Resources
Lisa M. McKenziea, Roxana Z. Wittera, Lee S. Newmana, John L. Adgatea
aColorado School of Public Health, University of Colorado – Anschutz Medical Campus,
5 Aurora, Colorado, USA
6 Address correspondence to L. McKenzie, Colorado School of Public Health, 13001 East 17
7 Place, Mail Stop B119, Aurora, CO 80045 USA. Telephone: (303) 724-5557. Fax: (303) 724-
Background: Technological advances (e.g. directional drilling, hydraulic fracturing), have led
11 to increases in unconventional natural gas development (NGD), raising questions about health
Objectives: We estimated health risks for exposures to air emissions from a NGD project in
14 Garfield County, Colorado with the objective of supporting risk prevention recommendations in
15 a health impact assessment (HIA).
Methods: We used EPA guidance to estimate chronic and subchronic non-cancer hazard indices
17 and cancer risks from exposure to hydrocarbons for two populations: (1) residents living >
18 mile from wells and (2) residents living
≤ . mile from wells.
Results: Residents living ≤ . mile from wells are at greater risk for health effects from NGD
20 than are residents living >
. mile from wells. Subchronic exposures to air pollutants during well
21 completion activities present the greatest potential for health effects. The subchronic non-cancer
22 hazard index (HI) of 5 for residents
≤ . mile from wells was driven primarily by exposure to
23 trimethylbenzenes, xylenes, and aliphatic hydrocarbons. Chronic HIs were 1 and 0.4. for
≤ . mile from wells and > . mile from wells, respectively. Cumulative cancer risks
25 were 10 in a million and 6 in a million for residents living
≤ . mile and > . mile from wells,
26 respectively, with benzene as the major contributor to the risk.
Conclusions: Risk assessment can be used in HIAs to direct health risk prevention strategies.
28 Risk management approaches should focus on reducing exposures to emissions during well
29 completions. These preliminary results indicate that health effects resulting from air emissions
30 during unconventional NGD warrant further study. Prospective studies should focus on health
31 effects associated with air pollution.
33 Key Words: natural gas development; risk assessment; air pollution; hydrocarbon emissions