An examination of 37 peer-reviewed studies published during 2012 through 2018 on hazardous air pollutants (HAPs) associated with oil and gas extraction operations determined which species have been linked to a specific upstream phase, process or source. The analysis considered 187 pollutants listed by the U.S. Environmental Protection Agency (EPA), including hydrogen sulfide, which was removed from the official U.S. EPA list in 1991.

A total of 61 unique HAP compounds were measured near upstream oil and gas operations or investigated from secondary data sources. The production phase had the largest number of HAPs sourced to different HAP compounds collected through primary measurements and recategorized. Source: Diane A. Garcia-Gonzales et al.equipment and operations and the greatest potential to emit the highest concentrations and the most varied mixture of HAPs over the longest time period. Pollutant exposure risks can increase if production equipment is co-located with condensate storage and wastewater impoundments.

In situ air pollutant levels were shown to be below health benchmarks, even though numerous health-based studies found evidence of a spatial relationship between HAP concentrations and incidence of cancer and non-cancer health end points near oil and gas development operations. Formaldehyde and acetaldehyde were identified as the most abundant carbonyl species when sampling ambient air near oil and gas facilities. Some studies reported that rural benzene, toluene, ethylbenzene and total xylene concentrations exceeded those measured in dense urban areas and at concentrations above health-based standards, with some concentrations over 2,900 ppb.

The analysis indicates that spatial sampling methodologies might fail to properly characterize exposures prior to atmospheric degradation and dispersion or pollutants, or that ambient air sampling timeframes are inappropriate for capturing episodic peak emission events characteristic of upstream activities. Additional investigations of emissions are warranted, with a focus on measurements and research that incorporate appropriate timeframes and proximity to oil and gas extraction on health impacts from chronic, low-level HAP exposures, among others.

Researchers from PSE Healthy Energy (California), University of California Berkeley, Cornell University, Lawrence Berkeley National Laboratory and University of California Los Angeles contributed to this study, which is published in Annual Review of Public Health.