Air Monitoring Stations Far Removed From Drilling Activities Do Not Represent Residential Exposures to Marcellus Shale Air Pollutants. Response to the Paper by Hess et al. on Proximity-Based Unconventional Natural Gas Exposure Metrics

Abstract

In their study “Assessing Agreement in Exposure Classification between Proximity-Based Metrics and Air Monitoring Data in Epidemiology Studies of Unconventional Resource Development” Hess et al [...]

Oil and gas production and spontaneous preterm birth in the San Joaquin Valley, CA

“…Further assessments of the air quality impacts of oil and gas operations should consider differences in the fate and transport of ambient air pollutants, account for meteorological factors, consider how the timing of production activities and active wells may affect emissions, and carefully select and specify appropriate statistical models. 26 …”

Critique of Well Activity Proxy Uses Inadequate Data and Statistics

“…While the selected air pollutant data were not likely to be goal-oriented with respect to the authors’ stated aims, it stands to reason that even a highly limited contribution of UNGD to the selected air pollutants could be associated with certain public health effects. Although the WA metric does not claim to represent air quality effects only [ 2 ], Hess et al argue that it could serve as a proxy of UNGD-related exposure at air quality monitoring sites. Assuming that this is correct, then regardless of the strength of the association between air pollutant and emissions proxy, a statistical test could reveal the possible significance.…”

“…Their testing found no “agreement” between the four “exposure categories” and the four WA metric categories. While it has previously been pointed out that the Kappa-statistic is likely not an appropriate statistic for the data at hand [ 2 ], the authors argue in their reply that its measure of “general agreement between exposure classifications based on WA and air pollutant concentrations” can be used to assess “potential exposure misclassification” [ 3 ]. They do not offer an example though, and a similar use cannot be found in the literature.…”

“…The recent publication, “Assessing Agreement in Exposure Classification between Proximity-Based Metrics and Air Monitoring Data in Epidemiology Studies of Unconventional Resource Development” by Hess et al claims to perform a validation of well-activity (WA) proximity models used in epidemiologic research studies of unconventional natural gas development (UNGD) [ 1 ]. While a previous comment already outlined several perceived flaws of this work [ 2 ], here I focus on and question both the premises and the conclusions of their work, based upon the selected air pollutants and the selected statistical test, respectively. The results presented in their work are inadequate to claim that “potential exposure misclassification can be assessed” through “general agreement between exposure classifications based on WA and air pollutant concentrations” [ 3 ].…”

Reply to Schade G. Comment on Hess et al. “Assessing Agreement in Exposure Classifications between Proximity-Based Metrics and Air Monitoring Data in Epidemiology Studies of Unconventional Resource Development.”

“…We appreciate the comments by Dr. Schade [ 1 ] and respond to each below. We would also encourage Dr. Schade and others to read our response [ 2 ] to an earlier comment on our paper [ 3 ] in which we pointed out, among other things, that 90% of subjects included in the epidemiology studies we critiqued lived far from shale development areas and likely had no exposure to air pollutants from these operations. This is problematic, given that subjects were categorized into exposure quartiles for the analyses, and likely explains why we found evidence of significant exposure misclassification.…”