The Links Among Unconventional Oil and Gas Development, Particle Radioactivity and Morality

Abstract

The rapid expansion of unconventional oil and gas development (UOGD) changed the energy market in the past decade, both domestically and globally. Enabled by the technological advancements in hydraulic fracturing and directional drilling, the UOGD could produce crude oil and natural gas from the low-permeability geological formations that were uneconomic to develop in the past. By the end of 2018, carbohydrates extracted from these unconventional formations accounted for 96% and 97% of the domestic crude oil and natural gas production, respectively. Compared with the rapid expansion, our knowledge about its impacts on the environment and residents of neighboring communities is falling far behind. There is an increasing body of literature associating living nearby UOGD sites to adverse health outcomes and harmful environmental exposure. However, current studies are subject to common limitations, including a lack of knowledge regarding exposure pathways, a lack of reliable exposure assessment, and a lack of causal modeling methods applied in investigating the potential associations. This dissertation is designed to address these knowledge gaps partially. In our first study, we investigated the causal association between exposure to UOGD and all-cause mortality in the Medicare beneficiaries residing in all major production regions of the U.S. We first estimated the association between all-cause mortality and the residential proximity to an active UOGD site; We subsequently divided the participants into two subgroups according to their relative position to the UOGD, a subgroup living upwind to UOGD, and a subgroup living downwind to UOGD, and re-evaluated the subgroup-specific effects. We found that UOGD has significantly greater effects on the residents living downwind, compared to those living upwind, after adjusting for proximity. Due to the independence of wind direction to residential proximity to UOGD, this association is considered causal. In our second study, we explored the association of UOGD activity to ambient particle radioactivity, which is a potential exposure pathway of UOGD. Ambient particle radioactivity is the radiometric character of particle matter, which in turn transports the radionuclides from the external to the internal environment, and then expose human tissues to high-energy α particles. We found a significantly positive association between the number of upwind UOGD wells and the gross-β radioactivity measurements monitored by a nationwide operational network. In our third study, we investigated the association of all-cause mortality with residential exposure to radon, which is the primary source of particle radioactivity. We applied the Difference-in-Difference experimental design, which is a quasi-experimental approach, to investigate the causal linkage in all Medicare beneficiaries residing in New England. We found that a per-unit increase in residential radon exposure is associated with an increment of 4% of all-cause mortality.