Assessing Residential Exposure Risk from Spills of Flowback Water from Marcellus Shale Hydraulic Fracturing Activity

Abstract

Identifying sources of concern and risk from shale gas development, particularly from the hydraulic fracturing process, is an important step in better understanding sources of uncertainty within the industry. In this study, a risk assessment of residential exposure pathways to contaminated drinking water is carried out. In this model, it is assumed that a drinking water source is contaminated by a spill of flowback water; probability distributions of spill size and constituent concentrations are fit to historical datasets and Monte Carlo simulation was used to calculate a distribution of risk values for two scenarios: (1) use of a contaminated reservoir for residential drinking water supply and (2) swimming in a contaminated pond. The swimming scenario did not produce risks of concern from a single exposure of 1 h duration, but 11 such 1-h exposures did produce risks of 10−6 due to radionuclide exposure. The drinking water scenario over a 30-year exposure duration produced cancer risk values exceeding 10−6 for arsenic, benzene, benzo(a)pyrene, heptachlor, heptachlor epoxide, pentachlorophenol, and vinyl chloride. However, this extended exposure duration is probably not realistic for exposure by a spill event. Radionuclides produced risks in the residential drinking water scenario of 10−6 in just 8 h, a much more realistic timeline for continual exposure due to a spill event. In general, for contaminants for which inhalation exposure was applicable, this pathway produced the highest risks with exposure from ingestion posing the next greatest risk to human health followed by dermal absorption (or body emersion for radionuclides). Considering non-carcinogenic effects, only barium and thallium exceed target limits, where the ingestion pathway seems to be of greater concern than dermal exposure. Exposure to radionuclides in flowback water, particularly through the inhalation route, poses a greater threat to human health than other contaminants examined in this assessment and should be the focus of risk assessment and risk mitigation efforts.

Public reporting of hydraulic fracturing chemicals in the USA, 2011–18: a before and after comparison of reporting formats

“…4 Analyses of ground and surface water samples near hydraulic fracturing sites have identified chemicals and by-products associated with hydraulic fracturing fluids and wastewater, including volatile organic compounds 5,6 and halides, 7,8 with spills and leakage representing possible contaminant pathways. [9][10][11] In 2016, the US Environmental Protection Agency (EPA) published a report on several mechanisms through which hydraulic fracturing fluids and associated wastewater might impact water supplies. 12 Furthermore, the EPA compiled oral toxicity data for chemicals in hydraulic fracturing fluids and found that 986 (91%) of 1084 did not have the evidence required to identify maximum safe chronic oral reference dose values.…”

Hydraulically Fractured Natural-Gas Well Microbial Communities Contain Genomic Halogenation and Dehalogenation Potential

“…To put these data into perspective, we surveyed organohalides reported in fluids produced from other Marcellus Shale natural-gas wells and O&G wells in other unconventional shale formations (Table S3). 5,6,9,10,12,13,39 Among the 20 compounds identified here, only five have been previously identified in HF wastewaters, chlorinated methanes (e.g., trichloro-), halogenated decanes (including 1-chlorohexa-, 1-iodo-2-methylun-, and 1-iodotetra-), and benzyl chloride (Figure 1A), highlighting the utility of this nontargeted high-resolution mass spectrometery approach with these chemically complex samples. Haloalkanes are the most structurally diverse compounds identified here and by others, 10,40,41 and although this is unsurprising considering the large abundance of aliphatic compounds in black shales, 42 existing analytical methods would also bias toward their detection.…”

Environmental injustice: Fracking

“…The backflow water from fracking has potential negative health effects through ingestion, inhalation, and dermal exposure because of contaminants such as Arsenic, Barium, Benzene, Copper, Lead, Thallium, Vinyl chloride, among others (Abualfaraj et al, 2018). Fracking sites have been found to infringe upon human rights and contribute to environmental injustices.…”