Drinking Water Contamination due to Hydraulic Fracturing in Western Australia: A Health Hazard Risk Assessment
Background
Hydraulic fracturing (fracking) is a stimulation technique to release gas from underground rock formations that would otherwise be impermeable.(1, 2) It involves the injection of fluid at pressures great enough to fracture the rock and release the gas inside.(1) The fracking process is shown in Figure 1 (Appendix A).(2) The fluid is predominantly water (75–99%) as well as proppant such as sand (usually 5–8% but may contribute up to 25%) and a variety of other chemical substances (1–5% combined).(1, 2) The fluid is injected into horizontally drilled wells up to 10,000 feet below the surface (Figure 1).(2) The proppant holds open the newly created fractures after the injection pressure is released, so the gas can flow through the fissures to the well (Figure 1).(1, 2) The gas is then stored and used as an energy source. This source of energy is currently on the rise and is likely to make a major contribution to future energy needs.(3) It is therefore essential to assess the health hazards associated with fracking. Comment by Author: Good intro
The Perth, Carnarvon, and Canning Basin’s in Western Australia (WA) have shale and tight rock formations potentially rich in natural gas (Figure 2, Appendix B).(2) Nearly three-quarters (73%) of recoverable shale gas in Australia is located in WA (Table 1, Appendix B).(2) WA will therefore be the community of interest in this health hazard risk assessment (HHRA).
Issue Identification
There are many environmental health issues of concern with fracking in WA, including soil and groundwater contamination, surface water contamination, the exacerbation of climate change due to the release of methane into the atmosphere, increased earthquake activity due to disruption of subsurface tectonic plates, and increased noise and vibration from the operation.(2, 4) This report will solely focus on drinking water contamination (groundwater and surface water), as this is the most common public health concern.(2) Comment by Author: Excellent. As you suggest, not all of these are equally likely (or of concern); e.g. climate change from methane release is less likely (or of concern) than local water contamination
In 2012, the Commonwealth Scientific and Industrial Research Organisation (CSIRO) conducted community meetings and workshops regarding shale gas development in WA.(2) Stakeholders, including community members, government representatives, and scientists, were present at the meetings.(2) The concerns related to drinking water, which would require risk assessment, that arose were:
· Impacts of fracking on human health through introduction of chemicals to surface and groundwater (2)
· Short and long term well integrity and potential impacts on groundwater quality and quantity(2)
· Disposal of waste water from wells and fracking – risk of contamination to surface and ground water(2)
· Contamination of groundwater from flow-back fluids due to
· Initial drilling process(2)
· Well manufacturing(2)
· Gas seepage post fracturing(2)
· Poorly stored or managed flow-back fluids at the surface(2)
· Contamination of surface water from flow-back fluids due to
· Surface spill of fracking fluids(2)
· Uncontrolled release of fluids in a blow-out(2)
· Floods or extreme weather causing overflow of waste water(2)
· Poor treatment of waste water prior to disposal in water ways(2)
Based on these issues of concern, the HHRA will focus on the risk of drinking water supply contamination from the result of the fracking process, including from well drilling, fracking fluids and the flow-back of fluids in wells. Comment by Author: Ok. Good to see the focus.
Hazard Identification
Fracking fluids contain hundreds of substances which could contaminate drinking water.(5) Elliott et al. identified 126 chemicals in fracking fluid with reproductive toxicity data, of which 103 (82%) are possibly associated with adverse reproductive effects.(5) Of 192 chemicals with developmental toxicity information, 95 (49%) are potentially associated with developmental toxicity.(5)
Last month (May 2016), DiGiulio et al. published a comprehensive analysis of all publicly available data and reports to evaluate the impact of fracking on underground sources of drinking water in the Pavillion, Wyoming, Field in USA. Chemical levels within the water were analysed using both pre-existing data and data gathered by the researchers. Figure’s 3-6 (Appendix C) show box and whisker plots of sodium (Na), potassium (K), chloride (Cl) and sulphate (SO4) levels in domestic wells in various studies.(6) Using combined data sets in and around the Pavillion Field, sodium, potassium and chloride concentrations were higher, and sulphate concentrations were lower, in produced water than would be expected (p = 6.6 × 10-19, 2.1 × 10-15, 2.6 × 10-16, 4.4 × 10-19 respectively).(6) Theseis data provides direct evidence of the impact to underground sources of drinking water at depths of stimulation.(6) Furthermore, potassium increased with calcium concentrations and sulphate increased with total dissolved solid (TDS) concentrations in domestic wells, but not in production wells.(6) Comment by Author: what is this p? statistical test comparing production well water with distant control water
A household survey was conducted in Washington County, Pennsylvania to determine the relationship between household proximity to natural gas wells and reported health symptoms.(7) The number of reported health symptoms was higher among those living <1km from the nearest gas well (Mean ± SD, 3.27 ± 3.72) compared with those living >2km from the nearest gas well (mean ± SD, 1.60 ± 2.14, p=0.0002).(7) A model which adjusted for age, sex, household education, smoking, awareness of environmental risk, work type, and household animals, reported skin conditions were more common in those living <1km compared with >2km from the nearest gas well (Odds Ratio=4.1, 95% CI: [1.4,12.3], p = 0.01).(7) Upper respiratory symptoms were also more prevalent in those living <1km from the nearest gas well (38%) than those living 1-2km or >2km from the nearest well (31% and 18% respectively).(7) This shows the presence of a dose response relationship between distance from wells and upper respiratory symptoms. Comment by Author: ok – some evidence (probably considered low quality for causation – according to Bradford Hill criteria.
Search Strategy
The search term, “(“hydraulic fracturing” OR *fracking) AND (“drinking water” OR groundwater OR “surface water”)” retrieved 84 results on PubMed, with 81 of these being published in the last 5 years. This was then limited to only 17 articles which were freely available online through the University of Adelaide. The same search term retrieved 541 results on Scopus, 388 of which were published in the last 5 years. Of these, 14 were published in Australia, with 11 published in the last 5 years. This is a relatively recent environmental health issue to arise, especially in Australia. The majority of relevant articles were not freely available online through the University of Adelaide, leaving a limited number of resources. Comment by Author: OK. Any review articles?
Exposure Assessment
The exposure of interest is oral ingestion of contaminated water. Exposure assessment would be carried out by comparing measured chemical concentrations at representative monitoring locations and comparing these to accepted health guidelines. Currently there areis no publicly available monitoring data in WA to identify or evaluate concentrations of chemicals that exist naturally in the environment prior to fracking taking place, and after the operations involved in fracking.(2) Comment by Author: good
A list of 195 substances, which may be present during the fracking process, was developed by The Department of Health (DOH).(2) A total of 22 substances are known to be used in the drilling process (Table 2, Appendix D), none of which have current guidelines.(2) Silica, bentonite clay and cristobalite are the only substances of this group known to be carcinogenic.(2) Exposure to these are primarily through inhalation and therefore the susceptible population would be employees handling the material.(8) Comment by Author: yes, this is the most clear risk
Table 3 (Appendix D) shows the 47 substances commonly used as additives in fracking fluid but not detected in analysis of flow-back fluids.(2) Only 3 of these substances have established guidelines.(2) The Australian Drinking Water Guidelines state that silica has no known adverse health effect in water but does alter taste and therefore has an aesthetic guideline only.(2) Sodium chloride does not have a current guideline but does effect taste at >200mg/L.(9) Two substances are known carcinogens, one a suspected carcinogen and one a possible carcinogen (Table 3).(2) One such substance, borax, can cause both developmental and reproductive toxicity.(10) Comment by Author: This is a complex cocktail of chemicals. The presence or absence of each substances may be confirmed, using specific assays that each have their limits of detection. However, the key point is how much? (so that a comparison may be made with each guideline value, using an appropriate exposure model.)
Table 4 (Appendix D) lists 35 substances used as additives in fracking fluid which are also detected in flow-back fluid.(2) Of these substances, 23 have guidelines for safe levels of oral intake and 3 have aesthetic guidelines.(2) Of the 35, 3 are known carcinogens (benzene, arsenic and chromium IV) and 6 are suspected carcinogens (Table 4).(2) Benzene has a carcinogenic potential to induce leukaemia and should not exceed 0.001mg/L in drinking water.(11) Arsenic is listed as a class 1 carcinogen due to evidence of increased risk of malignancy when ingested through drinking water.(8) Chromium IV is also a class 1 carcinogen but the evidence is based on inhalation, causing lung cancer.(8)
An additional 96 substances were found in the flow-back fluids that were not used in the fracking fluid (Tables 5 and 6, Appendix D).(2) Of these 6 are known, and 22 are suspected, to be carcinogenic.(2) Only radium 226 and 228, however, are carcinogenic via the oral route.(12)
Before fracking begins in a new area, a base liner assessment program which includes sampling of nearby water wells should be conducted.(13) Wells should also be sampled after fracking operations commence.(13) In order to obtain valid results, proper sampling and analysis protocols such as; using appropriate containers and seals, purging the water well prior to sample capture, following container filling procedures and following storage and holding time requirements should be followed.(13) Analyses should be conducted by an accredited laboratory using appropriate analysis methods.(13) Comment by Author: Clearly a work in progress. Sounds like there is limited information on actual human exposure. Most of it seems to be water concentration data, and mostly at the source.
To assess exposure, potential pathways for drinking water contamination must be identified. Table 7 (Appendix E) lists activities from which substances may be released during fracking operations.(2) Activities such as transportation, preparation of a task, drilling and well production, fuelling and tank refilling and treatment can all lead to the aforementioned substances being released into water sources (Table 7).(2) This can occur through leaks, surface spills, loss of well or dam integrity and seepage (Table 7).(2)
Risk Characterisation
Contamination of either surface or underground drinking water, which would render them unusable for consumption, is possible via many aforementioned mechanisms. The extent of the risk this would place on individuals consuming this water is not wholly known. Once a water source is contaminated it is difficult for it to be restored to its original quality. Application of the precautionary approach should therefore be applied.
Worst case hypothesised outcomes, assuming the drinking water supply is significantly contaminated and the exposed population receives sufficient dose are shown in table 8 (Appendix E). Health effects that may arise from ingestion, inhalation or skin exposure are; respiratory irritation, skin irritation gastrointestinal irritation, reproductive effects, liver or kidney effects, neurological effects and cancer (Table 8).(2) These health effects have been reported following significant exposures in humans or from animal laboratory testing.(2) However, although possible, there is no certainty that these outcomes would be experienced by any or all of those exposed. Exposure concentration, duration and frequency influence the likelihood, and severity, of outcomes. This was demonstrated by the study by Rabinowitz et al. with those living closer to the operations having greater health problems. Comment by Author: Good. Who do you think would be most susceptible to such contaminants? (amongst the “private drinking users”?) Are there a lot of people near these wells, or very few, and who are they? This is one of the common problems – risk assessors often fail to take into consideration the characteristics of the exposed population. Exposed population is mentioned on p26 of the WA report, then the authors forgot to say much (or anything) about it.
Risk Management and Communication
To minimise or eliminate the impact of contaminated water sources to WA residents, appropriate risk management must be put in place. This will need to incorporate: Comment by Author: All OK. Anything more specific on communication to the community. (or empowering the community)
· Employing best practice technologies and procedures to prevent significant chemical release into the environment(2)
· Stringent regulatory review and auditing of gas extraction activities to ensure all legislative requirements are being consistently met(2)
· Regular and timely notification of local stakeholders and the DOH of any significant changes to chemical concentrations(2)
· Mitigation strategies and plans to prevent further impacts(2)
Best practice technologies include international standards for well construction that must be met.(2) The wells must have several layers of cement as well as steel casing where they pass through underground water sources.(2) Before any activity can take place, the wells must be tested to pressures above what is required for fracking to ensure there are no leaks.(2)
A communication plan should be developed for the notification of incidents with the potential to impact public health. Ongoing consultation and collaboration between all relevant government agencies is vital.
The Australian Drinking Water Guidelines must be utilised as a key source. Those substances with standards should be carefully monitored to ensure they do not exceed the guidelines. Naturally existing chemicals in the area should be measured prior to any work taking place. Therefore, accurate comparisons can be drawn during the fracking process, allowing the true effect of the operation on water quality to be determined.
Example EH major assignment
Word Count: 2000
Page 1 of 17
References Comment by Author: Good. For ref 9, you could have used Australian drinking water guidelines
1. United States Environmental Protection Agency. Assessment of the impacts of hydraulic fracturing for oil and gas on drinking water resources. Washington: Office of Research and Development; 2015 June [cited 2016 June 7]. 25 p. Available from: https://www.epa.gov/sites/production/files/2015-07/documents/hf_es_erd_jun2015.pdf.
2. Government of Western Australia Department of Health. Hydraulic fracturing for shale and tight gas in Western Australian drinking water supply areas: human health risk assessment. Perth: Department of Health; 2015 June [cited 2016 June 7]. 64 p. Available from: http://ww2.health.wa.gov.au/~/media/Files/Corporate/Reports%20and%20publications/PDF/Hydraulic-Fracturing-HHRA-18June%202015.ashx.
3. Batley GE, Kookana RS. Environmental issues associated with coal seam gas recovery: Managing the fracking boom. Environmental Chemistry. [Article]. 2012;9(5):425-8. DOI: 10.1071/EN12136. Cited in: Scopus.
4. Carpenter DO. Hydraulic fracturing for natural gas: Impact on health and environment. Reviews on Environmental Health. [Article]. 2016;31(1):47-51. DOI: 10.1515/reveh-2016-0055. Cited in: Scopus.
5. Elliott EG, Ettinger AS, Leaderer BP, Bracken MB, Deziel NC. A systematic evaluation of chemicals in hydraulic-fracturing fluids and wastewater for reproductive and developmental toxicity. Journal of Exposure Science and Environmental Epidemiology. [Article in Press]. 2016. DOI: 10.1038/jes.2015.81. Cited in: Scopus.
6. Digiulio DC, Jackson RB. Impact to Underground Sources of Drinking Water and Domestic Wells from Production Well Stimulation and Completion Practices in the Pavillion, Wyoming, Field. Environmental Science and Technology. [Article]. 2016;50(8):4524-36. DOI: 10.1021/acs.est.5b04970. Cited in: Scopus.
7. Rabinowitz PM, Slizovskiy IB, Lamers V, Trufan SJ, Holford TR, Dziura JD, et al. Proximity to natural gas wells and reported health status: results of a household survey in Washington County, Pennsylvania. Environ Health Perspect. 2015 Jan;123(1):21-6. DOI: 10.1289/ehp.1307732.
8. International Agency for Research on Cancer. IARC monographs on the evaluation of carcinogenic risks to humans. Lyon; 2012 [cited 2016 June 10]. Vol 100C. Available from: http://monographs.iarc.fr/ENG/Monographs/vol100C/mono100C-14.pdf.
9. World Health Organisation. Guidelines for drinking-water quality. Fourth ed. Geneva: World Health Organisation; 2011.
10. Safe Work Australia. Hazardous substance information system; 2013 [cited 2016 July 8]. Available from: http://hsis.safeworkaustralia.gov.au/.
11. National Health and Medical Research Council. Australian Drinking Water Guidelines 6; 2011. Last Updated 2016 February [cited 2016 July 18] Available from: https://www.nhmrc.gov.au/_files_nhmrc/file/publications/nhmrc_adwg_6_february_2016.pdf.
12. International Agency for Research on Cancer. IARC monographs on the evaluation of carcinogenic risks to humans; 2011 [cited 2016 June 10]. Vol 79. Available from: http://monographs.iarc.fr/ENG/Monographs/vol79/mono79-17.pdf.
13. Groundwater protection council. Groundwater quality & testing. 2016 [cited 2016 June 11]. Available from: https://fracfocus.org/groundwater-protection/groundwater-quality-testing.
Appendix A: Hydraulic Fracturing
Figure 1: Schematic illustrating the process of hydraulic fracturing(2)
Appendix B: Shale Gas Resources in Australia
Figure 2: Australian basins with shale gas potential(2)
Table 1: Estimated Recoverable Shale Gas by Country(2)
Appendix C: Box and Whisker Plots
Figures 2 – 5
“Box and whisker plots of minimum and maximum, quartiles, median (line in boxes), mean (crosses in boxes) of (2) Na, (3) K, (4) Cl, (5) SO4 for domestic wells inventoried by Daddow and Plafcan in the Wind River Indian Reservation and Fremont County, respectively, sampled by EPA and WDEQ (PGDWXX series) greater than and less than 1 km from a production well, Wyoming Water Development Commission (WWDC series) greater than 1 km from a production well, EPA monitoring wells, and produced water and bradenhead water samples. Domestic wells sampled more than once, including data from Daddow, are represented with a mean value. Fourteen measurements in Daddow < 1 mg/L for potassium are not illustrated. Data points at MW01 and MW02 are samples collected during Phase III, IV, and V sample events”.(6)
Figure 2: Sodium (Na)(6)
Figure 3: Potassium (K)(6)
Figure 4 Chloride (Cl)(6)
Figure 5: Sulphate (SO4)(6)
Appendix D: Potentially Hazardous Substances in Fracking
Table 2: Substances used in the drilling process, guideline values and hazards(2)
Table 3: Substances used for hydraulic fracturing but not detected in flow-back fluid, guideline values and hazards(2) Comment by Author: Limit of detection
Table 4: Substances used for hydraulic fracturing and detected in flow-back fluid, guideline values and hazards(2) Comment by Author: At what level?
Table 5: Additional substances detected in flow-back fluid, guideline values and hazards(2) Comment by Author: At what level?
Table 6: Additional substances detected in flow-back fluid, guidelines values and hazards (continued)(2)
Appendix E: Exposure and Outcome Assessment
Table 7: Exposure Assessment – Identification of potential contamination events and associated exposure pathways(2)
Table 8: Possible outcomes from potential exposures(2)
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