Abstract
The extraction of coal seam gas (CSG) produces large volumes of potentially contaminated water. It has raised concerns about the environmental health impacts of the co-produced CSG water. In this paper, we review CSG water contaminants and their potential health effects in the context of exposure pathways in Queensland’s CSG basins. The hazardous substances associated with CSG water in Queensland include fluoride, boron, lead and benzene. The exposure pathways for CSG water are (1) water used for municipal purposes; (2) recreational water activities in rivers; (3) occupational exposures; (4) water extracted from contaminated aquifers; and (5) indirect exposure through the food chain. We recommend mapping of exposure pathways into communities in CSG regions to determine the potentially exposed populations in Queensland. Future efforts to monitor chemicals of concern and consolidate them into a central database will build the necessary capability to undertake a much needed environmental health impact assessment.
Introduction
Coal seam gas (CSG) water is a by-product of methane extraction. In order to produce methane from coal beds, water must be pumped out to the surface to lower the hydrostatic pressure allowing methane to diffuse from the coal microstructure and into the well bore. There is considerable uncertainty about the health effects of CSG water (AMA 2013). In some quarters, public discourse through the media indicates that there is a concern that CSG production make communities ill in Queensland (SBS 2012). This can probably only be answered through a detailed environmental health impact assessment undertaken for specific geographic locations and populations and this work has not yet been undertaken.
Numerous studies have documented health effects from the consumption of water contaminants leaching from coal units (Masursky 1962; Thomas Jr & Gluskoter 1974; Finkelman et al. 1999; Finkelman et al. 2002; Welch & Stollenwerk 2002; Kolker et al. 2006; Orem et al. 2007b; ATSDR 2011), such as Balkan endemic nephropathy (BEN), which is a serious kidney disease. Although the aetiology of BEN is still uncertain, one hypothesis suggests that toxic organics such as soluble polycyclic aromatic hydrocarbons (PAHs) may be leached from weathering of low-rank coals, and the long-term consumption of water containing the organic compounds result in BEN (Feder et al. 1991; Finkelman et al. 2002; Orem et al. 2007a). Orem et al. (2007b) found a range of organics in CSG water from Powder River Basin and water from coal aquifers in Powder River Basin which were similar to organic compounds found from BEN areas. Water samples from coal aquifers in Louisiana showed higher concentrations of organics; a meaningful association between high organic levels in drinking waters and renal/pelvic cancer has been found in the area (Orem et al. 2007b).
Additionally CSG production will produce a considerable volume of contaminated water. It is estimated that 15.4 GL of CSG water is produced in Queensland in 2011 (DEEDI 2012), and it is likely that 25 GL of CSG water will be produced annually in the Surat Basin, Queensland for the next 25 years (DEEDI 2009). This large volume of CSG water production is driving much of the interest in developing beneficial uses for CSG water, and environmentally acceptable disposal (Figure 1). However, pathways by which populations might be exposed to potentially contaminated CSG water are not well documented. This paper reviews the current understanding of CSG water quality issues, the potential adverse health effects of chemical contaminants found in CSG water and the potential human exposure pathways. Identifying and quantifying exposure pathways is one important step towards the development of full environmental health impact assessment.
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23 May 2014![]({"type":"image","src":"/na101/home/literatum/publisher/tandf/journals/content/cije20/2015/cije20.v025.i02/09603123.2014.915018/20150218/images/medium/cije_a_915018_f0001_oc.gif"})
Figure 1. (Color online) Major CSG basins in Queensland.
Hazardous substances associated with CSG water
Globally extracted CSG water will contain similar chemical compounds despite the geographic separation of basins and the differences in stratigraphy and geologic age. However, water chemistry gradually changes through the processes of biochemical reduction of sulphate, enrichment of bicarbonate and precipitation of calcium and magnesium (Van Voast 2003). These geochemical processes largely determine the in situ coal chemistry and consequently the natural contaminants that we can now expect in CSG water wherever it is extracted (Table 1).
Table 1. Potentially hazardous substances and physico-chemical properties found in CSG water, not necessarily at hazardous concentrations.
In the USA, Dahm et al. (2011) built a composite geochemical database for CSG water covering four basins: Greater Green River, Powder River Basin, Raton Basin and San Juan Basin. They found that sodium bicarbonate and sodium chloride type waters with Total dissolved solids (TDS) concentrations of 150 to 39,260 mg/L tended to dominate the CSG water quality spectrum (Dahm et al. 2011). In comparison, TDS of good quality drinking water is up to 500 mg/L and is between 36,000 and 38,000 mg/L for sea water (DERM 2011c). In addition, Dahm et al. (2011) found TDS, sodium adsorption ratio, temperature, iron and fluoride were water quality indicators which commonly exceeded drinking water standards and standards for beneficial applications such as livestock watering and irrigation. Beryllium and zinc did not exceed drinking water guidelines. Benzene was the only BTEX (benzene, toluene, ethylbenzene and xylenes) compound reported above drinking water standards and was found in 7 % of the wells of the database, mostly located in the Raton and San Juan Basins (Dahm et al. 2011). A study by Orem et al. (2007b) in the Powder River Basin identified organic compounds in the water samples including phenols, biphenyls, N-, O- and S-containing heterocyclic compounds, PAHs, aromatic amines, various non-aromatic compounds and phthalates. Most of these compounds (e.g. phenols, heterocyclic compounds and PAHs) are probably naturally occurring. A number of them are known to be toxic and many identified compounds have unknown toxicities. Although the concentrations of individual compounds were low, the long-term chronic exposure to these organic compounds is unknown (Orem et al. 2007b).
In Canada, ground water from monitoring wells in CSG exploration areas in south-eastern British Columbia have low salinity (about 250–1300 mg/L) and trace metal concentrations, but levels of iron, cadmium, chromium and zinc exceed the Canadian standards for aquatic life. Ground water does not contain BTEX or naphthalene (Harrison et al. 2000). Although CSG waters show similar chemical characteristics, the concentrations of constituents vary. CSG waters from two major coal deposits in Western Canada, Manville Formation and the Horseshoe Canyon/Belly River Group showed that trace elements such as arsenic, selenium and lead in Manville-produced waters were often above drinking water standards (Cheung et al. 2009).
In the southern hemisphere, CSG water quality from Maramarua, New Zealand shows low calcium, magnesium and sulphate concentrations, but high sodium, chloride and bicarbonate concentrations. Trace elements including boron, iron, manganese, barium, fluoride and zinc have also been detected (Taulis & Milke 2007). In NSW, Australia ground water from CSG exploration wells at Wyong area shows high concentration of TDS, sodium, chloride, barium, iodide and fluoride (Jones 2005).
Much less has been published about the CSG contaminants in Queensland (Table 2), and it has yet to be consolidated into a single monitoring database. However, it has been reported that average concentrations of BTEX compounds, phenolic compounds and PAHs of water chemistry from 47 wells within the Talinga gas field in Surat Basin, Queensland were below detection limits, although ranges of detected levels were not reported (Volk et al. 2011). CSG water from Roma showed Fluoride exceeded Australian drinking water guideline (ADWG) (URS 2011). Benzene was exceeding (2–15 ppb) ADWG in one of the monitoring bores at Daandine, Queensland (Arrow 2011). Samples collected from CSG producing coal in Bowen Basin to investigate the relationship between water quality/stable isotope data and gas/groundwater production presented concentrations of Iron, Aluminium and Fluoride above ADWG (Kinnon et al. 2010). Fluoride and Boron are identified, from one of Australian Pacific LNG reports, as the most concerning constituents of CSG water (Moran & Vink 2010). Samples from CSG wells in Talinga have shown high levels of Aluminium, Fluoride and Iron explained as naturally occurring (APLNG 2010). However, they are levelled out in ponds and removed through reverse osmosis before any uses (APLNG 2010). A summary of water quality data for Roma showed Fluoride, Mercury and Lead exceeded ADWG (URS 2009).
Table 2. CSG water elements/compounds in Queensland.
Consequently, ground water in contact with coal in Queensland has similar types of contaminants that would be expected in CSG extraction anywhere in the world. What has yet to be determined are the particular substances of concern in each producing area. Furthermore, it must be emphasised at this point that contaminants at source cannot be extrapolated to human exposure, dose and consequent health effects without a full environmental health impact assessment.
Known health effects from identified contaminants
The review for this section has two components: the health effects of CSG water compounds and indirect health risks of CSG water.
Health effects of CSG water compounds
Leukaemia
Benzene, a known carcinogen, is one of the hazardous substances found in CSG water. The Maximum Contaminant Level, which is the legal allowable level of a substance in drinking water, for Benzene is 0.005 mg/L and the Maximum Contaminant Level Goal is zero. Benzene can damage blood cells (ATSDR 2007a) and several studies have linked leukaemia with human exposure to benzene (WHO 2003a). Benzene also has adverse effects on the human immune system following intermediate and long-term inhalation exposure. There is a relationship between neurological effects and occupational exposure to Benzene via inhalation routes in the short and long term (ATSDR 2007a).
Fluorosis
High concentration of fluoride in drinking water can have adverse health effects on humans, animals and plants (Sharma et al. 2011a). Long-term exposure to fluoride can result in dental and skeletal fluorosis (Fawell & Bailey 2006). For example, one-seventh of people in the Karbianglong district of north-east India are suffering from dental or skeletal fluorosis due to high concentration of fluoride in drinking water resources (Kotoky et al. 2008). Moreover, in a large number of studies, high fluoride levels in drinking water have been associated with lower intelligence in children (Lu et al. 2000; Xiang et al. 2003; Rocha-Amador et al. 2007; Trivedi et al. 2007; Wang et al. 2007; Tang et al. 2008).
Developmental and reproductive toxicity of boron
Boron in drinking water guideline established by WHO is 0.5 mg/L (WHO 2003b). This guideline is under revision and the new guideline value for 2011 is 2.4 mg/L (Cortes et al. 2011). There are many studies on boron deficiency but not on boron toxicity. No data are available for the relationship between exposure to boron and cancer in humans (USEPA 2008; Kot 2009). According to United States Environmental Protection Agency (USEPA), the risk for foetus and testes increases as the level of boron exceeds 5 mg/L. It is stated that testes and the developing foetus are the most sensitive organs for boron toxicity (USEPA 2008). A human health risk assessment of boron in drinking water, which reviewed both toxicological and pharmacokinetic data, showed developmental and reproductive toxicity of boron from the experience of laboratory animals (Murray 1995). However, similar studies on pregnant and non-pregnant women did not show the same result. Therefore, the result of animal studies on boron toxicity in terms of fertility does not necessarily apply to humans (Korkmaz 2011).
Lead-related health effects
Lead has been associated with nephrotoxicity, central nervous system effects, cardiovascular disease, impaired fertility and adverse pregnancy outcomes (WHO 2011). Inorganic lead compounds are known as probable human carcinogen (ATSDR 2007b). A number of studies have been linked the adverse effect of lead exposure to human intelligence and brain function, the weight of evidence is greater for infants and children under 4 years of age (ATSDR 2007b; Hu et al. 2010; WHO 2011). Exposure to lead in pregnant women may lead to pre-term delivery (WHO 2011). Also, substantial studies have shown that the risk of hypertension increased with lead exposure (ATSDR 2007b).
Indirect health risks
CSG activities can increase the incident of standing water and with it the larval habitats for mosquitoes. Consequently, CSG activities indirectly result in increasing vector-borne diseases. According to the US Geological Survey West Nile Maps 2004, the Powder River Basin accounts for 30 % in 2002 and 70 % in 2003 of all human cases of the West Nile Virus (WNV) in Wyoming (Zou et al. 2006). The large volume of CSG water discharge into ponds makes the environment suitable for mosquito larvae. Other potential confounding factors (temperature and avian host availability) influence the risk of WNV. Culextarsalis habitat is increasing due to CSG development, and as Culextarsalis larval habitat is linked with ponds that can be used as water sources for domestic and wildlife species, these animals can be exposed to infected mosquitoes (Zou et al. 2006). Another study in the same area showed, in a normal rainfall year 2005, CSG ponds had the highest population of the WNV vector Culextarsalis and in a drought year 2004, agricultural areas had the highest mosquito population linked with increased irrigation (Doherty 2007).
CSG activities can impact native plant species distribution and patterns of non-native plant invasion. The changes in soils resulting from contact with CSG water may cause new plant species and increase salt-tolerant species in CSG sites (Veil et al. 2004). A study in the Powder River Basin suggests that CSG development may cause the establishment of non-native plants (Bergquist et al. 2007). Salt Cedar and Parthenium are weeds of national significance in Australia, due to the salinity in Australian soils, which increase in CSG fields such as the Darling Downs, Queensland (Natural Resource Management, 2007 and Weeds Australia, 2008 in CCAG 2008). This can be an issue for farmers, because Parthenium readily colonise native crops; also, it can cause allergic reactions such as dermatitis and hay fever in both humans and livestock (DEEDI 2011).
CSG water exposure pathways
To determine the pathways through which people can be exposed to CSG water, the uses and release mechanisms of CSG water need to be understood. The CSG industry has a number of challenges with both beneficial uses and disposal pathways of the extracted water (DNRME 2004) although it is recognised these pathways will vary regionally (Dahm et al. 2011). Pathways that can categorised into (a) surface releases, (b) underground releases and (c) impoundment, and beneficial uses that may or may not require treatment (Figure 2). Chemicals in CSG water can contact and/or enter human bodies not only through water exposure but also air exposure. There are some volatile chemicals such as benzene which can become airborne so exposure can occur via inhalation (ATSDR 2012). This is more likely to happen by using CSG water for dust suppression, site operations and irrigation and it could also expose people through evaporation of chemicals from ponds. All possible exposure routes for each pathways are described in Table 3.
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23 May 2014![]({"type":"image","src":"/na101/home/literatum/publisher/tandf/journals/content/cije20/2015/cije20.v025.i02/09603123.2014.915018/20150218/images/medium/cije_a_915018_f0002_oc.gif"})
Figure 2. Main pathways for CSG water exposure.
Table 3. Summary of generic exposure pathways for CSG water.
Beneficial uses of CSG water associated with human exposure
The “beneficial use” of CSG water refers to water extracted during a CSG operations but used in some constructive way, such as in stock watering (DERM 2010b). In the USA, CSG extraction has been undertaken for many years, with a variety of approaches to the use of CSG water. In the Powder River Basin, CSG water is managed by land application, being returned to shallow groundwater aquifers via infiltration basins, direct discharge to ephemeral or perennial streams, or infiltration impoundment (DOE 2003). Beneficial use categories in Colorado have included aesthetics and preservation of natural environments, irrigation, augmentation, livestock, commercial, minimum flow, domestic, municipal, fire protection, power, fishery, recreation, geothermal, silvicultural, groundwater recharge, snow-making, industrial, wildlife watering and wildlife habitat (ALL-Consulting 2003). In Queensland, beneficial uses of CSG water include irrigation (of high value), livestock watering, dust suppression and aquaculture (DERM 2010a).
Drinking water
CSG water can be used to augment municipal drinking water supplies. It can be used to recharge into groundwater resources or CSG water can be piped to locations where the water is needed for uses that include drinking. In the USA, 80 % of wells covering four CSG basins, previously discussed, require treatment for drinking water use. The most commonly exceeded parameters for drinking water applications include TDS and iron. If concentrations of iron, fluoride and TDS reduce to an acceptable level, the water of many wells in all basins will be suitable for drinking water. The Powder River Basin is more suitable for drinking water applications due to lower TDS, arsenic, barium, cadmium, chloride, lead, manganese, selenium and silver concentrations (Dahm et al. 2011). The quality of aquifers which receive CSG water, the quality of CSG water and the kind of treatment applied (if any) are factors that determine the level of risk (DNRME 2004). In Queensland, a CSG company has run a three-month trial for injection of treated CSG water into the Gubberamunda aquifer in Roma, with the purpose of augmenting the town water supplies (URS 2011).
Irrigation
While in most cases the water used for irrigation is blended (a mix of treated and untreated water) (QMEB 2012), reverse osmosis-treated water is used to irrigate some pasture crops and tree timber plantations in Queensland (NWC 2011). In the Gloucester Basin, NSW, untreated co-produced water from CSG pilot projects is being used for pasture irrigation (NWC 2011). The use of CSG water for irrigation purposes shows many complex challenges connected to soil, water and landscape management such as salt accumulation in the root zone, soil structure stability, excess drainage of water below the root zone and crop/plant productivity (DERM 2010a). Excess sodicity can decrease the permeability of soil to both air and water, and lower nutrient availability (Veil et al. 2004). As previously explained, crop irrigation using CSG water can result in bioaccumulation of metals in crops depending on CSG constituents and crop type. Additionally, farmers may be exposed to aerosolised water droplets created during the irrigation process through inhalation or through dermal contact. Finally, irrigation may lead to greater infiltration into ground water aquifers, and approximately 50 % of treated CSG water is estimated to be used for irrigation in Queensland (QMEB 2012).
Livestock watering
While livestock can tolerate a variety of different types of water, more than the human population, without side effects, abrupt changes of salinity might be detrimental. High levels of salts and elements may influence animal growth and production and even may cause illness and death (ALL-Consulting 2003). Animal tolerance also varies with species, age, water requirement, season of the year and physiological condition. Pregnant, lactating, young, weakened and aged stock can be more vulnerable due to being less tolerant of poorer quality water (DERM 2010a; ALL-Consulting 2003). There is also the possibility of contaminants entering the food chain resulting in the contamination of dairy and stock meat potentially exposing consumers. Arrow Energy in Queensland provides up to 4 ML/day of untreated CSG water to local beef cattle feedlots for stock watering by (NWC 2011).
Aquaculture
CSG water chemistry is different from seawater, and there are some concerns regarding the impact of this change chemicals. Studies have shown that two species of fish Barramundi and Mulloway can grow and survive in CSG water with simple improvements, but species such as Murray Cod cannot. Apart from water quality, other factors need to be considered for the survival and growth of chosen species. Bioaccumulation of contaminants that cause people to be indirectly exposed must be considered when evaluating contaminants in CSG water (DERM 2010a). A new concern raised about discharging CSG water into streams is that increasing salt-tolerant aquatic habitats may have effects on the ecosystem (Veil et al. 2004).
Site operations
Treated and untreated CSG water is often used for site operations such as dust suppression, drilling and hydraulic fracturing, which raises concerns regarding shallow aquifers and airborne occupational exposures (NWC 2011). CSG water constituents may accumulate beside roads on CSG tenures and infiltrate soil or shallow aquifers when being used for suppression (DERM 2010a). The other potential mechanism for release of chemicals is volatilisation from sprays; the main pathway for air concentrations of such chemicals is inhalation (ENVIRON-Australia 2010). Using CSG water for well development can pose the risk of migration through aquifer systems because of poor well development (DiGiulio et al. 2011). In Queensland, less than 5 % of CSG water is estimated to be used for dust suppression, industrial or urban use (QMEB 2012). For almost all uses, CSG water is treated in Queensland.
Surface releases associated with human exposure
Surface releases include planned discharges to surface waters and unplanned discharges to terrestrial environments that can result in run-off into surface waters. CSG producers are allowed to discharge the water into surface waters and land, despite the potential problem that disposal to streams may alter surface waters and riparian zones (EPA 2001), erode soils and sediments, change microclimates or salinise soils as a result of CSG water constituents (Fisher 2003). Discharges of CSG water into surface water and land can cause the infiltration of contaminants to drinking water aquifers (Veil et al. 2004). Another study suggests that the release of CSG water into arid and semiarid rangelands in rivers of the Powder River Basin can result in the precipitation of calcium carbonate in soils that consequently decreases infiltration rates and increases run-off and erosion (McBeth et al. 2003). Although CSG water in most cases is treated prior to discharge to surface water because environmental release of untreated water is not permitted on a large scale in Australia, disposal by direct discharge to a surface water body of up to 4.5 ML/day in the Bowen Basin has been recorded (NWC 2011).
CSG water is pumped from the coal seam and piped into constructed ponds (Young 2005) then transported through pipes or by trucks to treatment facilities (Simpson et al. 2003). Since CSG water is often extracted in locations where the potential beneficial uses are limited, CSG water is likely to be transported to locations where there are greater beneficial uses. For example, the construction of a 20 km buried pipeline that will be used to transport treated CSG water from QGC’s Kenya water treatment plant to the town of Chinchilla and local farmers has commenced (Waterweek 2011).
Surface spills or run-off of CSG water can occur due to pipeline rupture, tanker truck accidents, or other equipment or procedure failures in the transport or containment of CSG water. Pipeline failure occurred in 2011 resulting in a discharge of 10,000 litres of CSG water south of Narrabri, NSW, Australia (NSW-DTI 2011). In 2012, accidental release of drilling fluids into the Condamine River was reported in Queensland (ABC-News 2012). In 2010, a spill of 10,000 barrels of CSG water occurred in Wyoming, USA due to broken pipes. The water entered an ephemeral drainage and flowed to Barber Creek (WDEQ 2010). Although the health risk associated to such incidents is estimated to be low (Sharma et al. 2011b; Rozell & Reaven 2012), the likelihood and risk of unplanned CSG water release is an unknown in Queensland.
Underground releases and hydraulic fracturing
Underground releases of CSG water can be planned or unplanned. Planned release of untreated CSG water into underground strata is favoured in many areas of North America (USGS 2000; NWC 2011). Injection of untreated CSG water has occurred in Fairview Field, Queensland. Fairview 77 and Fairview 82 are injection wells with the capacity of about 2.4 ML per day. Untreated water has been injected into the Timbury Hills formation, which is an underlying aquifer in the area (URS 2009).
Unplanned underground or accidental releases can occur during extraction due to failures in bore casing and cementing practices, operations or changing production equipment (UT-Energy-Institute 2012). Although casing and cementing are barriers that isolate CSG water from moving behind the casing or from coming to the surface, there have been questions raised over the casing quality, failures in operations or changing production equipment such as tubing which is designed to be replaceable (APLNG 2011; NSW-Parliament 2012). One of the mechanisms for aqueous and gas phase transport postulated by the US Environmental Protection Agency in Wyoming is migration via boreholes due to insufficient or inadequate cement outside the production casing (DiGiulio et al. 2011).
Hydraulic fracturing or fracking may also increase the permeability and likelihood of migration of CSG water into surrounding aquifers, resulting in the contamination of pristine aquifers (NSW-Parliament 2012). Concerns about the social and environmental impact of hydraulic fracturing have been raised around the world (Lloyd-Smith & Senjen 2011). Fracking involves injection of a fluid, consisting of water, sand and chemicals, under pressure, into a coal seam to increase permeability and provide a pathway for gas to flow through the coal (DERM 2011b). It is estimated that anywhere from 10 to 90 % of the fracking fluid is pumped up to the surface. The fracking fluids can be impounded in evaporation pits, which is common practice in the western USA, or injected underground which is common in the eastern USA (Colborn et al. 2011). Fracking is used in approximately 8 % of CSG wells drilled in Queensland (DERM 2011b). According to Queensland’s CSG industry estimation, between 10 and 40 % of the wells may be fracked in the future (DERM 2011b). In Queensland, a study of one CSG operation showed that each well that required fracking consumed approximately 18,500 kg of additives (Lloyd-Smith & Senjen 2011). Further, a single well can be fracked 10 or more times (Colborn et al. 2011).
There is a relationship between proximity to gas production wells/hydraulically fractured gas production wells and concentration of aqueous and methane constituents in ground water. Fault and fracture systems in addition to lithology ultimately determine spatial relationship (DiGiulio et al. 2011). The geochemistry of gas found in drinking water matched gas in hydraulically fractured shale gas production sites in Marcellus and Utica shale formations in Pennsylvania and New York (Osborn et al. 2011). Potassium and chloride concentrations have been observed in a monitoring well in Pavillion, Wyoming where potassium hydroxide, potassium chloride, potassium metaborate and ammonium chloride were used in hydraulic fracturing. Alternate explanations for these inorganic geochemical anomalies include contamination from drilling fluids and additives, well completion materials and surface soil, with contamination from all these sources worsened by poor well development (DiGiulio et al. 2011).
A Texas study has found no evidence to link groundwater contaminations to fracking (UT-Energy-Institute 2012). It has said that such ground water contamination previously reported was due to failure of well casing and cementing. Moreover, surface spill of fracking fluid, which can migrate to underground water, is more likely to pose a risk than fracking itself. As a follow-up project, they are currently investigating hydrological connectivity between shale and overlaying and underlying units (UT-Energy-Institute 2012). The potential human health risks of hydraulic fracturing activities on drinking water aquifers in the USA have been assessed as insignificant (Sharma et al. 2011b).
In Queensland, Arrow Energy does not intend to use fracking in their Surat Gas Project (Coffey-Environments 2012). Australia Pacific LNG would use fracking in approximately 30 % of the production wells in the Surat Basin permit areas, which will be approximately 3000 fracked wells (URS 2010). In Santos’ gas fields, 78 % of wells were fracked in 2010 (Golder-Associates 2010).
Constituents of fracking fluids used by Australia Pacific LNG include 2-bromo2-nitro-1,3-propanediol, sodium hypochlorite, sodium hydoxide, sodium chloride, monoethanolamine borate, ferric chloride, guar gum, ethanol, sodium hydroxide, acetic acid, sodium thiosulfate, potassium chloride, terpenes and terpenoids (URS 2010). Fracking constituents used by another CSG company in Queensland consisted of potassium carbonate, teramethyl ammonium chloride, a proprietary compound, sodium persulfate, ethylene glycol, methanol, oxyalkylated alcohols, tetrakis phosphonium sulfate, boric oxide, methanol, gas oils (petroleum), cristobalite, quartz, oxy-1,2-ethanediyl, ethylene glycol monobutyl ether, sodium acetate and guar gum (Golder-Associates 2010). The National Assessment of human health and environmental risks from the chemicals used in fracking for CSG extraction in Australia has been started in 2012. It is a collaboration between the National Industrial Chemicals Notification and Assessment Scheme (NICNAS), the Commonwealth Scientific and Industrial Research Organisation and the Department of the Environment and Geoscience Australia. The results of the assessment are expected to be available in 2014 (NICNAS 2013). The likelihood of direct exposure to fracking fluid through the extraction of ground water was assessed by one CSG company in Queensland as unlikely and the consequences of exposure as moderate (Golder-Associates 2010). However, the role of fracking in generating new pathways for gas and CSG water migration has not yet been evaluated in Queensland.
Does underground release contaminate drinking water aquifers?
Aquifer connectivity is one of the factors that influence the transport of CSG water. The connectivity between coal seams and water aquifers is not well understood in Queensland or the USA (Helmuth et al. 2008). To determine whether CSG water flows between aquifers, one needs to know whether aquifers are connected or separated. When aquifers are connected, water can flow if ground water pressures are near or in equilibrium. Faults and poorly constructed bores also affect flow paths (Fennell et al. 2011). Understanding of groundwater flows between aquifers can be more complex due to anisotropic hydraulic conductivity. Interpretation of geophysical well logs analysis in the coal seam aquifer from the Powder River Basin, SE Montana, showed isotropic horizontal groundwater flows in coals due to the bedding configuration (Morin 2003).
A Queensland-based study assessed risk of CSG activities on overlaying and underlying water aquifers. It focused on whether coal seams are being recharged from surrounding aquifers, as a result of coal dewatering, and showed that some water aquifers are at risk of water flowing into the coal seams (Helmuth et al. 2008). While the direction of ground waters are usually towards coal rather than surrounding aquifers, the possibility of CSG water contaminating surrounding aquifers during depressurisation of coal seams is limited, but water quality can be altered due to the movement of water through the intervening strata (Helmuth et al. 2008) and a recent study has showed that the hydraulic gradient is from the Walloon Coal Measures, which is CSG producing coal in the Surat basin in Queensland, to the Condamine Alluvium in some areas, with a general deterioration in water quality downstream (QWC 2012). Also, the long-term risk of CSG water migration once extraction activities are complete has not been studied.
Moreover, in some areas coal seams are utilised as aquifers, such as the Walloon Coal Measures in the Surat Basin and the Bandanna Formation in the Bowen Basin. The Bandanna Formation is the source of water for 43 stock and domestic bores. The Walloon Coal Measures is the source of water for 1803 stock and domestic bores and 251 non-stock and domestic bores include agricultural, industrial and urban. (QWC 2012). It can be a natural pathway of exposure to coal aquifer water in Queensland, which may have similar composition to CSG water.
Impoundment of CSG water
Evaporation ponds are designed to contain or impound generally untreated CSG water until the water content has been removed by evaporation (DERM 2010b). There is a possibility of CSG water migration through either the floor or sides of the pond (DERM 2011a) and depending on soil conductivity, water may leach contaminants through the vadose zone and into shallow aquifers (Lipinski et al. 2008). High concentrations of organics including benzene, xylenes, gasoline-range organics and diesel-range organics have been detected in ground water samples from shallow monitoring wells in Pavillion, Wyoming where pits were previously used for the storage/disposal of drilling wastes, produced and flow-back waters. Pits are a source of contamination of many shallow aquifers with shallow stock and domestic wells, e.g. < 30 meters below ground surface (DiGiulio et al. 2011). Also, chemical vapour concentration downwind of the ponds may cause health hazards if volatile compounds in aerosols are inhaled (Kawamura & Mackay 1987; Saravanan et al. 2009). A study in the Powder River Basin, where many ponds were unlined, showed that infiltration from CSG water ponds dissolves and mobilises naturally occurring salts and minerals (Healy et al. 2011).
The NSW Government, in its Draft Code of Practice for CSG Exploration, prohibits the containment of CSG water for evaporation (NSW-Parliament 2012). Evaporation ponds are being phased out in Queensland, with a few exceptions; however, evaporation ponds for managing brine streams after reverse osmosis are allowed (NWC 2011). Since such ponds must be constructed in line with the Manual for Assessing Hazard Categories and Hydraulic Performance of Dams (DEHP 2012), the likelihood of contamination of soil and shallow aquifers due to spill or leakage from ponds is said to be unlikely (SANTOS 2008).
Exposure pathway summary
The pathways from the points that CSG water is introduced into human environments to reach the receptors following beneficial uses and releases have been identified (Table 3). However, it is beyond the scope of this work to explain their aggregative risk posed to a population (Figure 3), because of the dearth of local monitoring. Five exposure elements can be used to identify exposure pathways: (1) source or release points, (2) fate and transport, (3) exposure points/point of contact, (4) exposure route and (5) potential exposed population (ATSDR 2005). Pathways consist of both direct and indirect exposure.
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23 May 2014Figure 3. (Color online) The consolidation of potential exposure pathways for CSG water.
![]({"type":"image","src":"/na101/home/literatum/publisher/tandf/journals/content/cije20/2015/cije20.v025.i02/09603123.2014.915018/20150218/images/medium/cije_a_915018_f0003_oc.gif"})
Figure 3. (Color online) The consolidation of potential exposure pathways for CSG water.
Conclusion
CSG water contaminants and known health effects
Although major constituents of CSG water such as TDS seem to be similar in many basins, the level of such constituents varies from basin to basin; for example, salt content can give CSG water a range of very saline to similar to drinking water. Substantial water quality data for salinity and TDS are available (SANTOS 2012) because salinity appears to be the most challenging issue for the CSG industry and has received much more attention from regulators (DERM 2011c). However, this review reveals that our knowledge about temporal and spatial variability of CSG water chemistry in terms of the chemicals of health significance is still very limited in Queensland. It appears to be no centralised monitoring of CSG water to allow exposure pathway contaminant characteristic to be reliably estimated.
Contaminants in extracted CSG water are known to contain chemicals of health significance, such as fluoride, boron, lead, arsenic, benzene and PAHs (Jones 2005; Orem et al. 2007b; Cheung et al. 2009; Dahm et al. 2011). In Queensland, CSG water contains fluoride, iron, aluminium, boron, mercury, lead and benzene, but until monitoring data can be consolidated and used to undertake a broad-scale environmental health impact assessment, we will not be able to confidently assess health risks from CSG activity.
Exposure pathways for CSG water
This component of the review explores potential human exposure pathways from extracted CSG water. Although CSG water contaminants are well documented in the literature, there is little observational data available on the CSG water in Queensland that people are exposed to. This research documents available information about mechanisms that introduce CSG water into human environment and classifies them into the three main pathways of beneficial uses, surface and underground releases, but information is absent for incidental releases. The potential exposure pathways for CSG water include: (1) water used for municipal purposes; (2) recreational water activities in rivers; (3) occupational exposures; (4) extracting water from contaminated aquifers; and (5) indirect exposure through the food chain (DERM 2010a; Queensland-Government 2010; WDEQ 2010; NSW-DTI 2011; NWC 2011; URS 2011; QMEB 2012).
Based on current knowledge of underground movement of CSG water, the hydraulic gradient is generally towards coal; that is, contamination of surrounding aquifers is unlikely. However, understanding about underground movement of CSG water in the specific sense is not sufficient to rule out risk of migration of CSG water into adjacent aquifers. Thus, new research targeting a better understanding of risk associated with CSG water movement to surrounding aquifers is needed.
Apart from exposure pathways associated with CSG activities, there is an additional natural pathway of exposure through coal aquifer extraction in Queensland. The Walloon Coal Measure, a gas producing coal seam in the Surat basin, is one of the most used aquifers for agricultural, stock and domestic consumption whose ground water extraction estimated 16,900 ML per year (QWC 2012). CSG water composition can represent the chemistry of natural waters associated with the coal aquifer. Because the CSG extracted water will be similar to water extracted from the coal aquifers, this provides a potential analogue for future studies on potential health effects of long-term exposure to naturally occurring chemicals. These research findings suggest that the public health implications for populations using water extracted from coal aquifers could be a useful surrogate for potential CSG water impacts. The relationship between low-coal rank aquifers and high rate of BEN-like diseases, especially RPC, has been reported elsewhere (Orem et al. 2007a). Therefore, it should be determined whether there is any incidence of such disease in the areas where bores are tapped in the Walloon Coal Measure.
In view of the very large volume of water released by CSG activities, the large geographic extent of CSG activity in Queensland and the length of time over which exposure is likely to take place, the potentially exposed population could be geographically extensive. While the literature on human exposure to contaminants in CSG water is very limited, work could still be initiated on better understanding and defining the potentially exposed populations in the context of their demography and vulnerability.
Building the capability for environmental health impact assessments
Contaminants monitoring
Systematic monitoring and analysis of the chemicals of concern are recommended. Developing a coal quality database including data about coal rank, trace elements of coal, location of coal samples, together with the database including monitoring data can provide a foundation for research of this nature and make assessments based on accurate quantitative data possible. Apart from a centralised database to get comprehensive picture, making the data available to all researchers as per Queensland government data policy is required.
Pathways modelling
Mapping pathways into the local communities within CSG regions is needed to better understand where the potential intervention point may lie. To do this, new research aiming to better understand CSG water underground movement, compounds’ bioaccumulation, and health impacts on stock and human health effects of long-term exposure to low levels of chemicals needs to be undertaken by researchers. Additionally, the provision of a consolidated database of CSG water samples, discharges, uses and contamination incidents is required for both industry compliance and sound environmental management.
Community profiling
Community profiling is a useful tool to better understand who might be affected by CSG activities. The community profile should include the health, social and economic characteristics and vulnerabilities, available community resources and the geohydrologic setting. This information could be combined to provide more thorough monitoring of pathways. Communities can then be ranked in terms of concern and pilot environmental health impact assessment undertaken for those perceived to be at higher risk.
| Element/Compound | Location | Level | Reference |
|---|---|---|---|
| TDS, sodium, chloride, barium, iodide and fluoride | Jilliby, New South Wales | Exceeding Australian drinking water guideline | Jones (2005) |
| Boron, iron, manganese, barium, fluoride and zinc | Maramarua, New Zealand | Have been detected in CSG water | Taulis and Milke (2007) |
| Sodium, chloride and bicarbonate concentrations | Maramarua, New Zealand | High concentrations | Taulis and Milke (2007) |
| Arsenic, selenium and lead | Mannville, Western Canada | Exceeding drinking water guidelines | Cheung et al. (2009) |
| Iron, cadmium, chromium and zinc | British Columbia, Canada | Exceeding Canadian water-quality guidelines for aquatic life | Harrison et al. (2000) |
| Organic compounds including phenols, biphenyls, N-, O- and S-containing heterocyclic compounds, polycyclic aromatic hydrocarbons (PAHs), aromatic amines, various non-aromatic compounds and phthalates | Powder River Basin, USA | Concentrations of individual compounds are low (most <1 μg/L) | Orem et al. (2007b) |
| TDS, sodium adsorption ratio (SAR), temperature, iron and fluoride | A composite geochemical database covering four basins: Greater Green River, Powder River Basin, Raton Basin, San Juan Basin, USA | Exceeding standards for drinking, livestock and irrigation water applications | Dahm et al. (2011) |
| Beryllium and zinc | Four basins: Greater Green River, Powder River Basin, Raton Basin, San Juan Basin, USA | Detected but not exceeding drinking water standards | Dahm et al. (2011) |
| pH, cadmium, copper, selenium, silver and sulphate | Four basins: Greater Green River, Powder River Basin, Raton Basin, San Juan Basin, USA | Observed but rarely exceeded drinking water standards | Dahm et al. (2011) |
| Benzene | Raton Basin and the San Juan Basin, USA | Exceeding drinking water standards | Dahm et al. (2011) |
| Element/Compound | Concentrations (mg/L) | ADWG (mg/L) | Reference |
|---|---|---|---|
| Fluoride | 2.9 | 1.5 | URS (2011) |
| Benzene | 0.006 | 0.001 | Arrow (2011) |
| Iron | 0.57–16.60 | 0.3a | Kinnon et al. (2010) |
| Aluminum | <0.01–1.32 | 0.2a | |
| Fluoride | 1–3.7 | 1.5 | |
| Fluoride | Reported exceeding standards | 1.5 | Moran and Vink (2010) |
| Boron | 4 | ||
| Aluminum | 1.159 | 0.2a | APLNG (2010) |
| Fluoride | 4.140 | 1.5 | |
| Iron | 1.324 | 0.3a | |
| Fluoride | 2–3.1 | 1.5 | URS (2009) |
| Mercury | <0.1 | 0.001 | |
| Lead | 0.001–0.31 | 0.01 | |
| Iron | 0.029–190 | 0.3a |
a Insufficient data to set a guideline value based on health considerations, so an aesthetic value has been presented.
| Source | Fate and transport | Exposure point | Exposure route | Exposed population | |||
|---|---|---|---|---|---|---|---|
| Beneficial uses | Drinking water purposes | Water | Ingestion, dermal and inhalation | General population | |||
| Water | Ingestion | CSG Occ sectors | |||||
| Dust suppression | Aerosol | Inhalation | CSG Occ sectors | ||||
| Agriculture | Aerosol | Inhalation | AgriOcc sectors | ||||
| Stock watering | Bioaccumulation in stock dairy and meat | Food | Ingestion | General population | |||
| Irrigation | uptakes by plants | Food | General population | ||||
| Aquaculture | Bioaccumulation in aquatic organisms | Food | Ingestion | General population | |||
| CSG well development | Migration into aquifer systems | Extracted for domestic purposes | Water | Ingestion, dermal and inhalation | General population | ||
| Surface release | Run-off to rivers, lakes | Recreational use | Water | Ingestion, dermal and inhalation | General population | ||
| Bioaccumulation in aquatic organisms | Food | Ingestion | General population | ||||
| Infiltration through soil | Migration into aquifer systems | Extracted for domestic purposes | Water | Ingestion, dermal and inhalation | General population | ||
| Underground release | Migration into aquifer systems | Extracted for domestic purposes | Water | Ingestion, dermal and inhalation | General population | ||
| Impoundment of CSG water | Evaporation | Aerosols | Inhalation | CSG Occ sectors | |||
| Passage through the floor or sides of the dam | Migration into aquifer systems | Extracted for domestic purposes | Water | Ingestion, dermal and inhalation | General population |
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