The world’s petroleum and oil supply are being depleted at a rapid rate, which has necessitated the need to utilize alternate sources of energy. In 2001, unconventional source of energy contributed to only 1% of the energy needs of the US (Martin, 2015). By 2035, 46% of the energy required by the US is estimated to be provided by alternate sources of energy (Adgate, Goldstein & McKenzie, 2014). Apart from being an alternate source of energy, unconventional energy source such as natural gas extracted from shale beds are one of the cleanest sources of energy (Martin, 2015). One of the popular methods of extracting alternate sources of energy such as natural gas and shale gas is hydraulic fracking or hydrofracking. These methods are largely untested for environmental safety and might pose risks to human health. One of the major concerns in the hydrofracking methodology of extraction is the use of fluid additives, methane contamination of groundwater, depletion of soil ecosystem, damage to aquatic ecosystems due to spillage of enriched streams and surface water and increased sedimentation owing to soil erosion. The lack of research and data on long-term effects of hydrofracking on human health and the environment makes it difficult to assess the threat of fracking activities (Adgate et al., 2014).
Background
Steps involves in hydrofracking
The first step in hydrofracking is the drilling of a deep vertical wells of 150 m to 4000 m depth in the shale bed using industrial drilling machines and explosives, which is followed by high pressure injection of the fracking fluid. The fracking fluid is composed of 90% water, 0.5 to 2% fluid additive chemicals, and 9% sand. Sand, a proppant, helps in fracturing the cracks and fissures in the shale bed and keeps them open, thereby helping the trapped natural gas to release (Martin, 2015). The next step, called, flow back is initiated by dropping the water pressure, when the released natural gas rises up through another well drilled adjacent to the inundated well and into the pipelines for refining.
Most of the water (10-70%) that goes into fracturing the shale bed, called as the produced water, rises along with the natural gas and can be recycled for subsequent fracturing (Goldstein et al., 2014). In addition to the fluid additives, the produced water would also contain naturally occurring radioactive elements, which it comes in contact with during the fracturing process. Typically, a well can have a production life span of about 30 years. It is estimated that, decades of carrying out hydrofracking processes could affect the workers as well as the communities surrounding the site of extraction primarily due to chemical and nonchemical stressors (Adgate et al., 2014).
Fluid additives
The purpose of fluid additives is to aid in the proper flow of the proppant and water in by reducing friction, help the sand in keeping the fissures open for effective extraction of the natural gas, and prevent rusting (Burton et al., 2014). Fluid additives used in hydrofracking are clay stabilizers, biocides, surfactants, foamers, solvents, breakers, diluted acids and defoamers. Although the amount of chemical additives used in a cycle of hydrofracking is negligible, during the course of a well’s lifetime, the additives could build up and measure in thousands of gallons. While some of the chemicals added in the fracking fluid are harmless, chemicals such as lead, silica, boric acid, benzene, toluene and methanol are lethal (Korfmacher et al., 2013).
Current advances in hydrofracking
The technique of hydrofracking has undergone improvement by the use of 3D seismic imaging technology, a technique that helps in identification of gas-rich pockets for efficient drilling. The technology also helps in establishing the angle of the drilling to reduce the distance between the pockets and the surface, thereby reducing the extraction time (Martin, 2015).
Benefits of hydrofracking as argued by the proponents
Proponents of hydrofracking believe that harvesting the shale gas would help a struggling economy, make a country self-sufficient to a certain extent, and provide geo-political advantages. Land-owners whose properties are shale beds, earn 20% in royalties plus $6000 for every acre they lease to the oil company. The hydrofracking industry has provided more than 40,000 jobs and increased the government’s revenue by $4 billion (Martin, 2015).
Exposure pathways
Exposure through air
Air pollutants such as nitrogen oxide, silica, formaldehyde, hydrogen sulfide, toluene, ethylbenzene, and volatile compounds are released during hydrofracking, which are known toxins to humans (Shonkoff, Hays & Finkel, 2014). Drilling of the oil wells releases hydrocarbons that are thought to cause leukemia, myeloma and blood disorders (Adgate et al., 2014).
Exposure through water
As mentioned earlier, the produced water is recycled for subsequent cycles of hydrofracking; however, in cases where the total dissolved solid (TDS) is high in the produced water, the water is treated elsewhere and disposed at a different dumpsite. The dumping involves injecting of the produced water into already contaminated deep wells. Such wells are often unlined allowing contaminates to seep into the water table. Such a practice could contaminate the ground water (Shonkoff et al., 2014). Research on the effect of produced water on water table shows that the water near the dumpsites contain toxic chemicals in quantities higher than normal (Goldstein et al., 2014).
Analysis of the studies on the health hazards of hydrofracking
Air pollution
Hydrofracking releases air borne pollutants right from the drilling step right up to the flow back step. In addition to the actual fracking process, equipment run on diesel and automotive used for transportation too release air pollutants such as greenhouse gases that add to the existing air pollution. Chemicals such as silica, which are used as proppant, form respirable silica, which could lead to lung cancer, renal disorders, silicosis and chronic obstructive pulmonary disease (COPD) (Adgate et al., 2014; Esswein et al., 2013). A study by McKenzie et al. (2012) on the risks of air pollutants on the residents living near the hydrofracking sites during hydraulic drilling and directional drilling showed that the residents living closest to the site were at risk of chronic exposure to non-cancer hazard chemicals such as aliphatic hydrocarbons, benzene and trimethylebenzene. Residents who lived more than half a mile from the site were at greater risk of sub-chronic exposure to non-cancer hazard chemicals. The chronic risk suggested that the ailments would be neurological in nature while the sub-chronic exposure suggested that the ailments would be respiratory, neurological and blood-related. However, there are no studies that corroborate this claim, which makes it difficult to assess the extent to which hydrofracking is harmful to humans and the environment.
Water pollution
Hydrofracking is thought to cause water pollution due to the evidently high bromide levels in the potable water supplies within the vicinity of the fracking sites. Due to this reason, water purification processes have switched to using chloramines instead of chlorine to avoid the formation of brominated compounds that could be formed if chlorine were to be used. The surface water is also contaminated by hydrofracking activities in the form of soil erosion and sedimentation (Goldstein et al., 2014). The produced water contaminates the groundwater by overflowing into the water table present near the Earth’s surface on its way up. This claim has been proven by a study on potable water near fracking sites, which showed that 85% of the water samples under study contained methane in levels that were 17 times higher than the legal limit. To prove that the source of methane was indeed subterranean in origin and thermogenic in nature, the ratio of 13C isotope to the 2H-CH4 was calculated. Although the drinking water did contain excessive levels of methane, the researchers found no evidence or traces of fracking fluid in the potable water (Osborn, Vengosh, Warner & Jackson, 2011). Jackson and coworkers (2013) also observed similar reports on the Marcellus shale gas site.
Radioactive isotopes are a normal part of the produced water, which could contaminate the drinking water and make it unsafe for aquatic organisms, humans and animals that rely on that water source (Carvalho & Fajgelj, 2013).
Endocrine disruption
A study by Kassotis and coworkers (2013) on the chemical additives showed that these chemicals caused endocrine disruption in humans. Water samples were collected from drilling zones and compared with water samples from areas where no hydrofracking activities were being conducted. The test water samples contained chemicals that were known agents of anti-estrogenic and anti-androgenic activities. The study established that water samples near drilling sites were contaminated and that the concentration of the chemicals were proportional to their distance from the drilling sites. No further concrete evidence has surfaced in recent years that could verify these claims.
Occupational exposure to silica
As mentioned earlier, silica is a proppant, which in its breathable form is dangerous to the workers, especially the T-belt operators and sand movers. A study showed that 53% of the workers who closely handled silica had respirable silica in their lungs (Esswein et al., 2013).
Childhood cancer
A study on correlation between hydrofracking activities and leukemia showed negative correlation (Fryzek, Pastula, Jiang & Garabrant, 2013).
Conclusion
The evidence shows a severe lack of foundation that could relate hydrofracking to human health disorders. Although some of the studies lay a good foundation for further research, the current state of research does not prove that hydrofracking is capable of causing any risk to human health. However, lack of evidence might not mean that hydrofracking is safe. The safety of hydrofracking techniques, too, is yet to be proven. There is a dire need for in-depth analysis and positive correlation between the above-discussed risks to human health and hydrofracking. The study by McKenzie et al. (2012) mentioned that their study had limitations in the form of the use of 95% confidence interval and upper limit values of cancer and non-cancer risk. Their study did not have any clinical correlation, which made their research a weak study. Similarly, the findings of Kassotis et al. (2013) were not clinically corroborated. One consistent evidence found in many studies is that hydrofracking activities pollute groundwater by accumulating methane (Jackson et al., 2013; Osborn et al., 2011) and pose risk to humans in the form of silica dust exposure (Esswein et al., 2013). More research is required to prove risks of hydrofracking using clinical cases as evidences and eliminate concerns that have no foundation.
References
Adgate, J. L., Goldstein, B. D., & McKenzie, L. M. (2014). Potential public health hazards, exposures and health effects from unconventional natural gas development. Environmental science & technology, 48(15), 8307-8320.
Burton, G. A., Basu, N., Ellis, B. R., Kapo, K. E., Entrekin, S., & Nadelhoffer, K. (2014). Hydraulic “Fracking”: Are surface water impacts an ecological concern?. Environmental Toxicology and Chemistry, 33(8), 1679-1689.
Carvalho, F. P., & Fajgelj, A. (2013). Radioactivity in drinking water: routine monitoring and emergency response. Water, Air, & Soil Pollution, 224(6), 1-7.
Esswein, E. J., Breitenstein, M., Snawder, J., Kiefer, M., & Sieber, W. K. (2013). Occupational exposures to respirable crystalline silica during hydraulic fracturing. Journal of occupational and environmental hygiene, 10(7), 347-356.
Fryzek, J., Pastula, S., Jiang, X., & Garabrant, D. H. (2013). Childhood cancer incidence in Pennsylvania counties in relation to living in counties with hydraulic fracturing sites. Journal of Occupational and Environmental Medicine, 55(7), 796-801.
Goldstein, B. D., Brooks, B. W., Cohen, S. D., Gates, A. E., Honeycutt, M. E., Morris, J. B., & Snawder, J. (2014). The role of toxicological science in meeting the challenges and opportunities of hydraulic fracturing. Toxicological Sciences, 139(2), 271-283.
Jackson, R. B., Vengosh, A., Darrah, T. H., Warner, N. R., Down, A., Poreda, R. J., & Karr, J. D. (2013). Increased stray gas abundance in a subset of drinking water wells near Marcellus shale gas extraction. Proceedings of the National Academy of Sciences, 110(28), 11250-11255.
Kassotis, C. D., Tillitt, D. E., Davis, J. W., Hormann, A. M., & Nagel, S. C. (2013). Estrogen and androgen receptor activities of hydraulic fracturing chemicals and surface and ground water in a drilling-dense region. Endocrinology, 155(3), 897-907.
Korfmacher, K. S., Jones, W. A., Malone, S. L., & Vinci, L. F. (2013). Public health and high volume hydraulic fracturing. NEW SOLUTIONS: A Journal of Environmental and Occupational Health Policy, 23(1), 13-31.
Martin, S. (2015). Don't Throw the Baby out with the Frack Water: A Reasoned Look at the Benefits and Shortcomings of Hydraulic Fracturing. J. Envtl. & Sustainability L., 21, 419.
McKenzie, L. M., Witter, R. Z., Newman, L. S., & Adgate, J. L. (2012). Human health risk assessment of air emissions from development of unconventional natural gas resources. Science of the Total Environment, 424, 79-87.
Osborn, S. G., Vengosh, A., Warner, N. R., & Jackson, R. B. (2011). Methane contamination of drinking water accompanying gas-well drilling and hydraulic fracturing. proceedings of the National Academy of Sciences, 108(20), 8172-8176.
Shonkoff, S. B., Hays, J., & Finkel, M. L. (2014). Environmental public health dimensions of shale and tight gas development. Environmental Health Perspectives (Online), 122(8), 787.
