Literature Review on Fracking
The extraction of natural gas has been seen the much-needed reprieve in the face of increased energy demands globally. The natural gas present unexploited energy reserves that can be used to meet the energy deficits in the countries where there are natural gas deposits. Its extraction requires the use of advanced technologies. Fracking the main technology used in the exploitation of natural gas from the rocks beneath the earth’s surface where it is trapped. The biggest proportion of the new wells for the exploitation of natural gas (90%) utilizes hydraulic fracking as the technology of choice. While the natural gas derived from the process presents and additional energy source, the environmental and human impacts that are associated with the technology cannot be ignored. Numerous researchers have explored various themes characterizing the environmental and human impacts of hydraulic fracturing. This literature review seeks to determine the state of the research and identify the gaps in knowledge.
The effect of fracking on health is one of the themes that have been explored in research on hydraulic fracturing. The health effects on human beings that result from hydraulic fracturing are attributed to the toxicity of the chemicals used in the process (Colborn, Kwiatkowski, Schultz & Bachran, 2011). Colborn et al., (2011) finds that over 632 chemicals are employed in the fracking process. The assessment of these chemicals of potential effects on human beings showed that 75% had a negative effect on the gastrointestinal and respiratory systems, and the eyes and skin.
Colborn et al., (2011) also found that between 40% and 50% of the drugs had adverse effects on the immune, the brain and the central nervous system, the kidneys, and the cardiovascular system. 25% of the chemicals used in the fracking process were also found to cause mutations in the genetic makeup and cancer while another 37% were found to affect the endocrine system negatively. The health effects of which the chemicals have been named as causes manifest after a long period of exposure. This imposes an element of concern even though the mechanisms remain unknown at present. This is because many of the companies that engage in hydraulic fracturing do not disclose the list of the chemicals that they use. It behooves them to carry out a risk assessment to determine the effect that the chemicals have on human beings through both direct and indirect exposures in the short-term and the long-term.
There are more direct linkages between hydraulic fracturing and adverse health effects in humans. For instance, Kenneth (2014) found after analyzing air samples drawn from hydraulic fracturing sites that the silica levels exceeded the air standards in the existing Occupational Safety Health Administration. This means that the workers in these sites are predisposed to the health effects that result from overexposure to silica. Kenneth (2014) also found that the exposure to the silica was highest for employees who operated the T-belt and those who operated the sand movers. The exposure to the silica levels that exceed the levels established in the standards for worker safety puts the workers at risk silicosis. In addition to silicosis, the workers are also predisposed to other related conditions that include tuberculosis, lung cancer, chronic obstructive pulmonary disease, end-stage renal disease and the connective tissue disease.
One of the recurring themes is the long latency before the exposure to the silica levels manifests clinically. It also concerns that the analysis of air samples taken from fracturing sites exceeded the recommended levels for worker safety. It is important to know the radius from the hydraulic fracturing sites where the effects of the elevated silica levels are felt. The research by McKenzie et al., (2014) provides some answers to this question. Using linear regressions, McKenzie et al., (2014) attempted to determine the association between the proximity of the residences of pregnant women to sites for natural gas development to their birth outcomes retrospectively.
The researchers considered a ten-mile radius from the sites for natural gas development. Some of the birth outcomes assessed include preterm births, neural tube defects, oral clefts, low birth weight, and congenital heart defects. The researchers found that there was an increase in the prevalence of congenital heart defects with an increase in the exposure (McKenzie et al., 2014). The researchers also found that the highest levels of exposure were associated with the increased prevalence of neural tube defects. The conclusions were that the density of natural gas wells in a ten-mile radius and the proximity of the pregnant mothers to these wells increased the prevalence of congenital heart defects and greatly predicted the occurrence of neural tube defects (McKenzie et al., 2014).
While this information provides a direct linkage to the location of natural gas wells to adverse health effects in humans, there is a need for more specificity with regards to the exposures. This is necessary for the accurate development of models to describe and espouse on the effect of exposure and the occurrence of adverse health effects. The required specificity will give more credence to the existing information. This argument is supported by Werner, Vink, Watt and Jagals (2015) who point out the weakness in the epidemiological evidence linking the development of natural gas to the occurrence of adverse health effects on humans. Werner et al., (2015) found after a review of 109 studies that even though the arguments were theoretically valid, the epidemiological evidence adduced was weak.
Potential Impacts on the Environment
In addition to the direct effects on human health, hydraulic fracturing has also been the linked with environmental degradation. Many studies highlight the effects of the natural gas development technology on water quality. For instance, Vidic, Brantley, Vandenbossche, Yoxtheimer & Abad (2013), find that the development of shale gas has negative effects on the quality of water in the surrounding areas. Vidic et al., (2013) attribute these issues with water quality to the escape of methane gas from the constructed wells. When the methane gas escapes from the well, it migrates and contaminates the ground water. The escape of the methane gas is linked with faulty seals whose purpose is to keep the gas trapped in the constructed well.
However, and in keeping with the themes of the quality of the evidence and the resultant associations, there are concerns regarding the cause of methane contamination in many private underground wells. The disquiet about the matter is because the contamination can also be the result of natural processes and not the drilling of wells to harvest shale gas. Vidic et al., (2013) find that many of the areas where the issues of methane contamination have been highlighted have also reported methane contamination that is not related to the drilling of wells to harvest natural gas. This problem is further amplified by the absence of pre-drilling baseline data.
The other water quality issues related to hydraulic fracturing is the reuse of the wastewater that is used in the process. Colborn et al., (2011) had found that that over 632 chemicals are used in the process. The safe reuse of the wastewater is contingent on the removal of the chemicals. Even if the wastewater is not reused, there is the element of safe water management. Vidic et al., (2013) finds that with the maturity of the wells, the waste water may need to be disposed. The safe disposal of the water forms one of the issues because of the fact that it contains many chemicals. It is imperative that it is treated before disposal to ensure that it does not contaminate the underground water or other surface water bodies.
Myers (2012) also highlighted the issues of potential aquifer contamination on areas where the extraction of shale gas is done used hydraulic fracturing. Myers (2012) addresses the various pathways through which the aquifers get contaminated with the water used in the hydraulic fracturing. One of the pathways is the transportation of the contaminants through the cracks that occur when the rock formations are broken during hydraulic fracturing. The drilling of vertical drives also brings contaminants such as brine from the evaporite sources that are located deep in the earth’s crust to the surface. The injection of water in the shale wells at pressure creates a pressure differential that pushes the contaminants through the cracks to the aquifers.
Summary of Gaps
The review of the literature shows the existence of gaps in knowledge. Firstly, the quality of the evidence that links the various processes and chemicals used in hydraulic fracturing to adverse health effects has been questioned. This highlights the need for continued monitoring, especially because the effects of exposure have a long latency and may not manifest for a long time. Additionally, the baseline data that can be used for comparison models is missing in most cases. There is also inadequate information regarding the specificity of exposure to the various hazards related to hydraulic fracturing. This information is vital to understanding the impacts of hydraulic fracturing on the environment and humans fully.
Colborn, T., Kwiatkowski, C., Schultz, K., and Bachran, M. (2011). Natural gas operations from a public health perspective. Human and Ecological Risk Assessment: An International Journal, 17(5): 1039-1056.
Kenneth, R. (2014). Hydraulic fracturing and the risk of silicosis. Clinical Pulmonary Medicine, 21(4): 167-172.
McKenzie, L., Guo, R., Witter, R., Savitz, D., Newman, L., and Adgate, J. (2014). Birth Outcomes and Maternal Residential Proximity to Natural Gas Development in Rural Colorado. Environmental Health Perspectives, 122(4): DOI:10.1289/ehp.1306722
Myers, T. (2012). Potential Contaminant Pathways from Hydraulically Fractured Shale to
Aquifers. Ground Water. 50(6): 872-882.
Vidic, R., Brantley, S., Vandenbossche, J., Yoxtheimer, D. and Abad, D. (2013). Impact of shale gas development on regional water quality. Science, 340(6134):
Werner, A., Vink, S., Watt, K., and Jagals, P. (2015). Environmental health impacts of unconventional natural gas development: A review of the current strength of evidence. Science of the Total Environment, 505: 1127-1141.