*By Dr Elizabeth Cullen
It is widely accepted that world supplies of fossil fuels will begin to reduce in the very near future. By 2040, it is estimated that production levels of oil may be down to about 20% of the levels that we currently consume, a situation that is compounded by the fact that the world's population will have doubled at that stage.To meet this challenge, fracking, a new method of extracting fossil fuel from the earth, has been developed.
Although the process was developed in the 1970s and 1980s, it is only recently emerging as a widely used recovery technique. Fracking is primarily used to extract fossil fuel from shale rock. Shale is a sedimentary rock that, due to the pressure of overlying materials, becomes compacted over time. This forces moisture out and a solid, thinly layered rock is formed. Shale has a tendency to break along these thin parallel layers, a feature termed ‘fissility'. Fracking, by injecting a highly pressurised fluid to create or propagate fractures in these layers, increases the recovery rate of fossil fuels.
The fracking fluid contains additives, one of which, a quartz-rich sand termed a ‘proppant', keeps the fractures open. The fluid also contains chemicals, such as acids that help initiate the fractures, corrosion and scale inhibitors to protect the borehole lining, and gelling agents to alter the viscosity of the fluid.
Fracking is also a water intensive process; each well requires between two to five million gallons of water. The Irish Environmental Protection Agency has already published a preliminary study on the environmental risks related to fracking.
These include the possibility of contamination of drinking water and ground water with natural gas and other chemicals; the emission of volatile components such as carbon dioxide, benzene, methane and hydrogen sulphide; the emission of naturally occurring radioactive materials such as radium, thorium and uranium into the atmosphere; the leakage of contaminated drilling waste from storage ponds; and the potential for earthquakes.
This study, however, did not investigate possible health risks from this process.
We already know the contribution of specific environmental exposures such as smoking and the role of specific viruses. However, it is difficult to precisely quantify the contribution that environmental contamination makes to the incidence of cancer.
It has been estimated that between 8% and 9% of the disease burden in developed countries may be attributed to pollution. However, if an exposure to an environmental pollutant is widespread, the number of cases may be larger. Should we be concerned about the impact that fracking may have on the incidence of cancer?
The relationship between the environmental impacts of fracking and public health are complex. The issue of adverse health effects of fracking were addressed in a public health report undertaken in 2014 by the New York State Department of Health and reported as complex and ‘not fully understood'.
This report found that respiratory health could be adversely affected by the increased levels of particulate matter, polycyclic aromatic hydrocarbons (PAHs), and volatile organic compounds released by fracking. Particulate matter is categorised as a Grade 1 carcinogen by the International Agency for Research on Cancer.
Levels of PAHs at concentrations that may be contributing significantly to public health have been found close to active fracking sites. The excess lifetime cancer risk associated with exposure to PAHs, closest to active wells, was 2.9 in 10,000, which is above the US EPA's acceptable level. The risk estimate decreased by 30% when results from samplers closest to the wells were compared with those furthest from the wells.
Other air borne pollutants related to fracking have also been incriminated; sub chronic exposures to air pollutants were found to present the greatest potential for health effects, with residents living near fracking activities being at greater risk from adverse health effects, including cancer, than people living further away.
The chemicals of most concern were benzene, trimethylbenzenes, xylenes and aliphatic hydrocarbons.
The US Center for Disease Control in Atlanta reports that volatile organic compounds can result in damage to the liver, kidney, and central nervous system and notes that some of these compounds can cause cancer in animals; some are suspected or known to cause cancer in humans.
However, a study in Texas, conducted over more than a decade, found that there were no risk to health from the volatile organic compounds that emanated from fracking activities. While it was noted in this study that the levels of some volatile organic compounds were higher than the levels that would be expected in the average US citizen, it was thought that these levels were more likely due to exposure to dry cleaning compounds.
Recent data has also shown that natural gas drilling operations may result in elevated levels of endocrine-disrupting chemicals in surface and ground water. An increasing number of scientific studies suggest that these endocrine disrupting chemicals, particularly in combination, play a role in the development of hormone-related cancers.
The possibility of water contamination may arise when pockets of contaminated groundwater link with drinking water wells, allowing chemicals such as hydrocarbons, benzene, arsenic, and other contaminants into drinking water supplies and other bodies.
Other cancers have also been reported; in a retrospective analysis of cases of childhood cancer and fracking, a slightly higher incidence of tumours of the nervous system was found after fracking commenced. Overall, no increase in childhood cancers was observed.
It is clear that we do not have adequate knowledge to fully assess the health risks that fracking presents. All studies that investigated adverse health impacts from fracking, from January 1995 to March 2014, were reviewed for this paper. As would be expected, the majority of the studies were short-term, and very few examined health outcomes with a longer latency period such as cancer. A ‘clear gap' in the scientific knowledge was identified and the researchers noted that ‘public health concerns remain intense'.
The precise health impacts of fracking are not yet clear, nevertheless, one can approximate that they fall into three timeframes: short-, medium- and long-term. In the short-term, we might expect some impacts from factors such as increased vehicle traffic, noise, odour complaints and stress in the initial construction phases.
However, these should not pose long-term difficulties. In the medium-term and longer-term however, it is possible that we may see an increase in some of the diseases outlined above.
In addition, health may be compromised at any stage if the challenges that the maintenance of the fracking infrastructure poses are not met. These challenges have been outlined in a report prepared for the EU commission in 2012. They include issues such as ensuring the integrity of wells and other equipment throughout the development, operation and post-abandonment lifetime of the plant in order to avoid the risk of surface and/or groundwater contamination, and also ensuring that spillages of chemicals and waste waters with potential environmental consequences are avoided during the development and operational lifetime of the plant.
We, in Ireland, are only too aware of the consequences of failures in regulatory systems. An example of possible regulatory failure can be seen in the UK in relation to the possibility of earthquakes as a result of fracking. While it is widely accepted that fracking inherently poses ‘geomechanical risks',3 these risks can be assessed if the rock stresses and fracture networks are known before drilling commences, as changes in pore fluid pressure can be measured. However, two recent earthquakes near Blackpool in the UK have been attributed to fracking in a previously unmapped area, in a highly permeable fault zone located near the base of a well.
To assist us in quantifying the risks that environmental pressures, such as fracking, poses to health, we need a system to quantify the environmental pressures that patients with cancer experienced in their lives. We need a systematic surveillance system, possibly adopting the methodology of the Health Protection Surveillance Centre, whereby detailed information on exposure to putative sources of infectious diseases are ascertained for every patient who has suffered from one of many specified infectious diseases.
In a similar way, details of exposure to environmental issues could be documented for every new entrant in the Irish Cancer Register. Information on exposure could include occupation, previous areas of residence, history of uses of chemicals, use of mobile phones and other exposures. This could be combined with the results of bio monitoring, which has been described as the best method for measuring an individual's exposure to chemicals.
Unlike the US, there is no national bio monitoring system in Ireland, although a preliminary pilot project was recently undertaken.
The adoption of fracking is a step away from a solution to the problem of climate change. Our resources should be directed to low carbon methods of energy generation. No decision to allow fracking in Ireland will be made until the outcome of a major research programme has been undertaken, which will investigate the environmental impacts of fracking. This report must also include an assessment of the health impacts.
The question that concerns us is whether fracking will have an impact on the incidence of cancer in this country? The reality is that we just don't know yet but until we have a systematic method of assessing the contribution that fracking and other environmental issues may make to the development of cancer, we should decline the offer.
*Dr Elizabeth Cullen is a senior medical officer with the HSE and a committee member of the Irish Doctors' Environmental Association. This article was first published in the journal, Cancer Professional. (December 2015)
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