Shale gas development in Canada: what are the potential health effects?

©2015 8872147 Canada Inc. or its licensors CMAJ, February 17, 2015, 187(3) E99 Unconventional gas development, including high-volume hydrofracturing (fracking), has enabled a dramatic increase in North American shale gas drilling. In Canada, drilling is taking place in British Columbia and Alberta and is under active consideration in more populated areas of Quebec, New Brunswick and Nova Scotia. Public health and environmental concerns have led to vigorous debate, review by the Chief Medical Officer of Health of New Brunswick and a May 2014 report from the Council of Canadian Academies.1,2 In each case, the potential for adverse health effects has been recognized, although there is a paucity of data available to address health concerns.1–4 Unconventional gas development involves bending the drilling well shaft laterally within deep underground shale layers and using hydraulically pressurized liquid to fracture the shale, thereby releasing the gas locked within it. The surge in pace, frequency and intensity of shale gas exploration and extraction in the United States has led to public concern and varying responses. Some states have quickly embraced the process; others have imposed a moratorium until the potential health consequences are thoroughly considered. The potential human health risks associated with fracking fall into two main categories: short-term issues concerning worker and public safety, and long-term health effects resulting from air and water contamination.1,2 Some of these risks are common to other energy sources, and proponents of fracking are quick to note the potential health benefits of using natural gas over traditional fuels such as coal. Public concern often focuses on the chemical and physical agents associated with fracking. The fluid used often contains about 15% sand, and excessive exposure of workers to silica has been documented.5 About 1%–2% of fracking fluid is a mixture of six or more chemicals (Table 1). More than 500 different fracking chemicals are known, some of which are endocrine disrupters. Although methane is relatively nontoxic, it can cause explosions and fires. Shale gas also contains benzene, an agent associated with the development of leukemia. The mixture of agents naturally present underground and brought to the surface dissolved in flowback fluids during and subsequent to well completion contain brine and various amounts of radionuclides, metals and metalloids, such as iron, strontium, barium and arsenic.6 In some regions, flowback fluids must be disposed of at the surface, increasing the risk of human exposure. Predicting the toxicity of fracking mixtures is challenging, as is predicting possible chemical reactions that could create additional toxins.6 Measurement of air pollutants near drilling sites in Colorado suggested an increase in the risk of noncancer ailments.7 An increase in adverse birth outcomes in proximity to drilling sites has also been reported.8 Diesel emissions may contribute to the risk of lung cancer and acute respiratory effects such as asthma. The release of hydrocarbons, which varies from site to site, might contribute to ozone health effects in Canada.9 Anecdotal reports from residents near shale facilities describe symptoms including headaches, dizziness and nose bleeds. Among the more common self-reported symptoms are fatigue, irritation of the upper respiratory tract, burning eyes and shortness of breath.10,11 However, there are no formal epidemiologic studies or health impact assessments that support or refute these observations, or that consider vulnerable populations.1–4 Physicians should be aware of the sources of confusion over fracking that have contributed to public distrust and the social amplification of risk.4 Seemingly contradictory information about whether fracking is old or new, or has ever Shale gas development in Canada: What are the potential health effects?