Hydraulic fracturing, a process involving high pressure, a large volume of water, sand, and a few chemicals, has been used throughout the U.S. to stimulate production from oil and gas wells since the 1940s. It is neither new nor untested. It is also not without risk, although the attention given to this process has likely focused on the wrong risks. To understand why, it’s important to begin with what this process is and is not. CONTAMINATION INCIDENTS Hydraulic fracturing activities comprise a short period—approximately two weeks—in the thirty-year life cycle of a typical well. The window of opportunity for mishap during well stimulation is small when compared to the duration a well may be producing. Such mishaps may result in contamination of public or private drinking water supplies. Examples of contamination events that EPA has attributed to oil and gas wells include incidents in Bainbridge Township, Ohio; in Garfield County, Colo.; in Dimock Township, Penn.; and near Killdeer, N.D. Conclusions drawn from the Dimock study are the subject of ongoing controversy. A recent study conducted on the same wells and published in 2015 by the National Academy of Sciences (NAS) concluded that diesel-range organics found are likely the result of contamination from surface spills, not subsurface flow or infiltration during well stimulation activities. Another recent study conducted in the Wattenberg Field in Colorado published in the journal Water Research found that most methane-contaminated water wells were microbial in origin and that the remaining were the result of integrity failures such as in well casing or casing cement. It is not surprising that some of these instances occurred during the production cycle of a well as opposed to the comparatively short period one is undergoing stimulation via hydraulic fracturing. Various regulatory entities, including EPA, have put a great deal of effort into linking the down-hole injection of water and chemicals into a well bore to drinking water contamination. In a study published earlier this year, EPA concluded that hydraulic fracturing as a well stimulation activity has not had a widespread, systemic impact on drinking water resources in the U.S. The agency found a limited number of contamination events, however. It is important to note that the study included contamination events from spills to soil migrating into surface water reservoirs. In addition, “drinking water” as defined by the study includes not only those water resources currently in use, but also those that might possibly be used in the future. EPA acknowledges that these future water resources may not be potable, nor considered drinking water by other regulatory agencies at the moment. Events meeting these qualifiers notwithstanding, the only documented events where active hydraulic fracturing activities clearly contaminated drinking water in an aquifer occurred in Bainbridge Township, Ohio, in 2007 and near Killdeer, N.D., in 2010. Baker Hughes, a company that provides oil field services, estimates that approximately 110,000 wells were drilled domestically onshore between 2012 and 2014. Using a retroactive average figure of 36,700 wells per year for the period 2005 through 2015 yields a failure rate of approximately 1 per 184,000 wells (assuming most wells during that period were stimulated using hydraulic fracturing techniques). Is this an acceptable failure rate for progress toward domestic energy independence? CHEMICALS USED IN HYDRAULIC FRACTURING Much of the national “fracking” conversation has been dominated by chemicals and their possible hazards. Opponents of hydraulic fracturing and concerned citizens cite contamination events as a reason to regulate (or remove proprietary protection from) chemicals used in this process. Current peer-reviewed research—including papers published by NAS, Probate & Property, Science of the Total Environment, and the Groundwater Protection Council (GWPC)—does not appear to support a link between these events and exposure to chemicals beyond anecdotal claims. For individuals who assess exposure health risks as a vocation, the dose makes the poison—severity of response depends on dose. We recognize that some chemical substances have a dose below which little or no adverse response is observed (the LOAEL and the NOAEL). We also recognize that an exposure pathway must exist or be plausible to enable dose uptake. When subject to a minimal amount of scrutiny, dose potential for “frack chemicals” in groundwater is greatly reduced. A product category typically used in hydraulic fracturing mixtures is a biocide. Typically, the product is injected as part of the overall chemical/water mixture for the purpose of inhibiting bacterial growth, which can lead to various equipment integrity issues. A common active ingredient in many biocides on the market today is glutaraldehyde (CAS# 111-30-8). It works well on bacteria and, in inhalation doses exceeding 0.05 ppm, can be hazardous to people, according to ACGIH. Safety data sheets indicate that glutaraldehyde typically comprises 10 to 30 percent of many overall biocide product mixtures. It may be further mixed at a rate of a half-gallon per 1,000 gallons of water in the overall “frack fluid” mixture, according to GWPC. At that rate, glutaraldehyde is present in the mixture injected downhole at a concentration of about 150 parts-per-million by volume to a depth of 3,000–12,000 feet underground depending on the shale gas formation and fractured outward from the well bore. If some of those fractures traveled thousands of feet upward through rock, the 150 ppm(v) glutaraldehyde mixture could commingle with groundwater. For an average female living in the U.S. consuming the daily amount of total water as recommended by the Institute of Medicine, the projected dose would be 5.7 mg/kg/day. For an average male, the projected dose would be nearer 6.7 mg/kg/day. EPA suggests an NOAEL for glutaraldehyde of 16 mg/kg/day. The projected dose under this hypothetical circumstance is less than half of the NOAEL for glutaraldehyde. While complete absence of this contaminant and others in drinking water stores is the target, I believe that most scientists would conclude that typical toxicants in the home pose a greater health threat. If our business is about health risks, this one is comparatively low.
A Short Health Hazard Analysis of Hydraulic Fracturing