By Kelly A. Reynolds, MSPH, PhD

In the US, between 25,000 and 30,000 new wells were drilled via hydraulic fracturing (also known as fracking) from 2011-2014.1 Since 1990, more than 25 states were subject to this method of oil and gas extraction and approximately 9.4 million people in the US lived within a mile of a fracking well. Fracking has stimulated increased production of natural gas reserves and has elevated the US to being the projected global leader in natural gas production.2

Benefits beyond economics include expanded supply of a cleaner burning, less greenhouse-gas-producing product. Protecting local water supplies, minimizing water use, managing gas venting and disposing of waste products are major environmental concerns related to fracking that many fear are poorly monitored and regulated.

What is fracking?
Hydraulic fracturing was developed in the 1940s as a mechanism for efficient extraction of oil and natural gas from small reservoirs. In the early 2000s, innovations in horizontal drilling through deep underground, fractured shale formations made fracking more economical, resulting in rapid growth of the technique throughout the US and internationally.
Fracking allows access to narrow rock formations by drilling underground a mile or more vertically and then several thousand feet horizontally. The process of fracking utilizes millions of gallons of water mixed with sand and proprietary chemicals that are then pumped into the drilling region, filling small fissures and releasing shale gas into the well borehole. This natural gas is considered a cleaner alternative to oil and coal and increased use is being promoted as a means to lower US greenhouse gas emissions. Fracking has dramatically increased natural gas production in the US and globally. While cleaner-burning fuels are an environmental win, the use and loss of millions of gallons of water and potential for water and soil contamination in the fracking process is one reason the industry is highly controversial.

What are the environmental risks?
Environmentalists and scientists have long criticized fracking as major risks to the environment, including source drinking water supplies. Some of the more common concerns include depletion of water supplies, especially from regions where water is scarce, such as the arid southwest. Evaluation of water reuse options and sustainability for other uses such as drinking, irrigation or support of fish and other wildlife should be carefully and transparently considered. A formal structure for such safeguards and oversight, however, is not yet in place.

As with most industrial operations and mining, the fracking process utilizes a range of potentially hazardous chemicals that must be carefully managed to prevent leaks and spills. Of additional concern is the management of the liquid, post-fracking waste product. Fracking fluids may include hydrocarbons, heavy metals and salts, in addition to indigenous earth contaminants, such as naturally occurring radioactive materials. Disposal by re-injection of wastewater into the fissures below or collection and secure storage (either onsite or by transport to a treatment facility) are common practices. The water can also be recycled and used at the next well. While environmentalists are concerned with possible leaks from storage sites, the same risk exists with any industrial waste production. With proper containment, storage of fracking wastes should be no more of a problem than storage of other hazardous wastes. Still, surface leaks have occurred. Specifically, thousands of gallons of fracking fluid that spilled at a site in Dimock, PA contaminated groundwater in the Marcellus Shale region.

Fracking fluids may not be recovered and stored but could remain injected deep underground. Fracking may produce fissures in underground geologic formations that can provide new and easy pathways for contaminants to reach groundwater aquifers. Deep wells likely do not pose a risk of contaminant migration to drinking water wells but more shallow drilling operations may.

Groundwater wells in Pavillion, WY, only several hundred feet above fracking regions, have tested positive for fracking fluids. Many of the several hundred town residents reported adverse tastes and smells in their drinking water.3 Water testing eventually revealed the presence of harmful contaminants, including benzene, diesel and methane, all common fracking chemicals. Harmful byproducts may also occur in relation to fracking operations.4 Shallow (less than 2,000 feet) drilling is generally recognized as posing a greater risk for groundwater contamination.

Concerns more unique to fracking include the threat of earthquakes and infrastructure disturbances. In Youngstown, Ohio, a small earthquake (measuring 2 on the Richter scale) was documented and linked to wastewater injection, a process common to fracking. While this seismic activity was not felt above ground, questions remain as to what impact extensive fracking may have on current underground stresses.2

How can drinking water risks be mitigated?
A lack of federal regulation on fracking under the Safe Drinking Water Act is a serious omission in environmental protections. To safeguard both groundwater and surface water supplies, fracking waste and waste byproducts should be stringently monitored and regulated at both the federal and state levels.

According to an article by the Natural Resources Defense Council (NRDC), many recommended best practices for the fracking industry were developed by the industry itself. A 2009 report from the American Petroleum Institute provided industry well construction and integrity guidelines for fracking operations.5 The report focuses on protection of shallow aquifers with proper well design and construction. Further, recommendations generally involve geological and hydrological site mapping and risk evaluation to assess prevention of contaminant migration; baseline and continued ground and surface water quality monitoring; microseismic monitoring; disclosure of fracking chemicals used (pre- and post-use); restrictions on water withdrawals following an environmental and sustainability assessment; waste treatment before discharge; buffer zones between waste storage and source waters, as well as spill prevention methods. While such precautions are currently in use, there remains concern over a lack of uniform adoption of the guidelines.6

Future prospects
Much of the criticism of fracking was born out of a lack of transparency in industry operations and risks. Further, a lack of understanding related to precautionary measures for waste containment and resource management left the general public, environmentalists and research scientists questioning industry oversight and active responsibility. With such a rapidly growing industry and uncertain environmental impacts, a call for additional research and analysis of the possible social and environmental costs and benefits is warranted. In June 2015, US EPA published an assessment of fracking impacts on drinking water supplies stating that the process has the potential to impact drinking water sources.1 While the database is considered incomplete, at least 151 cases of spills in 11 states have been reported, ranging from volumes of 19 to 72,000 liters.

Where and when these contamination events will occur is largely unknown as the widespread practice of fracking and uncertainty related to well depth and hazard management practices remains. With an increased demand for oversight, there will likely be more transparency in the fracking industry as well as a growing understanding and analysis of the risk/benefit trade-off.


  1. US EPA. Assessment of the Potential Impacts of Hydraulic Fracturing for Oil and Gas on Drinking Water Resources. Extern Rev. 2015;(June):998. doi:EPA/600/R-15/047a.
  2. International Energy Agency. World Energy Outlook Special Report on Unconventional Gas. 2012. Accessed October 17, 2016.
  3. Ridlington E, Rumpler J. Fracking by the Numbers Key Impacts of Dirty Drilling at the State and National Level. Environ Am Res Policy Cent. 2013:47.
  4. Hoelzer K, Sumner AJ, Karatum O, et al. Indications of Transformation Products from Hydraulic Fracturing Additives in Shale-Gas Wastewater. Environ Sci Technol. 2016;50(15):8036-8048. doi:10.1021/acs.est.6b00430.
  5. American Petroleum Institute. Hydraulic Fracturing Operations—Well Construction and Integrity Guidelines. 2009. Accessed October 12, 2016.
  6. Mall A, Sinding K, Mordick B. Water Facts: Hydraulic Fracturing Can Potentially Contaminate Drinking Water Sources. 2012. Accessed October 12, 2016.

About the author
reynolds_kelly_new2016_mugDr. Kelly A. Reynolds is an Associate Professor at the University of Arizona College of Public Health. She holds a Master of Science Degree in public health (MSPH) from the University of South Florida and a doctorate in microbiology from the University of Arizona. Reynolds is WC&P’s Public Health Editor and a former member of the Technical Review Committee. She can be reached via email at [email protected]


Comments are closed.