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Author:  Cody Rogers

Contributed to Toxipedia as part of the University Partnerships Program.


Hydraulic fracturing, or “fracking,” is a common method of obtaining natural gas and oil from rock formations, particularly shale. The process involves the drilling of vertical and horizontal wells deep beneath the Earth’s surface (EPA). The natural gas is released from the rock formations following large amounts of water, proppants, and various chemicals that are forced under high pressure down a wellbore to fracture the underlying rock formations (“Groundwater Contamination”). There are an estimated 35,000 active fracturing wells throughout the United States as reported by industry (“Groundwater Contamination”). There are currently concerns over fracking’s effects on the health of populations that reside near fracking sites as well as the environment. These concerns are due to the chemicals involved in the process which have been linked to the development and exacerbation of many chronic illnesses. This contributes to a much lower quality of life for people in close geographical proximity to fracking sites along with an increased burden on our health care system which spends $2.1 trillion treating chronic disease annually (“Chronic Disease and Health Promotion”). From humanitarian, fiscal, and environmental perspectives, fracking has the potential to cause serious, long-term, negative consequences and mandates a closer look.

More information on the process and history of “fracking” can be found at This is a previously written Toxipedia article that has already described the process and history in great detail. This article will be more focused on the lack of oversight by the natural gas industry facilitated by bills passed by the federal government, the adverse effects on human health as well as the environment, and the downstream effects associated with prolonged fracturing. 

Lack of Oversight

Many concerns of health and public safety have arisen as hydraulic fracturing continues to become more prevalent. Opponents of the process worry about the potential impact fracking could have on the environment and human health. The impact largely depends on the ingredients of the fluid, which are commonly unspecified due to natural gas companies failing or resisting to release the information (“House of Representatives”). This lack of transparency is exacerbated by federal bills which protect fracking fluid components as trade secrets, severely restricting the abilities of toxicologists to accurately study the effects. These bills, which severely inhibit oversight, are commonly referred to as the “Haliburton Loophole.”

Chemical Descriptions

From 2005-2009, in an effort to investigate the components of fracking fluid, 14 of the leading natural gas companies in the United States were asked by the Committee on Energy and Commerce to fully disclose the ingredients and quantities typically used (“House of Representatives”). Despite this, the information volunteered by the natural gas companies was insufficient at best. However, the ingredients that were revealed were enough to warrant concern.

According to this effort, 780 million gallons of hydraulic fracking fluid were used over the five-year period. This number reflects the solution in its most concentrated form, before being mixed with water (“House of Representatives”). The 14 oil and natural gas companies investigated used over 2,500 fracturing products containing 750 different chemicals and additional ingredients (“House of Representatives”). Although some of the ingredients used were essentially inert or inactive, some were also extremely toxic and hazardous to the environment and human health. Methanol was found in 352 of the fracking products, making it one of the major constituents used. Methanol is a known air pollutant and can also adversely affect the nervous system even when ingested in minute amounts (“House of Representatives”, “EPA”). Even more troubling is the revelation that 29 of the chemicals found in 650 of the fracking products were considered to be known or possible carcinogens and regulated under the Safe Drinking Water act due to their detrimental effects on human health, or listed as hazardous air pollutants under the Clean Air Act (“House of Representatives”). According to the House Committee on Energy and Commerce, benzene, tolulene, xylene, and ethylbenzene, also known as “BTEX” were found in 60 of fracking products used during time course of the investigation. The paper lists each of the BTEX compounds as a regulated contaminant. Furthermore, benzene is a known human carcinogen (“House of Representatives”).

Environmental Implications

Once the extraction of the gas or oil has been completed and the pressure used to force the liquid down into the rock subsides, a majority of the solution naturally regurgitates (EPA). This fluid is a cocktail of natural and human-made (or anthropogenic) toxic substances, which in isolation, have been proven to cause a variety effects on humans and the environment. This fluid is commonly referred to as “flowback” or “wastewater” (“Groundwater Contamination”).  Due to the presence of concentrated toxic material, many water treatment plants lack the ability to effectively recycle this wastewater. As a result, it is usually stored in disposal wells, placed in evaporation pits, or discharged directly into surface water. Radioactive elements like radium (a known carcinogen) often remain in these environments long after the wastewater has dissipated (Webb et al). Two-thirds of all drinking water originates from surface water, illustrating the importance of keeping these sources clean and free of toxic substances (Webb et al).  Furthermore, a substantial portion of the injected fracking fluid never even surfaces as wastewater; its fate and the potential environmental ramifications remain largely unknown (Webb et al). 

Natural gas is largely comprised of methane, a powerful greenhouse gas that has been proven to impact global warming substantially (Howarth et al). According to Howarth et al, over the lifetime of a well, it is estimated that 3.6-7.9% of methane escapes during the process of fracking. This study estimates that the methane emissions associated with fracking are 30% more than the emissions from conventional gas (Howarth et al). In addition to atmospheric pollution, a study found methane in drinking water near fracking sites (“Methane Contamination”). This was determined by measuring the ratio of radioactive carbon present ("Hydraulic Fracturing for Natural Gas Pollutes Water Wells"). Researchers found that wells were the most severely affected water source, with concentrations of methane in 51 of the 60 that were tested ("Hydraulic Fracturing for Natural Gas Pollutes Water Wells").

Another area of concern deals with the possibility of toxic chemicals being distributed throughout the environment via aquifer contamination. The Ogallala is one of the world’s largest sources for freshwater. It extends 174,000 miles through the central United States ("Water Encyclopedia”). Opponents of fracking are concerned that chemicals could make their way into the Ogallala resulting in irreparable damage to the aquifer. If contaminated, there could be vast repercussions on farms nationwide. Farmers would be forced to irrigate their fields with the tainted water, which could then adversely affect any animal or human who ingests the crops. Dr. Sandra Steingraber brought to light the fact that organic farmers who have land near fracking sites are faced with the possible loss of organic certification if their crops and animals are contaminated (Steingraber).

Implications on Human Health

As hydraulic fracking becomes more prevalent, further studies are being conducted to provide insight on the effects it has on human health. Those published thus far indicate that over 130 chemicals used in fracking are considered endocrine disruptors as well as reproductive and developmental toxicants in animals and humans (Webb et al). 

Endocrine disrupting chemicals (EDCs) adversely affect the actions of hormones (Webb et al). Without endogenous hormones in the body, a healthy homeostatic balance is impossible to attain. EDC exposure can lead to multiple adverse health effects, most notably with the male and female reproductive systems. If pregnant mothers are exposed to EDCs, the offspring is likely to develop birth defects such as congenital heart defects. 

When exposed to the aforementioned BTEX chemicals, human males and laboratory animals exhibited a marked decrease in both the quantity and quality of their sperm. (Webb et al). These chemicals, as well as their metabolites, were found to directly target male reproductive organs and cause irreparable damage (Webb et al). 

Studies suggest the exposure of women to benzene, toluene, and heavy metals may be associated with an increased risk of spontaneous abortion (Webb et al). An unusually high number of miscarriages and stillbirths was reported in Glenwood Springs, Colorado and Vernal, Utah, both of which are active hydraulic fracking sites. New studies are underway to further investigate these findings (Webb et al).

Many of the chemicals involved in fracking exhibit lipophilic properties, which permit access across the placental barrier, adversely affecting the fetus. Some toxicants, such as persistent organic pollutants (POPs), are unable to be excreted or biotransformed. This ultimately leads to bioaccumulation within a pregnant mother (Webb et al). If metabolism or absorption rates should change, the toxicants are capable of re-entering the bloodstream and potentially damaging the fetus (Webb et al).   


Hydraulic fracturing has the potential to cause irreparable damage to human health and the environment. Lack of federal oversight allows fracking the exemption from the Clean Water Act and the Clean Drinking Water Act, warranting many questions and concerns. Those opposed to fracking are concerned of the potential hazardous effects it will have on human health and the environment. These risks and the uncertainty surrounding them illustrate the need for further unbiased research to take place.


"Chronic Diseases and Health Promotion." Centers for Disease Control and Prevention. Centers for Disease Control and Prevention, 09 May 2014. Web. 22 Apr. 2015.

"EPA." The Process of Hydraulic Fracturing. N.p., n.d. Web. 22 Apr. 2015.

"Groundwater Contamination." Water Research 19.8 (1985): 1080. Web. 22 Apr. 2015.

Howarth, Robert W., Renee Santoro, and Anthony Ingraffea. "Methane and the Greenhouse-gas Footprint of Natural Gas from Shale Formations." Climatic Change 106.4 (2011): 679-90. Web.

"Hydraulic Fracturing for Natural Gas Pollutes Water Wells." Scientific American Global RSS. N.p., n.d. Web. 22 Apr. 2015.

"Methane Contamination of Drinking Water Accompanying Gas-well Drilling and Hydraulic Fracturing." Methane Contamination of Drinking Water Accompanying Gas-well Drilling and Hydraulic Fracturing. N.p., n.d. Web. 22 Apr. 2015.

Representatives, United States House Of, Committee On Energy And Commerce, Minority Staff, and April 2011. CHEMICALS USED IN HYDRAULIC FRACTURING (2011): 1-30. Web. 22 Apr. 2015.

Steingraber, Sandra, Ph. D. The Potential Health Impacts of Hydraulic Fracturing Testimony before the New York State Assembly Standing Committees on Environmental Conservation and Health (n.d.): n. pag. Web.

"Water Encyclopedia." Ogallala Aquifer. N.p., n.d. Web. 22 Apr. 2015.

Webb, Ellen, Sheila Bushkin-Bedient, Amanda Cheng, Christopher D. Kassotis, Victoria Balise, and Susan C. Nagel. "Developmental and Reproductive Effects of Chemicals Associated with Unconventional Oil and Natural Gas Operations." Reviews on Environmental Health (n.d.): n. pag. Web.

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