The Environmental Externalities of Fracking, According to Peer-Reviewed Science

There are numerous scientific, peer-reviewed papers that have been published in recent years that point to the dangers of hydraulic fracking, and its impact on public health and the environment. 

The growing controversy over hydraulic fracturing seems to suffer from a lack of discussion on the concrete scientific evidence.  For instance, the documentary Gasland (2010) is widely touted as an excellent study on the dangers and harms of fracking among greens, despite the film being extremely unscientific (i.e. assuming that the methane in local drinking waters were from fracking, despite the fact that methane has naturally seeped into surface waters for decades).  But on the flip side, the industry’s response to criticism also tends to be unscientific, and fracking proponents seem to have a tendency of denying any externalities from unconventional operations whatsoever.

Thus, this piece seeks to examine scientific papers that analyze the externalities from fracking, and raise the bar for the growing debate.  In general, the science shows that fracking can cause a wide variety of problems, ranging from increased rates of birth defects to radiation contamination.


 Metal Contamination in Pennsylvania

The Marcellus Shale formation in Pennsylvania is a rapidly growing region of oil and gas extraction, much of it through fracking; as a result, there are massive amounts of wastewater (on the order of hundreds of millions of gallons per year) that need to be properly disposed of.  For many years, a good proportion of this wastewater was processed through either municipal sewage treatment plants, or  standard wastewater treatment plants.  After being processed, the wastewater (now supposedly normal and healthy) is returned to surface waters, like streams and rivers.  Of course, the big question is whether standard treatment plants can actually properly process the wastewater from fracking.

This paper (Ferrar 2013), published in March 2013 in Environmental Science & Technology, studied the outputs of three wastewater treatment plants in the Marcellus Shale, and whether they were able to properly treat fracking wastewater.  Turns out that while the concentrations of dangerous compounds were reduced by quite a bit, the output (also known as “effluent”) still contained very high levels of certain compounds:

The analysis of effluent samples…supports our first hypothesis that concentrations of analytes in effluent were above water quality criteria. Ba, Sr, and bromides are of particular public health concern. For the metals strontium and barium, both surpassed the federal [maximum contamination levels] MCL for drinking water (recommended, not regulated, MCL for Sr). (Ferrar 2013: 3478)

Of course, it is important to realize that this concentration will become diluted almost immediately, and will become increasingly diluted as the particles progress through the water; thus, it is not a given that these concentrations of toxins pose an immediate public health risk.  But as the paper cautions, there is also the probability of 1) the formation of plumes with above-regulation levels of metal concentrations, and 2) the inability for the metals to become diluted due to increasing levels of solutes, which will become an increasingly possibility as local carbon extraction increases (Ferrar 2012: 3479).

The paper goes on to note that after the Pennsylvania Department of Environmental Protection (PADEP) asked companies to stop sending their wastewater to local treatment plants, the contamination levels dropped to below regulation levels (Ferrar 2012: 3479).

Radiation Contamination in Pennsylvania

Despite PADEP’s actions to limit the wastewater that is sent to treatment plants, there are other causes for worry.  This paper (Warner 2013), published in October 2013 in Environmental Science & Technology, was somewhat of a follow-up to Ferrar 2013, in that it also studied the effects of treatment of wastewater by standard treatment plants.  It focuses on one treatment plant that “exclusively treat[s] oil and gas wastewater.” (Warner 2013: 11850).  The study found that the effluent contained elevated levels of certain problematic compounds, like salt, chlorides, and bromies; but most eye-opening was the high level of radiation (specifically, Radium) that was in the treatment plant’s output:

…immediately adjacent to the treatment facility discharge site we recorded much higher maximum activities of both Ra-226 (8732 Bq/kg) and Ra-228 (2072 Bq/kg) in the sediments. These Ra activities were 200 times greater than any background sediment samples collected either upstream of the facility or from other western PA rivers for sediment samples of similar grain size. (Warner 2013: 11855)

The mean activities (“activity” is the technical term for the amount of radiation) of Ra-226 and Ra-228 found in the soil around the plant’s discharge zone were 4255 Bq/kg and 1110 Bq/kg, respectively.  These levels are above standard regulations for radioactive waste in the United States.  As the paper notes:

These radioactivity levels are…above management regulations in the U.S. that range from 185 to 1850 Bq/kg. For example, in Michigan a radiation threshold that would require transportation of solid waste to a licensed radioactive waste disposal facility is 1850 Bq/kg. (Warner 2013: 11855)

Furthermore, it is fairly certain that this waste is a direct result of fracking operations, and not conventional oil and gas drilling, because of the analyzed ratios between Ra-226 and Ra-228, and comparison with the known Radium levels for the Marcellus wastewater.


Figure from Warner 2013

The paper notes two additional causes of concern.  First, while this radiation contamination is currently confined to a relatively small area (up to 200m downstream of the discharge site), the amount of radiation that is accumulating at the bottom of the river bed still poses a threat via bioaccumulation.  This is a process by radiation becomes increasingly concentrated as it moves up the food chain (from plants, to small herbivores, to carnivores, etc).  And second, there is also the issue of radioactivity in the waste products of the treatment plant.  Despite the effluent having relatively high levels of radioactivity, this still represents a fraction of what was present in the original, untreated wastewater.  This means the waste products of the plants are also radioactive: the fact that this waste, which is often dumped in residual landfills, present an even higher radiation exposure risk than the Radium that has accumulated in the river sediments (Warner 2013: 11855).

Air Pollution and Birth Defects in Colorado

Like Pennsylvania, Colorado is another state where unconventional drilling operations have skyrocketed over the past decade.  This has also lead to a host of scientific papers analyzing the effects of fracking on local public health.

This paper (McKenzie 2012), published in February 2012 in Science of the Total Environment, studied the air quality around fracking sites in Colorado, and their corresponding theoretical impact on public health.  The paper summarizes the ways in which unconventional drilling operations can pollute the local air:

As shown by ambient air studies in Colorado, Texas, and Wyoming, the NGD process results in direct and fugitive air emissions of a complex mixture of pollutants from the natural gas resource itself as well as diesel engines, tanks containing produced water, and on site materials used in production, such as drilling muds and fracking fluids. (McKenzie 2012: 80)

It’s also worth noting that fracking, due to its high dependency on water when compared to conventional drilling, requires far more gasoline-driven vehicles to transport water, sand, and wastewater back and forth than does normal oil and gas operations.


The study divided the area of study into two regions, defined by their proximity to gas wells: one region that held areas less than half a mile from a well, and the other region that held areas more than half a mile from a well.  The study then analyzed the probabilities of several different health outcomes, based on the measured concentration levels of various air pollutants:

Our results show that the non-cancer [hazard index] HI from air emissions due to natural gas development is greater for residents living closer to wells.  Our greatest HI corresponds to the relatively short-term (i.e., subchronic), but high emission, well completion period.  This HI is driven principally by exposure to trimethylbenzenes, aliphatic hydrocarbons, and xylenes, all of which have neurological and/or respiratory effects.  We also calculated higher cancer risks for residents living nearer to wells as compared to residents residing further from wells.  Benzene is the major contributor to lifetime excess cancer risk for both scenarios. (McKenzie 2012: 83)

It is worth noting the specific increase in cancer risk for people living closer to wells:

The cumulative cancer risks…were 6 in a million for residents >½ from wells and 10 in a million for residents ≤½ mile from wells. (McKenzie 2012: 83)

Unfortunately, the estimated increase in cancer risk isn’t the only bad news about air pollution from fracking.  A more recent study (McKenzie 2014) published January 2014 in Environmental Health Perspectives by many of the same authors as McKenzie 2012, analyzed the correlation between birth defects and proximity of the maternal home to gas wells.  This study hypothesized that there was a connection between air pollution from unconventional drilling operations and birth defects like congenital heart defects, neural tube defects, and others.  This is based on the fact that many of the pollutants that get into the air from fracking operations (including our old friend Benzene) are hypothesized to be teratogens–compounds that interfere with fetal development and cause birth defects and mutations (McKenzie 2014: 4).

The study analyzed 124,842 live births in rural Colorado, controlled for confounding factors like smoking, drinking, age, etc., and then divided the groups based on the proximity to wells, as well as density of nearby wells.  The results are somewhat complicated, and its worth reading the “Results” section of the paper, but in general the conclusion sums the implications up nicely:

This study suggests a positive association between greater density and proximity of natural gas wells within a 10-mile radius of maternal residence and greater prevalence of CHDs and possibly NTDs, but not oral clefts, preterm birth, or reduced fetal growth. (McKenzie 2014: 16)

 Endocrine-Disrupting Chemical Contamination in Colorado 

Teratogens from unconventional drilling operations don’t just pollute the air; they can also contaminate local waters.  This paper (Kassotis 2013), published in 2013 in Endocrinology, studied whether fracking was causing local waters to become contaminated with endocrine-disrupting chemicals (EDCs).  The study had two parts: first, to study whether certain suspected fracking chemicals are actually EDCs, and second, to measure the levels of these chemicals in surface and ground waters in rural Colorado.

The results of the first part of the study confirmed that fracking does use chemicals that exhibit a variety of hormone-disrupting capabilities.  In fact, this section was something of a ground-breaker, in that it was the first attempt to analyze the endocrine-disrupting capability of certain fracking chemicals:

To our knowledge this is the first report of antiestrogenic activity of ethylene glycol monobutyl ether, 2-ethylhexanol, ethylene glycol, diethanolamine, diethylene glycol methyl ether, sodium tetraborate decahydrate, 1,2-bromo-2-nitropropane-1,3-diol, n,n-dimethyl formamide, cumene, and styrene; and novel antiandrogenic activity of 2 ethylhexanol, naphthalene, diethanolamine, sodium tetraborate decahydrate, 1,2- bromo-2-nitropropane-1,3-diol, and cumene. (Kassotis 2013: 5).

The second part of the study, which analyzed the chemical activity levels at five different sites, found that unconventional drilling operations had lead to elevated levels of EDCs in local surface and ground waters:

Importantly, we found that water samples from sites with known natural gas drilling incidents had greater estrogen and androgen receptor activities than drilling sparse or absent reference sites. Very little estrogen or androgen receptor activity was measured in drilling-sparse reference water samples, moderate levels were measured in samples collected from the Colorado River (the drainage basin for all Colorado collection sites), and moderate to high activities were measured in water samples from Garfield County spill sites. The Garfield County spill sites were known to have various types of contamination including produced water (wastewater and chemical mixture recovered after hydraulic fracturing) pipe leaks, a produced water tank spill, the improper disposal of produced water into surface water, and a natural gas upwelling, which may have resulted in the distinct site-specific patterns of activities observed. (Kassotis 2013: 5)

It is important to note that there was no comparison of these elevated levels to any reference value (like a federal regulatory threshold or a medically-sanctioned limit for health effects).  But on the flip side, this could be a consequence of this type of research being so novel; perhaps there hasn’t been a proper thrust to characterize the health effects of fracking chemicals that are EDCs, and thus the standards of water concentration levels might not even exist in the first place.


It should be clear by now that the unconventional oil extraction is, in fact, stressful for the local environment.  But even then, the science remains limited; a key lesson, as with most things concerning environmental externalities, is that more science needs to be done, and that development and expansion of extractive industries should probably be done in a conservative and highly regulated fashion (if at all) until the science becomes more clear.

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