California’s Fracking Fluids

The Chemical Recipe

August 12, 2015

California’s Fracking Fluids: The health hazards of fracking chemicals

Since January 2014, oil and gas companies in California have been required to report all chemicals used in fracking or other well stimulation methods to the Division of Oil, Gas and Geothermal Resources, which publishes these Well Stimulation Public Disclosure reports on its website. (The website includes reports on some wells treated in December 2013.) From these reports, EWG reviewed the chemicals listed under the Well Stimulation Fluid Information tab (DOGGR 2015).

Through February 2015, a total of 691 fracking jobs were reported, all for oil wells and nearly all in Kern County. These fracking jobs used 197 distinct chemicals – typically 25 to 30 chemicals for each operation. (See Appendices 1 and 2 for the complete list of 197 chemicals, how often they were used and a summary of their health effects.) They include:

Fracking sand

After water, the second most commonly used ingredient in fracking fluid was sand – but not just any sand. Every fracking job in the state database used crystalline silica and calcined diatomaceous earth, which is largely composed of crystalline silica. If inhaled, airborne crystalline silica is a Proposition 65 carcinogen. Mining, transport, storage and use of these sands can result in hazardous air quality for miners, workers at fracking sites and people nearby (EWG 2015, NPR 2013).

Petroleum distillates

About 90 percent of the fracking jobs reported using chemicals refined from crude oil known as petroleum distillates. Diesel fuel – the only chemical prohibited in fracking under the federal Safe Drinking Water Act – is a petroleum distillate. The U.S. EPA does not consider the two types of distillates reported in the state database to be diesel. However, one is listed by the European Union as carcinogenic, and the other is an acute inhalation hazard, has nervous system effects and is toxic to aquatic life. Petroleum distillates can contain traces of BTEX chemicals – benzene and ethylbenzene, both Proposition 65 carcinogens; toluene, a Proposition 65 reproductive toxin; and xylene, a hazardous air pollutant.

Aromatic hydrocarbons

The fracking disclosure report lists 11 chemicals classified as aromatic hydrocarbons, including xylene, toluene, trimethylbenzene and naphthalene. Most have been linked to cancer, reproductive harm or hormone disruption. A recent study found that exposure to the BTEX chemicals, which are all aromatic hydrocarbons, may disrupt hormones even at exposure levels the EPA currently considers safe (Bolden et al, 2015). Although these chemicals were used less often – in about 2-to-5 percent of the fracking jobs reported – the levels of BTEX chemicals in EWG’s previous analysis of fracking wastewater were quite high (EWG 2015), suggesting that the wastewater may contain naturally occurring hydrocarbons from the petroleum deposits or shale formations.


Eight different biocides – chemicals that kill bacteria – are listed in the disclosures, with additives known as MIT5 and CMIT6 the most common. They are used to prevent the growth of bacteria that could clog or corrode the wells. They are poisonous by design, so it is not surprising that MIT and CMIT biocides are extremely toxic to aquatic life. In the environment, sunlight may break down biocides, but little is known about what happens to biocides after they are pumped down a well (Kahrilas et al 2014).

Glycol ethers and alcohols

The disclosure reports list 24 unique chemicals classified as glycol ethers or ethoxylated alcohols. Although many of them are ingredients in household cleaning products, they have been linked to health and environmental harms. Most of the alcohols are toxic to aquatic life and often contain as impurities ethylene oxide and 1,4 dioxane, both Proposition 65 carcinogens. Glycol ethers have been also linked to suspected endocrine disruption and reproductive harm in people.

Chemicals by category

Table 1 lists the categories of all reported fracking chemicals by use, how often each was used and examples of specific chemicals in that category.

Table 1.  Types and examples of chemicals reported by California fracking jobs from December 2014 to February 2015, with percentage of jobs using each type.

Chemical Purpose Percent of fracking jobs that reported using it Example of specific chemicals
Proppant Keeps fractures in the rock open for oil and gas to flow 100% crystalline silica (frac sand) diatomaceous earth
Breaker Reduces thickness of the fluid to release proppant into fractures. Allows fluid to flow after proppant has been added 100% ammonium persulfate sodium chloride hemicellulase enzyme
Gelling Agent Increases fluid thickness to suspend the proppant 97% guar gum petroleum distillates ethylene glycol
Clay control/
Locks clays in the rock to keep pore spaces open 97% magnesium chloride magnesium nitrate oxyaklylated amine quat
Inhibits growth of bacteria that reduce the amount of proppant carried 94% methylisothiazolinone chloromethylisothiazolinone
Crosslinker Maintain fluid viscosity 94% sodium tetraborate vinylidene chloride/methyl acrylate copolymer
Scale inhibitor Prevents mineral scale in pipes and in the rock 77% ethylene glycol nitrilo methylene phosphonic acid phosphonic acid ammonium chloride
Iron Control Prevents build-up of metal oxides 15% citric acid
Buffer/pH Control Adjusts and controls the pH of the fluid 15% sodium hydroxide
Solvent Separates oil and water mixtures 15% isoproponal
Surfactant Reduces fluid surface tension and improves fluid recovery 13% isotridecanol ethoxylate butoxy propanol methanol
Corrosion inhibitor Protects well and tubing from corrosion. 5% methanol isopropanol
Acid Dissolves minerals and forms cracks in rock 2% hydrochloric acid
Reduces friction of fluid in pipes to optimize rate and pressure > 1% ethylene glycol methanol glycerol

Source: EWG, from DOGGR Well Stimulation Public Disclosure Report.

5 Methylisothiazolinone

6 Chloromethylisothiazolinon