Toxic Stew

What’s in Fracking Wastewater

March 10, 2015

Toxic Stew: Chemicals in Waste Included Carcinogens And Neurotoxins


Since December 2013, drilling companies in California have reported using more than 200 distinct chemicals in hydraulic fracturing fluids (DOGGR, 2015). They range from relatively benign gelling agents such as guar gum to neurotoxins and known carcinogens  identified on California’s Proposition 65 list (OEHHA, 2015), including toluene and formaldehyde.

In California, chemicals typically make up 2 percent of the total volume of the fracking fluid – twice the concentration common in other states (CCST Webinar, 2015). A portion of the chemical-laced fluid returns to the surface as flowback, bringing with it naturally occurring formation water that can also contain chemicals released from the shale. The industry’s term for this wastewater (flowback plus formation water) is produced water. In this report wastewater is used to describe all produced water unless it is specifically known to be flowback or formation water.

From the Division’s records for 2014, EWG calculated that California operators used an average of 62,600 gallons of water in fracking jobs, and that on average only about 4 percent of the volume of the fluid was recovered. The amount of flowback varies greatly depending on the pressure in the field (Bohlen, 2015).

Not all the reported laboratory analyses of recovered fluids included data on all appropriate chemicals. Of the five companies that filed reports on chemical sampling, only one, Aera Energy LLC, provided complete and detailed data. Aera submitted more than 80 percent of the records in the database for 2014, and EWG used its reports for its analysis. Of the 460 records submitted by Aera through early January 2015, more than 167 reported that no sample had been taken or included no laboratory report at all. That left 293 records for EWG’s analysis, covering fracking operations conducted from January to November 2014.

Despite these limitations, this dataset holds more information about chemicals in fracking wastewater than ever before available. The laboratory analyses showed extremely high concentrations of contaminants, many of them listed under Proposition 65 (Table 2). Many of the chemicals, heavy metals and radiation levels exceeded the state’s standards for drinking water, known as Maximum Contaminant Levels (MCLs) (SWRCB, 2015). Others exceeded the state Public Health Goals (PHGs) set by the Office of Environmental Health Hazard Assessment as health-protective levels that public water systems should strive to achieve if feasible (OEHHA, 2015).

This wastewater would likely be diluted in an injected aquifer, but the reported concentrations are startling. Even low levels of many of these chemicals can cause problems in drinking water. “A single teaspoon of benzene, for example, is enough to contaminate more than 260,000 gallons of water to a level that exceeds the EPA’s drinking water standard…” (EWG, 2012). 

Here is a summary of what EWG’s analysis of the reports found:

BTEX petroleum chemicals (benzene, toluene, ethylbenzene and xylene)

  • Benzene was found in 99 percent of the samples. All detections exceeded the California drinking water standard, and 80 percent exceeded it by factors of 100 to 1,000. Benzene is listed as a known carcinogen under Proposition 65.
  • Toluene, a neurotoxin that is also listed as a potent reproductive toxin under Proposition 65, was detected in 83 percent of the samples at levels above the drinking water standard.
  • Ethylbenzene, a Proposition 65 carcinogen, was reported in excess of drinking water standards in 19 percent of the samples.
  • Xylene, a reproductive and developmental toxin, was found in 12 percent of the samples in amounts above the drinking water standard.

 Polynuclear Aromatic Hydrocarbons

  • Benzo(a)pyrene, listed as a carcinogen under Proposition 65, was detected in 17 samples at levels above the drinking water standard.


  • Arsenic, listed as a carcinogen under Proposition 65, was reported in excess of the drinking water standard in 45 percent of the samples.
  • Lead, a developmental toxin under Proposition 65 for which there is no safe level (CDC, 2012), was detected in 43 percent of the samples in amounts above the drinking water standard.
  • Chromium-6, also known as hexavalent chromium, a Proposition 65 carcinogen, turned up in 37 percent of the samples at above the drinking water standard.
  • Nickel, a Proposition 65 carcinogen, was found in 34 percent of samples at above the state’s Public Health Goal.
  • Cadmium, a Proposition 65-listed developmental and reproductive toxin also linked to lung, prostate and kidney cancer, was detected in 18 samples at levels above the drinking water standard (OEHHA, 2015).
  • Barium was measured at up to 160 times the drinking water standard in 78 percent of the samples. Ingesting high levels of barium over an extended period may increase blood pressure (EPA, 2015). Lower exposures for even a short time can result in vomiting, cramps, diarrhea and breathing difficulties (OEHHA, 2003).

Total Dissolved Solids

  • Total dissolved solids (TDS) were measured at above the drinking water standard in 97 percent of the samples. They are an indicator of dissolved salts in the water; high levels render water unfit for drinking.


  • Radiation from uranium was measured at levels exceeding the drinking water standard in six samples. Radiation from radium-226 and radium-228 in excess of the Public Health Goal was found in 94 percent and 89 percent of samples, respectively. Exposure to radiation may increase the risk of cancer (OEHHA, 2003).

Table 2. Toxic chemicals and other contaminants measured in fracking wastewater at levels exceeding California Maximum Contaminant Levels or Public Health Goals, 2014

Chemicals Parts per billion (ppb) Prop. 65 Exceeded MCL or PHG (293 samples)
Antimony 996 8,200 6 20   24% > MCL
Arsenic 1,094 15,000 10 0.0004 ✔︎ 45% > MCL
Barium 5,120 160,000 1,0001 2,000   78% > MCL
Benzene 703 7,700 1 0.15 ✔︎ 99% > MCL
Benzo(a)pyrene 7 35 0.2 0.0007 ✔︎ 17 samples > MCL
Berylium 47 290 4 1   20 samples > PHG
Cadmium 38 600 5 0.04 ✔︎ 18 samples > MCL
Chromium (total) 15 160 50     4 samples > MCL
Chromium-6 8 54 10 0.02 ✔︎ 37% > PHG
Copper 138 1,900 1,000* 300   7% > PHG
Ethylbenzene 193 1,200 300 300 ✔︎ 19% > MCL
Lead 520 5,800 15 0.2 ✔︎ 43% > MCL
Nickel 35 280 100 12 ✔︎ 34% > PHG
Selenium 1,892 16,000 50 30   35% > MCL
Silver 310 2,000 100*     18 samples >  MCL
Thalium 3,081 10,000 2 0.1   10 samples > MCL up to 5,000X
Toluene 1,113 11,000 150 150 ✔︎ 83% > MCL
Xylenes (total) 926 7,600 1,750 1,800   12% > MCL
Zinc 526 9,400 5,000*     7 samples > MCL
Ions and TDS Parts per million (ppm)  
Chloride (Cl-) 46,972 380,000 500*     90% > MCL
Fluoride (F-) 8 100 2 1   12% > MCL
Nitrate (NO3-) 23 270 45 45   8 samples > MCL
Sulfate (SO4-2) 149 2,200 500*     12 samples > MCL
Total dissolved solids (TDS) 120,050 1,400,000 1,000*     97% > MCL, 73% >10X
Radionuclides Picocuries per liter (piC/L)  
Gross alpha emitters 283 3,040 15   ✔︎ 26% > MCL
Radium 226 73 1,152   0.05 ✔︎ 94% > PHG
Radium 228 56 959   0.019 ✔︎ 89% of samples > PHG
Uranium 3 95 20 0.43 ✔︎ 6 samples > MCL

MCL (Maximum Contaminant Level): Legal limit allowed in drinking water by state law.
*Secondary MCL: Advisory-only guideline based on taste/smell/color for chemicals with no negative health effects.
PHG (Public Health Goal): Level the state says poses “no significant health risk if consumed for a lifetime.”
Prop. 65: State registry of chemicals known to cause cancer or birth defects.
piC/L: Intensity of radioactivity in a sample of material.
1 The California MCL for barium was set in 1977 at 1,000 ppb. In 1991 U.S. EPA recalculated its MCL at 2,000 ppb, and California adopted that same level as a PHG, but has not updated the state MCL.

Source: Environmental Working Group, from California DOGGR