Preliminary Hazard Assessment of Chemical Additives Used in Oil and Gas Fields that Reuse Their Produced Water for Agricultural Irrigation in The San Joaquin Valley of California. Technical Report

Preliminary Hazard Assessment of Chemical Additives Used in Oil and Gas Fields that Reuse Their Produced Water for Agricultural Irrigation in The San Joaquin Valley of California. Technical Report by Seth B.C. Shonkoff, William T. Stringfellow, and Jeremy K. Domen, September 2016, PSE Healthy Energy, Inc. Oakland, CA


Oil field produced water has been used to irrigate food crops in the Cawelo Water District since the mid-1990s. The practice has recently been expanded to the North Kern Water Storage District and produced water is being examined widely as a potential source of water for agriculture, livestock watering, drinking water and other uses. One important knowledge gap with respect to assessing potential human health and environmental hazards associated with reuse of oil field produced water for irrigation is an understanding of the types and amounts of chemical additives used during oil and gas development.

Disclosure of chemical use during oil and gas development is considered an important component for understanding the potential risks associated with hydraulic fracturing and other well stimulation activities and disclosure is an important component of creating effective regulation of hazardous chemicals. For instance, regulations developed under California Senate Bill 4 require the reporting and public disclosure of chemical additives used for hydraulic fracturing and other well stimulation activities common to oil and gas development. These disclosure requirements, however, do not apply to other common or routine oil and gas field activities such as drilling, well maintenance, routine acidizing, and well completions (State of California 2013). Hazardous chemicals are used throughout the entire oil and gas development process, not just during well stimulations (Economides et al. 2013; Fink 2015; Hudgins 1992; Hudgins 1994; Kelland 2014). Recent research shows that many of the same chemicals used in hydraulic fracturing and well stimulation are also used for other purposes in oil and gas development (Shonkoff et al. 2016; Shonkoff et al., under review).

The Central Valley Regional Water Quality Control Board (CVRWQCB) is investigating the use of produced water for agriculture and one of the issues being examined by the CVRWQCB and other stakeholders is how the use of chemicals for oil and gas production, including chemicals used in produced water management, may impact the quality and safety of produced water used for agriculture, including livestock watering, and recharging regional aquifers (CVRWQCB 2012).


A total of 173 chemical constituents were identified by unique name or CASRN. Of these 173 chemicals, 66 (38%) were classified as “trade secret” or did not have an associated valid CASRN and could not be positively identified. The remaining 107 chemicals (62%) were identified by CASRN, a definitive identifier, and could therefore be further evaluated for physical, chemical, and toxicological properties.

An evaluation of acute toxicity data (Table 1) shows that only five chemicals were classified
GHS category 2 for oral mammalian toxicity and no chemicals were GHS category 1, the most toxic category. In contrast, a total of 39 chemicals (36%) were classified as GHS category 1 or 2 for ecotoxicity, indicating that the chemicals may pose a significant hazard to aquatic environments. Fourteen chemicals (13%) had no available ecotoxicity or mammalian toxicity data and could not be ranked or evaluated (Table 2). Chemicals without published toxicity data should be evaluated further.

Of the 107 chemicals with CASRN, eight appeared on California’s Prop 65 list, eight were on
the U.S. EPA NPDWS and Health Advisory Chemical list, three were on the U.S. EPA CCL4,
twenty-two were on the California EPA Toxic Air Contaminant list, and eleven are considered hazardous air pollutants according to the Clean Air Act (Table 3). A total of ten chemicals were classified by the International Agency for Research on Cancer (IARC) as either carcinogenic or possibly carcinogenic in humans (Table 4). Inclusion on these lists suggests that these chemicals are recognized as being hazardous and subject to regulatory control under at least some circumstances.


In this preliminary assessment, we evaluated the list of chemicals reported as used in oil fields from which produced water is deployed for irrigation, for watering livestock, and for recharging groundwater in the San Joaquin Valley of California. We found a total of 173 different chemical additives were used in these oil and gas fields, of which more than one-third (38%) were not able to be sufficiently identified for preliminary hazard evaluation, largely due to the withholding of information under proprietary claims. Over 100 chemicals (62% of the total list) were identified by CASRN for acute toxicological properties, biodegradability, and environmental persistence using publically available data and toxicological screening software. The CASRN identified oil and gas field additives were also cross-referenced with a variety of lists used to identify or regulate chemicals suspected or known to cause negative environmental or health impacts if released into the environment. Of the chemicals that had a CASRN, we found that 46 (43%) of them can be classified as potential chemicals of concern from human health and/or environmental perspectives and require a more thorough investigation (Table 8). [Emphasis added]

Table 8. Oil and gas field chemical additives with CASRN identified by preliminary analysis as potential chemicals of concern. The last column on the right indicates why they appear on this table. Name CASRN Why compound appears on table*

Ethylbenzene 100-41-4 Prop 65, NPDWS, IARC 2B, CA TAC, CAA
Ethylene glycol 107-21-1 Prop 65, NPDWS, CCL4, CA TAC, CAA
Toluene 108-88-3 Prop 65, NPDWS, CA TAC, CAA
Antimony trioxide 1309-64-4 Prop 65, IARC 2B, CA TAC
Lithium carbonate 554-13-2 Prop 65
Methanol 67-56-1 Prop 65, CCL4, CA TAC, CAA
Naphthalene 91-20-3 Prop 65, GHS1 ECO, IARC 2B, NPDWS, CA TAC, CAA
Cumene 98-82-8 Prop 65, IARC 2B, NPDWS, CA TAC, CAA
Xylene 1330-20-7 NPDWS, CA TAC, CAA
1,3,5 Trimethylbenzene 108-67-8 Non-biodegradable§, NPDWS
Isoquinoline 119-65-3 Non-biodegradable§
1,2,3 Trimethylbenzene 526-73-8 Non-biodegradable§, NPDWS
Siloxanes and silicones 63148-62-9 Bioaccumulative, GHS1 ECO
Glutaraldehyde 111-30-8 GHS1 ECO, CA TAC
Hydroquinone 123-31-9 GHS1 ECO, CA TAC, CAA
Lithium hypochlorite 13840-33-0 GHS1 ECO
Sodium dichloroisocyanurate 2893-78-9 GHS1 ECO
Heavy aromatic naphtha 64742-94-5 GHS1 ECO
Iodine 7553-56-2 GHS1 ECO
Zinc chloride 7646-85-7 GHS1 ECO
Hydrochloric acid 7647-01-0 GHS1 ECO, CA TAC, CAA
Sodium hypochlorite 7681-52-9 GHS1 ECO
Copper sulfate pentahydrate 7758-99-8 GHS1 ECO
Hydrotreated light distillate 64742-47-8 GHS1 ECO
Stearic acid 57-11-4 GHS1 ECO
Kerosene 8008-20-6 GHS1 ECO
Dinonylphenyl polyoxyethylene 9014-93-1 GHS1 ECO
Acrolein 107-02-8 GHS2 MAM, GHS1 ECO, CCL4, CA TAC, CAA
Propargyl alcohol 107-19-7 GHS2 MAM
Cyclohexylamine 108-91-8 GHS2 MAM
Ethyl acetate 141-78-6 GHS2 MAM
Stoddard solvents 8052-41-3 GHS2 MAM, GHS1 ECO
Crystalline silica (quartz) 14808-60-7 IARC 1
Xenon radionuclide 14932-42-4 IARC 1, No toxicity data
Silica, crystalline, tridymite 15468-32-3 IARC 1, No toxicity data
Ethanol 64-17-5 IARC 1
Sulfuric acid 7664-93-9 IARC 1, CA TAC
Nickel sulfate 7786-81-4 IARC 1
Hydrofluoric acid 7664-39-3 CA TAC, CAA
Aluminum chloride hydroxide 12042-91-0 No toxicity data
Aluminum stearate 300-92-5 No toxicity data
Lithium chlorate 36355-96-1 No toxicity data
Polyamine 64114-46-1 No toxicity data
Coke, petroleum, calcined 64743-05-1 No toxicity data
Fatty acid oxyalkylate 70142-34-6 No toxicity data
Cellophane 9005-81-6 No toxicity data

[Would you like those chemicals and the secret chemicals in your drinking water, fruit, vegetables, beef, or to bathe in?]


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