California prohibits farmers from growing crops with chemical-laced wastewater from fracking. Yet the state still allows them to use water produced by conventional oil drilling—a chemical soup that contains many of the same toxic compounds.

When rumors spread several years ago that California was growing some of the nation’s nuts, citrus and vegetables with wastewater produced from hydraulic fracturing, known as fracking, regulators said that would be illegal.

Advances in fracking, a process that injects high-pressure chemical mixtures and sand into underground rock formations to stimulate the release of fossil fuels, revolutionized oil and gas extraction in the United States. But it alarmed environmental, public health and consumer groups, who were concerned that the massive quantities of highly toxic wastewater produced during fracking posed unacceptable threats to groundwater, ecosystems and communities.

California quickly moved to regulate fracking, and water regulators ruled that wastewater from fracking could not be used to irrigate crops, acknowledging that the extractive chemicals might taint the crops grown in the water.

But those same regulators have for years allowed farmers to irrigate nearly 100,000 acres of nuts, citrus and vegetables with wastewater from conventional oil drilling, even though many of the same chemicals are used in fracking and detected in fracking wastewater, a review of chemical disclosure lists and scientific studies by Inside Climate News has found. 

To cope with California’s perpetual droughts, state officials encourage recycling of water whenever possible, and have relied on oil field wastewater to help Kern County’s $7.6 billion agricultural industry stay afloat.

But scientists said in interviews that the state’s distinction between the two types of “produced water” is essentially meaningless. 

“It doesn’t matter from a chemical perspective if you’re hydraulically fracturing something or you’re doing even the most pedestrian, old-school oil production techniques,” said Seth Shonkoff, an expert on the health and climate impacts of oil and gas development and executive director of Physicians, Scientists and Engineers (PSE) for Healthy Energy. “Everything uses chemicals. And a lot of the chemicals are exactly the same.” 

An Inside Climate News analysis cross-referenced lists of chemicals that oil companies reported using in California to operate conventional oil wells with those reported by frackers in Texas, Ohio, Pennsylvania and West Virginia, and found many of the same chemicals. And research over the past several years has found that mixing chemicals together, as happens with both types of drilling, greatly elevates toxicity. 

Last fall, the Central Valley Regional Water Quality Control Board, which regulates the use of produced water to grow crops in Kern County, tried to allay public health concerns when it released a review of studies that it said found “no identifiable increased health risks” from irrigating crops with wastewater from conventional wells. 

Yet an investigation published in February by Inside Climate News, based on a review of science and interviews with a public health scientist affiliated with the board and other experts, showed that there was scant evidence to support the board’s claims. 

Inside Climate News also found that GSI Environmental, the firm that conducted the studies for the board, had regularly worked for Chevron, the biggest provider of produced water for irrigation, and received research funding from the chemical and fossil fuel industries. 

Inside Climate News’ analysis of chemicals used in fracking and conventional oil drilling found that nearly half the substances used by oil companies that sell their wastewater for crop irrigation in Kern County, many of them known to cause harm, were also used by fracking operators across the country, according to chemical disclosure records in California and a national fracking disclosure registry.

Scientists who study the potential of these chemicals to harm humans said in interviews that the long list of overlapping compounds in the two processes only begins to define the probable risks. That’s because the chemicals used in both fracking and conventional oil drilling interact with one another, and with other natural compounds like arsenic and anthracene, to produce new compounds that can be more toxic than the individual chemicals by themselves. 

The failure to consider these chemical “cocktail effects” was a key weakness of the GSI Environmental study that water regulators relied on to give the practice of irrigating crops with produced water a clean bill of health, scientists said. What’s more, the water regulators said the practice was safe even though GSI lacked toxicity information for the majority of potentially harmful chemicals, and failed to account for the fact that mixing chemicals together under high heat and pressure to extract Kern County’s famously tarry oil could produce even more toxic compounds. 

Overlapping Risks

Most states do not require oil companies to disclose the chemicals they use to extract fossil fuels during fracking or conventional drilling. Shonkoff discovered around 2015 that oil companies drew on the same set of chemicals for both operations, thanks to a rare rule from a Southern California air district requiring conventional drillers to publicly disclose the chemicals they put down wells. When Shonkoff compared chemicals used by California operators in routine operations with those used in fracking, he found “significant overlap.”

Growing crops with this water, in other words, meant people and the environment could be exposed to the same dangers that come with fracking. Shonkoff reported his findings at the expert panel’s first public meeting in 2016, and urged the water board to require operators to disclose all the chemicals they use. The board agreed. 

Conventional oil developers now have to report every product they use in Kern County, said Clay Rodgers, who led the Food Safety Project for the Central Valley water board. “We were able to get the list of every constituent in the products that are being used,” he said. 

The overlapping chemicals used by frackers and by oil companies in California that send irrigation water to Kern County farmers include scores of known and probable human carcinogens, including benzene and naphthalene, two dozen compounds like methanol and formaldehyde suspected of causing developmental and reproductive harm and more than a dozen that can disrupt endocrine function and lead to metabolic diseases, an Inside Climate News review of chemicals shows. 

In addition, produced water from Kern County and fracking operations around the country often contain highly toxic naturally occurring chemicals—including cancer-causing arsenic and cadmium—many of which were safely sequestered underground until brought back to the surface by conventional and fracking operations.

The same petroleum that is extracted from the ground provides the raw materials for industrial synthetic chemicals. As a result, many of the added chemicals found in produced water also come from natural sources. A number of these chemicals interfere with the endocrine system, including benzene and toluene, while others, including xylene and naphthalene, are linked to reproductive and developmental problems. Others, like lead and mercury, are neurotoxic. Some compounds cause multiple harmful effects.

Isabelle Cozzarelli, a research hydrologist with the U.S. Geological Survey who investigates spills of produced water, said that what proved most harmful to soil, plants and aquatic organisms in her studies were elevated levels of naturally occurring elements like chloride and potassium, as well as ammonium. All are common in both fracking and conventional wastewater. 

“And the organic carbon that’s in all of these fluids is readily biodegradable,” she said. While that might sound like a good thing, it can yield toxic byproducts.

Produced water can trigger chemical reactions that release arsenic, iron, and other toxic trace metals, Cozzarelli said.

These issues transcend distinctions between fracking and conventional drilling, she said.

So does the problem of chemical “transformation.” When the hundreds of added and natural chemicals break down or interact with each other under the extreme conditions of both fracking and oil extraction, any number of unknown compounds could emerge as byproducts, scientists who have studied the chemicals said. Yet the water board did not account for these compounds.

In a 2020 Environment International review of nearly 130 studies of chemicals detected in produced water, only 7 percent of those detected had been reported to the national fracking chemical registry. That’s likely partly because what comes out of a well in wastewater bears little resemblance to what goes in. 

Lead author Cloelle Danforth, a senior health scientist with the Environmental Defense Fund, cautioned that the studies mostly analyzed produced water from the Northeast’s Marcellus Shale, “because that’s where people had access.”

Danforth said she doesn’t know how the additives interacted with naturally occurring chemicals or how they may have changed under heat and pressure. “That’s why we focused on wastewater rather than what’s put ‘downhole,’ because we don’t know what’s going to change.”

The water board, by contrast, relied on its list of chemicals used to extract oil to conclude in September that growing crops with oil wastewater poses “no identifiable increased health risks.” 

A large share of the pistachios and almonds that feed the nation are grown in Kern County. About 95,000 acres of those nuts, along with carrots, citrus, grapes and a handful of other crops, are grown with produced water, even though questions about its safety remain.  

Conventional oil drilling dominates fossil fuel development in California, with fracking estimates ranging from 2 percent to 20 percent of production and the state vowing to ban new fracking by 2024. Yet California required only the fracking operations to disclose chemicals they used when it passed the nation’s first major fracking law in 2013. 

Regulating fracking was a “really important” first step, said Damon Nagami, senior attorney with the Natural Resources Defense Council. “But California’s regulations still have large gaps that we’ve been pushing the state to close for years.”

Nagami said he recognizes the potential for reusing produced water in drought-plagued states like California. “But this oil and gas wastewater shouldn’t be allowed to irrigate crops unless there’s conclusive proof that the practice is safe for consumers and farmworkers.”

Underestimating Risks of a Toxic Stew

Last year, an independent scientific organization that advises California policymakers issued a study of the quality of produced water. Information on toxicity is reported only for “pure compounds,” scientists with the California Council on Science and Technology, or CCST, noted, even though most chemical additives are mixed onsite or supplied premixed, and can react with other chemicals in the well.

If exposure to these chemicals does occur, the scientists warned, “it is unlikely that it will be limited to a single chemical compound.”

Yet standard toxicity tests don’t account for chemical interactions or for how complex mixtures of oil and gas additives interact with the suite of naturally occurring compounds in petrochemical reservoirs. Such an assessment, the scientists concluded, is critical to understanding chemical hazards and risks associated with reusing produced water.

Shonkoff, a lead author on the report, raised these concerns at the Central Valley water board’s food safety meetings. Yet the board proceeded with a plan to test for individual chemicals. 

In assuring the public that it’s safe to grow crops with produced water, the water board  directed GSI Environmental, the consulting firm with strong ties to the oil and gas industry, to compile a list of chemicals in produced water, identify those likely to pose a threat to human health and determine whether chemicals on the list contaminated crops irrigated with the wastewater. 

GSI tested almonds, carrots, oranges and 10 other crops grown with produced water for more than 100 individual chemicals. GSI—and subsequently the water board—concluded that any contaminants detected in the crop samples, including arsenic, cadmium and lead, fell within the normal range of concentrations for food. 

The board had asked GSI to focus on crops, even though Shonkoff and the board’s own scientific advisor warned that such results would be of limited value, due partly to inadequate analysis tools for testing crops, a letter obtained by Inside Climate News through a public records request shows. It would be better, they advised, to track the buildup of chemicals in water, soil and plants. The board did not take that advice. 

An even bigger problem, as the CCST report made clear, stems from the limits of testing single chemicals. Judging the toxicity of a sample with traces of scores of potentially toxic contaminants by testing one chemical at a time is like looking at the ceiling of the Sistine Chapel through a straw: it’s impossible to see the whole picture.

It’s hard to overstate the importance of looking at mixtures, said Thomas Zoeller, an emeritus biology professor at the University of Massachusetts who’s long studied contaminants’ effects on brain development. “When you begin to do that, you begin to see that what has been considered the safe level for a variety of individual chemicals is really not safe in the context of the other chemicals that we’re being exposed to.”

Andreas Kortenkamp, a professor of human toxicology at Brunel University London, just wrapped up two big projects investigating mixture effects.  

The first study evaluated more than two dozen chemicals that impair semen quality, and the second analyzed 20-plus chemicals linked to cognitive decline. Many of the chemicals that affect cognition, including arsenic, cadmium and lead, taint Kern County’s produced water. 

When you evaluate chemicals as mixtures, “the risk estimates go up massively,” said Kortenkamp, a world authority on the combined health effects of mixtures of environmental pollutants. The results have not been published yet.

Chemicals that appear benign on their own at barely detectable levels can produce harm when they interact with other chemicals by magnifying toxicity because they work in similar ways and produce similar effects, or by acting through different mechanisms that cause the same effects.

Yet regulators, like those at the water board, rarely evaluate chemical mixtures, and even when they do, they don’t group chemicals together that produce the same harms in different ways. That narrow approach keeps the number of chemicals that are evaluated together “as small as possible,” Kortenkamp said, even though “living organisms don’t care so much about mechanisms and our ideas about mode of action.” 

In 2015, Chris Kassotis, an endocrine toxicologist at Wayne State University, reported in the journal Endocrinology the first experimental evidence that a mixture of chemicals used in fracking and detected in fracking wastewater can disrupt hormones at levels found in the environment. He’s since published several studies focusing on a mixture of 23 chemicals commonly found in wastewater that exert potent effects on several hormones, chemical messengers that are critical for health. 

Fifteen of the chemicals in Kassotis’ endocrine-disrupting cocktail are used by Kern County oil companies that supply irrigation water.

In one study, Kassotis collected samples of produced water from fracking well pads, storage tanks and contaminated ponds in Colorado and West Virginia. The samples, like his concoction, triggered metabolic changes associated with obesity. Over the past several years, Kassotis and his colleagues have shown that his chemical stew alters immune function, reduces sperm counts and causes precancerous lesions in adult animals exposed to the chemicals in the womb.  

Kassotis can’t say whether the 15 chemicals used in conventional operations in Kern County could produce the same effects he’s seen with his own mixture. But he will say that his lab has demonstrated that all 15 chemicals produce toxic effects that are relevant to humans. 

Chemical Time Bombs

One thing that’s become clear to Thomas Borch after years of studying both conventional and unconventional oil and gas development is how much chemical use—and toxicity—varies by extraction site. “They all have their own magic, chemical packets to optimize oil and gas extraction,” said Borch, a professor at Colorado State University and an expert on produced water for beneficial reuse. “You might even see a lot of differences from well to well, depending on the company.”

In a 2020 study of a conventional oil field in Wyoming, Borch showed that lightly treated produced water that was discharged into a stream increased mutation rates in several lab tests, signaling cancer risk. The water contained dozens of toxic chemicals, Borch reported in in the journal Science of the Total Environment. 

Produced water from conventional wells in Kern County contains many of the chemicals Borch detected, including cancer-causing arsenic and cadmium and four other known or probable human carcinogens.

Borch believes compounds in the petroleum itself are driving the mutations. “It’s very well known that polycyclic aromatic hydrocarbons are carcinogens,” he said, referring to compounds found in crude oil. 

Nearly a dozen of those hydrocarbons are present in Kern County’s produced water. All are listed as priority pollutants by the Environmental Protection Agency, due to their adverse effects on human health, environmental persistence,  reactivity and “ability to transform into more active species.”

Arsenic occurs naturally in soils and in petroleum hydrocarbons, and taints the  groundwater in many parts of California, a result of the gradual degradation of hydrocarbons over time. “But once you bring that water up to the surface,” the USGS´Cozzarelli said, “there’s nothing natural about it.”

One of the biggest concerns for Zoeller, of the University of Massachusetts, is what he calls “invisible outcomes.” It’s possible to cause harmful effects that span generations, he said, by exposing pregnant mice to such low levels of a contaminant “that nobody would be able to measure it.”

If somebody doesn’t die right away from chemicals you can’t trace, but then suffers from chronic or deadly diseases later in life attributable to the chemicals, that’s an invisible outcome, Zoeller said. When it comes to growing crops with produced water, “you may not be able to say that this is going to be harmful, but you sure as hell can’t say it’s going to be safe.”

Growing crops with produced water, Kortenkamp said, “is a massive dissipation of further chemicals into the environment and into our lives without really asking or consulting us, when the baseline problem is already pretty serious.”

The chemicals used in Kern County have different chemical properties that affect how long they persist in the environment. Many will stick to soil, but then slowly seep into aquifers or drinking water, Kortenkamp said. “You’re just deliberately bringing out a cocktail of chemicals into the environment. It’s a time bomb.” 

Over and over, he said, chemicals once considered safe, simply because scientists lacked good methods to study them, prove dangerous years after they’ve become ubiquitous. “You see most of the hazards and risks after they’ve materialized through the study of human populations,” Kortenkamp said. “By then, it’s too late.”