In the last three years, farmers in parts of California's Central Valley irrigated nearly 100,000 acres of food crops with billions of gallons of oil field wastewater possibly tainted with toxic chemicals, including chemicals that can cause cancer and reproductive harm, according to an Environmental Working Group (EWG) analysis of state data.

Since 2014, oil companies reported that they used more than 20 million pounds and 2 million gallons of chemicals in their operations, including at least 16 chemicals the state of California classifies as carcinogens or reproductive toxicants under the state's Proposition 65 law. That recycled wastewater was then sold to irrigation districts largely in Kern County. The Central Valley Regional Water Quality Control Board has allowed the practice for at least four decades and only recently required the oil companies and water districts to disclose the details.



EWG detailed its findings in a report released Wednesday, two days before a public meeting of an expert panel convened to study the practice's safety. Although scientists don't know whether using oil field wastewater to grow crops poses a health risk to people who eat the food, the water board has refused to halt the practice until the expert panel releases its findings.

"The overlap of fracking chemicals and the chemicals used in conventional drilling is troubling," said Bill Allayaud, EWG's California director of government affairs. "The water board should have thoroughly studied and assessed this practice before allowing it.

"No one should stop eating produce from California," said Tasha Stoiber, an EWG senior scientist and author of the report. "But there are too many unanswered questions about whether crops could take up the chemicals in the wastewater and whether that could harm people's health. The only way to know for sure if this practice is safe for consumers, farm workers and the environment is to conduct a thorough and independent study."

The water board convened the expert panel after the use of oil field wastewater for irrigation came to light last spring, sparking concern from environmental groups and the news media. But the panel found it couldn't do its job without knowing which chemicals were used in the oil fields or to treat the water before its sale to irrigation districts. In response, the water board ordered the oil companies to disclose their chemical use.

The companies submitted records for 198 commercial additives. But the names of about 40 percent of the chemical ingredients were withheld as "trade secrets," so a complete analysis remains impossible.

The water board says because of concerns about chemicals used in fracking fluids, no water from fracked oil wells is used for crop irrigation. But EWG's analysis found that about 40 percent of the chemicals identified from the oil company disclosures have also been used in fracking in California, raising the question of a double standard.

"The overlap of fracking chemicals and the chemicals used in conventional drilling is troubling," said Bill Allayaud, EWG's California director of government affairs. "The water board should have thoroughly studied and assessed this practice before allowing it. But even as it plays catch-up, it is contemplating additional proposals to expand the practice. Until the safety of the public and the environment can be assured, this is irresponsible."



The lightly treated wastewater is blended with fresh water and then applied to almonds, pistachios and citrus trees, along with grapes, carrots, beans, tomatoes and potatoes grown throughout Kern and Tulare Counties. To date, only three limited studies have been conducted, all by consultants paid by the oil companies or the irrigation districts that buy the wastewater, including one that draws conclusions based on only five water samples collected on a single day.

EWG recommends that until independent scientific studies, free from conflicts of interest, can say whether it is safe to irrigate food crops with wastewater from oil fields, the state should suspend existing permits and declare a moratorium on new projects.