Recycled wastewater from oil field fracking is being used to irrigate some crops in California. When those fruits and vegetables get to the supermarket, should you know which ones they are?

California Assemblyman Mike Gatto, JD (D-Glendale) thinks so. “No one expects their lettuce to contain heavy chemicals from fracking wastewater,” he said in a news release. “Studies show a high possibility that recycled oil-field wastewater may still contain dangerous chemicals, even after treatment.”

Gatto has introduced a bill to require the labeling of any food grown with such water, one that has fueled a debate over the safety of fracking wastewater.

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Fracking, aka hydraulic fracturing, is the process of drilling into the earth and pumping a mixture of water and chemicals into the rocks at high pressure to fracture the rocks, freeing natural gas.

Proponents of using the recycled wastewater say it saves water, of which the state is in desperately short supply. Opponents point out that fracking involves a wealth of toxic chemicals, and although California does check for levels of salt and a few other substances in wastewater used for irrigation, it does not test that wastewater for oil industry chemicals.

And that’s a real problem, opponents say, because studies suggest hundreds of the chemicals are harmful to human health. In an investigation of the health impacts of 353 chemicals used in natural gas operations, researchers found that more than 75 percent of the chemicals could harm sensory organs and the respiratory and gastrointestinal system. Between 40 and 50 percent could hurt the nervous system, the immune system and the cardiovascular system and kidneys, 37 percent could hurt the kidneys, and a quarter could cause cancer and genetic mutations, according to a 2011 study published in the journal Human and Ecological Risk Assessment.

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“Consumers have a basic right to make informed decisions when it comes to the type of food that ends up on the family dinner table,” explained Gatto. “Labeling food that has been irrigated with potentially harmful or carcinogenic chemicals, such as those in recycled fracking water, is the right thing to do.

The issue is especially timely in drought-stricken California, where recycling oil-field wastewater is becoming increasingly common. Chevron sells 21 million gallons of recycled oil-field water each day to farmers in California’s Kern County who use it on some 45,000 acres, according to a recent article in the Los Angeles Times.

A key question is whether treating the wastewater removes the chemicals or brings levels to a safe level. Recent reports have suggested it doesn’t.

Although wastewater treatment removes excess oil and puts the water through a cleaning process, the non-profit environmental organization Water Defense found high levels of potentially dangerous chemicals acetone and methylene chloride in the treated wastewater. And a July 2015 report from the California Council on Science and Technology concluded that testing and treating oil-field wastewater “may not detect or remove” hazardous chemicals from fracking. The report recommended a ban on the reuse of fracking wastewater, at least until testing shows water treatment can reduce the concentration of chemicals to a safe level.

Meanwhile, nothing prevents farmers from watering crops labeled “organic” with oil-field wastewater. 

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Daniel S. Levine is an award-winning journalist who heads the Levine Media Group and hosts The Bio Report and RARECast podcasts. He was an editor of The Burrill Report and worked for the Oakland Tribune, Adweek, the San Francisco Business Times and other publications.