[Update: On November 30, the state of California officially listed chlorpyrifos as a brain-harming pesticide, making it possible for the state to remove the insecticide from the market.]

A year and a half ago, the Environmental Protection Agency (EPA) announced it would ban the use of the neurotoxic insecticide chlorpyrifos on food crops. Then, at the end of March—reversing course on decades of agency science and a decision that was years in the making—EPA Administrator Scott Pruitt announced that the agency would not ban the pesticide after all.

In the wake of Pruitt’s decision, and given overwhelming scientific evidence of adverse impacts on children’s neurological development, environmental and farmworker advocates in California are calling on their state, which uses more chlorpyrifos than any other, to ban the insecticide. As it has for other environmental issues—air quality, for example—California could take action on chlorpyrifos that would have nationwide impacts.

Chlorpyrifos has long been on the radar of California’s environmental health advocates. Since 1999, University of California, Berkeley researchers have been studying the effects of organophosphate pesticides—including chlorpyrifos—on children in the state’s farming communities. They’ve consistently found that exposure, which often begins prenatally, is linked to lower IQ, cognition and attention problems, and other adverse effects. State data also shows children’s exposure to be widespread.

A 2014 California Department of Public Health report found chlorpyrifos among the top 10 pesticides used within a quarter-mile of schools in the 15 agricultural counties studied. This puts thousands of children at risk of exposure.

Approximately one million pounds of chlorpyrifos—about 20 percent of what’s used nationwide—are applied annually in California to dozens of food crops, including almonds, citrus, grapes, and broccoli. The greatest use is in agricultural counties, like Fresno, Kern, and Tulare counties, where homes and schools are often adjacent to agricultural fields. State air monitoring in several of these communities has found chlorpyrifos levels that exceed EPA safety targets by three to 44 times.

“It’s time to get it out of the fields,” said United Farm Workers national vice president, Erik Nicholson.

EPA’s Contradictory Decision

With adverse neurodevelopmental effects well documented, the EPA has been restricting chlorpyrifos’ use. Most indoor residential uses, and use on tomatoes, are now banned. Use on various other food crops is restricted. The EPA also requires buffer zones around public spaces and homes. And in its 2016 human health risk assessment, the agency concluded that chlorpyrifos may be causing neurodevelopmental problems at extremely low levels of exposure. The EPA has also found residues on food at levels far above what it considers safe.

These neurodevelopmental effects have been found in lab studies and long-term studies of children exposed to chlorpyrifos. Additional research has found physical alterations in the brains of chlorpyrifos-exposed children that correspond to learning and behavior disorders.

“These results are really very consistent,” said Irva Hertz-Picciotto, professor of public health at the University of California, Davis and director of the university’s Environmental Health Sciences Center. She calls the outcome of children’s exposure to neurotoxic chemicals like chlorpyrifos “a chronic, silent epidemic.”

The EPA’s current decision results from a 10-year legal process that began in 2007. In October 2015, the agency proposed (in a press release that is no longer available on the EPA’s website) to ban chlorpyrifos for food crops because cumulative food and drinking water exposures could exceed safety limits.

Now, under Pruitt, the EPA says more study is needed and chlorpyrifos’ safety doesn’t have to be reconsidered until 2022.

“I think this is a very unfortunate decision,” said Philip Landrigan, dean of global health and a pediatrics professor at Mt. Sinai Hospital in New York. “Not only is it scientifically wrong but it’s also morally wrong. And it shows a blatant disregard for a very strong body of science.”

Agricultural trade groups, including the American Farm Bureau Federation and Corn Growers Association, welcomed the EPA decision, as did Dow AgroSciences, a major chlorpyrifos producer.

California has Authority to Ban Chlorpyrifos

On March 31, Californians for Pesticide Reform held rallies protesting the EPA’s decision—and calling for a state ban on chlorpyrifos—in Salinas, Fresno, and other agricultural communities in the state. “California has the independent authority to ban chlorpyrifos here,” Natural Resource Defense Council (NRDC) senior scientist Miriam Rotkin-Ellman told Civil Eats. “What we need is for California to follow the science.”

In fact, California can do just that. If state authorities determine the science doesn’t support its use, state-level authorities have the authority to ban a pesticide. For example, due to concern for its toxicity to bees, California refused to allow the pesticide sulfloxaflor to be used in the same way the EPA did. And under the state’s safe drinking water law, California is in the process of listing glyphosate—the active ingredient in Roundup—as a carcinogen, a move that goes well beyond the EPA.

A California chlorpyrifos ban would be a powerful market signal, since the state grows more than a third of U.S. vegetables and two-thirds of U.S. fruits and nuts. It could also significantly reduce children’s exposures, given the proximity of California homes and schools to active farm fields.

“It’s my hope that our Governor will follow through on his promise to lead when the feds fail us,” said Lucia Calderon, Safe Ag Safe Schools coalition coordinator in California’s Monterey and Santa Cruz Counties.

The state’s chlorpyrifos restrictions already exceed federal requirements. “In California, the pesticide cannot be used without licensing, training, and oversight by a county agricultural commission,” explained California Department of Pesticide Regulation (CDPR) spokesperson Charlotte Fadipe. California growers must explain “when, where, and how they want to use the pesticide,” and obtain county permits. Some counties require buffers of up to 150 feet between pesticide application and schools, rivers, or other sensitive sites.

In January, CDPR announced it would increase air monitoring for pesticides, including chlorpyrifos. “California,” Fadipe explained, “is the only state that monitors air as part of its continuous reevaluation of pesticides to ensure the protection of workers, public health, and the environment.”

But environmental health advocates say more rigorous monitoring is warranted, given the high levels found in agricultural communities. They’d also like to see tighter restrictions on pesticide use around schools, including for chlorpyrifos, which can easily drift from where it’s applied. “It’s fairly clear that the buffer zones currently proposed are nowhere [near] what’s needed to protect against chlorpyrifos,” said Rotkin-Ellman.

“The implication of the EPA’s decision could be far-reaching and that concerns me,” said Brenda Eskenazi, director of the University of California Berkeley’s Center for Environment Research and Children’s Health, who has led groundbreaking research investigating organophosphate pesticides’ impacts on children’s health. “These chemicals are poison and we have enough doubt about their safety that we need to be reconsidering their use.”

As for the EPA decision, “It’s not over yet,” said Patti Goldman, managing attorney with Earthjustice, which is representing NRDC and PANNA in a lawsuit aimed at compelling the EPA to act rather than wait for more evidence. “The real tragedy,” said Goldman, is “as the delay keeps going on, more children are being exposed every year.”

“It’s an outrage that the science is being ignored at the federal level but a real travesty to have it ignored in the state when we know what’s at stake for children’s lives,” said Rotkin-Ellman.

Update: In a similar vein, the Food and Drug Administration in May 2017 declined to ban perchlorate in dry food packaging, despite research showing significant exposures and likely health impacts from the chemical, which is used as an anti-static agent in food packaging.

Editor’s note: This post has been updated to reflect the fact that sulfloxaflor is not a neonicotinoid pesticide, though it does also have significant negative impacts to bees, and that California significantly restricted but did not fully ban its use.