FRESNO, Calif. (AP) — California will tighten rules on how much farmers can use a common pesticide listed by the nation’s most productive agricultural state as a chemical known to cause cancer, regulators told The Associated Press on Thursday.

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The change doesn’t ban the pesticide Telone but creates a uniform rule for its application each year. The rule is drawing criticism from farmers who call it a key way to fight pests and fear the crackdown could lead to rising food prices.

The U.S. Environmental Protection Agency does not limit annual use of Telone, and California is the only state to restrict how much can be applied, said Charlotte Fadipe, spokeswoman for the state Department of Pesticide Regulation.

Growers inject Telone into the soil to kill pests before planting new orchards, vineyards and crops, such as sweet potatoes, carrots and strawberries.

It dissipates before crops are planted, and officials say harmful residue isn’t found in food. Rather, the fumes released when it is first applied can potentially cause health issues when people breathe it in over long periods of time.

Brian Leahy, director of the pesticide regulation department, announced the new rule that he said protects public health while allowing farmers to keep an important tool to kill pests. It goes into effect Jan. 1.

“I believe that overhauling the way we manage the pesticide, to be based upon a fixed amount, will be health-protective and simpler to manage,” Leahy said in a statement.

Now, farmers are allowed to use 90,250 pounds of the chemical each year within 6 square miles. They can carry over unused amounts from one year to the next — potentially doubling the base allowance. Until recently, they could also request a waiver from the state to use more than double the limit in a year, officials said.

The new rule limits the annual allowance to 136,000 pounds with no option for carrying over unused amounts. Farmers also will not be permitted to use the chemical in December, when California’s weather conditions make the air concentrations of the pesticide higher, officials said.

Merced sweet potato farmer Bob Weimer, criticized the stricter regulation, saying that Telone is an essential way to kill pests in California, which grows nearly half of the nation’s fruits, nuts and vegetables.

“It’s going to have an impact on consumers,” Weimer said. “There’s no question about it.”

Farmers like him are already limited in ways to kill pests, he said, adding that the change doesn’t make sense because his fields are miles from the nearest community.

Telone came under fire recently when the Oakland-based Center for Environmental Health sued its maker, Dow Agro-Sciences LLC. The health advocacy group contends that Dow fails to warn people in farming communities throughout California when Telone is being used, as required by law.

No direct cases of illness have been linked to Telone, but Caroline Cox, the centers’ researcher director, says the state’s job is to protect residents in the face of grave consequences.

“We can’t wait for that particular kind of information,” she said. “It takes so long, and it’s so hard to get.”