Environmental Protection Agency Administrator Scott Pruitt called chlorpyrifos “crucial to U.S. agriculture.” (Melina Mara/The Washington Post)

The new head of the Environmental Protection Agency refused Wednesday to ban a commonly used pesticide that the Obama administration had sought to outlaw based on mounting concerns about its risks to human health.

The chemical compound chlorpyrifos, also known as Lorsban, has been used by farmers for more than a half-century to kill pests on crops including broccoli, strawberries and citrus. The EPA banned its spraying indoors to combat household bugs more than a decade ago. But only in recent years did the agency seek to ban its use in agriculture, after mounting scientific evidence that prenatal exposure can pose risks to fetal brain and nervous system development.

Under President Barack Obama, the EPA proposed in 2015 to revoke all uses of chlorpyrifos on food — a move taken in response to a petition filed by the Natural Resources Defense Council and Pesticide Action Network North America. A federal judge had given the EPA until Friday to decide whether to finalize its ban of the pesticide.

On Wednesday, EPA Administrator Scott Pruitt decided the answer would be no.

“We need to provide regulatory certainty to the thousands of American farms that rely on chlorpyrifos, while still protecting human health and the environment,” Pruitt said in a statement. “By reversing the previous administration’s steps to ban one of the most widely used pesticides in the world, we are returning to using sound science in decision-making — rather than predetermined results.”

His statement argued that the “public record lays out serious scientific concerns and substantive process gaps in the proposal.”

Sheryl Kunickis, director of the Office of Pest Management Policy at the Department of Agriculture, agreed with the decision.

“It means that this important pest management tool will remain available to growers, helping to ensure an abundant and affordable food supply for this nation and the world,” she said in a statement. “This frees American farmers from significant trade disruptions that could have been caused by an unnecessary, unilateral revocation of chlorpyrifos tolerances in the United States.”

The chemical industry also pushed hard against a chlorpyrifos ban. Dow AgroSciences, which manufactures the pesticide, said late last year that the Obama administration’s assessment of its safety “lacks scientific rigor.” The company said it “remains confident that authorized uses of chlorpyrifos products, as directed, offer wide margins of protection for human health and safety.”

But dozens of scientific researchers, doctors and public health professionals had joined the environmental groups in urging the EPA to prohibit all use of chlorpyrifos.

“With each year of delay in canceling food tolerances and agricultural and other uses of chlorpyrifos, more children are unnecessarily at elevated risk for problems in learning, social skills, motor function, and other developmental domains,” a group of supporters wrote in a letter to the agency early this year. “We strongly urge EPA to finalize its assessment and cancel all remaining uses of chlorpyrifos as expeditiously as possible.”

Environmental activists were incensed Wednesday, saying that Pruitt had ignored substantial evidence of potential harms.

“The chance to prevent brain damage in children was a low bar for most of Scott Pruitt’s predecessors, but it apparently just wasn’t persuasive enough for an administrator who isn’t sure if banning lead from gasoline was a good idea,” Environmental Working Group president Ken Cook said in a statement. “Instead, in one of his first major decisions as head of the EPA, like a toddler running toward his parents, Pruitt leaped into the warm and waiting arms of the pesticide industry.”