Autism, attention-deficit hyperactivity disorder, dyslexia, and other brain-related impairments have been diagnosed in millions of children in recent years. So it caused quite a stir last year when scientists identified chlorpyrifos as one of a dozen industrial chemicals fueling what they called a “pandemic of developmental neurotoxicity.”

Chlorpyrifos, an organophosphate pesticide, is classified as a neurotoxin because it disrupts neurotransmission, essentially how brain cells communicate. According to the National Pesticide Information Center, it is also the active ingredient in dozens of commercial pesticides, used to control a wide range of insects on crops like corn, almonds, apples, and oranges. According to Dow AgroSciences, which manufactures the pesticide Dursban using chlorpyrifos, it has been used on more than 50 agricultural crops.

Scientists’ neurodevelopmental concerns bolster efforts by the Pesticide Action Network (PAN) of North America and the Natural Resources Defense Council (NRDC)—which, in 2007, petitioned the U.S. Environmental Protection Agency (EPA) to ban chlorpyrifos on food. After eight years of “partial reports, missed deadlines, and vague promises of future action,” on August 10, the U.S. Court of Appeals for the Ninth Circuit made clear that the EPA must issue a full and final response to the petition by October 31.

Here’s what you need to know in light of the agency’s pending decision.

1. The EPA’s delay is “egregious.”

The delays prompted the U.S. Court of Appeals for the Ninth Circuit to take the unusual step of issuing a writ of mandamus to the EPA—essentially an order to, finally, make a decision. The wording of the court ruling [PDF] is striking: “EPA’s ambiguous plan to possibly issue a proposed rule nearly nine years after receiving the administrative petition is too little, too late. This delay is egregious and warrants mandamus relief.”

The ruling goes on to note that the delay is even more troubling given that, “EPA’s latest status report says that it has ‘concerns about the risks to farmworkers’ who are exposed to chlorpyrifos and states that ‘complex regulatory proceedings’ may be necessary.”