Chlorpyrifos is an organophosphate insecticide. It is no longer registered for use inside homes except as bait in containers, but it is still used in agriculture, on golf courses, and to control public health pests such as fire ants. Chlorpyrifos blocks an enzyme that stops nerve cells from firing without stopping. If the enzyme is blocked, the nerves don't send normal signals, and the nervous system fails. Chlorpyrifos is used in agriculture, but it is no longer registered for residential use.
If you have questions about this, or any pesticide-related topic, please call NPIC at 1-800-858-7378 (8:00am - 12:00pm PST), or email at firstname.lastname@example.org.