Canada's pesticide regulator repeatedly ignored red flags raised by its own scientists about the health risks posed by the pesticide chlorpyrifos, stalling a review of the pesticide for close to 20 years, documents obtained by the environmental group Ecojustice reveal. All the while, health concerns raised here at home and worldwide about the pesticide were never publicly shared. Commonly used on crops like wheat, in greenhouses and to kill mosquitoes, chlorpyrifos harms the nervous system and can cause brain defects in children. People are typically exposed by consuming contaminated food residue or water. Canadian farmers used on average 360,000 kilograms of the pesticide each year between 2008 and 2016, and a 2017 federal Canadian health survey found traces of chlorpyrifos on 99 per cent of foods sampled.