Organophosphate pesticides are the most widely used insecticides in the world; they are also (according to WHO), one of the most hazardous pesticides to vertebrate animals. While the toxic effects of high levels of organophosphates are well established, the effects of long-term low-level exposure are still controversial.
A meta-analysis involving 14 studies and more than 1,600 participants, reveals that the majority of well-designed studies undertaken over the last 20 years have found a significant association between low-level exposure to organophosphates and impaired cognitive function. Impairment was small to moderate, and mainly concerned psychomotor speed, executive function, visuospatial ability, working memory, and visual memory.
 . Neurobehavioral problems following low-level exposure to organophosphate pesticides: a systematic and meta-analytic review. Critical Reviews in Toxicology [Internet]. 2013 ;43(1):21 - 44. Available from: http://informahealthcare.com/doi/abs/10.3109/10408444.2012.738645?prevSearch=allfield%253A%2528%2527Neurobehavioral%2Bproblems%2Bfollowing%2Blow-level%2Bexposure%2Bto%2Borganophosphate%2Bpesticides%253A%2Ba%2Bsystematic%2Band%2Bmeta-analytic%2Breview%2527