Chronic Pesticide Exposure – An Attempt to Quantify the Neurobehavioral Impact

Introduction: There is little controversy about the health impact of acute poisonings due to pesticide exposure. Whether chronic pesticide exposure has a neurobehavioral impact even in the absence of acute poisonings remains a question of debate. A meta-analysis of occupational studies focusing organophosphates was conducted to quantify the evidence on this issue.  

Methods: Nineteen studies providing 21 samples were included. Twenty-four tests mainly covering the domains of attention, memory and motor performance were analyzed as they were employed in at least three studies. The meta-analysis used effect sizes to estimate the impact of exposure by a random effects model.  

Results: In a preliminary analysis negative overall effects were computed for all tests, p-values <= 0.05 were obtained for 12 tests. Significantly lower performances of the exposed individuals were related to attention and motor performance. Overall effect sizes of d>0.50 were calculated for five tests and indicated medium sized effects. Comparisons between the individual effect sizes of these studies and outcomes from studies investigating acute effects of poisoning showed different distributions in the size of effects. In the samples with acute poisoning 63% of the effect sizes were larger than d=0.50, while only 31% were larger in the samples under scrutiny here.  

Discussion: The analysis provided evidence that also chronic exposure in the absence of poisonings exerts negative effects on performance. In addition, an exposure-effect relationship was suggested. Despite the often insufficient exposure characterization it seems possible to investigate exposure-effect relationships, either by comparisons among groups of studies as shown here or by analyzing studies with differently exposed.