Original Contribution to Environmental Toxicology: Characterizing the Neurotoxic Effects of Mixed Pesticide Exposure on Adolescent Brain Development in Agricultural Communities in Benue State

Adolescent brain development is a period of heightened neurological vulnerability to environmental neurotoxicants, and mixed organophosphate and pyrethroid pesticide exposure in Nigerian agricultural communities during this critical window may produce lasting neurodevelopmental impairment that has not been investigated in the sub-Saharan African literature. This dissertation characterizes the neurotoxic effects of chronic mixed pesticide exposure on adolescent brain development and cognitive function in farming communities in Benue State, North Central Nigeria. A prospective observational study was conducted with 480 adolescents aged twelve to seventeen years recruited from high-exposure farming communities and matched low-exposure comparison communities. Pesticide exposure was assessed through urinary dialkyl phosphate metabolites (organophosphate biomarkers) and pyrethroid metabolite profiling at three time points over eighteen months. Neurodevelopmental assessment employed a validated neuropsychological battery measuring executive function, working memory, processing speed, attention, and visuospatial reasoning. Electroencephalography was conducted on a sub-sample of sixty participants. Structural equation modeling tested the causal pathway from pesticide exposure biomarkers to neurocognitive outcomes, adjusting for socioeconomic status, nutritional status, educational opportunity, and sex. Results demonstrated significant inverse associations between cumulative organophosphate exposure and executive function (beta = -0.31) and working memory scores (beta = -0.28). EEG data showed altered frontal cortex activation patterns in high-exposure adolescents. The dissertation makes an original contribution to developmental neurotoxicology in the African context and provides empirical evidence for pesticide regulatory policy reform. Keywords: neurotoxicology, pesticide exposure, adolescent brain development, Benue State, cognitive function.