Simultaneous exposure to organophosphate and pyrethroid pesticides and effects on brain health in humans. A systematic review

Organophosphate and pyrethroid pesticides are widely used, but their combined effects on brain health remain unclear. This study analyzed observational research from 2014 to 2024 on their simultaneous exposure and its association with neurobehavioral, neurodegenerative, and neurological disorders through a systematic review following PRISMA guidelines in PubMed and Web of Science. Studies assessing co-exposure with validated methods and reporting brain health outcomes were included, while reviews, animal studies, and those without simultaneous exposure data were excluded. Risk of bias in cohort studies was evaluated using ROBINS-E. Of the 34 studies included, nine were cohort studies, four with low risk of bias and four with concerns related to sample size or exposure assessment. Three linked co-exposure to attention deficits and cognitive decline in children. Evidence on neurodegenerative diseases and autism spectrum disorder was inconsistent due to conflicting results. Cross-sectional and case-control studies associated co-exposure with depression and anxiety but lacked follow-up data. Variability in exposure assessment reduced comparability. Research remains limited, indicating possible neurodevelopmental effects and the need for standardized methodologies to refine risk assessment.