Pesticide detection in postmortem serum, hair, and cerebrospinal fluid from cases of sudden unexpected death in infancy: a registry-based study

Abstract Sudden unexpected death in infancy (SUDI) is the leading cause of death between 1 month and 1 year in France. Its underlying mechanisms and the role of environmental exposures remain poorly understood. Pesticides may theoretically contribute to SUDI through neurotoxic pathways, but biomonitoring studies of SUDI cases are scarce, limiting etiological research. We aimed to assess pesticide exposure in SUDI cases and to explore potential factors associated with exposure across three biological matrices: hair, serum and cerebrospinal fluid (CSF). We analyzed pesticide exposure markers in post-mortem serum samples ( n = 98), hair ( n = 57), and CSF ( n = 97) from SUDI cases in France. Twenty-seven organochlorine pesticides were measured in serum and CSF, and 27 pesticides of various families in hair. We performed clustering based on exposure detection within each matrix and used logistic regression to assess associations between exposure clusters and several factors. Banned but persistent organochlorines, including p,p′-DDE, HCB, and β-HCH, were detected in serum. β-HCH and p,p′-DDE were also present in CSF. Hair samples revealed biomarkers of exposure to chlorpyrifos, fipronil, and cypermethrin/permethrin. Serum clusters with the highest detection were associated with higher birthweight and breastfeeding. CSF clusters with the highest detection were associated with breastfeeding and younger age at death. Conclusion : Although these findings do not yet clarify SUDI risk factors and mechanisms, they support the analytical feasibility of using post-mortem multi-matrix samples for pesticide exposure investigations. The detection of pesticides in the CSF of very young infants warrants further investigation of potential neurotoxicity. What is Known: • SUDI remains a leading cause of infant mortality, with largely unknown etiology. • Pesticide neurotoxicity is a plausible contributor, but data on pesticide exposure in SUDI cases are scarce. What is New: • Diverse pesticides were detected in the serum, CSF, and hair of SUDI cases. • These findings call for etiological studies on SUDI and pesticide exposure.