Effects of Dioxin Exposure on Brain Regional Volumes of Fathers from Birth Cohorts in Herbicide-Sprayed and Unsprayed Areas in Vietnam.

We previously reported that the fathers of the Bien Hoa birth cohort in Vietnam showed altered brain regional gray matter volumes, as measured by magnetic resonance imaging, and social anxiety traits associated with perinatal dioxin exposure. In the present study, we aimed to compare gray matter volumes and social anxiety scale scores between dioxin-exposed fathers in Bien Hoa and unexposed controls in an unsprayed area. Fat-based bioassay-toxic equivalency levels in serum were used to indicate dioxin exposure in adulthood. Results indicated that the longer Bien Hoa residency group (≥30 years) exposed to dioxins during the perinatal period and early childhood showed higher gray matter volumes in the right and left temporal lobes than controls. However, no significant differences in temporal lobe gray matter volumes were found between the shorter Bien Hoa residency group (<30 years) and controls. Furthermore, the longer, but not shorter, Bien Hoa residency group showed higher social-emotional subscale scores than controls. Additionally, fat-based bioassay-toxic equivalency levels were inversely correlated with gray matter volumes in several right temporal gyri. These findings suggest biphasic life stage-dependent adverse effects of dioxin exposure: perinatal dioxin exposure increases gray matter volumes, especially in the temporal lobe, which leads to neurodevelopmental disorders with socio-emotional disturbances, whereas dioxin exposure after brain development decreases cortical gray matter volumes, possibly leading to cognitive dysfunction.