Impacts of perinatal dioxin exposure on gaze behavior in 2-year-old children in the largest dioxin-contaminated area in Vietnam

Fifty-five children aged 2 years from a birth cohort in the largest dioxin-contaminated area in Bien Hoa city, Vietnam participated in this survey to examine gaze behavior. Exposure levels were indicated by 2,3,7,8-tetrachlorodibenzo-p-dibenzodioxin (TCDD) and toxic equivalent of polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran (TEQ-PCDD/Fs) levels in maternal breast milk. The percentage of the total fixation duration on the face (% Face), mouth (% Mouth), and eye areas (% Eyes) when viewing silent and conversation scenes was used as gaze behavior indices. When they reached 3-year-old, autistic behavior was assessed using the Autism Spectrum Rating Scale (ASRS). A general linear model adjusted for confounding factors was used to compare gaze indices and ASRS scores between high and low dioxin exposure groups. Effects of perinatal dioxin exposure on gaze behavior were found only when viewing conversation scenes indicated by lower % Face for boys in high TCDD exposure group and lower % Eyes for girls in high TEQ-PCDD/Fs group. Increased autistic traits showed by higher ASRS scores at 3-year-old were found in both gender in the high TCDD exposure group. These findings indicate that perinatal TCDD and TEQ-PCDD/Fs exposure may reduce gaze behavior in 2-year-old children, predicting increased autistic traits at 3-year-old.