Altered Sex Ratio at Birth with Maternal Exposure to Dioxins in Vietnamese Infants.

Excess female births (lower sex ratio at birth) associated with paternal exposure to 2,3,7,8-tetrachlordibenzo-p-dioxin (TCDD) have been reported in Italy. However, no significant effects of maternal TCDD exposure on the sex ratio were reported. We investigated the effects of maternal TCDD exposure and the toxic equivalent quantity of polychlorinated dibenzo-p-dioxins/dibenzofurans (TEQ-PCDD/Fs) on the sex ratio at birth in 576 Vietnamese infants from three birth cohorts. TCDD and TEQ-PCDD/Fs in breast milk were stratified (low, mild, moderate, and high) as maternal exposure markers. Logistic regression analysis was used to investigate associations between female birth and dioxin exposure groups after adjusting for confounders. In sprayed and unsprayed areas, adjusted odds ratios (ORs) of female birth (reference: low-TCDD group) were 2.11 in the moderate-TCDD group and 2.77 in the high-TCDD group, which were significantly associated with increased TCDD exposure. In sprayed areas, a significantly increased OR in the high-TCDD group was observed. No significant associations, however, were found between having a girl and TEQ-PCDD/F levels. These results suggest that maternal TCDD exposure may alter the sex ratio at birth among Vietnamese residents of areas with high dioxin contamination.

Impact of dioxin exposure on brain morphometry and social anxiety in men living in the most dioxin-contaminated area in Vietnam.

BACKGROUND: Previously, we reported that the global brain volume was significantly higher in men with estimated perinatal dioxin exposure in Vietnam. In this study, we aimed to clarify which brain lobes, consisting of several gyri, contributed to the increased global brain volume. We then analyzed associations between changes in brain volume and social anxiety symptoms to investigate the role of structural changes of the brain on social anxiety following perinatal dioxin exposure. METHODS: Thirty-three men living near the dioxin-contaminated Bien Hoa airbase, underwent MRI examination. The regional gray matter volumes were extracted using the SPM12 in a MATLAB environment, and compared between subgroups with and without perinatal dioxin exposure estimated from their maternal residency in Bien Hoa during pregnancy. The social anxiety questionnaire for adults (SAQ-A30) was used to assess social anxiety. RESULTS: In both hemispheres, higher gray matter volume in the frontal and temporal lobes, particularly in the superior frontal gyrus, superior temporal gyrus, and temporal pole were found in men with perinatal dioxin exposure. Superior temporal gyrus volume was significantly higher in men with perinatal exposure also after adjusting for reduction of its volume associated with increasing 1,2,3,7,8-PentaCDD levels in blood. Increased volume of these gyri, which showed higher volume in men with perinatal exposure, was associated with increased SAQ-A30 scores. CONCLUSION: Perinatal dioxin exposure may increase the brain volume of gyri involved in social behavior, which was associated with increased social anxiety symptoms, suggesting functional effects accompanied the morphological effects of dioxin exposure.

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in blood samples from historically herbicide-sprayed areas and rural and industrialized unsprayed areas in Vietnam.

We investigated dioxin concentrations in the blood of residents living in areas with different sources of dioxin pollution in Vietnam. A total of 823 individual blood samples were collected in 2014-2015 from residents of 16 provinces in Vietnam who were born between 1972 and 1976, and who lived in rural unsprayed areas (the control area), industrialized unsprayed areas (the industrialized area), and areas in which herbicides were sprayed during the Vietnam War (the sprayed area). After blood collection, pooled samples were obtained by combining 10-25 individual samples by age and sex for each area. A total of 6, 10, and 26 pooled blood samples were obtained for the control area, industrialized area, and sprayed area, respectively. The concentrations of 17 polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans were quantified in each pooled blood sample. The concentrations of TCDD, 1,2,3,7,8,9-HxCDD, 1,2,3,7,8-PeCDF, and OCDF were significantly higher in the sprayed area than in the unsprayed area, which comprised the control and industrialized areas. The toxic equivalents of PCDDs, TCDD, 1,2,3,7,8-PeCDF, and 1,2,3,6,7,8-HxCDF were significantly higher in the sprayed area than in the control area. No significant difference in dioxin concentration was found between the sprayed and industrialized areas after adjusting for sex. The 1,2,3,6,7,8-HxCDF concentration was significantly higher in the industrialized area than in the control area. The findings indicate that there are different dioxin congener blood profiles in residents of industrialized areas and areas in which herbicides were historically sprayed during the Vietnam War.

Neurodevelopmental Effects of Perinatal TCDD Exposure Differ from Those of Other PCDD/Fs in Vietnamese Children Living near the Former US Air Base in Da Nang, Vietnam.

This study reports that children exposed to 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD), the major toxin in Agent Orange, from the breast milk of mothers residing near the former Da Nang US air base in Vietnam may have specific alterations in higher brain functions, resulting in social and communication deficits, including autism spectrum disorder (ASD). After the age of 8 years, girls with high TCDD showed increased attention deficit hyperactivity disorder (ADHD)-like behaviors and altered mirror neuron activity, which is often observed in children with ASD. However, no significant relationship between autistic traits and toxic equivalency values of polychlorinated dibenzodioxins and polychlorinated dibenzofurans (TEQ-PCDD/Fs) was found in these children. Notably, boys with high levels of TEQ-PCDD/Fs showed poor language and motor development in the first 3 years of life, although boys with high TCDD levels did not. However, at 8 years of age, boys with high TCDD showed reading learning difficulties, a neurodevelopmental disorder. These findings suggest that perinatal TCDD exposure impacts social-emotional cognitive functions, leading to sex-specific neurodevelopmental disorders-learning difficulty in boys and ADHD in girls. Future studies with a greater number of children exposed to high levels of TCDD are necessary to estimate the threshold values for neurodevelopmental effects.

Dioxin Congener Patterns in Breast Milk Samples from Areas Sprayed with Herbicide during the Vietnam War 40 Years after the War Ended.

Large amounts of herbicides containing polychlorinated dibenzo-p-dioxins and dibenzo-furans (PCDD/Fs) were sprayed in South Vietnam during the Vietnam War. Levels of PCDD/Fs in the environment of South Vietnam remained high even 40 years later. A total of 861 breast milk samples (597 from three areas sprayed with herbicides, Quang Tri, Da Nang, and Bien Hoa, and 264 from three unsprayed areas in North Vietnam) were collected between 2007 and 2015 and the PCDD/F concentrations in the samples were determined. Levels of TEQ-PCDD/Fs and 17 PCDD/F congeners were higher in the sprayed area samples than the unsprayed area samples. We found particular PCDD/F congener patterns for different areas. High tetrachlorodibenzo-p-dioxin (TCDD) concentrations were found in Bien Hoa, high TCDD and 1,2,3,6,7,8-hexadibenzo-p-dioxin concentrations were found in Da Nang, and high 1,2,3,4,6,7,8-heptadibenzo-p-dioxin concentrations were found in Quan Tri. High 1,2,3,4,7,8-hexadibenzofuran and 1,2,3,4,6,7,8-heptadibenzofuran concentrations were also found in Da Nang and Quang Tri. However, breast feeding may have caused associations between the TCDD and polychlorinated dibenzofuran congener concentrations. Advanced statistical analysis will need to be performed in future to assess the characteristic PCDD/F congener profiles in breast milk samples from areas of Vietnam previously sprayed with herbicides.

Perinatal Dioxin Exposure and Attention Deficit Hyperactivity Disorder (ADHD) Symptoms in Children Living in a Dioxin Contamination Hotspot in Vietnam.

We examined children in Da Nang, a dioxin contamination hotspot in Vietnam, twice at 5 and 8 years of age, and investigated sex- and age-dependent differences in the effects of dioxin exposure on attention deficit hyperactivity disorder (ADHD) symptoms. We also studied autistic traits in children with ADHD symptoms. A total of 163 children participated in follow-up surveys at 5 and 8 years of age and were included in the present analysis. ADHD symptoms were assessed using an ADHD rating scale with inattention and hyperactivity-and-impulsivity (hyperactivity) subscales. Autistic behaviors were evaluated using the Autism Spectrum Rating Scale (ASRS). Perinatal dioxin exposure was indicated by dioxin levels in maternal breast milk. In boys, hyperactivity scores were significantly higher in the high 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) group only at 5 years of age. In girls, hyperactivity scores at 8 years of age were significantly higher in the high TCDD group, which was significantly associated with those at 5 years of age. In girls, ASRS unusual behavior scores were significantly higher with higher TCDD exposure and hyperactivity scores at 8 years of age. These results suggest that high perinatal TCDD exposure may increase ADHD likelihood and autistic traits, particularly in girls of 7-8 years of age.

Effect of Perinatal Dioxin Exposure Originating from Agent Orange on Gaze Behavior in 3-Year-Old Children Living in the Most Dioxin-Contaminated Areas in Vietnam.

We investigated the effect of perinatal dioxin exposure indicated by dioxins in breast milk on children's gaze behavior. We studied 142 children aged 3 years from the 2012 Bien Hoa birth cohort in a hotspot of dioxin contamination in Vietnam. Children's faces were viewed using the eye-tracking method. Associations between gaze behavior of faces and neurodevelopmental indices and head circumference were analyzed to determine whether poor gaze behavior indicates increased autistic traits in these children. The gaze fixation duration on facial areas when viewing 10 still images of children was calculated as the gaze behavior index. Autistic behavior was assessed using the Autism Spectrum Rating Scale, and language development was evaluated by the Bayley Scales of Infant and Toddler Development, Ver. 3. The face fixation duration (%) significantly decreased as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) concentrations increased in a dose−effect manner in girls, which suggested atypical gaze behavior for watching human faces. Furthermore, these girls with atypical gaze behavior showed lower social communication scores and smaller head sizes, suggesting increased autistic traits in girls. In conclusion, our findings show sex-specific effects (girls > boys) of perinatal TCDD exposure on gaze behavior in young children.

Effects of perinatal dioxin exposure on mirror neuron activity in 9-year-old children living in a hot spot of dioxin contamination in Vietnam.

BACKGROUND: For 8 years, we have followed up a birth cohort comprising 241 mother-and-infant pairs living around the Da Nang airbase, a hot spot of dioxin contamination in Vietnam, and have reported the impacts of perinatal dioxin exposure on the neurodevelopment of children at various ages. In the present study, 9 years after birth, we investigated the effects of perinatal dioxin exposure on mu and theta rhythms by analyzing EEG power during the execution and observation of hand movements, which indicate mirror neuron system activity. METHODS: One hundred fifty-five 9-year-old children (86 boys and 69 girls) from the Da Nang birth cohort participated in the EEG examination with free viewing of hand movements. The dioxin levels in their mothers' breast milk, measured 1 month after birth, were used as perinatal dioxin exposure markers. A log transform of the ratio of EEG power during execution or observation of the hand movements relative to the power during observation of a bouncing ball for theta and mu rhythms was used to evaluate mirror neuron activity. RESULTS: In both brain hemispheres, the log power ratio in the theta band was significantly higher (i.e., less reduction of power) during observation of hand movements in girls exposed to high levels of TCDD. In boys, however, dioxin congeners other than TCDD, including HxCDDs and several PCDF congeners, contributed to increased log power ratios in the theta band. Particularly for PCDF congeners, the log power ratios in the lowest group among 4 exposure groups were lowest and significantly increased (i.e., decreasing reduction of power) with increasing dose. CONCLUSION: Perinatal TCDD exposure may influence the mirror neuron system of the brain, which plays an important role for social-emotional behavior in children, particularly in girls living in a hot spot of dioxin contamination in Vietnam.

Effects of perinatal dioxin exposure on neonatal electroencephalography (EEG) activity of the quiet sleep stage in the most contaminated area from Agent Orange in Vietnam.

OBJECTIVE: To investigate the effects of perinatal dioxin exposure indicated by dioxins in breast milk on neonatal electroencephalography (EEG) power in the quiet sleep stage, and associations with neurodevelopmental outcomes at 2 years of age. STUDY DESIGN: Fifty-one mother-newborn pairs were enrolled for neonatal EEG analysis in the quiet sleep stage from a birth cohort recruited at a prefecture hospital in Bien Hoa city, Vietnam. Relative EEG power in intra-burst-intervals and high-voltage-bursts in the trace alternant pattern were computed from EEG data during the quiet sleep stage. Forty-three mother-child pairs participated in a 2-year follow-up survey to examine neurodevelopment using the Bayley-III scale and gaze behavior exhibited by fixation duration on the face of a child talking in videos. The general linear model and regression linear model were used for data analysis after adjusting for confounding factors. RESULTS: Perinatal dioxin exposure, particularly 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure, influenced relative EEG power values mainly in the intra-burst-interval part of the trace alternant pattern in the quiet sleep stage. In intra-burst-intervals, decreased frontal delta power and increased frontal and parietal alpha power values in the left hemisphere and temporal beta power values in the right hemisphere were associated with increased TCDD exposure, with significant dose-response relationships. Almost none of the relative power values in these brain regions were associated with Bayley III scores, but relative delta power values were significantly associated with face fixation duration in left frontal and parietal regions at 2 years of age. CONCLUSION: Perinatal dioxin exposure influences neuronal activity in the quiet sleep stage, leading to poor communication ability indicated by gaze behavior in early childhood.

Effects of perinatal dioxin exposure on learning abilities of 8-year-old children in Vietnam.

BACKGROUND: We have followed a birth cohort from 2008 to 2009 near a dioxin-contaminated area of Da Nang, Vietnam, and investigated the effects of perinatal dioxin exposure on neurodevelopment from infancy to pre-school age. The present study aimed to investigate the effects of perinatal dioxin exposure on the learning abilities of the elementary-school children from the Da Nang birth cohort. METHODS: From 241 mother-infant pairs recruited at baseline (134 boys and 107 girls), 185 (76.8%) participated in a follow-up when the children were 8 years of age (108 boys and 77 girls). The children's perinatal dioxin exposure was estimated using the dioxin levels in their mothers' breast milk. The Colorado Learning Difficulties Questionnaire (CLDQ) was used to evaluate the children's learning difficulties. Math- and language-achievement scores were obtained using paper-based tests. Reading fluency was examined by having the children read passages in Vietnamese. RESULTS: In boys exposed to high levels of 2,3,7,8-tetrachlorodibenzodioxin (2,3,7,8-TetraCDD), CLDQ reading scores were significantly higher (worse), and language achievement scores were significantly lower. Boys exposed to high levels of 2,3,7,8-TetraCDD as well as high levels of the toxic equivalent (TEQ) of polychlorodibenzodioxins and polychlorodibenzofurans (PCDDs/Fs) had higher numbers of reading errors. Reading errors were higher and math achievement scores were lower with increasing concentrations of 1,2,3,4,7,8-HexaCDD and 1,2,3,4,6,7,8-HeptaCDD. In girls, no significant differences of any learning ability markers were found between high and low exposure groups to TEQ-PCDDs/Fs and these 3 congeners. CONCLUSIONS: Perinatal dioxin exposure may have adverse effects on the learning abilities of school children, especially boys.

Perinatal dioxin exposure and neurodevelopment of 2-year-old Vietnamese children in the most contaminated area from Agent Orange in Vietnam.

Bien Hoa airbase is the most contaminated area of dioxin contamination from Agent Orange in Vietnam, but little is known about the neurodevelopmental effects of perinatal dioxin exposure on children living nearby. We recruited 210 mother-newborn resident pairs in 2012 and 78 pairs in 2015 and followed them for 2 years to assess the children's neurodevelopment. As a control group, we used 120 mother-child pairs recruited in 2014 in the Ha Dong district of Ha Noi City, an unexposed area. Perinatal dioxin exposure levels were indicated by levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and toxic equivalency values of polychlorodibenzodioxins, polychlorodibenzofurans, and nonortho-polychlorinated biphenyls (TEQ-PCDD/Fs/noPCBs) in maternal breast milk. The Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III) were used to assess neurodevelopment, and scores in each domain were compared between children with different exposure levels using general linear regression models and stratification by sex. Decreased expressive and composite language scores in boys and gross motor scores in girls were found in children exposed to TCDD ≥ 5.5 (pg/g lipid) compared with children with TCDD < 1.8. However, in matched pair analysis between children with TCDD ≥ 5.5 and <1.8 (pg/g lipid), lower expressive and composite language scores in boys exposed to TCDD ≥ 5.5 were significant, but lower gross motor scores in girls did not reach statistical significance. In addition, significant association was found between levels of PCDD congeners other than TCDD and gross motor scores in boys. These findings suggest that perinatal exposure of TCDD and other PCDD congeners affects development of language and gross motor skills, respectively, in boys at 2 years of age exposed to dioxins originating from Agent Orange in Vietnam.