Nguyen Hung Minh

Determination of PCDD/Fs in breast milk of women living in the vicinities of Da Nang Agent Orange hot spot (Vietnam) and estimation of the infant's daily intake.

Seventeen toxic congeners of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were determined in breast milks using the high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) method. Twenty seven breast milk samples were collected from primiparae who have lived over 5 years in wards namely Chinh Gian, An Khe, Khue Trung, and Hoa Thuan Tay which are located near the Da Nang Agent Orange hot spot (the AO/Dioxin hot spot). The samples were then analyzed for PCDD/F residues in order to assess the human exposure to dioxins from the AO/Dioxin hot spot, especially health risk to the breast-fed infants. The average TEQ levels in the four studied cohorts ranged from 8.1 to 26 pg/g lipid, with the highest level up to 51 pg TEQ/g lipid found in the An Khe ward. The TEQ level was correlated with geographical position and ranking in the order of Khue Trung, Hoa Thuan Tay, Chinh Gian and An Khe. The mean estimated PCDD/Fs infants daily intake in the cohort of Khue Trung, Hoa Thuan Tay, Chinh Gian and An Khe was about 41, 122, 124, and 134 pg TEQ/kg bw/day, respectively, which are much higher than the tolerable daily intake proposed by the World Health Organization (4 pg TEQ/kg bw/day).

A relationship in adrenal androgen levels between mothers and their children from a dioxin-exposed region in Vietnam

Over the past decades, southern Vietnam has been burdened by dioxins from contaminated herbicides sprayed during the Vietnam War. In a previous study, we found that dioxin exposure decreased levels of salivary dehydroepiandrosterone (DHEA), an adrenal androgen, in 3-year-old children. In present study, to assess the relationship between adrenal hormones disruption in lactating mothers and in children, we compared mother-child pairs from dioxin- and nondioxin-contaminated regions. In 2010 and 2011, mother-child pairs from a dioxin hotspot region (n=37) and a non-contaminated region (n=47) were recruited and donated breast milk and serum samples for dioxin and steroid hormones determination. Mothers were 20-30years old and had given birth to their first child between 4 and 16weeks previously. One year later, saliva samples were collected from the children. Dioxin levels in breast milk were determined by gas chromatography/high-resolution mass spectrometry. Salivary DHEA, cortisol in children and androstenedione (A-dione), estradiol, cortisol, and DHEA in maternal serum were analyzed by liquid chromatography/tandem mass spectrometry. Concentrations of dioxin congeners in the hotspot region were 2- to 5-fold higher than in samples from the non-contaminated region. Salivary DHEA levels in children and serum A-dione levels in mothers were significantly higher in the hotspot region; no difference was found in the levels of other hormones. Moreover, there was a significant positive correlation between the elevated hormone levels in mothers and children (r=0.62, p<0.001). Several dioxin congeners exhibited strong significant dose-response relationships with salivary DHEA and serum A-dione levels. Our findings suggest that dioxin disrupts adrenal androgens in mothers and breastfeeding children through the same mechanism.

Androgen disruption by dioxin exposure in 5-year-old Vietnamese children: Decrease in serum testosterone level

Dioxins have been suspected to be potential substances causing endocrine disruptions in humans. We are conducting the research in one of three dioxin exposure areas (hotspots) in Vietnam. We previously reported that the salivary dehydroepiandrosterone (DHEA) level decreased in 3-year-old Vietnamese children and that it was significantly inversely correlated with polychlorinated dibenzodioxin/dibenzofuran levels in their mothers breast milk. In this study, we investigated the influence of exposure to dioxin on steroid hormone biosynthesis in the same children when they reached 5 years of age, focusing on androgens. Thirty-five and 50 mother-child pairs from dioxin hotspot and non-sprayed areas, respectively, participated in this study. Maternal breast milk was donated at 4 to 16 weeks postpartum in 2008 to measure dioxin levels by gas chromatography/high-resolution mass spectrometry. Serum was collected from 5-year-old children in 2013. Seven steroid hormones were measured by liquid chromatography/mass spectrometry. Most dioxin congeners in breast milk were 2- to 10-fold higher in the hotspot than in the non-sprayed area. DHEA and testosterone (T) were significantly lower in the hotspot and showed negative correlations with most dioxin congeners. Similar results were observed for the activities of cytochrome P450-17, 20 lyase (CYP17 lyase), and 17β-hydroxysteroid dehydrogenase (HSD). Conversely, the elevated androstenedione (A-dione) level and 3β-HSD activity in children from the hotspot were positively correlated with dioxin levels. Moreover, a positive correlation was shown between T and 17β-HSD. It is possible that dioxin inhibits 17β-HSD activity, leading to a decrease in the T level. Multiple regression analysis indicated that dioxin had a strong association with the DHEA, A-dione, and T levels. In conclusion, the present study suggests that dioxin is associated with low levels of DHEA and T and inhibition of the activity of steroidogenic enzymes such as CYP17 lyase and 17β-HSD in 5-year-old children.

Reply to the letter to the editor “TCDD and birth weight of Vietnamese infants”

Thank you very much for your comments on and interest in our article. We appreciate the opportunity to explain our study in more detail. First, regarding the small proportions of the total toxic equivalents (TEQs) that were attributable to TCDD in our study, it is true, as Dr. Boffetta and Dr. Scialli mentioned, that TCDD contributed only a small proportion of the total toxic equivalent (TEQ) concentration. We have previously published a paper entitled “Residual congener pattern of dioxins in human breast milk in southern Vietnam” (Tawara et al., 2011). We found a higher concentration of each congener in the herbicide-sprayed commune than in the non-sprayed commune, and we used cluster analysis to investigate the PCDD/DF congener patterns in the samples from the sprayed commune. The congener patterns were dominated by the more-chlorinated (hexa-, hepta-, and octa-chlorinated) PCDD/DF congeners. We have also previously determined PCDD/DF concentrations in serum from older Vietnamese men (Manh et al., 2014) living in the same areas as the subjects of this study. Older men are very different subjects to the lactating mothers who were the subjects of this study. In the serum samples from the older men, TCDD contributed 10.0% of the total PCDD/DF TEQ in the “hotspot region” and 13.4% in the control region. These contributions were relatively low and were similar to the contributions we found in our current study. The PCDD/DFs in milk and serum were determined using a GC-HRMS method, and this analytical method was validated. We cannot determine why TCDD contributed a small proportion of the total TEQ concentration. However, it has been more than 40 years since herbicides containing PCDD/DFs have been sprayed on the study area. The halflives of the different PCDD/DF congeners need to be taken into consideration. PCDD congeners with fewer chlorine substituents generally have shorter half-lives than PCDD congeners with more chlorine substituents. For example, 1,3,6,8TCDD, 1,3,7,9-TCDD, HpCDD, and OCDD in sediment have been found to have half-lives of 4.4 ± 1.7, 4.6 ± 1.9, 6.2 ± 3.1, and 6.0 ± 2.8 years, respectively (Segstro et al., 1995). Unfortunately, we cannot find any studies of biological half-lives of PCDD/DFs in Vietnam. Regarding recall bias, we collected a breast milk sample from each lactating mother and asked her to report the birth weight of her child at the same time. Therefore, no mother knew the PCDD/DF concentrations in her breast milk when she reported the birth weight of her child. If recall bias affected our study, as Dr. Boffetta and Dr. Scialli suggest, most mothers in the hotspot area would have emphasized the low birth weights of their children. However, we did not find any significant differences between the Responsible editor: Philippe Garrigues