Evaluation of the dioxin-like toxicity in soil samples from Thua Thien Hue province using the AhR-CALUX bioassay - An update of Agent Orange contamination in Vietnam

A critical review on quantitative evaluation of aqueous toxicity in water quality assessment

Conventional chemical techniques have inherent limitations in detecting unknown chemical substances in water. As a result, effect-based methods have emerged as a viable alternative to overcome these limitations. These methods provide more accurate and intuitive evaluations of the toxic effects of water. While numerous studies have been conducted, only a few have been applied to national water quality monitoring. Therefore, it is crucial to develop toxicity evaluation methods and establish thresholds based on quantifying toxicity. This article provides an overview of the development and application of bioanalytical tools, including in vitro and in vivo bioassays. The available methods for quantifying toxicity are then summarized. These methods include aquatic life criteria for assessing the toxicity of a single compound, comprehensive wastewater toxicity testing for all contaminants in a water sample (toxicity units, whole effluent toxicity, the potential ecotoxic effects probe, the potential toxicology method, and the lowest ineffective dilution), methods based on mechanisms and relative toxicity ratios for substances with the same mode of action (the toxicity equivalency factors, toxic equivalents, bioanalytical equivalents), and effect-based trigger values for micropollutants. The article also highlights the advantages and disadvantages of each method. Finally, it proposes potential areas for applying toxicity quantification methods and offers insights into future research directions. This review emphasizes the significance of enhancing the evaluation methods for assessing aqueous toxicity in water quality assessment.

Gas chromatography-triple quadrupole mass spectrometry as a cost-effective method for the determination of polychlorinated dibenzo-p-dioxins and furans in contaminated soils

The aim of this study was to evaluate the performance of gas chromatography (GC)-triple quadrupole mass spectrometry (QqQ, MS/MS) as an alternative to the standard GC-high resolution mass spectrometry (GC-HR/MS) for soils contaminated with polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). GC-QqQ (MS/MS) using a dynamic multiple reaction monitoring (dMRM) mode was optimized for the quantitative analysis of 17 PCDD/Fs. A comparative study between GC-QqQ (MS/MS) and GC-HR/MS was carried out to validate the results of actual field soil samples. Although GC-HR/MS has excellent sensitivity and selectivity, the validation parameters obtained by GC-QqQ (MS/MS) also met the recommended criteria of the standard method. The results for total and I-TEQ (international toxic equivalent) value of the PCDD/F concentrations of over 86.0 pg/g and 4.3 pg I-TEQ/g, respectively, in actual field soil samples showed good agreement between the two methods, falling within ±25% relative difference. In consideration of the remediation goal (100 pg I-TEQ/g), GC-QqQ (MS/MS) can be an alternative cost-effective method for use in soil remediation research.

Impairment of the gut health in Danio rerio exposed to triclocarban

Triclocarban (TCC) is the principal component in personal and health care products because it is a highly effective, broad-spectrum, and safe antibacterial agent. TCC has recently been discovered in aquatic creatures and has been shown to constitute a health danger to aquatic animals. Although several studies have looked into the toxicological effects of TCC on a variety of aquatic animals from algae to fish, the possible gut-toxicity molecular pathway in zebrafish has never been thoroughly explored. We investigated the gut-toxic effects of TCC on zebrafish by exposing them to different TCC concentrations (100 and 1000 μg/L) for 21 days. We discovered for the first time that the MAPK and TLR signaling pathways related to gut diseases were significantly altered, and inflammation (up-regulation of TNF-α, IL-6, and IL-1β) caused by TCC was confirmed to be largely mediated by the aryl hydrocarbon receptor (AHR) and its related cytokines. This was found using the results of qPCR, a transcriptome analysis, and molecular docking (AHR, AHRR, CYP1A1 and CYP1B1). Furthermore, high-throughput 16S rDNA sequencing demonstrated that TCC exposure reduced the bacterial diversity and changed the gut microbial composition, with the primary phyla Fusobacteria and Proteobacteria, as well as the genera Cetobacterium and Rhodobacteraceae, being the most affected. TCC exposure also caused damage to the gut tissue, including an increase in the number of goblet cells and a reduction in the height of the columnar epithelium and the thickness of the muscular layer, as shown by hematoxylin and eosin staining. Our findings will aid in understanding of the mechanism TCC-induced aquatic toxicity in aquatic species.

Elevated congenital heart disease birth prevalence rates found in Central Vietnam and dioxin TCDD residuals from the use of 2, 4, 5-T herbicides (Agent Orange) in the Da Nang region

Congenital heart disease (CHD) birth prevalence rate in Da Nang City and two adjacent provinces in Central Vietnam reported by Giang et al. in 2019 was 20.09/1000 births, much higher than any CHD birth rates previously reported. In this current study, three physicians trained in pediatric cardiology reanalyzed and reclassified the Giang et al 2019 cardiac anomalies data, eliminating singular small PDAs and separating cardiac defects into 27 contemporary CHD subgroups. These CHD subgroups were then statistically compared with Liu et al. 2019 Global CHD birth prevalence study of Asian Low-Middle Income Countries (LMIC) CHD subgroup rate of 9.34/1000 births (95% CI 8.07-10.70). Despite applying newer diagnostic criteria and refining the cardiac anomalies data, the Da Nang region continued to show significantly (p<0.0001) elevated total CHD birth prevalence rates at 14.71/1000 births (95% CI 12.74-16.69) compared to the Asian LMIC CHD birth prevalence rate 9.34/1000 births. This finding raises the question of whether environmental persistence of the contaminant dioxin TCDD from 2,4,5-T herbicides (Agent Orange) used during the Vietnam War (1961-1971) in the Da Nang region might be a factor associated with elevated CHD birth prevalence, as it is not present in other LMIC surrounding Vietnam. We recommend testing of soils and sediments in rural and agricultural areas in Central Vietnam that received high volume applications of contaminated herbicides to assess the relationship of the higher CHD birth prevalence rate and the presence of residual dioxin TCDD. Enhanced fetal cardiac echocardiograpy in the region to screen for CHD would enable early interventions and could improve outcomes for infants and children.