A Comprehensive Evaluation of Dioxins and Furans Occurrence in River Sediments from a Secondary Steel Recycling Craft Village in Northern Vietnam

This first study investigated the presence of dioxins and furans in river sediments around a craft village in Vietnam, focusing on Secondary Steel Recycling. Sediment samples were collected from various locations along the riverbed near the Da Hoi Secondary Steel Recycling village in Bac Ninh province. The analysis was conducted using a HRGC/HRMS-DFS device, detecting a total of 17 dioxin/furan isomers in all samples, with an average total concentration of 288.86 ng/kg d.w. The concentrations of dioxin/furan congeners showed minimal variation among sediment samples, ranging from 253.9 to 344.2 ng/kg d.w. The predominant compounds in the dioxin group were OCDD, while in the furan group, they were 1,2,3,4,6,7,8-HpCDF and OCDF. The chlorine content in the molecule appeared to be closely related to the concentration of dioxins and their percentage distribution. However, the levels of furan isomers did not vary significantly. The distribution of these compounds was not dependent on the flow direction, as they were mainly found in solid waste and are not water-soluble. Although the hepta and octa congeners had high concentrations, when converted to TEQ values, the tetra and penta groups (for dioxins) and the penta and hexa groups (for furans) contributed more to toxicity. Furthermore, the source of dioxins in sediments at Da Hoi does not only originate from steel recycling production activities but also from other combustion sites. The average total toxicity was 10.92 ng TEQ/kg d.w, ranging from 4.99 to 17.88 ng TEQ/kg d.w, which did not exceed the threshold specified in QCVN 43:2017/BTNMT, the National Technical Regulation on Sediment Quality. Nonetheless, these levels are still concerning. The presence of these toxic substances not only impacts aquatic organisms in the sampled water environment but also poses potential health risks to residents living nearby.

Developing an Improved Strategy for the Analysis of Polychlorinated Dibenzo-p-Dioxins/Furans and Dioxin-like Polychlorinated Biphenyls in Contaminated Soils Using a Combination of a One-Step Cleanup Method and Gas Chromatography with Triple Quadrupole Mass Spectrometry

Soils contaminated with polychlorodibenzo-p-dioxins (PCDDs), polychlorodibenzofurans (PCDFs), and dioxin-like (dl) polychlorinated biphenyls (PCBs), known as persistent organic pollutants (POPs), have garnered global attention because of their toxicity and persistence in the environment. The standard method for target analytes has been used; however, it is an obstacle in large-scale sample analysis due to the comprehensive sample preparation and high-cost instrumental analysis. Thus, analytical development of inexpensive methods with lower barriers to determine PCDDs/Fs and dl-PCBs in soil is needed. In this study, a one-step cleanup method was developed and validated by combining a multilayer silica gel column and Florisil micro-column followed by gas chromatography with triple quadrupole mass spectrometry (GC-QqQ-MS/MS). To optimize the separation and quantification of 17 PCDDs/Fs and 12 dl-PCBs in soils, the sample cleanup and instrumental conditions were investigated. For quantification method validation, spiking experiments were conducted to determine the linearity of the calibration, recovery, and method detection limit of PCDDs/Fs and dl-PCBs using isotopic dilution GC-QqQ-MS/MS. The applicability of the simultaneous determination of PCDDs/Fs and dl-PCBs was confirmed by the recovery of native target congeners and labeled surrogate congeners spiked into the quality-control and actual soil samples. The results were in good agreement with the requirements imposed by standard methods. The findings in this work demonstrated the high accessibility of the sample cleanup and analysis methods for the efficient determination of PCDDs/Fs and dl-PCBs in contaminated soils.

The role of endocrine disruptors in female infertility

INTRODUCTION

 According to the World Health Organization, infertility is a public health problem that affects around 48 million couples and 186 million individuals worldwide. Endocrine disruptors are one of the causes that raise more concern, given that it is a problem that has evolved with the progress of society. Many chemicals are used by food industry, entering food chain, and directly affecting human health. Endocrine disruptors have the capacity of interfering with the normal hormonal action, metabolism, and biosynthesis, which can lead to a variation of the normal hormonal homeostasis. Some of these endocrine disruptors are highly associated with diseases that are positively correlated with female infertility, such as polycystic ovary syndrome, endometriosis, irregular menstrual cycle and also disturbances on processes as steroidogenesis and development of the ovarian follicles.

RESULTS

The present literature review covers various aspects of the possible relationship between endocrine disruptors and female infertility. Bisphenol A and its metabolites, phthalates, dioxins, organochlorine, and organophosphate compounds are groups of chemicals considered to have the capacity to disrupt endocrine activity and herein addressed. The results reported in in vivo studies and in clinical trials addressing endocrine disruptors and female infertility were discussed as well as their possible mechanism of action.

CONCLUSIONS

Large, double-blind, placebo-controlled randomized clinical trials are needed to better understand the mechanisms of action of endocrine disruptors in female infertility, as well as the doses and frequency of exposure responsible for it.

Association of PKLR gene copy number, expression levels and enzyme activity with 2,3,7,8-TCDD exposure in individuals exposed to Agent Orange/Dioxin in Vietnam

2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) is the most toxic congener of dioxin and has serious long-term effects on the environment and human health. Pyruvate Kinase L/R (PKLR) gene expression levels and gene variants are associated with pyruvate kinase enzyme deficiency, which has been identified as the cause of several diseases linked to dioxin exposure. In this study, we estimated PKLR gene copy number and gene expression levels using real-time quantitative PCR (RT-qPCR) assays, genotyped PKLR SNP rs3020781 by Sanger sequencing, and quantified plasma pyruvate kinase enzyme activity in 100 individuals exposed to Agent Orange/Dioxin near Bien Hoa and Da Nang airfields in Vietnam and 100 healthy controls. The means of PKLR copy numbers and PKLR gene expression levels were significantly higher, while pyruvate kinase enzyme activity was significantly decreased in Agent Orange/Dioxin-exposed individuals compared to healthy controls (P < 0.0001). Positive correlations of PKLR gene copy number and gene expression with 2,3,7,8-TCDD concentrations were observed (r = 0.2, P = 0.045 and r = 0.54, P < 0.0001, respectively). In contrast, pyruvate kinase enzyme activity was inversely correlated with 2,3,7,8-TCDD concentrations (r = -0.52, P < 0.0001). PKLR gene copy number and gene expression levels were also inversely correlated with pyruvate kinase enzyme activity. Additionally, PKLR SNP rs3020781 was found to be associated with 2,3,7,8-TCDD concentrations and PKLR gene expression. In conclusion, PKLR copy number, gene expression levels, and pyruvate kinase enzyme activity are associated with 2,3,7,8-TCDD exposure in individuals living in Agent Orange/Dioxin-contaminated areas.

Assessment of PCDD/Fs Emission during Industrial-Organic-Solid-Waste Incineration Process in a Fluidized-Bed Incinerator

This study was conducted in a fluidized-bed incineration plant, evaluating the formation, emission and flux of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from industrial-organic-solid-waste (IW) incineration. The results revealed that both the total (or I-TEQ) concentrations of toxic and 136 total PCDD/Fs in flue gas (FG), fly ash (FA) and bottom ash (BA)were ramped up to a higher level than those during municipal-solid-waste (MSW) incineration. A possible explanation was the chlorine (Cl) content of IW. However, the emitted PCDD/Fs in FG (FA/BA) still fulfilled the criteria. Subsequently, similar distribution patterns of PCDD/F isomers were observed in subsystems, indicating a unified formation-pathway. De novo synthesis was detected as the dominant formation-pathway of PCDD/Fs, while high-temperature and precursor syntheses were excluded. DD/DF chlorination formed PCDD/Fs to some extent. Furthermore, the mass flow chart indicated that PCDD/Fs output in primary FG was significantly strengthened (>1000 times) by de novo synthesis, from 1.25 μg I-TEQ/h to 1.67 mg I-TEQ/h. With effective cleaning by APCS, 99.6% of PCDD/Fs in FG were purified. PCDD/Fs in the gas phase were finally emitted at a discharge rate of 7.25 μg I-TEQ/h. However, accumulated FA took most PCDD/Fs into the environment (>99%), reaching 3.56 mg I-TEQ/h.

Presence and risks of polycyclic aromatic hydrocarbons, dioxins and dioxin-like PCBs in dietary plant supplements as elucidated by a combined DR CALUX® bioassay and GC-HRMS based approach

Plant-based dietary supplements may contain undesirable contaminants such as polycyclic aromatic hydrocarbons, dioxins and dioxin-like polychlorinated biphenyls (dl-PCBs) due to the sources of raw materials or processing methods used. The presence of these contaminants in a series of herbal supplements sold on the Ghanaian market for improving sexual performance was examined using the DR CALUX^® bioassay in combination with GC-HRMS analysis. Overall, cell responses at 4 and 48 h exposure to extracts prepared without an acid-silica clean-up were relatively higher than the responses obtained from extracts prepared with an acid-silica clean-up. This indicated that the 40 supplements contained only low levels of stable aryl hydrocarbon receptor (AhR) agonists like polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dl-PCBs, while some contained substantial amounts of less stable AhR-agonists. Ten supplements selected for confirmation with GC-HRMS analysis contained PCDD/Fs and dl-PCBs at levels ranging from 0.01 to 0.19 pg toxic equivalent (TEQ)/g only, while the level of the sum of 4 polycyclic aromatic hydrocarbons (Σ4PAHs) representing less stable AhR agonists, ranged from not detected (ND) to 25.5 ng/g. These concentrations were in line with the responses observed in the DR CALUX^® bioassay. The concentration of PCDD/Fs and dl-PCBs corresponded to estimated daily intakes (EDIs) ranging from 0.01 to 1.20 pg TEQ/day, or 0.001 to 0.12 pg TEQ/kg bw/week for a 70 kg bw consumer, which was below the established tolerable weekly intake (TWI) of 2 pg TEQ/kg bw/week, thus indicating low concern for consumers' health. Similarly, the EDIs based on the detected Σ4PAHs in supplements ranged from 7.2 to 111 ng/day, or 0.1 to 1.6 ng/kg bw/day, which corresponded to MOE values above 10,000, indicating a low health concern.

α-Tocopherol Prevents Sperm Apoptosis and Necrosis in Rats Exposed to 2,3,7,8-Tetrachlorodibenzo-p-dioxin

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a persistent organic pollutant that induces overproduction of reactive oxygen species (ROS). Studies on avoiding the adverse effects of dioxin pollution exposure are needed in all aspects, including reproductive health. This study aimed to determine the effect of α-tocopherol on superoxide dismutase (SOD) and malondialdehyde (MDA) levels, live spermatozoa, apoptosis, and necrosis in male rats exposed to dioxin as a model. Thirty healthy 12-week-old male rats were randomly divided into five groups. Rats in the control group were given corn oil twice daily at 4-hour intervals. The remaining rats were given TCDD 700 mg/kg BW daily, followed by administration of corn oil and α-tocopherol at doses of 77, 140, and 259 mg/kg BW/d for T0, T1, T2, and T3 groups, respectively. The treatments were conducted for 45 days; all rats were euthanized to collect blood and testicular samples on day 46. The results showed that exposure of TCDD resulted in a decrease in SOD activity and live spermatozoa and increased MDA level and death, apoptosis, and necrosis of spermatozoa (T0) compared to the control (C) group (p < 0.05). The administration of α-tocopherol, starting from the doses of 77 (T1), 149 (T2), and 259 mg (T3) per kg BW, was sequentially followed by returning MDA levels, recovering SOD activities, and restoration in the percentage of living, dead, apoptotic, and necrotic spermatozoa, similar (p > 0.05) to those of the control group. It could be concluded that the administration of α-tocopherol resolves the harmful effects of TCDD on the viability of spermatozoa in rats as a model.

In silico prediction of nuclear receptor binding to polychlorinated dibenzofurans and its implication on endocrine disruption in humans and wildlife

Polychlorinated dibenzofurans (PCDFs) are known to cause endocrine disruption in humans and wildlife but the mechanisms underlying this disruption have not been adequately investigated. In this paper, the susceptibility of the endocrine system to disruption by PCDF congeners via nuclear receptor binding was studied using molecular docking simulation. Findings revealed that some PCDF congeners exhibit high probabilities of binding to androgen receptor in its agonistic and antagonistic conformations. In depth molecular docking analysis of the receptor-ligand complexes formed by PCDFs with androgen receptor in its agonistic and antagonistic conformations showed that, these complexes were stabilized by electrostatic, van der Waals, pi-effect and hydrophobic interactions. It was also observed that PCDF molecules mimic the modes of interaction observed in androgen-testosterone and androgen-bicalutamide complexes, utilizing between 65 and 83% of the amino acid residues used by the co-crystallized ligands for binding. This computational study suggests that some PCDF congeners may act as agonists and antagonists of androgen receptor in humans and wildlife via inapproprate binding to the receptor.

Phase distribution of PCDD/Fs in flue gas from municipal solid waste incinerator with ultra-low emission control in China

Polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) are the key pollutants of municipal solid waste incineration (MSWI). In this study, the characteristics of 17 toxic 2,3,7,8-substituted congeners in flue gas along six air pollution control devices (APCDs) were investigated in a 400 t/d moving grate furnace located in a typical megacity of Shenzhen, China. The phase distribution and removal efficiency of the different APCDs were analyzed, especially the effect of the selective catalytic reduction (SCR) device. The results showed that PCDD/F TEQs were 59.5%, 67.1%, and 72.5% partitioned into the gas phase (XAD-2 and condensed water) at the economizer outlet, fabric filter outlet, and stack, respectively. Furthermore, the three-year-old catalyst in the SCR tended to remove PCDDs, especially those in the solid phase (filter thimble). More importantly, the PCDF TEQs at the SCR inlet and outlet were 1.045 × 10^-3 and 1.568 × 10^-3 ng I-TEQ/Nm³, respectively, which meant that the SCR might be ineffective for PCDF TEQ removal. A continuous chlorination of lower chlorinated PCDD/Fs increased the ratio of PCDFs and PCDDs from 0.73 at the SCR inlet to 1.76 at the SCR outlet. This work indicated the asynchronized inefficient removal of PCDD/Fs and nitrogen oxide for this three-year-old catalyst. The obtained results provide suggestions for the entire process of curbing PCDD/F emissions and obtaining ultra-low emission from MSWI.

Long-term effects of thin layer capping in the Grenland fjords, Norway: Reduced uptake of dioxins in passive samplers and sediment-dwelling organisms

The Grenlandfjords in South East Norway are severely contaminated with dioxins from a magnesium smelter operated between 1950 and 2001. In 2009, the proposal of thin-layer capping as a potential mitigation method to reduce spreading of dioxins from the fjord sediments, resulted in the set-up of a large-scale field experiment in two fjord areas at 30 and 100 m depth. After capping, several investigations have been carried out to determine effects on benthic communities and bioavailability of dioxins. In this paper we present the results on uptake of dioxins and furans (PCDD/F) in passive samplers and two sediment-dwelling species exposed in boxcores collected from the test plots during four surveys between 2009 (after cap placement) and 2018. Sediment profile images (SPI) and analyses of dioxins revealed that the thin (1-5 cm) cap layers became buried beneath several centimeters of sediments resuspended from adjacent bottoms and deposited on the test plots after capping. Uptake reduction ratios (R) were calculated as dioxins accumulated in cores collected from capped sediments divided by dioxins accumulated in cores collected from uncapped reference sediments. Cap layers with dredged clay or crushed limestone had only short-term positive effect with R-values increasing to about 1.0 (no effect) 1-4 years after capping. In spite of the recontamination, cap layers with clay and activated carbon had significant long-term effects with R-values slowly increasing from 0.12-0.33 during the first three years to 0.39-0.46 in 2018, showing 54-61% reduced uptake of dioxins (PCDD/F-TE) nine years after capping with AC.

Severe dioxin-like compound (DLC) contamination in e-waste recycling areas: An under-recognized threat to local health

Electrical and electronic waste (e-waste) burning and recycling activities have become one of the main emission sources of dioxin-like compounds (DLCs). Workers involved in e-waste recycling operations and residents living near e-waste recycling sites (EWRS) are exposed to high levels of DLCs. Epidemiological and experimental in vivo studies have reported a range of interconnected responses in multiple systems with DLC exposure. However, due to the compositional complexity of DLCs and difficulties in assessing mixture effects of the complex mixture of e-waste-related contaminants, there are few studies concerning human health outcomes related to DLC exposure at informal EWRS. In this paper, we have reviewed the environmental levels and body burdens of DLCs at EWRS and compared them with the levels reported to be associated with observable adverse effects to assess the health risks of DLC exposure at EWRS. In general, DLC concentrations at EWRS of many countries have been decreasing in recent years due to stricter regulations on e-waste recycling activities, but the contamination status is still severe. Comparison with available data from industrial sites and well-known highly DLC contaminated areas shows that high levels of DLCs derived from crude e-waste recycling processes lead to elevated body burdens. The DLC levels in human blood and breast milk at EWRS are higher than those reported in some epidemiological studies that are related to various health impacts. The estimated total daily intakes of DLCs for people in EWRS far exceed the WHO recommended total daily intake limit. It can be inferred that people living in EWRS with high DLC contamination have higher health risks. Therefore, more well-designed epidemiological studies are urgently needed to focus on the health effects of DLC pollution in EWRS. Continuous monitoring of the temporal trends of DLC levels in EWRS after actions is of highest importance.

Health effects of nutrients and environmental pollutants in Baltic herring and salmon: a quantitative benefit-risk assessment

BACKGROUND

Health risks linked with dioxin in fish remain a complex policy issue. Fatty Baltic fish contain persistent pollutants, but they are otherwise healthy food. We studied the health benefits and risks associated with Baltic herring and salmon in four countries to identify critical uncertainties and to facilitate an evidence-based discussion.

METHODS

We performed an online survey investigating consumers' fish consumption and its motivation in Denmark, Estonia, Finland, and Sweden. Dioxin and methylmercury concentrations were estimated based on Finnish studies. Exposure-response functions for several health endpoints were evaluated and quantified based on the scientific literature. We also quantified the infertility risk of men based on a recent European risk assessment estimating childhood dioxin exposure and its effect on sperm concentration later in life.

RESULTS

Baltic herring and salmon contain omega-3 fatty acids and vitamin D, and the beneficial impact of these fishes on cardiovascular diseases, mortality, and the risk of depression and cancer clearly outweighs risks of dioxins and methylmercury in people older than 45 years of age and in young men. Young women may expose their children to pollutants during pregnancy and breast feeding. This study suggests that even in this critical subgroup, the risks are small and the health benefits are greater than or at least similar to the health risks. Value of information analysis demonstrated that the remaining scientific uncertainties are not large. In contrast, there are several critical uncertainties that are inherently value judgements, such as whether exceeding the tolerable weekly intake is an adverse outcome as such; and whether or not subgroup-specific restrictions are problematic.

CONCLUSIONS

The potential health risks attributable to dioxins in Baltic fish have more than halved in the past 10 years. The new risk assessment issued by the European Food Safety Authority clearly increases the fraction of the population exceeding the tolerable dioxin intake, but nonetheless, quantitative estimates of net health impacts change only marginally. Increased use of small herring (which have less pollutants) is a no-regret option. A more relevant value-based policy discussion rather than research is needed to clarify official recommendations related to dioxins in fish.