The 2022 world health organization reevaluation of human and mammalian toxic equivalency factors for polychlorinated dioxins, dibenzofurans and biphenyls

In October 2022, the World Health Organization (WHO) convened an expert panel in Lisbon, Portugal in which the 2005 WHO TEFs for chlorinated dioxin-like compounds were reevaluated. In contrast to earlier panels that employed expert judgement and consensus-based assignment of TEF values, the present effort employed an update to the 2006 REP database, a consensus-based weighting scheme, a Bayesian dose response modeling and meta-analysis to derive "Best-Estimate" TEFs. The updated database contains almost double the number of datasets from the earlier version and includes metadata that informs the weighting scheme. The Bayesian analysis of this dataset results in an unbiased quantitative assessment of the congener-specific potencies with uncertainty estimates. The "Best-Estimate" TEF derived from the model was used to assign 2022 WHO-TEFs for almost all congeners and these values were not rounded to half-logs as was done previously. The exception was for the mono-ortho PCBs, for which the panel agreed to retain their 2005 WHO-TEFs due to limited and heterogenous data available for these compounds. Applying these new TEFs to a limited set of dioxin-like chemical concentrations measured in human milk and seafood indicates that the total toxic equivalents will tend to be lower than when using the 2005 TEFs.

High mortality and high PCDD/Fs exposure among residents downwind of municipal solid waste incinerators: A case study in China

Studies on the human body burden of dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in populations around municipal solid waste incinerators (MSWIs) in China are limited. The objective of this study was to assess the potential adverse health effects of an 8-year MSWI on the surrounding population and identify possible exposure pathways. We hypothesized that the MSWI would result in different environmental impacts and population health outcomes between upwind and downwind of its 3 km vicinity. We conducted a 10-year retrospective mortality survey on the population surrounding the MSWI. Then, we selected 50 residents aged 50 years or older on each of the upwind and downwind sides of MSWI to test serum PCDD/Fs. Meanwhile, environmental and food exposures to PCDD/Fs were tested for selected residents. The age-adjusted mortality rates were significantly higher for residents downwind than upwind, but no significant difference was found in the standardized mortality ratio before and after the MSWI operation. The toxic equivalents (TEQ) and major congeners of PCDD/Fs were significantly higher in the sera of the downwind residents than in the upwind. The PCDD/Fs in air, soil, dust, and vegetables on the downwind side were not significantly different from those on the upwind side, but the mean concentrations of PCDD/Fs in downwind hen eggs was significantly higher than those from upwind. In conclusion, downwind residents living within 3 km of the MSWI had higher age-adjusted mortality and serum level of PCDD/Fs than upwind residents. This higher mortality rate among downwind residents was not associated with MSWI. However, the higher levels of PCDD/Fs in downwind hen eggs suggest that the downwind population dioxin exposure was related to their location.

Mortality in Yusho patients exposed to polychlorinated biphenyls and polychlorinated dibenzofurans: a 50-year retrospective cohort study

BACKGROUND

In 1968, the Yusho incident resulted in accidental exposure to polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans (PCDFs), and related compounds in Japan. This study updated the risk of mortality in Yusho patients.

METHODS

We obtained updated cohort data for all Yusho patients for the period 1968-2017. We calculated standardized mortality ratios (SMRs) for all-cause and cause-specific mortality over a 50-year follow-up period compared with the general population in Japan.

RESULTS

A total of 1664 Yusho patients with 63,566 person-years of follow up were included in the analysis. Among males, excess mortality was observed for all cancers (SMR: 1.22, 95% confidence interval [CI]: 1.02 to 1.45) and lung cancer (SMR: 1.59, 95% CI: 1.12 to 2.19). Among females, increased mortality was observed for liver cancer (SMR: 2.05, 95% CI: 1.02 to 3.67). No significant increase was seen in non-cancer-related mortality compared with the general population.

CONCLUSIONS

Carcinogenic risk in humans after exposure to PCBs and PCDFs remains higher among Yusho patients. Our findings suggest the importance of care engagement and optimum management to deal with the burden of Yusho disease.

Inhibition of polychlorinated dibenzo-p-dioxins and dibenzofurans by phosphorus-containing compounds in model fly ash

Waste incineration is a preferred method in China to dispose the municipal solid waste, but controlling the production of highly toxic polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans effectively during incineration is both challenging and imperative. In this study, the suppression of PCDD/Fs by various phosphorus-containing compounds was explored, and the mechanisms responsible for the inhibition were studied in detail. The experiments took place in a lab-scale vertical tubular reactor at 350 °C under a simulated flue gas (12 vol% O₂ in N₂ flow), and both the off-gases and residues were collected for PCDD/Fs analysis. The scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to characterize the reaction residues. The experimental results revealed that NH₄H₂PO₄ and (NH₄)₂·HPO₄ showed the highest inhibitory effect (57.2% and 57.3%, respectively) on the PCDD/Fs formation, followed by CaHPO₄ with inhibition efficiency of 39.1%. In contrast, KH₂PO₄ and K₂HPO₄ barely inhibited the generation of the PCDD/Fs. The inhibitory effect of NH₄H₂PO₄ and (NH₄)₂·HPO₄ was similar to that of nitrogen-based inhibitors. At the same time, it was proven that the inhibitory activity of CaHPO₄ might be due to the reaction of it with Cu²⁺ forming stable compounds.

Detection of high PBDD/Fs levels and dioxin-like activity in toys using a combination of GC-HRMS, rat-based and human-based DR CALUX® reporter gene assays

Brominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) are increasingly reported at significant levels in various matrices, including consumer goods that are manufactured from plastics containing certain brominated flame retardants. PBDD/Fs are known ligands for the aryl hydrocarbon receptor (AhR) but are not yet considered in the hazard assessment of dioxin mixtures. The aim of the present study was to determine if PBDD/Fs levels present in plastic constituents of toys could pose a threat to children's health. PBDD/Fs, unlike their chlorinated counterparts (PCDD/Fs), have not been officially assigned toxic equivalence factors (TEFs) by the WHO therefore, we determined their relative potency towards AhR activation in both human and rodent cell-based DR CALUX® bioassays. This allowed us to compare GC-HRMS PBDD/F congener levels, converted to total Toxic Equivalents (TEQ) by using the PCDD/F TEFs, to CALUX Bioanalytical Equivalents (BEQ) levels present in contaminated plastic constituents from children's toys. Finally, an estimate was made of the daily ingestion of TEQs from PBDD/Fs-contaminated plastic toys by child mouthing habits. It is observed that the daily ingestion of PBDD/Fs from contaminated plastic toys may significantly contribute to the total dioxin daily intake of young children.

Polychlorinated dibenzo-dioxins and polychlorinated dibenzo-furans exposure and altered lung function: The mediating role of oxidative stress

The lung has been reported to be one of the target organs of polychlorinated dibenzo-dioxins and polychlorinated dibenzo-furans (PCDD/Fs) in many toxicological studies. While the associations between PCDD/Fs exposure and lung function levels have not been investigated thoroughly. This study aimed to explore these associations and the potential mediating role of oxidative stress. In this study, 201 foundry workers and 222 non-exposed general residents were recruited from central China, and their lung function parameters were measured. Air and food samples were collected to determine the PCDD/Fs levels for individual PCDD/Fs exposure estimation. Serum PCDD/Fs levels were determined in a subgroup of individuals randomly selected from the study population to reflect the body burden. It was found that each 1-unit increase in ln-transformed concentration of PCDD/Fs exposure (fg TEQ/bw/day) was associated with a 0.47 L decrease in FVC and a 0.25 L decrease in FEV₁. Each 1-unit increase in ln-transformed concentration of serum PCDD/Fs (fg TEQ/g lipid) was associated with a 0.36 L decrease in FVC and a 0.24 L decrease in FEV₁. Urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) was not only positively related to PCDD/Fs exposure, but also inversely associated with FVC and FEV₁ are FVC (β = -0.15, 95% CI: -0.22 to -0.08) and FEV₁ (β = -0.07, 95% CI: -0.13 to -0.02). Mediation analysis revealed that urinary 8-OHdG mediated 12.22% of the associations of external PCDD/Fs exposure with FVC levels, 28.61% and 27.87% of the associations of serum PCDD/Fs with FVC and FEV₁ levels respectively. Our findings suggested that PCDD/Fs exposure was associated with decreased lung function levels by a mechanism partly involving oxidatively generated damage to DNA.

Spatial and temporal variation, source profile of PCDD/Fs in the atmosphere of a municipal waste incinerator in China

The mass concentrations, toxic equivalent quantity (TEQ) concentrations and congener profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the stack flue gas and ambient air of municipal solid waste incinerator (MSWI) were monitored in this study to evaluate the levels, emission characteristics, seasonal variation and emission sources of PCDD/Fs. Thirty-one ambient air samples were collected from four sites around MSWI during 2016-2017, and twelve stack flue gas samples were collected from one MSWI. Results showed that the PCDD/Fs concentrations of the stack flue gas ranged from 0.0077 to 0.021 ng I-TEQ/Nm³, with an average value of 0.016 ng I-TEQ/Nm³. The ambient air samples collected in 2016 and 2017 ranged from 0.017 to 0.27, and 0.035-0.27 pg I-TEQ/Nm³, with an average value of 0.078 and 0.10 pg I-TEQ/Nm³, respectively. The 2, 3, 4, 7, 8-PCDF always contributes most to toxicity both in stack flue gas and ambient air samples. PCDD/Fs in the ambient air of the study area showed significant seasonal differences, and the total concentration of PCDD/Fs was highest in winter, which was about 3.5-7.5 times that of summer. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used to determine the correlation between MSWI emissions and PCDD/Fs in ambient air. It is worth mentioning that MSWI is not the main source of PCDD/Fs in ambient air.

The impact of maternally derived dioxins on embryonic development and hepatic AHR signaling in a long-lived apex predator

Dioxins and related contaminants are highly pervasive in aquatic systems and elicit deleterious effects in exposed organisms. Because dioxins exhibit a proclivity to bioaccumulate, long-lived predatory species are particularly vulnerable to their persistence in the environment. We have previously reported elevated expression of CYP1A2, a biomarker of dioxin exposure, in American alligator embryos collected from the Tom Yawkey Wildlife Center (YWC). This coastal population inhabits a system with historical dioxin contamination associated with industrial activities. Herein, we utilize ecological attributes of the alligator to address the persistence of dioxins and furans in yolk and their potential to drive changes in hepatic function. Specifically, we assess variation in expression of AHR signaling components in embryos and its connection to contaminant levels in matched yolk samples. Compared to a reference population, TEQ levels and total penta-, hexa-, octa-substituted CDDs were elevated at YWC. Contrary to predictions, TEQ levels were not significantly related to hepatic AHR1B or CYP1A2 expression. However, a significant association was detected between expression of both factors and embryo:yolk mass ratios, wherein decreasing embryo mass was negatively associated with CYP1A2 but positively associated with AHR1B. These findings suggest that variation in embryonic metabolism and developmental progression likely influence AHR signaling and dioxin toxicity in alligators and potentially other oviparous species. While dioxin concentrations observed in alligators in this study are lower than historical values reported for other wildlife species inhabiting this system, they indicate the continued presence and possible long-term influence of these contaminants in a high trophic status species.

Associations between polychlorinated dibenzo-dioxins and polychlorinated dibenzo-furans exposure and oxidatively generated damage to DNA and lipid

Polychlorinated dibenzo-dioxins and polychlorinated dibenzo-furans (PCDD/Fs) have been reported to induce reactive oxygen species and oxidative stress, but the dose-response relationships have not been explored in molecular epidemiological studies. In this study, a total of 602 participants were recruited, comprising of 215 foundry workers, 171 incineration workers and 216 residents living more than 5 km away from the plants as the reference group. Individual PCDD/Fs exposures were estimated according to PCDD/Fs levels of working and living ambient air and daily foods. Urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 8-iso-prostaglandin-F2α (8-isoPGF2α) were determined to reflect oxidatively generated damage to DNA and lipid. Generalized linear models were used to access the associations between PCDD/Fs exposure and oxidative stress biomarkers. We found that PCDD/Fs exposure and urinary oxidative stress biomarkers of workers were all higher than those of the reference group. Significantly positive exposure-response relationships between individual PCDD/Fs exposures and urinary 8-oxodG and 8-iso-PGF2α were found. Each 1-unit increase in ln-transformed levels of PCDD/Fs exposure generated a 0.78 nmol/mmol creatinine increase in ln-transformed 8-oxodG and a 0.50 ng/mmol creatinine increase in ln-transformed 8-isoPGF2α in foundry workers, a 0.49 nmol/mmol creatinine increase in ln-transformed 8-oxodG and a 0.26 ng/mmol creatinine increase in ln-transformed 8-isoPGF2α in incineration workers, compared with the reference group. And such associations were not modified by tobacco use. Our findings could help to understand the dose-response relationships between PCDD/Fs and oxidatively generated damage to DNA and lipid, and provide an epidemiologic basis for conducting research on the carcinogenesis and other toxicity mechanisms of PCDD/Fs.

Effects of perinatal dioxin exposure on development of children: a 3-year follow-up study of China cohort

The purpose of this study was to investigate the longitudinal effects of perinatal exposure to dioxin on physical growth in a 3-year follow-up study. In 2015, 27 mother-infant pairs living in an electronic waste (e-waste) dismantling region and 35 pairs living in a control region were enrolled in the present study. Breast milk samples were collected at 4 weeks after birth. Physical growth, including weight, height, and head and chest circumferences, was measured at 6 months and 3 years of age. Dioxin levels in the breast milk were measured by gas chromatography/high-resolution mass spectrometry. Levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin and toxic equivalency values in maternal breast milk of polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and PCDDs/PCDFs were significantly higher in women residing in the e-waste dismantling region. In 3-year-old boys, inverse associations were found between height and PCDDs-TEQ. In girls, positive associations were found between height and 2,3,7,8-TetraCDD, PCDDs-TEQ, and PCDDs/PCDFs-TEQ, and for weight and PCDDs-TEQ and PCDDs/PCDFs-TEQ at 3 years of age. In this study, sex-specific differences were observed in children, in whom dioxin exposure decreased growth in boys but increased growth in girls during the first 3 years of life.

Thermal oxidation of dieldrin and concomitant formation of toxic products including polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F)

This paper examines the gas phase thermal decomposition of dieldrin and associated formation of toxic combustion products including polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F). Volatile Organic Carbon (VOC) analysis revealed the formation of pentachlorostyrene (PCS), hexachlorostyrene (HCS) and polychlorinated naphthalene as toxic combustion products generated during the combustion of dieldrin. The thermal pyrolysis of dieldrin resulted in the formation of chlorinated benzenes and chlorinated phenols, which are known PCDD/F precursors. The formation of PCDD/F commenced around 823 K @ 5s residence time and results indicate a preference for the formation of PCDF over PCDD under all experimental conditions studied. Subsequent experiments, to examine the yield of PCDD/F as a function of temperature, reveal the progressive chlorination of PCDD/F with temperatures up to 923 K. Octachlorodibenzofuran (OCDF) was the major dioxin congener detected in the oxidation of dieldrin. The highest toxicity factor for dioxin formation was recorded at 923 K with a 6% O₂ content in the feed gas and corresponds to 6.24 ng TEQ WHO 2005/mg of dieldrin and total PCDD/F concentration of 96.8 ng/mg of dieldrin.

Perinatal polychlorinated biphenyls and polychlorinated dibenzofurans exposure are associated with DNA methylation changes lasting to early adulthood: Findings from Yucheng second generation

Epigenome-wide DNA methylation has not been studied in men perinatally exposed to PCBs and dioxins. Therefore, we examined whether perinatal exposure to polychlorinated biphenyls (PCBs) and polychlorinated dibenzofurans (PCDFs) induces sustained methylation changes lasting to early adulthood. We used the Illumina HumanMethylation450 BeadChip to assess DNA methylation in whole blood among Yucheng second generation (people perinatal exposed to high PCBs and PCDFs) compared with referents. Thirty male offspring from the Yucheng cohort were randomly selected and matched with 30 male offspring from the Yucheng' neighborhood referents with similar backgrounds. Methylation differences between the Yucheng second generation and non-exposed referents were identified using a P value < 1.06 × 10^-7. Differential DNA methylation with epigenome-wide statistical significance was observed for 20 CpGs mapped to 11 genes, and 19 CpGs were correlated with gestational levels of PCBs or PCDF toxic equivalency (PCDF-TEQ) with the same direction of effect. Among the 11 genes, AHRR and CYP1A1 are involved in the aryl hydrocarbon receptor signaling pathway known to mediate dioxin toxicity. MYO1G, FRMD4A, ARL4C, OLFM1, and WWC3 were previously reported to be related to carcinogenesis. This is the first study examining genome-wide DNA methylation among people perinatally exposed to high concentrations of PCBs and PCDFs. We observed novel differential methylation of several genes, indicating that modifications of DNA methylation associated with perinatal PCB and PCDF exposure may persist in exposed offspring for more than 20 years. Furthermore, involvement of several carcinogesis-related genes suggested a potential in utero epigenetic mechanisms.

TCDD Toxicity Mediated by Epigenetic Mechanisms

Dioxins are highly toxic and persistent halogenated organic pollutants belonging to two families i.e., Polychlorinated Dibenzo-p-Dioxins (PCDDs) and Polychlorinated Dibenzo Furans (PCDFs). They can cause cancer, reproductive and developmental issues, damage to the immune system, and can deeply interfere with the endocrine system. Dioxins toxicity is mediated by the Aryl-hydrocarbon Receptor (AhR) which mediates the cellular metabolic adaptation to these planar aromatic xenobiotics through the classical transcriptional regulation pathway, including AhR binding of ligand in the cytosol, translocation of the receptor to the nucleus, dimerization with the AhR nuclear translocator, and the binding of this heterodimeric transcription factor to dioxin-responsive elements which regulate the expression of genes involved in xenobiotic metabolism. 2,3,7,8-TCDD is the most toxic among dioxins showing the highest affinity toward the AhR receptor. Beside this classical and well-studied pathway, a number of papers are dealing with the role of epigenetic mechanisms in the response to environmental xenobiotics. In this review, we report on the potential role of epigenetic mechanisms in dioxins-induced cellular response by inspecting recent literature and focusing our attention on epigenetic mechanisms induced by the most toxic 2,3,7,8-TCDD.

The role of CuZn- and Mn-superoxide dismutases in earthworm Eisenia andrei kept in two distinct field-contaminated soils

Polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs), together with polycyclic aromatic hydrocarbons (PAHs), represent highly toxic and persistent organic environmental pollutants, especially due to their capability for bioaccumulation in fatty tissues. To observe the environmentally relevant effect of these compounds on earthworms, two soils naturally contaminated with PCDD/Fs and PAHs were used in our experiments. We focused on the role of CuZn- and Mn-superoxide dismutases. We assembled a full-length sequences of these molecules from Eisenia andrei earthworm and confirmed their activity. We demonstrated the significant reduction of CuZn-SOD on both mRNA and enzyme activity levels and increased levels of reactive oxygen species in earthworms kept in PCDD/F-polluted soil, which corresponds to the observed histopathologies of the earthworm intestinal wall and adjacent chloragogenous tissue. The results show an important role of CuZn-SOD in earthworm tissue damage caused by PCDD/Fs present in soil. We did not detect any significant changes in the mRNA expression or activity of Mn-SOD in these earthworms. In earthworms maintained in PAH-polluted soil the activity of both CuZn-SOD and Mn-SOD significantly increased. No histopathological changes were detected in these worms, however significant decrease of coelomocyte viability was observed. This reduced viability was most likely independent of oxidative stress.

Hyperpigmentation and higher incidence of cutaneous malignancies in moderate-high PCB- and dioxin exposed individuals

Polychlorinated biphenyls (PCB) are well known persistent and toxic environmental pollutants. Our aim was to identify effects of moderate-high exposure to dioxin-like (dl) and non-dioxin-like (ndl)-PCBs on the skin in order to provide more insight in the pathophysiological effects of these compounds. We performed a dermatological examination on 92 former workers from a transformer recycling company with known elevated serum PCB and/or dioxin (polychlorinated dibenzo-p-dioxin/polychlorinated dibenzo-p-furan (PCDD/F)) levels. In addition, we performed a skin cancer screening over a period of seven years (2010-2016) on resp. 268, 271, 210, 149, 92, 129 and 79 participants. We found a higher incidence of acne and malignancies of the skin (malignant melanoma, basal cell carcinoma and mycosis fungoides) in the workers compared to normal population. The probability of having hyperpigmentation on the skin was statistically significantly higher in workers with higher sumPCBs- (OR:1.09(1.12-2.17)), dioxin-like (dl)-PCBs- (OR:1.56(1.12-2.17)) and dioxin (PCDD/Fs) (OR:1.09(1.02-1.16)) levels. Age was a confounding factor in this model. Formation of hyperpigmentation could be an indicator for (moderate-high) exposure to toxic compounds like PCBs. The higher incidence of cutaneous malignancies found in the workers might be associated with PCB- and dioxin exposure, warranting further investigation on larger cohorts.

Multiple linear regression based congener profile correlation to estimate the toxicity (TEQ) and dioxin concentration in atmospheric emissions

The formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) is governed by complex chemical reactions with complex kinetic models. The simulation of Municipal Solid Waste incinerators, or other industrial thermal processes, is a powerful tool that can be used to optimize and control them, and reducing the number of components to simulate is mandatory for a proper use. In this study it has been determined that only the formation of 3 of the 17 main PCDD/F congeners can be considered as linearly independent. This fact has been used to establish linear regression models that are able to estimate properly the total amount and toxicity of a sample considering only the amount of 1,2,3,6,7,8-HxCDD, OCDF and 2,3,7,8-TCDF. All models have been validated using new samples performing a close approach to the real values provided by complete analytical studies. The average relative error is 3.5% and the maximum relative error is below 9% for these new testing samples. The main goal of our investigation is to build a dynamic simulation process of a MSW facility and include the dioxins formation on it using these models.

Use of polychlorinated biphenyl and toxic equivalent concentrations in scat from mink(Neovison vison) fed fish from the upper Hudson River to predict dietary and hepatic concentrations and health effects

To evaluate health effects associated with consumption of fish contaminated with polychlorinated biphenyls (PCBs) from the upper Hudson River, farm-raised mink were fed diets containing fish collected from the river. Endpoints assessed included adult reproductive performance, offspring growth and mortality, and organ mass and pathology of adults and their offspring. Scat samples were collected from adult males at the time of necropsy and from adult females just prior to whelping. Scat samples were analyzed for PCBs, polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs). The present study provides the results of these analyses and compares ∑PCB and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxic equivalent (TEQ) concentrations in scat with dietary and hepatic concentrations associated with effects reported previously. Dry weight concentrations of ∑PCBs and ∑TEQs in scat generally increased with dietary concentration and reflected corresponding increases in hepatic concentrations of ∑PCBs and ∑TEQs. Maternal concentrations of ∑PCBs in scat expressed on a dry, wet, and lipid weight basis predicted to result in 50% kit mortality (LC50) were 1.0, 0.30, and 12 μg ∑PCBs/g. Concentrations of ∑PCBs in scat expressed on a dry, wet, and lipid weight basis predicted to result in 50% incidence of a previously reported jaw lesion (EC50) were 1.7, 0.48, and 24 μg ∑PCBs/g in adult females and 2.5, 0.87, and 19 μg ∑PCBs/g in adult males. Environ Toxicol Chem 2018;37:563-575. © 2017 SETAC.

Assessment of Ah receptor transcriptional activity mediated by halogenated dibenzo-p-dioxins and dibenzofurans (PXDD/Fs) in human and mouse cell systems

Polybrominated and mixed bromo/chloro dibenzo-p-dioxins and dibenzofurans (PXDD/Fs) are emerging environmental contaminants of concern. Thus far, an understanding of the toxicological behavior of these chemical species and their impact upon human health is incomplete. Here we utilized human and mouse hepatocellular carcinoma cell lines to examine the ability of differentially halogenated PXDD/F congeners to induce aryl hydrocarbon receptor (AHR)-mediated transcriptional activity. Dose-response experiments in reporter cell lines identified varied potencies among differentially halogenated PXDD/F isomers by comparison of EC₅₀ values relative to the prototypical AHR agonist, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Brominated PXDD/F species displayed reduced capacity to activate the mouse AHR, compared to TCDD. Only BrCl₃ dibenzo-p-dioxin was found to have a greater relative potency than TCDD to induce human AHR transcriptional activity. Human cells required ∼10-29-fold higher ligand concentrations to induce analogous AHR activity, relative to mouse cells. Decreased sensitivity of the human AHR to brominated dibenzofuran congeners directly corresponded to the number of bromine functional groups. Mixtures of these compounds exhibited an additive effect on AHR activation. The data also support the inclusion of mixed halogenated dibenzo-p-dioxins and dibenzofurans into routine environmental screening procedures as well as more thorough toxicological characterization of PXDD/Fs.

The influence of the Cucurbitaceae on mitigating the phytotoxicity and PCDD/PCDF content of soil amended with sewage sludge

The study evaluates the impact of sewage sludge on OECD - Organization for Economic Cooperation and Development and vegetable soil phytotoxicity, measured using three test species: Lepidium sativum, Sinapis alba and Sorghum saccharatum, and total and TEQ PCDD/PCDF (toxic equivalency polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans) soil concentration, measured using HRGC/HRMS - High Resolution Gas Chromatography/High Resolution Mass Spectrometry. It also evaluates the effect of zucchini and cucumber cultivation during 5-weeks period on mitigating these parameters. The application of 3, 9 and 18 t/ha of sewage sludge gradually increases the phytotoxicity of both OECD and vegetable soil. In the case of OECD soil, the highest roots growth inhibitions were observed for S. alba (73%, 86% and 87%, respectively) and the lowest for S. saccharatum (7%, 59% and 70%), while in vegetable soil inhibitions were averagely 25% lower. Sludge application also led to a 38% (3 t/ha), 169% (9 t/ha) and 506% (18 t/ha) increase in PCDD/PCDF concentration, and the TEQs were augmented by 15%, 159% and 251%. Both soil phytotoxicity and total and TEQ PCDD/PCDF concentrations were diminished as a result of zucchini and cucumber cultivation. The maximum reduction of soil phytotoxicity (83%) was observed as an effect of cucumber cultivation, while zucchini was 11% less effective. Zucchini, in turn, was more efficient in PCDD/PCDF removal (37% reduction), followed by cucumber (24%). Such differences were not observed in the case of TEQ reductions (68% and 66% for zucchini and cucumber cultivation, respectively).

WHO/UNEP global surveys of PCDDs, PCDFs, PCBs and DDTs in human milk and benefit-risk evaluation of breastfeeding

Since 1987, the World Health Organization (WHO) carried out global surveys on polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) in human milk. This study presents a review of the three most recent surveys from 2000 to 2010, including DDT. The objective was to identify global quantitative differences and provide baseline information for 52 countries or provide time-trends for countries with previous data. Individual human milk samples were collected following a WHO-designed procedure and combined to form a national pooled sample. Here, we report global levels for PCDDs, PCDFs, PCBs and the sum of o,p'-DDT, p,p'-DDT, o,p'-DDE, p,p'-DDE, o,p'-DDD and p,p'-DDD (ΣDDTs). A concise risk-benefit evaluation related to human milk contamination with these persistent organic pollutants (POPs) was also done. Large global and regional differences were observed. Levels of PCDDs and PCDFs were highest in India and some European and African countries. PCB levels were highest in East and West Europe. The highest levels of ΣDDTs were found in less industrialized countries. A temporal downward trend for PCDDs, PCDFs and PCBs is indicated. A risk-benefit assessment indicates that human milk levels of PCDDs, PCDFs and PCBs are still significantly above those considered toxicologically safe, while ΣDDTs are below or around those considered safe. With respect to potential adverse health effects, a more dominant role of in utero exposure versus lactational exposure is indicated. If potential adverse effects are balanced against positive health aspects for (breastfed) infants, the advantages of breastfeeding far outweigh the possible disadvantages. Our observations provide a strong argument to plea for further global source-directed measures to reduce human exposure further to dioxin-like compounds.

Molecular and cellular response of earthworm Eisenia andrei (Oligochaeta, Lumbricidae) to PCDD/Fs exposure

The acute toxicity of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) was investigated in the earthworm Eisenia andrei using filter paper toxicity test. Protein content, catalase (CAT) activity, and histology of intestinal wall (chloragogen cells and intestinal epithelium) were investigated in earthworms exposed for 48 h to 0 (control), 0.5, 1.0, and 1.5 ng/cm² PCDD/Fs. The results showed an increase in the total protein content 1.56- (p = 0.104), 1.66- (p = 0.042), and 2.26-fold (p < 0.001), respectively, compared to control. The average ± standard deviation of tissular CAT activity showed no significant differences; it was 36.01 ± 7.65, 36.17 ± 9.45, 36.08 ± 9.80, and 40.01 ± 6.98 U/g tissue, respectively. However, the average specific activity of CAT ± standard deviation was significantly decreased (p < 0.001) at all doses compared to control; it was 2.93 ± 0.42, 1.93 ± 0.53, 1.80 ± 0.38, and 1.53 ± 0.44 U/mg protein, respectively. There was a progressive damage in both of the intestinal villi and the chloragogenous tissue associated with the incrementing doses. Since the toxic mixture altered the investigated biomarkers of E. andrei within 48 h, the cellular and molecular alterations resulted from the filter paper contact test could be utilized as a rapid toxicity assessment tool of environmental contamination with dioxins/furans and to assess consequent potential adverse effects on soil biota and other organisms in the ecosystem.

Polychlorinated biphenyls and dibenzofurans increased abnormal sperm morphology without alterations in aneuploidy: The Yucheng study

In 1979, more than 2000 persons ingested rice oil contaminated with polychlorinated biphenyls and polychlorinated dibenzofurans; this event was called the "Yucheng accident." An increased percentage of oligospermia, reduced ability of sperm to penetrate oocytes, and reduced percentage of male offspring were reported in Yucheng men. This study examined whether the sperm sex ratio and chromosome aneuploidy are responsible for our observed findings in Yucheng men. In 1999-2000, Yucheng men and their neighborhood referents aged 37-50 years were recruited for physical examination, followed by semen analysis. The semen samples were analyzed for chromosomal aneuploidy through fluorescent in situ hybridization according to an established procedure in our laboratory. A total of 50 Yucheng men and 34 neighborhood referents volunteered to participate in the study. Although abnormal morphology was mildly increased, no differences were observed in sperm percentages, with normal numbers of chromosomes X, Y, and 8 in the two groups. The percentage of sperm with aneuploidy of the sex chromosomes or chromosome 8 and of that with diploidy did not vary between both groups. The normal X/Y sperm ratio was not different between the groups. However, among Yucheng men, 8% had a normal X/Y sperm ratio of >1.4, and no neighborhood referent showed such an elevated X/Y ratio. Chromosomal aneuploidy was not elevated in Yucheng men. The mechanisms underlying the reduced sperm capability of oocyte penetration and changed offspring sex ratio in Yucheng men remain undetermined.

Dust levels of polybrominated diphenyl ethers (PBDEs) and polybrominated dibenzo-p-dioxins/furans (PBDD/Fs) in the Taiwanese elementary school classrooms: Assessment of the risk to school-age children

Elementary school classroom dust is an important source of exposure to polybrominated dibenzo-p-dioxins/furans and diphenyl ethers (PBDD/DF/DEs) for school-age children. Our goal is thus to investigate concentrations of PBDD/DF/DEs in elementary school classroom dust to further assess the impact on school-age children via ingestion. The dust from classrooms, including both normal (NR) and computer classrooms (CR), was collected from six urban and four rural schools. Fourteen PBDEs and twelve PBDD/Fs were measured using high-resolution gas-chromatography/high-resolution mass-spectrometry. The mean levels of Σ₁₄PBDEs in NR and CR dust from the urban classrooms were 370 and 2510ng/g and those whose dust from the rural classrooms were 464 and 1780ng/g. The means of ΣPBDD/Fs were 0.0401ng-WHO₂₀₀₅-TEQ/g (concentration: 4.72ng/g) in urban NR dust, 0.0636ng-WHO₂₀₀₅-TEQ/g (7.51ng/g) in urban CR dust, 0.0281ng-WHO₂₀₀₅TEQ/g (3.60ng/g) in rural NR dust, and 0.0474ng-WHO₂₀₀₅TEQ/g (6.28ng/g) in rural CR dust. The PBDEs pattern in NR dust was quite different from that in CR dust, but the PBDD/Fs patterns in NR and CR dust were similar. A linearly significant correlation coefficient (n=20, r=0.862, p<0.001) was found between ΣPBDEs and ΣPBDD/Fs in NR and CR dust, indicating that the PBDEs and PBDD/Fs in the dust may be from the same sources in the elementary school classrooms. This study assessed the risks (daily intake and cancer and non-cancer risks) of PBDEs and PBDD/Fs for the children from the classroom dust, and the calculated risk values did not exceed the related thresholds. With regard to the exposure scenarios for school-age children in an indoor environment, the results suggest that they might ingest more dust PBDD/DF/DEs in their homes than in the schools. In conclusion, the exposure of Taiwanese elementary school children to PBDD/DF/DEs via indoor dust was with a safe range based on our findings.

Concentrations and spatial patterns of organic contaminants in tree swallow (Tachycineta bicolor) eggs at United States and binational Great Lakes Areas of Concern, 2010-2015

Tree swallows, Tachycineta bicolor, were sampled across the Great Lakes basin in 2010 through 2015 to provide a system-wide assessment of current exposure to organic contaminants. The results provide information identified as critical by regulators to assess the "bird or animal deformity or reproductive problems" beneficial use impairment. Eggs were collected from 69 sites across all 5 Great Lakes, including 27 Areas of Concern (AOCs), some with multiple sites, and 10 sites not listed as an AOC. Concentrations of organic contaminants in eggs were quantified and compared with background and reproductive effect thresholds. Approximately 30% of AOCs had geometric mean concentrations of total polychlorinated biphenyls (PCBs) at or below average background exposure (0.34 μg/g wet wt). Exposure to polybrominated diphenyl ethers (PBDEs) was minimal, and only 3 of 27 AOCs and 1 non-AOC had geometric mean concentrations that exceeded background for tree swallows (96 ng/g wet wt). Concentrations of both PCBs and PBDEs were 10 to 20 times below the lower limit associated with impaired hatching success. In contrast, geometric mean concentrations of polychlorinated dibenzo-p-dioxin and furan (PCDD-F) toxic equivalents (TEQs) at the Saginaw River and Bay AOC and Midland, Michigan, USA (a non-AOC site), exceeded the lower limit for hatching effects (181 pg/g PCDD-F TEQs). The rest of the sites had geometric mean concentrations of PCDD-F TEQs below background levels (87 pg/g PCDD-F TEQs). Other organic contaminants, including p,p'-dichlorodiphenyldichloroethylene, mirex, heptachlor, and chlordane, were at or below background or adverse effect concentrations. Environ Toxicol Chem 2016;35:3071-3092. Published 2016 Wiley Periodicals Inc on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Composition profiles and health risk of PCDD/F in outdoor air and fly ash from municipal solid waste incineration and adjacent villages in East China

In present study, composition profiles and health risk of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in outdoor air and fly ash from domestic waste treatment center (DWTC) were studied. In addition, the composition profiles and health risk of PCDD/F in outdoor air from adjacent villages were researched and used to quantitatively analyze the difference between onsite workers and adjacent villagers. Moreover, the difference between old intake method and new inhalation dosimetry method in the process of assessing the health risk of PCDD/Fs in outdoor air was quantitatively compared and analyzed. The results of this study were summarized as follows. (1) The 95th percentile carcinogenic risk (CR) and non-carcinogenic risk (non-CR) for onsite workers and adjacent villagers were much lower than the threshold values of 10(-6) and 1.0, respectively, suggesting no potential health risk. (2) The 95th percentile CR for onsite workers was 1.27×10(-8) and was 64.8 times higher than that of adjacent villagers (1.99×10(-10)). (3) The 95th percentile non-CR for onsite workers and adjacent villagers were 1.37×10(-4) and 1.31×10(-7), respectively. (3) Accidental ingestion of fly ash was the largest contributor to CR and non-CR for onsite workers, contributing 62.98% and 64.04% to CR and non-CR, respectively. (4) The CR and non-CR of PCDD/Fs in outdoor air for onsite workers and adjacent villagers which calculated by old intake method was much higher than the results from new inhalation dosimetry method. The results quantitatively showed the levels and potential risks of PCDD/Fs posed by a DWTC site, which can be helpful to predict the influence from DWTC sites and promote the management of DWTC in China.

Effect of pyrolysis temperature on potential toxicity of biochar if applied to the environment

Biochars have increasingly been used as adsorbents for organic and inorganic contaminants in soils. However, during the carbonization process of pyrolysis, contaminants, including polycyclic aromatic hydrocarbons (PAHs) and polychlorinated dioxins and furans (PCDD/DF) can be generated. In this study, biochars made from sawdust, were prepared at various temperatures ranging from 250 to 700 °C. The Microtox^® and rat hepatoma cell line H4IIE-luc assays were used to characterize the general toxic and effects, mediated through the aryl hydrocarbon receptor (AhR), or dioxin-like potencies of organic extracts of biochars. The greatest total concentrations of PAHs (8.6 × 10² μg kg^-1) and PCDD/DF (6.1 × 10² pg g^-1) were found in biochar generated at 400 °C and 300 °C, respectively. Results of the H4IIE-luc assay, which gives total concentrations of 2,3,7,8-TCDD equivalents (TEQ_H4IIE-luc), indicated that total potencies of aryl hydrocarbon receptor (AhR) agonists were in decreasing order: 300 °C > 250 °C > 400 °C > 500 °C > 700 °C. The 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQ_chem) calculated as the sum of products of 16 PAHs and 17 PCDD/DF congers multiplied by their respective relative potencies (RePs) was less than that of TEQ_H4IIE-luc determined by use of the bioanalytical method, with the H4IIE-luc assay, which measures the total dioxin-like potency of a mixtures. The ratio of TEQ_chem/TEQ_H4IIE-luc was in the range of 0.7%-3.8%. Thus, a rather small proportion of the AhR-mediated potencies extracted from biochars were identified by instrumental analyses. Results of the Microtox test showed similar tendencies as those of the H4IIE-luc test, and a linear correlation between EC50 of Microtox test and EC20 of H4IIE-luc test was found. The results demonstrated that biochars produced at higher pyrolysis temperatures (>400 °C) were less toxic and had lower potencies of AhR-mediated effects, which may be more suitable for soil application.

Potential for Phytoremediation of PCDD/PCDF-Contaminated Sludge and Sediments Using Cucurbitaceae Plants: A Pilot Study

The current study evaluates the impact of sewage sludge and urban reservoir sediment on changes in total and Toxic Equivalency (TEQ) PCDD/PCDF concentration in soil and phytotoxicity measured using three test species: Lepidium sativum, Sinapis alba, and Sorghum saccharatum, during 5 weeks of Cucurbita pepo L. cv 'Atena Polka' (zucchini) cultivation. 'Atena Polka' was found to reduce total PCDD/PCDF concentration by 37 % in soil amended with sludge and 32 % in soil treated with sediment from an urban reservoir. The TEQ reduction was almost twofold greater: 68 % in soil amended with sludge and 52 % with urban sediment. Addition of sludge increased root growth inhibition of L. sativum, S. alba and S. saccharatum, from 44 % to 90 %. Observed inhibitions were, however, reduced by 'Atena Polka' cultivation, and as high as 32 % promotion in root length was noted. Amendment with urban sediment, in turn, resulted in an initial 1 %-36 % promotion of root growth, while 'Atena Polka' cultivation reduced this positive effect by inhibition as high as 26 %. Results demonstrated positive influence of 'Atena Polka' on the phytotoxicity alleviation and mitigation of total and TEQ PCDD/PCDF concentrations in soil treated with bio-solids from sewage sludge and an urban reservoir.

A cross-sectional analysis of dioxins and health effects in municipal and private waste incinerator workers in Japan

This cross-sectional study was intended to examine health effects of 678 male workers employed during an 8-yr period from 2000 to 2007 at 36 municipal and private waste incineration plants in Japan. Blood samples were obtained for analysis of concentrations of dioxins including coplanar polychlorinated biphenyls (coplanar PCBs) and evaluation of health effects. Health effects including diabetes were surveyed via a physician's interview or clinical data from blood samples. There was a certain difference in serum concentrations of polychlorinated dibenzofurans (PCDFs) between the incinerator workers and Japanese general population, although no differences in the concentrations of total dioxins or polychlorinated dibenzo-p-dioxins (PCDDs) were found between the two groups. A few positive correlations between serum levels of PCDDs and PCDFs and the results of laboratory and physiological tests were found, but coplanar PCBs showed significant relations with 14 parameters of the tests. The background serum levels of PCDDs, PCDFs and total dioxins were significantly associated with the prevalence of diabetes. No essential differences in serum concentrations of total dioxins and in prevalence of diabetes between our subjects and the general population suggested that the incinerator workers were marginally exposed to dioxins in the workplace without any recognizable adverse health effects.