The Seveso accident: A look at 40 years of health research and beyond

Technological disasters in Asia: Epidemiological profile from the year 2000 to 2021

BACKGROUND

Technological disasters in Asia have significant public health and environmental implications, but there is limited epidemiological analysis of these events. This study aims to characterize the epidemiological profile of technological disasters in Asia from 2000 to 2021, focusing on morbidity and mortality trends.

METHODS

A retrospective descriptive observational analysis was conducted using data from emergency events database (EM-DAT), DesInventar, NatCAt, and Sigma. The study categorized disasters into transport, industrial, and miscellaneous accidents. Statistical analyses were used to examine frequencies, trends, and correlations among the different disaster types.

RESULTS

From 2000 to 2021, Asia experienced 2333 technological disasters, with transport accidents being the most frequent (55.77%), followed by industrial (26.10%) and miscellaneous accidents (18.13%). The overall trend showed a statistically significant decrease in the frequency of these disasters and in average mortality and injury rates. The study highlighted the varying impact of different disaster types, with industrial accidents causing the highest fatality and affected rates despite being less frequent than transport accidents.

CONCLUSIONS

The study indicates a declining trend in the frequency and severity of technological disasters in Asia, reflecting improved safety measures and disaster management. However, the high impact of industrial accidents underscores the need for targeted prevention strategies.

Multi-media environmental fate of polychlorinated dibenzo-p-dioxins and dibenzofurans in China: A systematic review of emissions, presence, transport modeling and health risks

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) are notorious persistent organic pollutants (POPs) with proven toxicity to human and ecosystems. This review critically evaluates existing research, emphasizing knowledge gaps regarding PCDD/F emissions, environmental behavior, human exposure, and associated risks in China. The current emission inventory of PCDD/Fs in China remains highly uncertain, both in terms of total emissions and emission trends. Moreover, existing monitoring data primarily focus on areas near pollution sources, limiting comprehensive understanding of the overall spatiotemporal characteristics of PCDD/F pollution. To address this, we propose a novel approach that integrates the Multi-media Urban Mode (MUM) model with an atmospheric chemical transport model that includes a dual adsorption model to capture gas-particle partitioning of PCDD/Fs in the atmosphere. This coupled model can simulate the transport and fate of PCDD/Fs in multi-media environments with high spatiotemporal resolution, facilitating a nuanced understanding of the impacts of emissions, climate, urbanization and other factors on PCDD/F pollution. Additionally, dietary ingestion, particularly from animal-derived foods, is identified as the predominant source (up to 98%) of human exposure to PCDD/Fs. While the changes in dietary structure, population distribution, and age structure can influence human exposure to PCDD/Fs, their impacts have not yet been quantified. The proposed model lays the foundation for a systematic assessment of health risks from PCDD/F exposure through various pathways by further incorporating a food chain model. Overall, this review offers a comprehensive strategy for assessing PCDD/F pollution, encompassing the entire continuum from emissions to environmental impacts.

Mortality and cancer incidence in a population exposed to TCDD after the Seveso, Italy, accident (1976-2013)

OBJECTIVES

The Seveso accident (1976) caused the contamination with 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD) in an area north of Milan, Italy. We report the results of the update of mortality and cancer incidence in the exposed population through 2013.

METHODS

The study cohort includes subjects living in three contaminated zones with decreasing TCDD soil concentrations (zone A, B and R) and in a surrounding uncontaminated territory (reference). Poisson models stratified/adjusted for gender, age and period were fitted to calculate rate ratios (RRs) and 95% CIs.

RESULTS

In zone A in males, we found elevated mortality from circulatory diseases in the first decade after the accident (17 deaths, RR 2.00, 95% CI 1.24 to 3.23). In females, mortality from diabetes mellitus was increased, with a positive trend across zones. Incidence of soft tissue sarcoma was increased in males in zone R in the first decade (6 cases, RR 2.62, 95% CI 1.01 to 6.83). In females in zone B, there was an excess of non-Hodgkin's lymphoma after 30 years (6 cases, RR 2.87, 95% CI 1.14 to 7.23). Multiple myeloma was increased in the second decade in females in zone B (4 cases, RR 5.09, 95% CI 1.82 to 14.2) and in males in zone R (11 cases, RR 2.15, 95% CI 1.08 to 4.26). In males in zone R, there was a leukaemia excess after 30 years (23 cases, RR 2.02, 95% CI 1.04 to 3.93).

CONCLUSIONS

Although with different patterns across gender, zone and time, we confirmed previous results of increased cardiovascular diseases, diabetes, soft tissue sarcoma, and lymphatic and haematopoietic cancers.

Dioxins vs. PFAS: Science and Policy Challenges

BACKGROUND

Dioxin-like chemicals are a group of ubiquitous environmental toxicants that received intense attention in the last two decades of the 20th century. Through extensive mechanistic research and validation, the global community has agreed upon a regulatory strategy for these chemicals that centers on their common additive activation of a single receptor. Applying these regulations has led to decreased exposure in most populations studied. As dioxin-like chemicals moved out of the limelight, research and media attention has turned to other concerning contaminants, including per- and polyfluoroalkyl substances (PFAS). During the 20th century, PFAS were also being quietly emitted into the environment, but only in the last 20 years have we realized the serious threat they pose to health. There is active debate about how to appropriately classify and regulate the thousands of known PFAS and finding a solution for these "forever chemicals" is of the utmost urgency.

OBJECTIVES

Here, we compare important features of dioxin-like chemicals and PFAS, including the history, mechanism of action, and effective upstream regulatory strategies, with the objective of gleaning insight from the past to improve strategies for addressing PFAS.

DISCUSSION

The differences between these two chemical classes means that regulatory strategies for dioxin-like chemicals will not be appropriate for PFAS. PFAS exert toxicity by both receptor-based and nonreceptor-based mechanisms, which complicates mixtures evaluation and stymies efforts to develop inexpensive assays that accurately capture toxicity. Furthermore, dioxin-like chemicals were unwanted byproducts, but PFAS are useful and valuable, which has led to intense resistance against efforts to restrict their production. Nonetheless, useful lessons can be drawn from dioxin-like chemicals and applied to PFAS, including eliminating nonessential production of new PFAS and proactive investment in environmental remediation to address their extraordinarily long environmental persistence. https://doi.org/10.1289/EHP14449.

Impact of dioxins on reproductive health in female mammals

Extensive research has been conducted to investigate the toxicological impact of dioxins on mammals, revealing profound effects on the female reproductive system in both humans and animals. Dioxin exposure significantly disrupts the intricate functions of the ovary, a pivotal organ responsible for reproductive and endocrine processes. This disruption manifests as infertility, premature ovarian failure, and disturbances in sex steroid hormone levels. Comprehensive studies, encompassing accidental human exposure and experimental animal data, have raised a wealth of information with consistent yet varied conclusion influenced by experimental factors. This review begins by providing an overarching background on the ovary, emphasizing its fundamental role in reproductive health, particularly in ovarian steroidogenesis and hormone receptor regulation. Subsequently, a detailed examination of the Aryl hydrocarbon Receptor (AhR) and its role in governing ovarian function is presented. The review then outlines the sources and toxicity of dioxins, with a specific focus on AhR involvement in mediating reproductive toxicity in mammals. Within this context, the impact of dioxins, notably 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), on Folliculogenesis and Preimplantation embryos is discussed. Furthermore, the review delves into the disruptions of the female hormonal system caused by TCDD and their ramifications in endometriosis. Notably, variations in the effects of TCDD on the female reproductive and hormonal system are highlighted in relation to TCDD dose, animal species, and age. As a forward-looking perspective, questions arise regarding the potential involvement of molecular mechanisms beyond AhR in mediating the female reproductive toxicity of dioxins.

Protective effect of didymin against 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin-induced reproductive toxicity in male rats

PURPOSE

2, 3, 7, 8-Tetrachlorodibenzo-p-dioxin (TCDD) is one of the most potent environmental toxicants, which causes oxidative stress and adversely affects the male reproductive system. The current study aimed to evaluate the ameliorative role of didymin (DDM) against TCDD-induced testicular toxicity.

METHODS

Forty-eight male Sprague-Dawley rats were divided into four equal groups (n=12). (i) Control group, (ii) TCDD-induced group was provided with 10 μg/kg/day of TCDD, (iii) TCDD + DDM group received 10 μg/kg/day of TCDD and 2 mg/kg/day of DDM, and (iv) DDM-treated group was administered with 2 mg/kg/day of DDM. After 56 days of treatment, biochemical, steroidogenic, hormonal, spermatogenic, apoptotic, and histopathological parameters were estimated.

RESULTS

TCDD affected the biochemical profile by reducing the activities of antioxidant enzymes, while increasing the levels of malondialdehyde (MDA) and reactive oxygen species (ROS). Furthermore, it decreased the expressions of steroidogenic enzymes, 3β-hydroxysteroid dehydrogenase (HSD), 17β-HSD, steroidogenic acute regulatory protein (StAR), cholesterol side-chain cleavage enzyme (CYP11A1), and 17α-hydroxylase/17, 20-lyase (CYP17A1), as well as reduced the levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and plasma testosterone. Besides, epididymal sperm count, viability, and motility were decreased, while sperm morphological anomalies were increased. Moreover, TCDD altered the apoptotic profile by up-regulating the expressions of Bax and caspase-3, while downregulated the Bcl-2 expression. Additionally, histopathological damages were prompted due to TCDD administration. However, DDM restored all the TCDD-induced damages owing to its antioxidant, anti-apoptotic, and androgenic potential.

CONCLUSION

Our data suggested that DDM might play its role as a therapeutic agent against TCDD-prompted testicular toxicity.

Etiology of Male Infertility: an Update

Spermatogenesis is a complex process of germ cell division and differentiation that involves extensive cross-talk between the developing germ cells and the somatic testicular cells. Defective endocrine signaling and/or intrinsic defects within the testes can adversely affect spermatogenic progression, leading to subfertility/infertility. In recent years, male infertility has been recognized as a global public health concern, and research over the last few decades has elucidated the complex etiology of male infertility. Congenital reproductive abnormalities, genetic mutations, and endocrine/metabolic dysfunction have been demonstrated to be involved in infertility/subfertility in males. Furthermore, acquired factors like exposure to environmental toxicants and lifestyle-related disorders such as illicit use of psychoactive drugs have been shown to adversely affect spermatogenesis. Despite the large body of available scientific literature on the etiology of male infertility, a substantial proportion of infertility cases are idiopathic in nature, with no known cause. The inability to treat such idiopathic cases stems from poor knowledge about the complex regulation of spermatogenesis. Emerging scientific evidence indicates that defective functioning of testicular Sertoli cells (Sc) may be an underlying cause of infertility/subfertility in males. Sc plays an indispensable role in regulating spermatogenesis, and impaired functional maturation of Sc has been shown to affect fertility in animal models as well as humans, suggesting abnormal Sc as a potential underlying cause of reproductive insufficiency/failure in such cases of unexplained infertility. This review summarizes the major causes of infertility/subfertility in males, with an emphasis on infertility due to dysregulated Sc function.

Alteration of biomass toxicity in torrefaction - A XDS-CALUX bioassay study

Torrefaction constitutes one of the promising technologies for the management of waste biomass and the production of high-carbon products for combustion, gasification, adsorption of pollutants or soil treatment. Unfortunately, waste biomass may be contaminated with toxic persistent organic pollutants, such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDF) and dioxin-like biphenyls (dl-PCB). Literature does not provide consistent measurements on how the low-temperature thermochemical processing, such as torrefaction, affects the toxicity of biomass. This contribution assesses how a torrefaction treatment, conducted at 200 °C, modifies the toxicity due to PCDD/PCDF/dl-PCB in biomass. We deploy the XDS-CALUX biotest on five types of waste biomass (sewage sludge, tree bark, cattle manure, spent coffee ground, common reed), before and after treatment. The content of total dioxin- & biphenyl fraction compounds in the raw biomass, investigated in this study, varies from 0.14 to 3.67 pg BEQ·g-1d.m., and in the torrefied biomass between 0.17 and 6.00 pg BEQ·g-1d.m.; BEQ stands for bioanalytical equivalent. This increase is statistically insignificant at p = 0.05, taking into account all types of examined biomass. This proves that low-temperature torrefaction cannot detoxify biomass, i.e., chars, produced from biomass characterized by elevated concentration of PCDD/PCDF/dl-PCB, will reflect the contamination of the feedstocks. With respect to heavy metals, we conclude that only the content of Cd in biomass, and, to a lesser extent, the abundance of Cu and Fe, modify the toxicity of this material during its thermochemical treatment at low temperature.

Transgenerational Transmission of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) Effects in Human Granulosa Cells: The Role of MicroRNAs

Endocrine-disrupting chemicals (EDCs) might contribute to the increase in female-specific cancers in Western countries. 2,3,7,8-tetrachlordibenzo-p-dioxin (TCDD) is considered the "prototypical toxicant" to study EDCs' effects on reproductive health. Epigenetic regulation by small noncoding RNAs (sncRNAs), such as microRNAs (miRNA), is crucial for controlling cancer development. The aim of this study was to analyze transcriptional activity and sncRNA expression changes in the KGN cell line after acute (3 h) and chronic (72 h) exposure to 10 nM TCDD in order to determine whether sncRNAs' deregulation may contribute to transmitting TCDD effects to the subsequent cell generations (day 9 and day 14 after chronic exposure). Using Affymetrix GeneChip miRNA 4.0 arrays, 109 sncRNAs were found to be differentially expressed (fold change < -2 or >2; p-value < 0.05) between cells exposed or not (control) to TCDD for 3 h and 72 h and on day 9 and day 14 after chronic exposure. Ingenuity Pathway Analysis predicted that following the acute and chronic exposure of KGN cells, sncRNAs linked to cellular development, growth and proliferation were downregulated, and those linked to cancer promotion were upregulated on day 9 and day 14. These results indicated that TCDD-induced sncRNA dysregulation may have transgenerational cancer-promoting effects.

Association between cumulative airborne dioxin exposure and non-Hodgkin's lymphoma risk in a nested case-control study within the French E3N cohort

BACKGROUND

Dioxins are a family of chemical molecules that are chlorinated, lipophilic, and bio-accumulative. They are thought to enhance the risk of non-lymphoma Hodgkin's due to their known carcinogenic properties (NHL). This is the first epidemiological research to investigate the relationship between repeated emissions of airborne dioxin exposure and the risk of NHL.

OBJECTIVE

A case-control study nested within the French E3N cohort of 98,995 women covered by the health insurance provider of the national education system evaluated the association between cumulative airborne dioxin exposure and NHL risk.

MATERIALS AND METHODS

NHL incident cases (368) and controls (368) were compared. Over the duration of the study, participants' residential histories and the locations of industrial sites were gathered (1990-2008). Using a Geographic Information System (GIS)-based exposure index, the cumulative exposure to airborne dioxins for each participant was calculated at the individual address level. The odds ratios (OR) and 95 % confidence intervals (CI) were calculated using multivariable conditional logistic regression models (CI).

RESULTS

The log-transformed continuous cumulative dioxin exposure index was substantially correlated with the risk of NHL (OR1.2 (95 % CI 1.0,1.4) for an increase in log-TEQ/m2 of 4.4, or one standard deviation). The combined chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL) subtype was significantly associated with NHL histological subtypes (OR 1.6 (95 % CI 1.1,2.3)).

CONCLUSION

The findings of this study demonstrate a significant positive correlation between cumulative airborne dioxin exposure and the risk of NHL in women, and more specifically, a significant positive association for the CLL & SLL subtype. These results help to support the attempts to reduce the exposure to dioxins in the air.

Rapid Non-Contact Detection of Chemical Warfare Agents by Laser Photoacoustic Spectroscopy

Nerve agents have recently been used in battlefield operations, espionage wars, and terrorist attacks. These compounds, like some pesticides, cause organophosphate poisoning. The rapid, noncontact detection of a sarin simulant in the liquid phase has been demonstrated at the Diagnostics and Metrology Laboratory of the Italian National Agency for New Technologies, Energy and Sustainable Economic Development using laser photoacoustic spectroscopy, an infrared absorption technology. The first measurements, carried out with an experimental system based on a quantum cascade laser and developed for the assessment of food authenticity in the "fingerprint region", show that a detection limit of one nanolitre is within the reach of the instrument when chemometric analysis is applied.

Biomass Pyrolysis-Derived Biochar: A Versatile Precursor for Graphene Synthesis

Graphene, a two-dimensional carbon allotrope with a honeycomb structure, has emerged as a material of immense interest in diverse scientific and technical domains. It is mainly produced from graphite by mechanical, chemical and electrochemical exfoliation. As renewable energy and source utilization increase, including bioenergy from forest and woody residues, processed, among other methods, by pyrolysis treatment, it can be expected that biochar production will increase too. Thus, its useful applications, particularly in obtaining high-added-value products, need to be fully explored. This study aims at presenting a comprehensive analysis derived from experimental data, offering insights into the potential of biomass pyrolysis-derived biochar as a versatile precursor for the controlled synthesis of graphene and its derivatives. This approach comprehended the highest energy output and lowest negative environmental footprint, including the minimization of both toxic gas emissions during processing and heavy metals' presence in the feedstock, toward obtaining biochar suitable to be modified, employing the Hummers and intercalation with persulfate salts methods, aiming at deriving graphene-like materials. Material characterization has revealed that besides morphology and structural features of the original wooden biomass, graphitized structures are present as well, which is proven clearly by Raman and XPS analyses. Electrochemical tests revealed higher conductivity in modified samples, implying their graphene-like nature.

Effect of TCDD exposure in adult female and male mice on the expression of miRNA in the ovaries and testes and associated reproductive functions

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an environmental contaminant found widely across the world. While animal and human studies have shown that exposure to TCDD may cause significant alterations in the reproductive tract, the effect of TCDD on the expression of miRNA in the reproductive organs has not been previously tested. In the current study, we exposed adult female or male mice to TCDD or vehicle and bred them to study the impact on reproduction. The data showed that while TCDD treatment of females caused no significant change in litter size, it did alter the survival of the pups. Also, TCDD exposure of either the male or female mice led to an increase in the gestational period. While TCDD did not alter the gross morphology of the ovaries and testes, it induced significant alterations in the miRNA expression. The ovaries showed the differential expression of 426 miRNAs, of which 315 miRNAs were upregulated and 111 miRNA that were downregulated after TCDD exposure when compared to the vehicle controls. In the testes, TCDD caused the differential expression of 433 miRNAs, with 247 miRNAs upregulated and 186 miRNAs downregulated. Pathway analysis showed that several of these dysregulated miRNAs targeted reproductive functions. The current study suggests that the reproductive toxicity of TCDD may result from alterations in the miRNA expression in the reproductive organs. Because miRNAs also represent one of the epigenetic pathways of gene expression, our studies suggest that the transgenerational toxicity of TCDD may also result from dysregulation in the miRNAs.

The Potential Influence of Uremic Toxins on the Homeostasis of Bones and Muscles in Chronic Kidney Disease

Patients with chronic kidney disease (CKD) often experience a high accumulation of protein-bound uremic toxins (PBUTs), specifically indoxyl sulfate (IS) and p-cresyl sulfate (pCS). In the early stages of CKD, the buildup of PBUTs inhibits bone and muscle function. As CKD progresses, elevated PBUT levels further hinder bone turnover and exacerbate muscle wasting. In the late stage of CKD, hyperparathyroidism worsens PBUT-induced muscle damage but can improve low bone turnover. PBUTs play a significant role in reducing both the quantity and quality of bone by affecting osteoblast and osteoclast lineage. IS, in particular, interferes with osteoblastogenesis by activating aryl hydrocarbon receptor (AhR) signaling, which reduces the expression of Runx2 and impedes osteoblast differentiation. High PBUT levels can also reduce calcitriol production, increase the expression of Wnt antagonists (SOST, DKK1), and decrease klotho expression, all of which contribute to low bone turnover disorders. Furthermore, PBUT accumulation leads to continuous muscle protein breakdown through the excessive production of reactive oxygen species (ROS) and inflammatory cytokines. Interactions between muscles and bones, mediated by various factors released from individual tissues, play a crucial role in the mutual modulation of bone and muscle in CKD. Exercise and nutritional therapy have the potential to yield favorable outcomes. Understanding the underlying mechanisms of bone and muscle loss in CKD can aid in developing new therapies for musculoskeletal diseases, particularly those related to bone loss and muscle wasting.

Origin, dietary exposure, and toxicity of endocrine-disrupting food chemical contaminants: A comprehensive review

Endocrine-disrupting chemicals (EDCs) are a growing public health concern worldwide. Consumption of foodstuffs is currently thought to be one of the principal exposure routes to EDCs. However, alternative ways of human exposure are through inhalation of chemicals and dermal contact. These compounds in food products such as canned food, bottled water, dairy products, fish, meat, egg, and vegetables are a ubiquitous concern to the general population. Therefore, understanding EDCs' properties, such as origin, exposure, toxicological impact, and legal aspects are vital to control their release to the environment and food. The present paper provides an overview of the EDCs and their possible disrupting impact on the endocrine system and other organs.

Thermal Susceptibility of Nickel in the Manufacture of Softeners

The chemical industry includes a wide range of factories focused on obtaining final products as: (i) plastics; (ii) chemical fibers; (iii) rubber; (iv) perfumery and cosmetic products; and (v) cleaning products. Although the level of safety in the activities and installations of this sector is very high, the use of dangerous substances implies an increased risk of suffering an accident involving the emission of hazardous substances, as well as endangering the safety of workers. In the case of the manufacture of softeners, the presence of isopropanol (C3H8O), and dimethyl sulfate (CH3)2SO4), have been reported to be the accident cause in most of the cases. The European accident database (eMars) reported an accident in which the presence of impurities of nickel (Ni) in the hydrogenated tallow used as raw material for softener production may have increased thermal reactivity and the chances of spontaneous combustion. This paper analyzes the results obtained with the Maciejasz Index (MI) to understand the thermal susceptibility of these substances in liquid state. The results show that combinations of nickel (hydrogenated tallow catalyst) with other liquid substances (isopropanol, dimethyl sulfate, and sulfuric acid) are not sufficiently reactive with oxygen to cause a spontaneous combustion.

Functions of the aryl hydrocarbon receptor (AHR) beyond the canonical AHR/ARNT signaling pathway

The aryl hydrocarbon receptor (AHR) is a ligand-dependent transcription factor regulating adaptive and maladaptive responses toward exogenous and endogenous signals. Research from various biomedical disciplines has provided compelling evidence that the AHR is critically involved in the pathogenesis of a variety of diseases and disorders, including autoimmunity, inflammatory diseases, endocrine disruption, premature aging and cancer. Accordingly, AHR is considered an attractive target for the development of novel preventive and therapeutic measures. However, the ligand-based targeting of AHR is considerably complicated by the fact that the receptor does not always follow the beaten track, i.e. the canonical AHR/ARNT signaling pathway. Instead, AHR might team up with other transcription factors and signaling molecules to shape gene expression patterns and associated physiological or pathophysiological functions in a ligand-, cell- and micromilieu-dependent manner. Herein, we provide an overview about some of the most important non-canonical functions of AHR, including crosstalk with major signaling pathways involved in controlling cell fate and function, immune responses, adaptation to low oxygen levels and oxidative stress, ubiquitination and proteasomal degradation. Further research on these diverse and exciting yet often ambivalent facets of AHR biology is urgently needed in order to exploit the full potential of AHR modulation for disease prevention and treatment.

Serum levels of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in a sample of Lebanese pregnant women: The role of dietary, anthropometric, and environmental factors

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are unintentionally produced, toxic environmental chemicals that persist for long years and bioaccumulate along the food chain, contaminating humans through diet. A particularly critical population subgroup is pregnant women given the adverse health effects on fetuses and newborns. Several anthropogenic sources of exposure to PCDD/Fs exist in Lebanon. Therefore, the aim of the present cross-sectional study is to measure the levels of PCDD/Fs in a sample of pregnant women in Lebanon and to explore potential associated factors. In this study, we measured serum concentrations of seven dioxins and ten furans, among 423 pregnant women recruited at delivery, using gas chromatography MS/MS. Among 269 participants, maternal sociodemographic information was collected including vicinity to landfills, incineration, pesticide use, industrial activity, and smoking. Anthropometric data were registered regarding pre-pregnancy body mass index (BMI), pre-pregnancy weight loss from restrictive diet, and gestational weight gain. Intake of major food groups generally related to PCDD/Fs was reported (fish, red meat, poultry, and dairy). Bivariate and multivariate analyses were performed to identify associations. PCDD/Fs were detected in 0 to 56.1% of the sample. Geometric mean concentrations were 75.5 (2.35) pg/g lipid and 2.25 (1.39) TEQ₂₀₀₅ pg/g lipid for total dioxins, and 2.66 (1.76) pg/g lipid and 0.34 (1.78) TEQ₂₀₀₅ pg/g lipid for total furans. Levels were relatively lower than levels previously observed in France, Germany, Mexico, Ghana, and Japan. Red meat consumption was the most consistently associated factor with a 2.38-2.57 fold increase in PCDD/F levels. Pre-pregnancy weight loss showed inverse associations with PCDD/F congeners. Vicinity to illegal incineration was also associated with a 2.32-2.43 fold increase in PCDD/F levels. In conclusion, results showed the importance of dietary, anthropometric, and environmental factors in the present sample's exposure to PCDD/Fs, in a region that contains anthropogenic sources of contamination.

Feed as a source of dioxins and PCBs

Dioxins (PCDD/PCDF) and polychlorinated biphenyls (PCBs) are a group of undesirable chemicals classified as persistent organic pollutants (POPs). The main route of human exposure to these compounds is through the diet (about 80%), with food of animal origin being the predominant source. For this reason, animal feed can contribute significantly to the presence of these compounds in food. The aim of this study was to present the concentrations of dioxins and PCBs as well as congener profiles in feed exceeding the acceptable limits (277/2012/EU). In addition, an attempt was made to identify the source of contamination for the different types of contaminated feedstuffs. Among a total of 743 samples of feed materials from the Polish market tested between 2013 and 2021, exceedances of the maximum levels of dioxins and PCBs were found in 21 samples (2.8%). The largest group among the non-compliant feed samples were feed materials of plant origin (43%) followed in decreasing order by vegetable oils and fats of animal origin (24%), materials of mineral origin (9%), and fish oils and meals (5%). The exceedances of the dioxin limits in the category feed materials of plant origin were only caused by dried materials (pulp, dried alfalfa, dried apple). Furthermore, for 8 (1%) samples, the concentrations of test substances exceeding the Action Levels (AL) were recorded.

Impact of mixtures of persistent organic pollutants on breast cancer aggressiveness

INTRODUCTION

Breast cancer (BC) is frequent with a poor prognosis in case of metastasis. The role of the environment has been poorly evaluated in its progression. We searched to assess whether a mixture of pollutants could be responsible of BC aggressiveness.

METHODS

Patients undergoing surgery for their BC were prospectively included in the METAPOP cohort. Forty-two POPs were extracted, among them 17 dioxins (PCDD/F), 16 polychlorobiphenyls (PCB), 8 polybromodiphenylethers (PBDE) and 2,2',4,4',5,5'-hexabromobiphenyl (PBB153) were measured in the adipose tissue surrounding the tumor. BC aggressiveness was defined using tumor size and metastasis (distant or lymph nodes). Two complementary models were used to evaluate the impact of the mixture of pollutants: the BKMR (Bayesian Kernel machine regression) and WQS (weighted quantile sum regression) models. The WQS estimates the weight (positive or negative) of a certain chemical based on its quantile and the BKMR model applies a kernel-based approach to estimate posterior inclusion probabilities. The sub-group of patients with a body mass index (BMI) > 22 kg/ m² was also analyzed.

RESULTS

Ninety-one patients were included. Of these, 38 patients presented a metastasis, and the mean tumor size was 25.4 mm. The mean BMI was 24.5 kg/m² (+/- 4.1). No statistical association was found in the general population. However, in patients with a BMI > 22 kg/ m², our mixture was positively associated with tumor size (OR: 9.73 95 %CI: 1.30-18.15) and metastasis (OR = 3.98 95 %CI = 1.09-17.53) using the WQS model. Moreover, using the BKMR model on chemical families, dioxin like chemicals and PCDD were associated with a higher risk of metastasis.

DISCUSSION

These novel findings identified a mixture associated with breast cancer aggressiveness in patients with a BMI > 22 kg/ m².

Effects of dioxins on animal spermatogenesis: A state-of-the-art review

The male reproductive system is especially affected by dioxins, a group of persistent environmental pollutants, resulting in irreversible abnormalities including effects on sexual function and fertility in adult males and possibly on the development of male offspring. The reproductive toxicity caused by dioxins is mostly mediated by an aryl hydrocarbon receptor (AhR). In animals, spermatogenesis is a highly sensitive and dynamic process that includes proliferation and maturation of germ cells. Spermatogenesis is subject to multiple endogenous and exogenous regulatory factors, including a wide range of environmental toxicants such as dioxins. This review discusses the toxicological effects of dioxins on spermatogenesis and their relevance to male infertility. After a detailed categorization of the environmental contaminants affecting the spermatogenesis, the exposure pathways and bioavailability of dioxins in animals was briefly reviewed. The effects of dioxins on spermatogenesis are then outlined in detail. The endocrine-disrupting effects of dioxins in animals and humans are discussed with a particular focus on their effects on the expression of spermatogenesis-related genes. Finally, the impacts of dioxins on the ratio of X and Y chromosomes, the status of serum sex hormones, the quality and fertility of sperm, and the transgenerational effects of dioxins on male reproduction are reviewed.

Comparative Toxicotranscriptomics of Single Cell RNA-Seq and Conventional RNA-Seq in TCDD-Exposed Testicular Tissue

In this report, we compare the outcomes and limitations of two methods of transcriptomic inquiry on adult zebrafish testes exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) during sexual differentiation: conventional or bulk RNA-seq (bulk-seq) and single cell RNA sequencing (scRNA-seq) data. scRNA-seq has emerged as a valuable tool for uncovering cell type-specific transcriptome dynamics which exist in heterogeneous tissue. Our lab previously showed the toxicological value of the scRNA-seq pipeline to characterize the sequelae of TCDD exposure in testes, demonstrating that loss of spermatids and spermatozoa, but not other cell types, contributed to the pathology of infertility in adult male zebrafish exposed during sexual differentiation. To investigate the potential for technical artifacts in scRNA-seq such as cell dissociation effects and reduced transcriptome coverage, we compared bulk-sequenced and scRNA-seq-paired samples from control and TCDD-exposed samples to understand what is gained and lost in scRNA-seq vs bulk-seq, both transcriptomically and toxicologically. We hypothesized that the testes may be sensitive to tissue disruption as they contain multiple cell types under constant division and/or maturation, and that TCDD exposure may mediate the extent of sensitivity. Thus, we sought to understand the extent to which this dissociation impacts the toxicological value of data returned from scRNA-seq. We confirm that the required dissociation of individual cells from intact tissue has a significant impact on gene expression, affecting gene pathways with the potential to confound toxicogenomics studies on exposures if findings are not well-controlled and well-situated in context. Additionally, a common scRNA-seq method using cDNA amplified from the 3' end of mRNA under-detects low-expressing transcripts including transcription factors. We confirm this, and show TCDD-related genes may be overlooked by scRNA-seq, however, this under-detection effect is not mediated by TCDD exposure. Even so, scRNA-seq generally extracted toxicologically relevant information better than the bulk-seq method in the present study. This report aims to inform future experimental design for transcriptomic investigation in the growing field of toxicogenomics by demonstrating the differential information extracted from sequencing cells-despite being from the same tissue and exposure scheme-is influenced by the specific protocol used, with implications for the interpretation of exposure-induced risk.

Impact of High-Throughput Model Parameterization and Data Uncertainty on Thyroid-Based Toxicological Estimates for Pesticide Chemicals

Chemical-induced alteration of maternal thyroid hormone levels may increase the risk of adverse neurodevelopmental outcomes in offspring. US federal risk assessments rely almost exclusively on apical endpoints in animal models for deriving points of departure (PODs). New approach methodologies (NAMs) such as high-throughput screening (HTS) and mechanistically informative in vitro human cell-based systems, combined with in vitro to in vivo extrapolation (IVIVE), supplement in vivo studies and provide an alternative approach to calculate/determine PODs. We examine how parameterization of IVIVE models impacts the comparison between IVIVE-derived equivalent administered doses (EADs) from thyroid-relevant in vitro assays and the POD values that serve as the basis for risk assessments. Pesticide chemicals with thyroid-based in vitro bioactivity data from the US Tox21 HTS program were included (n = 45). Depending on the model structure used for IVIVE analysis, up to 35 chemicals produced EAD values lower than the POD. A total of 10 chemicals produced EAD values higher than the POD regardless of the model structure. The relationship between IVIVE-derived EAD values and the in vivo-derived POD values is highly dependent on model parameterization. Here, we derive a range of potentially thyroid-relevant doses that incorporate uncertainty in modeling choices and in vitro assay data.

Obesity II: Establishing causal links between chemical exposures and obesity

Obesity is a multifactorial disease with both genetic and environmental components. The prevailing view is that obesity results from an imbalance between energy intake and expenditure caused by overeating and insufficient exercise. We describe another environmental element that can alter the balance between energy intake and energy expenditure: obesogens. Obesogens are a subset of environmental chemicals that act as endocrine disruptors affecting metabolic endpoints. The obesogen hypothesis posits that exposure to endocrine disruptors and other chemicals can alter the development and function of the adipose tissue, liver, pancreas, gastrointestinal tract, and brain, thus changing the set point for control of metabolism. Obesogens can determine how much food is needed to maintain homeostasis and thereby increase the susceptibility to obesity. The most sensitive time for obesogen action is in utero and early childhood, in part via epigenetic programming that can be transmitted to future generations. This review explores the evidence supporting the obesogen hypothesis and highlights knowledge gaps that have prevented widespread acceptance as a contributor to the obesity pandemic. Critically, the obesogen hypothesis changes the narrative from curing obesity to preventing obesity.

A Statistical Analysis of Hazardous Chemical Fatalities (HCFs) in China between 2015 and 2021

To study the occurrence characteristics of hazardous chemical accidents in China, mathematical analysis methods were used to study hazardous chemical fatalities (HCFs) in recent years. This research focused on selecting seven accident characteristics including time characteristics, geographical characteristics, accident type characteristics, hazardous chemical types, hazardous chemical production links, accident cause characteristics, and accident classification. The research results show that: (1) the occurrence of HCFs has obvious time-domain and regional characteristics, the number of casualties on Wednesday working days is the largest, 9:00–11:00 (inclusive) and 15:00–16:00 (inclusive) in a day are the two time periods with the largest number of incidents, the number of hazardous chemical accidents and deaths in economically developed coastal provinces is relatively high; (2) Analyze according to the type of accident statistics, the number of accidents and deaths caused by explosions, poisoning, asphyxiation, and fire are the largest; (3) Analyze according to the type of hazardous chemicals, drugs, compressed gas and liquefied gas, flammable solids, and spontaneous combustion materials, as well as flammable materials when wet are the types of hazardous chemicals that cause the most casualties; (4) Analyze according to the type of hazardous chemical accidents, the number of accidents and deaths caused in the production process is the largest; (5) Analyze according to the type of unsafe behavior by personnel, operator errors, the ignorance of safety, and the ignorance of warnings are the main causes of injuries and deaths caused by hazardous chemicals.; (6) Through single-factor feature analysis and multi-feature comprehensive cross-discussion, countermeasures, and suggestions for preventing and controlling accidents in hazardous chemical enterprises are put forward according to the characteristics of accidents caused by different accident characteristics.

Molecular Probes, Chemosensors, and Nanosensors for Optical Detection of Biorelevant Molecules and Ions in Aqueous Media and Biofluids

Synthetic molecular probes, chemosensors, and nanosensors used in combination with innovative assay protocols hold great potential for the development of robust, low-cost, and fast-responding sensors that are applicable in biofluids (urine, blood, and saliva). Particularly, the development of sensors for metabolites, neurotransmitters, drugs, and inorganic ions is highly desirable due to a lack of suitable biosensors. In addition, the monitoring and analysis of metabolic and signaling networks in cells and organisms by optical probes and chemosensors is becoming increasingly important in molecular biology and medicine. Thus, new perspectives for personalized diagnostics, theranostics, and biochemical/medical research will be unlocked when standing limitations of artificial binders and receptors are overcome. In this review, we survey synthetic sensing systems that have promising (future) application potential for the detection of small molecules, cations, and anions in aqueous media and biofluids. Special attention was given to sensing systems that provide a readily measurable optical signal through dynamic covalent chemistry, supramolecular host-guest interactions, or nanoparticles featuring plasmonic effects. This review shall also enable the reader to evaluate the current performance of molecular probes, chemosensors, and nanosensors in terms of sensitivity and selectivity with respect to practical requirement, and thereby inspiring new ideas for the development of further advanced systems.

Molecular mechanism of benzo [a] pyrene regulating lipid metabolism via aryl hydrocarbon receptor

BACKGROUND

Benzo [a] pyrene (BaP), a potent carcinogen, has been proved that it has toxicological effects via activation the aryl hydrocarbon receptor (AhR) pathway. AhR can participate in regulating lipogenesis and lipolysis. This topic will verify whether BaP regulates lipid metabolism via AhR.

METHODS

(1) C57BL/6 mice were gavaged with BaP for 12 weeks to detect serum lipids, glucose tolerance, and insulin resistance. Morphological changes in white adipose tissue (WAT) were detected by Hematoxylin and Eosin staining. The mRNA expression levels of adipogenesis-related factors included recombinant human CCAAT/enhancer binding protein alpha (C/EBPα), peroxisome proliferator-activated receptor gamma (PPARγ), and fatty acid binding protein 4 (FABP4) and inflammatory factors included nuclear factor kappa-B (NF-κB), monocyte chemotactic protein-1 (MCP-1), and tumor necrosis factor alpha (TNF-α) were detected using PCR. (2) Neutral lipid content changes in differentiated 3 T3-L1 adipocytes treated with BaP with and w/o AhR inhibitor were detected by Oil red staining. The protein expression levels of adipogenesis- and decomposition-related factors included PPARγ coactivator-1 alpha (PGC-1α), and peroxisome proliferation-activated receptor alpha (PPARα) were detected using western blotting. The mRNA expression levels of inflammatory factors were detected using PCR.

RESULTS

(1) BaP inhibited body weight gain, decreased lipid content, increased lipid levels, and decreased glucose tolerance and insulin tolerance in mice; (2) BaP reduced the expressions of C/EBPα, PPARγ, FABP4, PGC-1α, and PPARα and increased the expressions of NF-κB, MCP-1, and TNF-α by activating AhR.

CONCLUSION

BaP inhibit fat synthesis and oxidation while inducing inflammation by activating AhR, leading to WAT dysfunction and causing metabolic complications.

Dioxin-like Activity in Pregnant Women and Indices of Fetal Growth: The ACCEPT Birth Cohort

Exposure to lipophilic persistent organic pollutants (lipPOPs) elicits a number of species- and tissue-specific toxic responses, many of which involve the aryl hydrocarbon receptor (AhR). This study aims to measure the combined serum dioxin-like activity of lipPOPs in Greenlandic Inuit pregnant women and the associations with fetal growth indices. The combined dioxin-like activity of serum lipPOPs extracts was determined using the AhR reporter gene bioassay and expressed as pico-gram (pg) TCDD equivalent (TEQ) per gram serum lipid [AhR-TEQ (pg/g lipid)]. Significant AhR-TEQ was found in >87% of serum samples with the median level of 86.2 pg TEQ/g lipid. The AhR-TEQ level positively correlated with the marine food intake biomarker n-3/n-6 polyunsaturated fatty acids ratio, while negatively correlated with body mass index and parity. Women giving birth to infants with low birth weight (<2500 g) and length (<50 cm) had higher AhR-TEQ level compared to those with normal weight and length infants. For previous smokers, we found significant inverse associations between maternal AhR-TEQ level and fetal growth indices. In conclusion, exposure of Greenlandic Inuit pregnant women to dioxin-like compounds through traditional marine food can adversely influence the fetal growth via induced AhR activity. Smoking might have modifying effects.

Experimental Evidence of 2,3,7,8-Tetrachlordibenzo-p-Dioxin (TCDD) Transgenerational Effects on Reproductive Health

Previous studies have demonstrated that endocrine disruptors (EDs) can promote the transgenerational inheritance of disease susceptibility. Among the many existing EDs, 2,3,7,8-tetrachlordibenzo-p-dioxin (TCDD) affects reproductive health, including in humans, following direct occupational exposure or environmental disasters, for instance the Agent Orange sprayed during the Vietnam War. Conversely, few studies have focused on TCDD multigenerational and transgenerational effects on human reproductive health, despite the high amount of evidence in animal models of such effects on male and female reproductive health that mimic human reproductive system disorders. Importantly, these studies show that paternal ancestral TCDD exposure substantially contributes to pregnancy outcome and fetal health, although pregnancy outcome is considered tightly related to the woman’s health. In this work, we conducted a systematic review of the literature and a knowledge synthesis in order (i) to describe the findings obtained in rodent models concerning TCDD transgenerational effects on reproductive health and (ii) to discuss the epigenetic molecular alterations that might be involved in this process. As ancestral toxicant exposure cannot be changed in humans, identifying the crucial reproductive functions that are negatively affected by such exposure may help clinicians to preserve male and female fertility and to avoid adverse pregnancy outcomes.

Environmental Exposure to Endocrine Disrupting Chemicals Influences Genomic Imprinting, Growth, and Metabolism

Genomic imprinting is an epigenetic mechanism that results in monoallelic, parent-of-origin-specific expression of a small number of genes. Imprinted genes play a crucial role in mammalian development as their dysregulation result in an increased risk of human diseases. DNA methylation, which undergoes dynamic changes early in development, is one of the epigenetic marks regulating imprinted gene expression patterns during early development. Thus, environmental insults, including endocrine disrupting chemicals during critical periods of fetal development, can alter DNA methylation patterns, leading to inappropriate developmental gene expression and disease risk. Here, we summarize the current literature on the impacts of in utero exposure to endocrine disrupting chemicals on genomic imprinting and metabolism in humans and rodents. We evaluate how early-life environmental exposures are a potential risk factor for adult metabolic diseases. We also introduce our mouse model of phthalate exposure. Finally, we describe the potential of genomic imprinting to serve as an environmental sensor during early development and as a novel biomarker for postnatal health outcomes.

Praegnatio Perturbatio-Impact of Endocrine-Disrupting Chemicals

The burden of adverse pregnancy outcomes such as preterm birth and low birth weight is considerable across the world. Several risk factors for adverse pregnancy outcomes have been identified. One risk factor for adverse pregnancy outcomes receiving considerable attention in recent years is gestational exposure to endocrine-disrupting chemicals (EDCs). Humans are exposed to a multitude of environmental chemicals with known endocrine-disrupting properties, and evidence suggests exposure to these EDCs have the potential to disrupt the maternal-fetal environment culminating in adverse pregnancy and birth outcomes. This review addresses the impact of maternal and fetal exposure to environmental EDCs of natural and man-made chemicals in disrupting the maternal-fetal milieu in human leading to adverse pregnancy and birth outcomes-a risk factor for adult-onset noncommunicable diseases, the role lifestyle and environmental factors play in mitigating or amplifying the effects of EDCs, the underlying mechanisms and mediators involved, and the research directions on which to focus future investigations to help alleviate the adverse effects of EDC exposure.

Multiple persistent organic pollutants in mothers' breastmilk: Implications for infant dietary exposure and maternal thyroid hormone homeostasis in Uganda, East Africa

Persistent organic pollutants (POPs) are ubiquitous contaminants with adverse health effects in the ecosystem. One of such effects is endocrine disruption in humans and wildlife even at background exposure concentrations. This study assessed maternal breastmilk concentrations of POPs; brominated flame retardants (BFRs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs), and the potential health risks posed to the nursing infants. We also evaluated the association of these POPs with total 3,3',5-triiodo-L-thyronine (T₃), L-thyroxine (T₄), and 3,3',5'-triiodo-L-thyronine (rT₃) levels measured in human breast milk. Thirty breastmilk samples were collected from Kampala, Uganda between August and December 2018. Hexabromobenzene was not detected while the maximum level of 2,2',4,4',5,5'-hexabrombiphenyl was 64.7 pg/g lw. The median levels of total indicator PCBs, PBDEs, dioxin-like PCBs, and PCDD/Fs in the samples were 159 pg/g lw, 511 pg/g lw, 1.16 pg TEQ/g lw, and 0.4 pg TEQ/g lw, respectively. These levels were lower than those reported in other countries. Owing to their bio accumulative nature, PCBs -81, -169, and ∑PCDD/Fs increased with increase in maternal age. Estimated dietary intakes for dioxin-like PCBs and PCDD/Fs were lower than those reported elsewhere but were higher than the WHO tolerable daily intakes suggesting potential health risks to nursing infants. In adjusted single pollutant models, PCB-126, PCB-169, and ∑PCB_TEQ were negatively associated with T₃, while 1,2,3,4,5,7,8-HpCDF was positively associated with rT₃. Although these associations did not persist in multipollutant models, our findings suggest potential thyroid hormone disruption by POPs in mothers. This may reduce the levels of thyroid hormones transferred from the mother to the neonates and, hence, adversely influence infant growth. A temporal study with a bigger sample size is required to corroborate these findings.

Association of persistent organic pollutants with sensorimotor neuropathy in participants with and without diabetes or prediabetes: Results from the population-based KORA FF4 study

BACKGROUND

Concentrations of persistent organic pollutants (POPs) have been associated with an increased type 2 diabetes (T2D) risk. It remains unclear whether POPs are also associated with the risk of diabetes complications including neuropathy and evidence on this topic is scarce. We aimed to investigate the hypothesis that low-dose background concentrations of POPs were positively associated with distal sensorimotor polyneuropathy (DSPN).

METHODS

This cross-sectional study was based on data from the second follow-up (FF4, 2013-2014, N = 2279) of the population-based KORA S4 study (Augsburg, Germany). The study sample consisted of 200 participants, including four groups of 50 persons each with known T2D, prediabetes, newly diagnosed diabetes, and normal glucose tolerance (NGT) based on an oral glucose tolerance test. We analyzed the association of six most abundant serum concentrations of POPs, including polychlorinated biphenyls (PCBs) as well as organochlorine (OC) pesticides, with DSPN by multivariable logistic regression adjusted for age, sex, glycaemic status, body mass index, physical activity, smoking and alcohol consumption. We assessed effect modification by age, sex, glycaemic status and obesity and conducted two-pollutant models to check the robustness of the estimates.

RESULTS

For all pollutants, the main models indicated no significant association of having DSPN but pointed to rather decreased odds for DSPN. Two-pollutant models supported these findings, though only the association between the combination of PCB-138 and beta-hexachlorocyclohexane (β-HCH) (OR: 0.59; 95% CI: 0.35-0.99) with DSPN became significant. No effect modification was found by age, sex, glycaemic status and obesity.

CONCLUSION

Low-dose concentrations of POPs were not associated with increased odds of having DSPN in T2D, prediabetes and NGT.

Persistent organic pollutants at the synapse: Shared phenotypes and converging mechanisms of developmental neurotoxicity

The developing nervous system is sensitive to environmental and physiological perturbations in part due to its protracted period of prenatal and postnatal development. Epidemiological and experimental studies link developmental exposures to persistent organic pollutants (POPs) including polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, polybrominated diphenyl ethers, and benzo(a)pyrene to increased risk for neurodevelopmental disorders in children. Mechanistic studies reveal that many of the complex cellular processes that occur during sensitive periods of rapid brain development are cellular targets for developmental neurotoxicants. One area of research interest has focused on synapse formation and plasticity, processes that involve the growth and retraction of dendrites and dendritic spines. For each chemical discussed in this review, we summarize the morphological and electrophysiological data that provide evidence that developmental POP exposure produces long-lasting effects on dendritic morphology, spine formation, glutamatergic and GABAergic signaling systems, and synaptic transmission. We also discuss shared intracellular mechanisms, with a focus on calcium and thyroid hormone homeostasis, by which these chemicals act to modify synapses. We conclude our review highlighting research gaps that merit consideration when characterizing synaptic pathology elicited by chemical exposure. These gaps include low-dose and nonmonotonic dose-response effects, the temporal relationship between dendritic growth, spine formation, and synaptic activity, excitation-inhibition balance, hormonal effects, and the need for more studies in females to identify sex differences. By identifying converging pathological mechanisms elicited by POP exposure at the synapse, we can define future research directions that will advance our understanding of these chemicals on synapse structure and function.

Endocrine-Disrupting Chemicals: Introduction to the Theme

BACKGROUND

Endocrine-disrupting chemicals (EDCs) are natural or synthetic compounds deriving from different human activities and are widely spread into the environment, contributing to indoor and outdoor pollution. EDCs may be conveyed by food and water consumption and skin, airways, placental, and breastfeeding. Upon entering the circulation, they can interfere with endocrine system homeostasis by several mechanisms.

AIM

In this narrative review, the authors overviewed the leading mechanisms by which EDCs interact and disrupt the endocrine system, leading to possible human health concerns.

RESULTS

The leading mechanisms of EDCs-related toxicity have been illustrated in in vitro studies and animal models and may be summarized as follows: receptor agonism and antagonism; modulation of hormone receptor expression; interference with signal transduction in hormone-responsive cells; epigenetic modifications in hormone-producing or hormone-responsive cells; interference with hormone synthesis; interference with hormone transport across cell membranes; interference with hormone metabolism or clearance; interference with the destiny of hormone-producing or hormone-responsive cells.

DISCUSSION

Despite these well-defined mechanisms, some limitations do not allow for conclusive assumptions. Indeed, epidemiological and ecological studies are currently lacking and usually refer to a specific cluster of patients (occupational exposure). Methodological aspects could further complicate the issue since these studies could require a long time to provide useful information. The lack of a real unexposed group in environmental conditions, possible interference of EDCs mixture on biological results, and unpredictable dose-response curves for some EDCs should also be considered significant limitations.

CONCLUSION

Given these limitations, specific observational and long-term studies are needed to identify at-risk populations for adequate treatment of exposed patients and effective prevention plans against excessive exposure to EDCs.

Attenuation of growth hormone production at the fetal stage is critical for dioxin-induced developmental disorder in rat offspring

Although dioxins and related chemicals have been suspected to disrupt child development, their toxic mechanism remains poorly understood. Our previous studies in rat fetuses revealed that maternal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a highly-toxic dioxin, suppresses fetal synthesis of pituitary growth hormone (GH) that is essential for development. This study examined the hypothesis that attenuating GH expression in fetuses triggers developmental disorders. Treating pregnant rats with 1 μg/kg TCDD reduced the circulating level of GH and its downstream factor, insulin-like growth factor-1 (IGF-1), in the offspring only during the fetal and early neonatal stages. Although maternal TCDD exposure resulted in low body weight and length at babyhood and defects in the learning and memory ability at adulthood, GH supplementation in TCDD-exposed fetuses restored or tended to restore the defects including IGF-1 downregulation. Moreover, maternal TCDD exposure decreased the number of GH-positive cells during the fetal/neonatal stage. A microarray analysis showed that TCDD reduced the expression of death-associated protein-like 1 (DAPL1), a cell cycle-dependent proliferation regulator, in the fetal pituitary gland. In addition, TCDD treatment attenuated proliferating cells and cyclin mRNA expression in the fetal pituitary gland. Aryl hydrocarbon receptor (AHR)-knockout fetuses were insensitive to TCDD treatment, indicating that the TCDD-induced reduction in DAPL1 and GH mRNAs expression was due to AHR activation. Finally, DAPL1 knockdown suppressed GH and cyclin D2 expression in fetal pituitary cells. These results provide a novel evidence that dioxin suppresses GH-producing cell proliferation and GH synthesis due to partly targeting DAPL1, thereby impairing offspring development.

Dioxin exposure associated with fecundability and infertility in mothers and daughters of Seveso, Italy

STUDY QUESTION

Is there an association between 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure and fecundability and infertility among Seveso women and their daughters?

SUMMARY ANSWER

TCDD exposure is associated with a decrease in fecundability and increased risk of infertility in women, as well as their daughters.

WHAT IS KNOWN ALREADY

In animal studies, maternal exposure to TCDD is associated with decreased fertility in offspring. Effects of TCDD are mediated by activation of the aryl hydrocarbon receptor (AHR) pathway.

STUDY DESIGN, SIZE, DURATION

The Seveso Women's Health Study (SWHS) has followed 981 women exposed to TCDD in a 1976 accident since 1996. In 2014, we initiated the Seveso Second Generation Study to follow-up their children.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We obtained information on pregnancy history including time of trying to conceive from SWHS women and their daughters who were 18 years or older. We considered TCDD exposure as initial 1976 serum TCDD concentration and estimated TCDD at pregnancy. We examined relationships of TCDD exposure with time to pregnancy (TTP, the monthly probability of conception within the first 12 months of trying) and infertility (≥12 months of trying to conceive). We also assessed contributions of polymorphisms in the AHR pathway via genetic risk score.

MAIN RESULTS AND THE ROLE OF CHANCE

Among SWHS women (n = 446), median TTP was 3 months and 18% reported taking ≥12 months to conceive. Initial 1976 TCDD (log10) was associated with longer TTP (adjusted fecundability odds ratio = 0.82; 95% CI 0.68-0.98) and increased risk of infertility (adjusted relative risk = 1.35; 95% CI 1.01-1.79). TCDD at pregnancy yielded similar associations. Among SWHS daughters (n = 66), median TTP was 2 months and 11% reported taking ≥12 months to conceive. Daughters showed similar, but non-significant, associations with maternal TCDD exposure.

LIMITATIONS, REASONS FOR CAUTION

A limitation of this study is time to pregnancy was reported retrospectively, although previous studies have found women are able to recall time to conception with a high degree of accuracy many years after the fact. The number of SWHS daughters who had a live birth was small and we were unable to examine fecundability of SWHS sons.

WIDER IMPLICATIONS OF THE FINDINGS

Consistent with previous findings in animal studies, our study found that TCDD exposure may be associated with decreased fertility in Seveso mothers and potentially in their daughters exposed in utero. There may be susceptible genetic subgroups. The literature has largely considered the genetics of the AHR pathway in the context of male fertility but not female fertility, despite strong biological plausibility. These findings should be replicated in larger populations and of different ancestry. Future studies in Seveso should examine the sons and the grandchildren of exposed mothers given the animal literature suggesting potential heritable epigenetic effects.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by grant numbers F06 TW02075-01 from the National Institutes of Health, R01 ES07171 and 2P30-ESO01896-17 from the National Institute of Environmental Health Sciences, R82471 from the U.S. Environmental Protection Agency and #2896 from Regione Lombardia and Fondazione Lombardia Ambiente, Milan, Italy. J.A. was supported by F31ES026488 from the National Institutes of Health. The authors declare they have no actual or potential competing financial interests.

TRIAL REGISTRATION NUMBER

N/A.

Aryl Hydrocarbon Receptor and Dioxin-Related Health Hazards-Lessons from Yusho

Poisoning by high concentrations of dioxin and its related compounds manifests variable toxic symptoms such as general malaise, chloracne, hyperpigmentation, sputum and cough, paresthesia or numbness of the extremities, hypertriglyceridemia, perinatal abnormalities, and elevated risks of cancer-related mortality. Such health hazards are observed in patients with Yusho (oil disease in Japanese) who had consumed rice bran oil highly contaminated with 2,3,4,7,8-pentachlorodibenzofuran, polychlorinated biphenyls, and polychlorinated quaterphenyls in 1968. The blood concentrations of these congeners in patients with Yusho remain extremely elevated 50 years after onset. Dioxins exert their toxicity via aryl hydrocarbon receptor (AHR) through the generation of reactive oxygen species (ROS). In this review article, we discuss the pathogenic implication of AHR in dioxin-induced health hazards. We also mention the potential therapeutic use of herbal drugs targeting AHR and ROS in patients with Yusho.

Animal Toxicology Studies on the Male Reproductive Effects of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin: Data Analysis and Health Effects Evaluation

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a well-known environmental poison that exist in the environment for many years. However, its effect on the male reproductive system has not been clearly stated. We conducted a meta-analysis of the effect of TCDD on the male reproductive system of rodents about TCDD. Results showed that that TCDD exposure reduced the testis weight (weighted mean difference [WMD]: -0.035, 95% confidence interval [CI]: -0.046 to -0.025), sperm count (WMD: -35, 95% CI: -42.980 to -27.019), and blood testosterone concentration (WMD: -0.171, 95% CI: -0.269 to -0.073). According to our research results, TCDD can cause damage to the male reproductive system of rodents through direct or indirect exposure. In order to further explore the potential hazards of TCDD to humans, more human-related research needs to be carried out.

New perspective on the regulation of acetylcholinesterase via the aryl hydrocarbon receptor

Acetylcholinesterase (AChE, EC 3.1.1.7) plays important roles in cholinergic neurotransmission and has been widely recognized as a biomarker for monitoring pollution by organophosphate (OP) and carbamate pesticides. Dioxin is an emerging environmental AChE disruptor and is a typical persistent organic pollutant with multiple toxic effects on the nervous system. Growing evidence has shown that there is a significant link between dioxin exposure and neurodegenerative diseases and neurodevelopmental disorders, most of which involve AChE and cholinergic dysfunctions. Therefore, an in-depth understanding of the effects of dioxin on AChE and the related mechanisms of action might help to shed light on the molecular bases of dioxin impacts on the nervous system. In the past decade, the effects of dioxins on AChE have been revealed in cultured cells of different origins and in rodent animal models. Unlike OP and carbamate pesticides, dioxin-induced AChE disturbance is not due to direct inhibition of enzymatic activity; instead, dioxin causes alterations of AChE expression in certain models. As a widely accepted mechanism for most dioxin effects, the aryl hydrocarbon receptor (AhR)-dependent pathway has become a research focus in studies on the mechanism of action of dioxin-induced AChE dysregulation. In this mini-review, the effects of dioxin on AChE and the diverse roles of the AhR pathway in AChE regulation are summarized. Additionally, the involvement of AhR in AChE regulation during different neurodevelopmental processes is discussed. These AhR-related findings might also provide new insight into AChE regulation triggered by diverse xenobiotics capable of interacting with AhR.

Age at menarche in Seveso daughters exposed in utero to 2,3,7,8-tetrachlorodibenzo-p-dioxin

Supplemental Digital Content is available in the text.

In utero exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is associated with delayed pubertal development in animal studies. No epidemiologic study has investigated this association. We examined the relationship of in utero exposure to TCDD with reported age at onset of menarche in female children born to a unique cohort of TCDD-exposed women resulting from an explosion in Seveso, Italy, on 10 July 1976.

Age-dependent vulnerability of the ovary to AhR-mediated TCDD action before puberty: Evidence from mouse models

In female mammals, puberty and fertility are regulated by the synthesis of estradiol (E2) by the ovaries at the infantile stage and at the approach of puberty, a process which may be affected by endocrine disrupting chemicals (EDC)s acting through the Aryl hydrocarbon receptor (AhR). However, there is no information on AhR-mediated regulation of ovarian estrogenic activity during these developmental periods. Here, we assessed in mouse models, the intrinsic and exogenous ligand-induced AhR action on E2 synthesis at the infantile stage (14 days postnatal (dpn)) and at the approach of puberty (28 dpn). Intrinsic AhR pathway became activated in the ovary at the approach of puberty, as suggested by the decreased intra-ovarian expression in prototypical and steroidogenesis-related AhR targets and E2 contents in Ahr knockout (Ahr^-/-) mice versus Ahr^+/+ mice exclusively at 28 dpn. Accordingly, AhR nuclear localization in granulosa cells, reflecting its activity in cells responsible for E2 synthesis, was much lower at 14 dpn than at 28 dpn in C57BL/6 mice. However, AhR signaling could be activated by exogenous ligands at both ages, as revealed by FICZ- and TCDD-induced Ahrr and Cyp1a1 expression in C57BL/6 mice. Nevertheless, TCDD impacted ovarian estrogenic activity only at 28 dpn. This age-related AhR action may be ligand-dependent, since FICZ had no effect on E2 synthesis at 28 dpn. In conclusion, AhR would not regulate ovarian estrogenic activity before the approach of puberty. Its activation by EDCs may be more detrimental to reproductive health at this stage than during infancy.

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.

Prenatal dioxin exposure and thyroid hormone levels in the Seveso second generation study

BACKGROUND

In animal studies, perinatal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) alters thyroid homoeostasis and thyroid hormone concentrations; epidemiologic evidence is limited.

OBJECTIVES

We aimed to determine the association of prenatal exposure to TCDD with thyroid hormone concentrations in the Seveso Second Generation Study, a unique cohort of children born to TCDD-exposed women resulting from a 1976 chemical factory explosion in Seveso, Italy.

METHODS

We included 570 children (288 female, 282 male) with complete follow-up data, including a fasting blood draw. Serum levels of total and free thyroxine (T4), free triiodothyronine (T3), and thyroid stimulating hormone (TSH) were measured using immunoassays. We defined prenatal TCDD exposure as: 1) maternal initial TCDD concentration measured in serum collected soon after the explosion and 2) maternal TCDD estimated at pregnancy.

RESULTS

Compared to the lowest quartile (Q1), maternal initial serum TCDD was associated with lower free T3 (Q2: adj-β = -0.13, 95%CI -0.26, 0.00; Q3: adj-β = -0.22, 95%CI -0.35, -0.09; Q4: adj-β = -0.14, 95%CI -0.28, 0.00; p-trend = 0.02). In participants with high thyroid antibody status, inverse associations between maternal initial serum TCDD and free T3 were significantly stronger than in participants with normal antibody status (p-interaction = 0.02). We also observed a positive association between maternal initial serum TCDD and TSH concentrations in participants with high thyroid antibody status (Q2: adj-β = 11.4%, 95%CI -25.2, 66.1; Q3: adj-β = 49.0%, 95%CI 3.0, 115.5; Q4: adj-β = 105.5, 95%CI 36.6, 209.2; p-trend < 0.01) but not in those participants with normal antibody status (p-interaction < 0.01). Similar results were found for TCDD estimated at pregnancy.

DISCUSSION

Our results suggest prenatal exposure to TCDD, a potent endocrine-disrupting compound, may alter thyroid function later in life. Populations with additional thyroid stress may be particularly susceptible to in utero exposure of thyroid disrupting chemicals.

Casting a wide net: use of diverse model organisms to advance toxicology

Toxicology - the study of how chemicals interact with biological systems - has clear relevance to human health and disease. Persistent exposure to natural and synthetic chemicals is an unavoidable part of living on our planet; yet, we understand very little about the effects of exposure to the vast majority of chemicals. While epidemiological studies can provide strong statistical inference linking chemical exposure to disease, research in model systems is essential to elucidate the mechanisms of action and to predict outcomes. Most research in toxicology utilizes a handful of mammalian models that represent a few distinct branches of the evolutionary tree. This narrow focus constrains the understanding of chemical-induced disease processes and systems that have evolved in response to exposures. We advocate for casting a wider net in environmental toxicology research to utilize diverse model systems, including zebrafish, and perform more mechanistic studies of cellular responses to chemical exposures to shift the perception of toxicology as an applied science to that of a basic science. This more-inclusive perspective will enrich the field and should remain central to research on chemical-induced disease.

Mechanisms of Testicular Disruption from Exposure to Bisphenol A and Phtalates

Great attention has been paid in recent years to the harmful effects of various chemicals that interfere with our natural hormone balance, collectively known as endocrine-disrupting chemicals (EDCs) or endocrine disruptors. The effects on the reproductive system of bisphenol A (BPA) and phthalates have received particular attention: while they have a short half-life, they are so widespread that human exposure can be considered as continuous. Evidence is often limited to the animal model, disregarding the likelihood of human exposure to a mixture of contaminants. Data from animal models show that maternal exposure probably has harmful effects on the male fetus, with an increased risk of urogenital developmental abnormalities. After birth, exposure is associated with changes in the hypothalamic-pituitary-testicular axis, hindering the development and function of the male genital pathways through the mediation of inflammatory mechanisms and oxidative stress. The epidemiological and clinical evidence, while generally confirming the association between reproductive abnormalities and some phthalate esters and BPA, is more contradictory, with wildly different findings. The aim of this review is therefore to provide an update of the potential mechanisms of the damage caused by BPA and phthalates to reproductive function and a review of the clinical evidence currently available in the literature.

Prenatal dioxin exposure and glucose metabolism in the Seveso Second Generation study

BACKGROUND

Exposure to endocrine disrupting compounds such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) during susceptible developmental windows may alter risk of metabolic disease later in life. Animal studies of in utero and lactational TCDD exposure report associations with alterations in insulin sensitivity and energy homeostasis, but epidemiologic evidence is limited. We examined the relationship of prenatal TCDD exposure with markers of glucose homeostasis in the Seveso Second Generation study, a unique cohort of children born to TCDD-exposed women resulting from a 1976 explosion in Seveso, Italy.

METHODS

We included 426 children who were 18 years or older with complete follow-up data including a fasting blood draw. Insulin and glucose were measured and the updated homoeostatic model assessment was used to estimate insulin resistance (HOMA2-IR) and beta-cell function (HOMA2-B). Prenatal TCDD exposure was defined in two ways, as initial maternal serum TCDD concentration and TCDD estimated at pregnancy.

RESULTS

The children (222 female, 204 male) averaged 28.6 (±6.0) years. We found a 10-fold increase in TCDD estimated at pregnancy was inversely associated with insulin (adj-β = -1.24 μIU/mL, 95% confidence interval (CI): -2.38, -0.09) and HOMA2-B (adj-β = -10.2% decrease, 95% CI: -17.8, -1.9) among daughters, but not sons (insulin: adj-β = 0.57 μIU/mL, 95% CI: -0.84, 1.98, P for interaction = 0.04; and HOMA2-B: adj-β = 0.8% increase, 95% CI -10.7, 13.9, P for interaction = 0.11). Similar effect modification was observed for TCDD estimated at pregnancy and HOMA2-IR (P for interaction = 0.13). The models for initial maternal serum TCDD showed similar effect modification by child sex. The observed associations in daughters showed evidence of mediation by body mass index, which we have previously found to be associated with prenatal TCDD exposure in female offspring.

CONCLUSION

These results suggest prenatal exposure to TCDD is associated with lower insulin resistance and beta compensation in female offspring, and show evidence of mediation by body mass index.

Nonpersistent endocrine disrupting chemicals and reproductive health of women

Nonpersistent endocrine disrupting chemicals (npEDCs) are exogenous chemicals or mixtures of industrial agents that can interfere with the normal action of hormone with a shorter half-life and lower liposolubility. These are commonly found in plastics, medical equipment, detergents, and cosmetics. Recently, role of npEDCs on the changes of ovary and/or uterus development and alterations in hormonal signaling has been emphasized. However, many controversial results exist on the effects of npEDCs and reproductive health of women. Thus, we have focused to review the scientific evidence of a causal relationship between exposure to npEDCs and representative female reproductive issues such as menstrual cycle, endometriosis, uterine fibroids, polycystic ovarian syndrome and infertility/subfertility. Though not all studies indicated a positive correlation of npEDCs with female reproductive issues, the reviewed data illustrated that the majority of the available data strengthen the evidence of reproductive health-related actions of npEDCs. In future, recommendations should be made in order to reduce human exposure to npEDCs and to protect from steadily increasing reproductive health risks.

Metatranscriptomic Analysis of the Mouse Gut Microbiome Response to the Persistent Organic Pollutant 2,3,7,8-Tetrachlorodibenzofuran

Persistent organic pollutants (POPs) are important environmental chemicals and continued study of their mechanism of action remains a high priority. POPs, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,7,8-tetrachlorodibenzofuran (TCDF), and polychlorinated biphenyls (PCBs), are widespread environmental contaminants that are agonists for the aryl hydrocarbon receptor (AHR). Activation of the AHR modulates the gut microbiome community structure and function, host immunity, and the host metabolome. In the current study, male C57BL6/J mice were exposed, via the diet, to 5 µg/kg body weight (BW) TCDF or 24 µg/kg BW of TCDF every day for 5 days. The functional and structural changes imparted by TCDF exposure to the gut microbiome and host metabolome were explored via 16S rRNA gene amplicon sequencing, metabolomics, and bacterial metatranscriptomics. Significant changes included increases in lipopolysaccharide (LPS) biosynthesis gene expression after exposure to 24 µg/kg BW of TCDF. Increases in LPS biosynthesis were confirmed with metabolomics and LPS assays using serum obtained from TCDF-treated mice. Significant increases in gene expression within aspartate and glutamate metabolism were noted after exposure to 24 µg/kg BW of TCDF. Together, these results suggest that after exposure to 24 µg/kg BW of TCDF, the gut microbiome increases the production of LPS and glutamate to promote localized gut inflammation, potentially using glutamate as a stress response.