Polychlorinated Dibenzo-p-dioxins Research Articles

Comprehensive model for predicting toxic equivalents (TEQ) reduction due to dechlorination of polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/F congeners)

Remediation-focused predictive tools for polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) rely on transformation models to evaluate the reduction in total contaminant load and toxic equivalency (TEQ). In this study, a comprehensive model predicting the profiles of PCDD/F congeners and the associated TEQs was developed. The model employs first-order kinetics to describe the transformation of 256 reactions for 75 PCDD congeners and 421 reactions for 135 PCDF congeners. It integrates the growth of anaerobic microbial guilds using Monod kinetics on hydrogen release compounds and stoichiometric growth for Dehalococcoides sp. The effects of temperature, salinity, pH, and availability of vitamin B12 (a cofactor) were also integrated. The PCDD/F congeners model was used to extract the first-order dechlorination rate constants from a number of pure culture and mixed microbial microcosm studies. Simulations for the transformation of PCDD/F congeners at concentrations representative of the Tittabawassee or Saginaw Rivers and watershed in MI, USA were carried out. For a starting TEQ of 5000 ng per kg dry sediment (ppt), the model predicted a decrease in the overall TEQ to below 2000 ppt after 2.6 years and below 250 ppt after ∼21 years. The developed model may be used for extracting rates from microcosm studies and to evaluate the effect of engineering interventions on TEQ reduction.

Urban air PCDD/Fs: Dry deposition fluxes and mass transfer coefficients determined using a water surface sampler

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) cause significant environmental concerns. Atmospheric PCDD/Fs permeate water bodies and other ecosystems through wet and dry deposition. In an urban site, dry deposition flux samples of gaseous phase PCDD/Fs were collected by a water surface sampler (WSS) operated between June 2022 and June 2023. There is a conspicuous absence of literature on the direct measurement of dry deposition flux levels in the gaseous phase of PCDD/Fs. In the study, PCDD/Fs in the gas phase reaching the WSS dissolved in the water according to Henry's Law. The PCDD/Fs in the water were transferred to an XAD-2 resin column, sorbing the dissolved PCDD/Fs. The average monthly gas phase dry deposition flux was 34.07 ± 9.35 pg/m2-day (7.35 ± 2.16 pg I-TEQ/m2-day). The highest flux was measured in March (49.53 pg/m2-day), and the lowest was in August (18.64 pg/m2-day). These values indicated the direct flux from air to water. The atmospheric concentration of the gas-phase ranged from 68.38 to 126.88 fg/m3 (13.22–25.01 fg I-TEQ/m3). Dry deposition fluxes and concentrations of atmospheric PCDD/Fs were bigger in the colder months than in the warmer months. This was probably due to a significant increase in residential heating during the colder months, decreased photochemical reactions, and lower mixing heights. Regarding congeners in the dry deposition flux and concentration values in I-TEQ units, 2,3,7,8-TCDD compound predominated with the proportions of 31.61 ± 7.76% and 29.09 ± 12.34%, respectively. Concurrently measured dry deposition flux (Fg) and ambient air concentration (Cg) of PCDD/Fs were considered in the determination of mass transfer coefficient (MTC = Fg/Cg) calculation for each PCDD/F congener. The average MTC for targeted 17 PCDD/Fs was 0.45 ± 0.15 cm/s, and it fluctuated between 0.89 ± 0.30 cm/s for 2,3,7,8-TCDF and 0.2 ± 0.16 cm/s for OCDD.

Global dioxin research trends and focal points: A century-long visual and bibliometric analysis (1923-2022).

Dioxin-like compounds, recognized by the World Health Organization (WHO) as among the most enduring toxic chemical substances in the environment, are linked to various occupational activities and industrial accidents worldwide. The aim of this study was to examine and present research publications on dioxins, pinpoint current research trends, identify research gaps, and highlight potential avenues for future exploration in the field. The study period for relevant research articles ranged from 1923 to December 31, 2022, and these articles were sourced from the Scopus database. The analysis involved the identification of key contributors to the field and the visualization of topics, themes, and international collaboration. VOSviewer software (version 1.6.20) was used for visualization analysis. A total of 11,620 publications on dioxins were documented in the Scopus database. The predominant category of these documents comprised 9780 original articles, which represents 84.17% of the total publications. The United States lead in the number of publications, with 3992 (34.35%), followed by Japan, with 1429 (12.3%), China, with 1005 (8.65%), and Germany, with 974 (8.38%). Before 2002, scholarly attention in this field focused primarily on the health effects, environmental fate, and mechanism of toxicity of tetrachlorodibenzo-p-dioxin (TCDD). However, a noticeable change in research focus has been observed since 2002, highlighting the emergence of a topic related to the health effects and environmental fate of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PFDFs). This study is the first to conduct a comprehensive quantitative bibliometric analysis of dioxins over time. These findings indicate a significant increase in the overall growth of the dioxin literature over the past 30 years. These findings may prove crucial in guiding and organizing subsequent investigations related to dioxins.

Accumulation Patterns of Polychlorinated Dibenzo-p-Dioxins, Dibenzofurans and Dioxin-like Polychlorinated Biphenyls in Sediments of the South-Eastern Baltic Sea

The current research paper presents the results of the first regional assessment of sediment contamination by dioxins (polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dl-PCBs)) in the south-eastern part of the Baltic Sea (Lithuanian and Polish marine areas) during the periods of 2014 and 2019–2020. In total, 143 surface and core sediment samples were taken of existing offshore dredged-soil-disposal sites in the area of the former shipyard in the Port of Gdynia (Poland), as well as in a profile from the nearshore to the deeps of the Gdansk basin, following the natural pattern of sediment migration in the region. The obtained results indicated wide variation in both the total content of the investigated compounds as well as the profiles of congeners, indicating the likely sources of their origin. Based on the obtained concentration characteristic profiles of the congeners, we determined the amount of dioxins and the likely sources of their origin in the Gdansk Basin. The profiles showed elevated contents of octa- and hepta-chlorodibenzodioxins (OCDD and HpCDD) in the sediments, while the fractions of most other toxic congeners were considerably lower. The domination of OCDF in the spectrum of the studied PCDFs suggests the possible contribution of industrial processes. The obtained results have filled the gaps in our knowledge while providing a perfect background for more detailed discussions concerning the accumulation of dioxins in surface sediments from the south-eastern part of the Baltic Sea.

Đánh giá mức độ phát thải của các chất polyclodibenzo-p-dioxin và polyclodibenzofuran phát sinh không chủ định từ lò đốt rác chất thải sinh hoạt và rác thải công nghiệp ở Việt Nam

Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) are the most toxic substances among the group of unintentional persistent organic pollutants (U - POP) generated from many sources, in which domestic and industrial waste incinerators are the highest emission risk. Assessment of pollution potential and dioxin/furan emissions from incinerators in developing countries, including Vietnam, is still limited; especially in-depth studies on the content and characteristics of PCDD/PCDF emitted into the atmosphere. Therefore, the research team evaluated the emission potential and characteristics of 07 PCDD and 10 PCDF, those are considered to be the most toxic isomers and congeners, from stack gas samples collected from incinerators at 33 facilities in 11 provinces in Vietnam. The total concentration of PCDD/PCDF in the industrial incinerators’ emission ranged from 37.3 to 3348.6 pg TEQs/m3 and domestic waste incinerators had lower total concentrations and fluctuated within about 37.3-1323.8 pg TEQs/m3. The characteristic of incinerator emissions is that the proportion of 2,3,7,8- TCDD accounts for 2.9 to 9.04%. The highest contributing concentrations were congeners 1,2,3,7,8-PeCDD, with its contributing percentage from 22.95-32.42%. The second largest contributor is congeners 2,3,4,7,8- PeCDF, accounting for 20.94- 21.50% of the total toxic congeners of PCDD/PCDF in both types of incinerators. However, in terms of toxic equivalency (TEQ), the concentration of industrial waste incinerators is much higher than that of domestic waste incinerators. The results of stack gas samples showed that the PCDD/PCDF content for domestic waste incinerators has 5/17 establishments that exceeded the permissible standard threshold: 0.6 ng/Nm3, according to QCVN 61-MT:2016/BTNMT. Industrial waste incinerators have 5/16 establishments that exceeded the permissible standard threshold: 0.6ng/Nm3 for furnaces with a capacity of 300kg/hour according to QCVN 30:2012/BTNMT.

Prediction of Base-Catalyzed Hydrolysis Kinetics of Polychlorinated Dibenzo-p-Dioxins by Density Functional Theory Calculations.

Polychlorinated dibenzo-p-dioxins (PCDDs), comprising 75 congeners, have gained considerable attention from the general public and the scientific community owing to their high toxic potential. The base-catalyzed hydrolysis of PCDDs is crucial for the assessment of their environmental persistence. Nonetheless, owing to the substantial number of congeners and low hydrolysis rates of PCDDs, conducting hydrolysis experiments proves to be exceedingly time-consuming and financially burdensome. Herein, density functional theory and transition state theory were employed to predict the base-catalyzed hydrolysis of PCDDs in aquatic environments. Findings reveal that PCDDs undergo base-catalyzed hydrolysis in aquatic environments with two competing pathways: prevailing dioxin ring-opening and reduced reactivity in the hydrolytic dechlorination pathway. The resultant minor products include hydroxylated PCDDs, which exhibit thermodynamic stability surpassing that of the principal product, chlorinated hydroxydiphenyl ethers. The half-lives (ranging from 17.10 to 1.33 × 1010 h at pH = 8) associated with the base-catalyzed hydrolysis of PCDDs dissolved in water were shorter compared to those within the water-sediment environmental system. This observation implies that hydroxide ions can protect aquatic environments from PCDD contamination. Notably, this study represents the first attempt to predict the base-catalyzed hydrolysis of PCDDs by using quantum chemical methods.

Investigating the presence of dioxins in drinking water: implications for public health

ABSTRACT The presence of highly toxic dioxins, specifically polychlorinated dibenzo-p-dioxins (PCDDs), in drinking water is a matter of great concern due to their long-lasting nature and harmful effects. In this study, we detected three out of the five dioxin congeners: 2, 3, 7, 8-tetrachlorodibenzodioxin (TCDD), 1, 2, 3, 7, 8-pentachlorodibenzo-p-dioxin (PeCDD), and octachlorodibenzo-p-dioxin (OCDD). The investigation revealed that three dioxins were present in water samples of winter season, while TCDD and OCDD were found in the summer season. The geometric mean concentrations of PCDDs were 229.9 ng/L (winter) and 108.4 ng/L (summer), exceeded the maximum contaminant level of 30 pg/L set by the USEPA in surface water. The estimated daily intake of PCDDs for residents through drinking water was 273.97 ng-WHO2005-TEQ/kg/days during winter and 78.875 ng-WHO2005-TEQ/kg/days during summer. Our study emphasizes the urgent need for further research on persistent organic pollutants in drinking water to safeguard public health and community well-being.

The association between polychlorinated dibenzo-p-dioxin exposure and cancer mortality in the general population: a cohort study.

Earlier research has indicated that being exposed to polychlorinated dibenzo-p-dioxins (PCDDs) in the workplace can heighten the likelihood of cancer-related deaths. Nevertheless, there is limited information available regarding the connection between PCDD exposure and the risk of cancer mortality in the general population (i.e., individuals not exposed to these substances through their occupation). The National Health and Nutrition Examination Survey (NHANES) detected PCDDs in the general population, and the death data were recently updated as of December 31, 2019. We conducted Cox regression analysis and controlled for covariates including age, gender, ethnicity, educational attainment, physical activity, alcohol intake, NHANES survey period, BMI category, cotinine concentration, and household earnings. After accounting for confounding factors, the findings indicated that for each incremental rise of 1 log unit in 1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin, there was a 76% rise in the likelihood of death from any cause, with a p value of 0.003. An increase of 1 log unit in the concentration of 1,2,3,4,6,7,8-heptachlorodibenzofuran could potentially lead to a 90% higher risk of cancer mortality, as indicated by a p value of 0.034 and a 95% confidence interval of 0.05-2.43. As the concentrations of 1,2,3,4,6,7,8-heptachlorodibenzofuran increased, the dose-response curve indicated a proportional rise in the risk of cancer mortality, accompanied by a linear p value of 0.044. The sensitivity analysis demonstrated that our findings were resilient. In the general population, an elevated risk of cancer mortality was observed in PCDDs due to the presence of 1,2,3,4,6,7,8-heptachlorodibenzofuran. Mechanistic research is required to further confirm it.

Distribution of PCDD/Fs and PCBs at different locations in a circulating fluidised bed municipal solid waste incinerator.

This study investigates a circulating fluidised bed (CFB) incineration plant to examine the concentrations and fingerprints of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs) at five locations downstream of the post-combustion zone. Sampling encompassed both flue gas and ash, spanning from the high-temperature superheater to the outlet of the baghouse filter, thus covering a wide range of flue gas temperatures. The analysis reveals a continuous increase in PCDD/F and PCB concentrations in the flue gas from the superheater to the inlet of the air pollution control system (APCS). The maximum concentrations observed were 75.8ng/Nm3 for PCDDs, 219ng/Nm3 for PCDFs, and 763ng/Nm3 for PCBs. These values represent 9.14, 11.5, and 6.37 times their respective concentrations at the outlet of the high-temperature superheater. Concurrently, the levels of PCDD/Fs and dioxin-like PCBs (dl-PCBs) in the ash steadily increased along the cooling path of the flue gas within the plant. Comparing dl-PCBs to the total amount of 209 PCB congeners, it was evident that dl-PCBs exhibited a trend more akin to that of PCDD/Fs. A robust linear correlation was observed between dl-PCBs and PCDD/Fs (R2 = 0.99, p < 0.001), surpassing that between PCBs and PCDD/Fs (R2 = 0.92, p < 0.01), suggesting that dl-PCBs share closer formation pathways with PCDD/Fs. Additionally, elemental composition analysis of fly ash samples aimed to explore potential links between fly ash characteristics and PCDD/F and PCB formation. The Cl/S ratio increased from 1.58 to 5.13 with decreasing flue gas temperature. Principal component analysis (PCA) was employed to visualise the concentrations of PCDD/Fs and PCBs in the flue gas alongside elemental contents in the fly ash. With the exception of PCBs in ash, all other PCDD/Fs and PCBs in fly ash exhibited positive correlations with both carbon (C) and chlorine (Cl). Furthermore, a positive relationship between C/Cl and PCDD/Fs-PCBs in fly ash implies that fly ash serves as the primary reaction surface for dioxin generation during low-temperature heterogeneous catalytic reactions.

Quality of cultured eels as affected by pollution sources and risk assessment of dioxins and dioxin-like polychlorinated biphenyls

AbstractThe aim of this research was to determine the residues of dioxins and dioxin-like polychlorinated biphenyls in cultured eel and find out the source of pollution and the distribution pattern of eels. One hundred samples of eel, 4 fodder samples, and 12 environmental samples (water, plants, and soil) were collected from 4 cities and counties in Jiangxi Province, China. The contents of 17 kinds of dioxins (PCDD/Fs) and 12 kinds of dioxin-like polychlorinated biphenyls (dl-PCBs) were determined by high-resolution gas chromatography-tandem mass spectrometry, and the exposure risk was evaluated by using risk index. The total toxicity equivalence quantity (TEQ) of dioxin and dioxin-like polychlorinated biphenyls in eel and fodder samples collected in the study area were 0.65 ± 0.31 pg/g and 0.10 ± 0.02 pg/g, respectively. Dl-PCBs were the main dioxin pollution in eel and fodder samples. 2,3',4,4',5-pentachlorodiphenyl and 2,3,3',4,4'-pentachlorobiphenyl were the main contributing monomers. The environmental samples were mainly polluted by polychlorinated dibenzo-p-dioxins (PCDDs), with the main contributing monomer being Octachlorodibenzodioxins (OCDD), while 3,3',4,4',5-pentachlorobiphenyl and 2,3,4,7,8-pentachlorodibenzofuran were the main toxic compounds in eel and fodder. The dioxin pollution of eels cultured in Jiangxi Province was mainly from fodder polluted via dl-PCBs. The meat segment VI (tail) exhibited a strong enrichment effect of polychlorinated benzofurans (PCDFs). It should be the key part for dioxins and dioxin-like polychlorinated biphenyls assessment. Further, the results were helpful to improve the edible safety of eel products and the efficiency of the risk assessment of dioxins and dioxin-like polychlorinated biphenyls in fish. Graphical Abstract

Dioxin(-like)-Related Biological Effects through Integrated Chemical-wide and Metabolome-wide Analyses.

Dioxin(-like) exposures are linked to adverse health effects, including cancer. However, metabolic alterations induced by these chemicals remain largely unknown. Beyond known dioxin(-like) compounds, we leveraged a chemical-wide approach to assess chlorinated co-exposures and parent compound products [termed dioxin(-like)-related compounds] among 137 occupational workers. Endogenous metabolites were profiled by untargeted metabolomics, namely, reversed-phase chromatography with negative electrospray ionization (C18-negative) and hydrophilic interaction liquid chromatography with positive electrospray ionization (HILIC-positive). We performed a metabolome-wide association study to select dioxin(-like) associated metabolic features using a 20% false discovery rate threshold. Metabolic features were then characterized by pathway enrichment analyses. There are no significant features associated with polychlorinated dibenzo-p-dioxins (PCDDs), a subgroup of known dioxin(-like) compounds. However, 3,110 C18-negative and 2,894 HILIC-positive features were associated with at least one of the PCDD-related compounds. Abundant metabolic changes were also observed for polychlorinated dibenzofuran-related and polychlorinated biphenyl-related compounds. These metabolic features were primarily enriched in pathways of amino acids, lipid and fatty acids, carbohydrates, cofactors, and nucleotides. Our study highlights the potential of chemical-wide analysis for comprehensive exposure assessment beyond targeted chemicals. Coupled with advanced endogenous metabolomics, this approach allows for an in-depth exploration of metabolic alterations induced by environmental chemicals.

Micropollutants in biochar produced from sewage sludge: A systematic review on the impact of pyrolysis operating conditions

Biochar obtained from sewage sludge serves as a valuable soil amendment in agriculture, enhancing soil properties by increasing the nutrient content, cation exchange capacity, water retention, and oxygen transmission. However, its utilisation is hampered by the presence of micropollutants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), and volatile organic compounds (VOCs). Previous studies indicate that the type and amount of micropollutants can be significantly adjusted by selecting the right process parameters. This literature review provides an overview of how (1) pyrolysis temperature, (2) carrier gas flow and type, (3) heating rate, and (4) residence time affect the concentration of micropollutants in biochar produced from sewage sludge. The micropollutants targeted are those listed by the European Biochar Certificate (EBC) and by the International Biochar Institution (IBI), including PAHs, PCDD/Fs, PCBs and VOCs. In addition, per- and poly-fluoroalkyl substances (PFAS) are also considered due to their presence in sewage sludge.The findings suggest that higher pyrolysis temperatures reduce micropollutant levels. Moreover, the injection of a carrier gas (N2 or CO2) during the pyrolysis and cooling processes effectively lowers PAHs and PCDD/Fs, by reducing the contact of biochar with oxygen, which is crucial in mitigating micropollutants. Nevertheless, limited available data impedes an assessment of the impact of these parameters on PFAS in biochar. In addition, further research is essential to understand the effects of carrier gas type, heating rate, and residence time in order to determine the optimal pyrolysis process parameters for generating clean biochar.

Toxicokinetic modeling of the transfer of polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) into milk of high-yielding cows during negative and positive energy balance

A toxicokinetic modeling approach was used to study the transfer of 7 polychlorinated dibenzo-p-dioxins (PCDDs), 10 dibenzofurans (PCDFs), 12 dioxin-like polychlorinated biphenyls (dl-PCB) and 3 non-dioxin like (ndl) PCBs in dairy cows. The model describes the concentration–time profile of each congener in milk and blood of high-yielding dairy cows. It was parametrized using an in-house transfer study with 3 cows exposed to a defined synthetic congener mixture for two dosing periods, as well as 3 control cows to account for background exposure. The first dosing was administered during negative energy balance (NEB) after calving, and the second during positive energy balance (PEB) in late lactation. Results include extrapolated steady-state transfer rates and elimination half-lives, many of which have never been reported before. Transfer rates (TRs) were significantly higher during the NEB by a median of 27%, likely due to an increase in non-milk elimination during PEB. The difference draws attention to the influence of the metabolic state of food-producing animals in risk assessment. Comparison of the TRs derived here with those reported in the literature showed that they were, in median, 43% higher in the NEB phase and 16% higher in the PEB phase probably because we report TRs in steady-state unlike most literature sources.

OR06-06 Association Between Mixed Dioxin Exposure And Thyroid Functions In U.S. Adults: A Comparison Of Three Statistical Models

Abstract Disclosure: C. Han: None. S. Lee: None. E.N. Pearce: None. Background: Previous studies of the relationship between dioxin exposure and thyroid function have usually been based on multi-chemical linear models and results have been inconsistent. However, complex nonlinear relationships and interactions between mixed dioxin exposures and thyroid function have not been studied. We applied three different statistical models to assess the joint effect of 20 dioxins on thyroid function. Methods: A total of 6 polychlorinated dibenzo-p-dioxins (PCDDs), 10 polychlorinated dibenzofurans (PCDFs), 4 dioxin-like polychlorinated biphenyls (DL-PCBs) and serum TSH were measured in the serum of U.S. adults by the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2010. We fitted multivariable logistic regression, weighted quantile sum (WQS) regression, and Bayesian kernel machine regression (BKMR) models to estimate the association of individual and mixed dioxin exposures with high TSH. Results: Among the 2818 individuals included in our analysis, 1.99% had TSH &amp;gt;5.6 uIU/mL. In the multivariable logistic regression established for each single dioxin, 1,2,3,7,8-pncdd, 1,2,3,4,7,8-hxcdd, 1,2,3,6,7,8-hxcdd, 1,2,3,7,8,9-hxcdd, 1,2,3,4,7,8-Hexachlorofuran, 1,2,3,6,7,8-Hexachlorofuran, 3,3',4,4',5,5'-hexachlorobiphenyl, 3,3',4,4',5-Pentachlorobiphenyl, and 2,3,7,8-Tetrachloro-p-dioxin were positively associated with high TSH, and 3,4,4',5-Tetrachlorobiphenyl was negatively associated with high TSH. In the WQS regression model, the WQS index was significantly associated (OR (95% CI): 2.03 (1.06, 3.88)) with high TSH, and 1,2,3,7,8-pncdd (weighted at 0.24) made the largest contribution. In the BKMR analysis, a significant positive association was found between mixed dioxin exposure and high TSH when all dioxins were at their 55 to 70th percentile, compared to their 50th percentile. TSH was lower when all dioxins were at their 30th to 45th percentile, compared to their 50th percentile. Conclusion: By comparing the three statistical models, we concluded that the whole-body burden of 20 dioxins was significantly positively associated with high TSH. 1,2,3,7,8-pncdd played the most important roles in hypothyroidism. Presentation: Thursday, June 15, 2023

Analysis of PCDD/Fs in environmental samples by using gas chromatography in combination with high resolution mass spectrometry: optimization of sample preparation

ABSTRACT This study developed a simple, economical and time-saving clean-up procedure based on an in-house packed column system for the determination of the most toxic-relevant 17 PCDD (polychlorinated dibenzo-p-dioxin) and PCDF (polychlorinated dibenzofuran) congeners in environmental samples following accelerated solvent extraction. The extract solution was cleaned up using a manually packed column system consisting of a multi-layer silica gel column and an activated carbon column. After clean-up, dioxins and furans were analysed by using gas chromatography in combination with high-resolution mass spectrometry. Isotopic labelled spiking experiments investigated the recovery of all dioxin and furan congeners. Then, the clean-up procedure for environmental samples was validated by applying the analysis of both clean soil reference material (CRM EDF-5183) and heavily contaminated sediment reference material (CRM EDF-5184) samples, as well as participating in the proficiency test (PT) for sediment samples. The recovery efficiency of isotope-labelled standard compounds in certified reference material (CRM) samples and PT samples ranged from 35% to 101% and between 46.1% and 105%, respectively. The mass concentrations of 17 PCDD/Fs in CRM samples were in the acceptable range. The absolute z-score value for each PCDD/F congener in the PT samples was below 1, confirming the analytical procedure’s high accuracy. The applied clean-up procedure in this study has demonstrated accuracy, repeatability and a significant increase in sample extraction/preparation productivity by reducing the time for sample preparation.

Pubertal progression in relation to peripubertal exposure to organochlorine chemicals in a cohort of Russian boys.

Peripubertal concentrations of serum dioxins and polychlorinated biphenyls (PCBs) have demonstrated associations with altered age of pubertal onset and sexual maturity in boys, but associations with pubertal progression have received less attention. The Russian Children's Study is a prospective cohort of 516 boys enrolled in 2003-2005 at age 8 or 9 and followed annually up to 19 years of age. Serum concentrations of dioxin-like toxic equivalents (TEQs), polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and non-dioxin-like PCBs (NDL-PCBs) and whole blood lead levels (BLLs) were quantified from blood samples collected at study entry (age 8-9). Testicular volume (TV) was assessed annually using a Prader orchidometer. Pubertal trajectories were identified by applying Group-Based Trajectory Models (GBTMs) to TV measured from ages 8-19. Associations of peripubertal serum TEQs, PCDDs, PCDFs, and NDL-PCBs with specific progression trajectories were modeled using multinomial logistic regression, adjusting for each boy's birthweight, and for BLL, body mass index and nutritional factors at study entry. Among 489 eligible boys with available exposure measures, we identified three pubertal trajectories using GBTMs: slower (34% of boys), moderate (48%) and faster (18%). Boys with higher peripubertal serum TEQs had higher adjusted odds of being in the moderate versus faster trajectory (adjusted odds ratio (aOR) 1.79, 95% CI 1.01, 3.13) and the slower versus faster trajectory (aOR 1.52, 95% CI 0.82, 2.78) per 1 log unit increase in serum TEQs. Boys with higher peripubertal serum PCDFs had higher adjusted odds of being in the moderate compared to the faster trajectory (aOR 1.92, 95% CI 1.20, 3.03) and of being in the slower versus the faster trajectory (aOR 1.42, 95% CI 0.91, 2.33) per 1 log unit increase. Boys with higher NDL-PCBs had higher adjusted odds of being in the faster trajectory versus the moderate (aOR 2.56, 95% CI 0.91-7.20) or slower (aOR 3.31, 95% CI 1.07, 10.25) trajectory. Boys with higher blood lead levels also had higher adjusted odds of being in the slower trajectory of pubertal progression, compared to either the faster (aOR 1.47, 95% CI 0.89, 2.44) or moderate (aOR 1.20, 95% CI 0.83, 1.75) trajectories, per 1 log unit increase in BLL, although these associations did not attain statistical significance. Boys' peripubertal exposure to dioxins and certain PCBs may alter pubertal progression.

Experimental Study on the Transfer of Polychlorinated Biphenyls (PCBs) and Polychlorinated Dibenzo-p-dioxins and Dibenzofurans (PCDD/Fs) into Milk of High-Yielding Cows during Negative and Positive Energy Balance.

Dioxin-like polychlorinated biphenyls (dl-PCBs) as well as polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) are a major concern for food safety, especially in fat-containing foods of animal origin, such as milk. Due to the lipophilic character of PCDD/Fs and PCBs, it is of special interest to explore whether the metabolic state of high-yielding cows influences the transfer rates into milk. Five German Holstein cows were orally exposed to a mixture of 17 PCDD/Fs, 12 dl-PCBs, and 6 non-dioxin-like PCBs (ndl-PCBs) for two dosing periods of 28 days each. The first period covered the negative energy balance (NEB) after calving, while the second period addressed the positive energy balance (PEB) in late lactation. Each dosing period was followed by a depuration period of around 100 days. During the NEB phase, the transfer rates of 14 PCDD/Fs and 7 dl-PCBs quantified were significantly (p ≤ 0.1) higher compared to the PEB phase, indicating an influence of the metabolic state on the transfer. Furthermore, the congener-specific transfer rates (0.3-39%) were in the range of the results from former studies. This indicates that the milk yield of the exposed cows is not the only determining factor for the transfer of these congeners into milk.

Biodegradability analysis of Dioxins through in silico methods: Model construction and mechanism analysis

The biodegradation treatment of dioxins has long been of interest due to its good ecological and economic effects. In this study, the biodegradability of polychlorinated dibenzo-p-dioxins (PCDDs) were investigated by constructing machine learning and multiple linear regression models. The maximum chlorine atomic charge (qHirshfeldCl+), which characterizes the biodegradation ability of PCDDs, was used as the response value. The random forest model was used to rank the importance on the 1471 descriptors of PCDDs, and the BCUTp-1 h, QXZ, JGI4, ATSC8c, VE3_Dt, topoShape, and maxwHBa were screened as the important descriptors by Pearson's correlation coefficient method. A quantitative structure-activity relationship (QSAR) model was constructed to predict the biodegradability of PCDDs. In addition, the extreme gradient boosting (XGBoost) and random forest model were also constructed and proved the good predictability of QSAR model. The biodegradability of polychlorinated dibenzofurans (PCDFs) can also be predicted by the constructed three models from a certain level after adjusting some model parameters, which further proved the versatility of the models. Besides, the sensitivity analysis of the QSAR model and a 3D-QSAR model was developed to investigate the biodegradability mechanisms of PCDDs. Results showed that the descriptors BCUTp-1 h, JGI4, and maxwHBa were the key descriptors in the biodegradability effect by the sensitivity analysis of the QSAR model. Coupled with the results of PCDDs biodegradability 3D-QSAR model, BCUTp-1 h, JGI4, and maxwHBa were confirmed as the main descriptors that affect the biodegradability of dioxins. This study provides a novel theoretical perspective for the research of the biodegradation of both PCDDs and PCDFs dioxins.

Molecular Modelling of Polychlorinated Dibenzo-p-Dioxins Non-Covalent Interactions with β and γ-Cyclodextrins.

Polychlorinated dibenzo-p-dioxins (PCDD) are persistent organic pollutants which result as byproducts in industrial or combustion processes and induce toxicity in both wildlife and humans. In this study, all seven PCDD, tetrachlorinated dibenzo-p-dioxins (TCDD), pentachlorinated dibenzo-p-dioxins (P5CDD), hexachlorinated dibenzo-p-dioxins (H6CDD), heptachlorinated dibenzo-p-dioxins (H7CDD), and octachlorinated dibenzo-p-dioxins (OCDD) were studied in interaction with two cyclodextrins, β-CD and γ-CD, resulting in a total of 40 host-guest complexes. The flexibility of the cyclodextrins was given by the number of glucose units, and the placement of the chlorine groups on the dioxins structure accounted for the different complex formed. Various geometries of interaction obtained by guided docking were studied, and the complexation and binding energy were calculated in the frame of MM+ and OPLS force fields. The results show that the recognition of the PCDD pollutants by the CD may be possible through the formation of PCDD:CD inclusion complexes. This recognition is based on the formation of Coulombic interactions between the chlorine atom of the PCDD and the primary and secondary hydroxyl groups of the CD and van der Waals interaction of the CD hydrophobic cavity with PCDD aromatic structures. Both MM+ and OPLS calculus resulted in close values for the complexation and binding energies. Molecular mechanics calculations offer a proper insight into the molecular recognition process between the PCDD compounds and CD molecules, proved by a good description of the C-H···O bonds formed between the guest and host molecules. It was shown for the first time that CD may efficiently trap PCCDs, opening the way for their tremendous potential use in environmental remediation.

Occurrence and dietary intake of dioxins, furans (PCDD/Fs), PCBs, and flame retardants (PBDEs and HBCDDs) in baby food and infant formula

This study determines the levels of 49 persistent organic pollutants which were grouped into polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and hexabromocyclododecanes (HBCDDs), in infant formula and varieties of baby food. The analyzed samples (n = 80) came from stores all over Poland.The presence of PCDD/F, PCDD/F/PCB and non dioxin-like (ndl)-PCB congeners above the maximum levels stipulated in Commission Regulation (EU) No 1259/2011 was not detected in any sample. The determined average content of PCDD/Fs/dl-PCBs in the tested baby foods was in the range of 4–10 % of the maximum level, and content of ndl-PCBs was in the range of 2–6 % of the maximum level. Despite these low levels of dioxins, furans, and PCBs, a risk analysis assuming weekly consumption of the recommended food intake showed exceedances of the tolerable weekly intake (TWI).The content of flame retardants was low in all examined categories of food for children and infant formula. The lower-bound concentration of the sum of HBCDD isomers (LB ∑HBCDDs) ranged from below the limit of quantification (LOQ) to 0.0313 ng/g w.w. and the concentration of ∑PBDEs was in a 0.001–1.014 ng/g w.w. range. Neither infant formula nor baby food contributed considerably to infant exposure to HBCDDs or PBDEs.Our research indicates that the safe exposure thresholds for dioxins and PCBs in foods for infants and young children may be too high and perhaps it may be necessary to amend the legislation setting acceptable limits for baby food. It seems reasonable to introduce a recommendation on the frequency of food consumption for children and the control of raw materials for food production, in particular fish and cow milk, should be a permanent control point in the food safety assurance system.