Polychlorinated Dibenzo-p-dioxins And Furans Research Articles

Polychlorinated dibenzodioxins/furans and dioxin-like polychlorinated biphenyls in fish and crustaceans of a recreationally fished estuary, following targeted remediation

Polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) are a suite of harmful chemicals (hereafter collectively referred to as ‘dioxins’), and their emission into aquatic habitats leads to persistent contamination of sediments, aquatic food-webs, and seafoods. Quantifying contaminant levels in seafood species is important for the ongoing management of exposure risk by fishers, particularly after any remediation actions. We present dioxin concentrations in four seafood species (Yellowfin Bream Acanthopagrus australis, Sea Mullet Mugil cephalus, Eastern School Prawn Metapenaeus macleayi, and Eastern King Prawn Penaeus plebejus) in a recreationally fished estuary, in relation to a contaminated site that has undergone a remediation process, partially removing contaminated sediments (Homebush Bay, Port Jackson, New South Wales, Australia). Dioxin concentrations in these species were measured before (2005/6) and after (2015/16) remediation at a range of locations in and around the remediated site. Dioxin concentrations and congener profiles differed substantially among taxa, and concentrations were frequently higher than Australian screening criteria. The two prawn species showed evidence of a decline in dioxin concentrations after remediation, but the fish species only showed a declining dioxin concentration with distance from the contaminated site (not between periods). There were some minor changes in the congener profile for some species following remediation. While there was evidence for greatly reduced dioxin concentrations in prawn species following remediation, the complex patterns for fish were likely affected by environmental changes, species-specific and temporal changes in lipid content, and animal movement patterns. Future monitoring may aid interpretation of the patterns and modelling of exposure risk associated with seafood consumption into the future.

Distribution of PAHs, PCBs, and PCDD/Fs in products from full-scale relevant pyrolysis of diverse contaminated organic waste

Biomass pyrolysis is the anoxic thermal conversion of biomass into a carbon rich, porous solid, often called biochar. This could be a better waste management alternative for contaminated organic wastes than incineration, due to the useful properties of biochar and potential for carbon sequestration. There are, however, concerns about the potential formation/destruction of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs). Six organic wastes, including digested sewage sludges, wood wastes, and food waste reject, were pyrolyzed (500–800°C) in a full-scale relevant unit (1–5 kg biochar hr−1). Removal efficiencies for PCBs and PCDD/Fs were > 99% in the produced biochars. Biochar PAH-content (2.7–118 mgkg−1) was not significantly correlated to feedstock or temperature. PAHs (2563–8285 mgkg−1), PCBs (22–113 µgkg−1), and PCDD/Fs (1.8–50 ngTEQ kg−1) accumulated in the pyrolysis condensate, making this a hazardous waste best handled as a fuel for high temperature combustion. Emission concentrations for PAHs (0.22–421 µgNm−3) and PCDD/Fs (≤2.7 pgTEQ Nm−3) were mainly associated with particles and were below the European Union’s waste incineration thresholds. Emission factors ranged from 0.0002 to 78 mg tonne−1 biochar for PAHs and 0.002–0.45 µgTEQ tonne−1 biochar for PCDD/Fs. PCDD/F-formation was negligible during high temperature (≥500 °C) biomass pyrolysis (69–90% net loss)

The Role of Sediment Records in Environmental Forensic Studies: Two Examples from Italy of Research Approaches Developed to Address Responsibilities and Management Options

The coupling of scientific evidence from sediment cores with historical information represents an effective way to reconstruct and quantify recent anthropogenic impacts in transitional and marine-coastal areas. These are both key points pertaining to studies that aim at establishing the responsibility for envi ronmental pollution. Good practices for the selection of sampling sites and specific survey techniques are fundamental to understand pollution histories and dynamics, together with reliable dating methods and analytical procedures. In addition, a certain degree of flexibility and willingness to explore different research pathways is necessary, particularly when unexpected questions arise from scientific data or from requests posed by authorities in charge of preliminary investigations or court debates. In this paper, two different study cases are reviewed, and the approaches developed to tackle with specific issues are presented. Its main purpose is both to explain study paths undertaken to answer challenging scientific-legal questions and to provide examples for developing countries that present similar risks of uncontrolled industrialization. Results were used in preliminary investigations or court debates for the attribution of responsibility for environmental pollution to past or present industrial managements. In addition, they were fundamental for other studies aiming at implementing models that simulate the fate and distribution of contaminants and human exposure. In the Augusta Harbor, an integrated approach merged archive information, bathymetry, and high-resolution seismic profiles with the results of an independent tracer (hexachlorobenzene, HCB). This approach helped attribute the presence of high surficial Hg concentrations to resuspension and redistribution of deep sediments caused by dredging and maritime traffic and not to active outfalls. In the Venice Lagoon, an extensive literature search supported analytical results for the correct identification of industrial processes responsible for the contamination by polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) in the canals of the Porto Marghera Industrial Area. In addition, sedimentary profiles of PCDD/Fs in local salt marshes (“barene”) recorded well the events relative to the industrial development and management of the area reported by historical documents, confirming their potential for this kind of investigation.

Assessment of PCDD/Fs formation and emission characteristics at a municipal solid waste incinerator for one year

Municipal solid waste incineration (MSWI) has become a predominant emission source of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs). Research focusing on the impact of operating conditions, environmental changes, and operating time on the generation and emissions of PCDD/Fs has not been resolved. To this end, this study tracked and investigated the PCDD/Fs and 17 congener emissions of a typical grate incinerator (800 t/d) continuously for one year. Results showed that the PCDD/Fs concentration at the boiler outlet, stack inlet, and bag filter, including normal and abnormal operation conditions, ranges from 2.11E-02–41.86 ng I-TEQ/Nm3, 7.00E-04–6.76 ng I-TEQ/Nm3, and 1.12–2.90E+03 ng I-TEQ/Nm3, respectively. The 2,3,4,7,8-P5CDF has the highest contribution in all samples, in which a proportion of TEQ ranged from 30 % to 77.73 %. Moreover, by applying the correlation analysis between PCDD/Fs and operating parameters, the emission characteristic is mainly affected by incinerators and boilers during the normal period, and it is affected by the whole MSWI process under abnormal conditions. In addition, the PCDD/Fs emission from the MSWI plant gradually increases from spring to winter. This study is beneficial for supporting the control of PCDD/Fs emission reduction and assisting the operators to optimize the relevant operating parameters of the MSWI plant to achieve a stable and up-to-substandard emissions during the operation period.

Footprints in compositions, PCDD/Fs and heavy metals in medical waste fly ash: Large-scale evidence from 17 medical waste thermochemical disposal facilities across China.

Chemical compositions, polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) profiles and heavy metals (HMs) leachability of medical waste fly ash (MWFA) from 17 thermochemical treatment facilities in eight Chinese provinces were first investigated. Large-scale and extended monitoring revealed high chloride and Zn contents and similar PCDD/Fs congener profiles in MWFA. Particularly, the PCDD/Fs and HMs concentrations implied greater toxicity than that observed for municipal solid waste incinerator fly ash (MSWIFA). The maximum international toxic equivalent value of PCDD/Fs in MWFA was 40 times that of MSWIFA, and the leaching concentrations of Zn and Hg were 15 and 4 times those of MSWIFA, respectively. Notably, MWFA characteristics suggest the possibility of recycling and sustainable disposal solutions owing to the high Cl and Zn content with good recovery instead of landfill disposal. Similarities in chemical composition, PCDD/Fs homolog distribution, and water-solubility of chloride salts allows co-processing of MWFA and MSWIFA via water-washing detoxification and thermal treatment, such as that used in cement kilns. This study supplements existing literature on the characteristics and risk management of MWFA.

Formation of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) in the electrochemical oxidation of polluted waters with pharmaceuticals used against COVID-19

The COVID-19 pandemic has produced a huge impact on our lives, increasing the consumption of certain pharmaceuticals, and with this, contributing to the intensification of their presence in wastewater and in the environment. This situation demands the implementation of efficient remediation technologies, among them, electrochemical oxidation (ELOX) is one the most applied. This work studies the application of ELOX with the aim of eliminate pharmaceuticals used in the fight against COVID-19, assessing its degradation rate, as well as the risk of formation of toxic trace by-products, such as unintentional POPs like polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). To this end, model solutions containing 10 mg L-1 of dexamethasone (DEX), paracetamol (PAR), amoxicillin (AMX), and sertraline (STR) with two different electrolytes (NaCl and Na2SO4) have been evaluated. However, electrochemical systems that contain chloride ions in solution together with PCDD/Fs precursor molecules may lead to the formation of these highly toxic by-products. So, PCDD/Fs were quantified under conditions of complete degradation of the drugs. Furthermore, the presence of PCDD/Fs precursors such as chlorophenols was determined, as well as the role of Cl-, Cl• and SO4•− radicals in the formation of the by-products and PCDD/Fs. The maximum measured concentration of PCDD/Fs was around 2700 pg L-1 for the amoxicillin case in NaCl medium. The obtained results emphasise the importance of not underestimating the potential formation of these highly toxic trace by-products, in addition to the correct selection of oxidation processes and operation variables, in order to avoid final higher toxicity in the medium.

Polychlorinated biphenyls and polychlorinated dibenzo-p-dioxins and furans in imported canned fish in Nigeria and risk assessment

ABSTRACT Concentrations of polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) were measured in imported canned fish such as mackerel, sardine and tuna to evaluate the risk relating to human consumption of these products. Gas chromatography-mass spectrometry (GC/MS) was used to evaluate the concentrations of PCBs and PCDD/Fs in the samples. The 28 PCB concentrations in the canned mackerel, tuna and sardine ranged from 0.33 to 9.48 ng g −1, <LOQ to 8.8 ng g−1 and <LOQ to 15.1 ng g−1, respectively, while the 14 PCDD/Fs concentrations varied from 0.06 to 4.70 ng g−1 for mackerel, 0.72 to 9.43 ng g−1 for tuna and not detected to 22.0 ng g −1 for sardines. Health risk analysis suggests that ingestion of these samples could lead to adverse non-carcinogenic and carcinogenic risks over a lifetime.

Multi-omics responses in tree swallow (Tachycineta bicolor) nestlings from the Maumee Area of Concern, Maumee River, Ohio

A multi-omics approach was utilized to identify altered biological responses and functions, and to prioritize contaminants to assess the risks of chemical mixtures in the Maumee Area of Concern (AOC), Maumee River, OH, USA. The Maumee AOC is designated by the United States Environmental Protection Agency as having significant beneficial use impairments, including degradation of fish and wildlife populations, bird or animal deformities or reproduction problems, and loss of fish and wildlife habitat. Tree swallow (Tachycineta bicolor) nestlings were collected at five sites along the Maumee River, which included wastewater treatment plants (WWTPs) and industrial land-use sites. Polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzo p dioxins and furans (PCDD/Fs), and chlorinated pesticide concentrations were elevated in Maumee tree swallows, relative to a remote reference site, Star Lake, WI, USA. Liver tissue was utilized for non-targeted transcriptome and targeted metabolome evaluation. A significantly differentially expressed gene cluster related to a downregulation in cell growth and cell cycle regulation was identified when comparing all Maumee River sites with the reference site. There was an upregulation of lipogenesis genes, such as PPAR signaling (HMGCS2, SLC22A5), biosynthesis of unsaturated fatty acids (FASN, SCD, ELOVL2, and FADS2), and higher lipogenesis related metabolites, such as docosapentaenoic acid (DPA), docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and arachidonic acid (AA) at two industrial land-use sites, Ironhead and Maumee, relative to WWTP sites (Perrysburg and SideCut), and the reference site. Toledo Water, in the vicinity of the other two industrial sites and also adjacent to a WWTP, showed a mix of signals between industrial land-use and WWTP land-use. PAHs, oxychlordane, and PBDEs were determined to be the most likely causes of the differentiation in biological responses, including de novo lipogenesis and biosynthesis of unsaturated fatty acids.

Determination of polychlorinated dibenzo-p-dioxins and furans in food samples by gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) and comparison with gas chromatography-high resolution mass spectrometry (GC-HRMS)

Although gas chromatography–triple quadrupole mass spectrometry (GC-MS/MS) has been applied to the determination of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) in various food samples, there is insufficient evidence to evaluate its equivalence with gas chromatography–high resolution mass spectrometry (HRMS). In the present study, two GC-MS/MS instruments with different ion sources (advanced electron ionization [EI] and atmospheric pressure chemical ionization [APCI]) were evaluated for detecting trace levels of PCDD/Fs in various foods. GC-EI-MS/MS and GC-APCI-MS/MS showed good linear relationships for 17 PCDD/Fs (0.01–200 ng/mL, R2 > 0.999), and the relative standard deviations of the relative response factors were 3–18%. The limit of quantitation range of the PCDD/Fs was 0.005–0.101 ng/mL with GC-APCI-MS/MS and 0.006–0.201 ng/mL with GC-EI-MS/MS. The capabilities of the GC-MS/MS methods were evaluated for determination of PCDD/Fs in reference materials and real food samples. Statistical analyses showed that the toxic equivalents (TEQs) were comparable to those obtained with GC-HRMS, and the methods had good sensitivity, repeatability, and reproducibility. No difference was found between the results from the GC-MS/MS techniques and GC-HRMS when the PCDD/Fs concentrations were greater than 10−2 pg/g. The results suggest that when the total TEQ is greater than 0.57 pg TEQ/g (lipid weight) or 0.052 pg TEQ/g (wet weight), GC-MS/MS techniques could be used as a complementary approach to GC-HRMS. Both GC-EI-MS/MS and GC-APCI-MS/MS have similar sensitivity, selectivity, and stability to HRMS and could be used as confirmation methods for the analysis of trace PCDD/Fs in animal foods.

The first German total diet study (BfR MEAL Study) confirms highest levels of dioxins and dioxin-like polychlorinated biphenyls in foods of animal origin.

The first German Total Diet Study, called the BfR MEAL Study, generated a comprehensive dataset of polychlorinated dibenzo-p-dioxins and -furans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) in foods representative for the consumption habits in households in Germany. PCDD/Fs and dl-PCBs are persistent organic pollutants. Dietary intake is considered to be the most relevant exposure pathway for humans. Levels were examined in 300 foods that were prepared as typically consumed by the population in Germany. Highest PCDD/F and dl-PCB levels were detected in animal-based foods such as fish, butter, dairy products, liver, and meat. The comparison of conventionally and organically produced foods revealed a trend to slightly higher contents in organically produced foods. Sampling discriminated by region and season showed no major differences. Analysed occurrence data will improve future dietary exposure and food safety assessments in Germany.

Dehalobium species implicated in 2,3,7,8-tetrachlorodibenzo-p-dioxin dechlorination in the contaminated sediments of Sydney Harbour Estuary

Polychlorinated dibenzo-p-dioxins and furans (PCDD/F) are some of the most environmentally recalcitrant and toxic compounds. They occur naturally and as by-products of anthropogenic activity. Sydney Harbour Estuary (Sydney, Australia), is heavily contaminated with PCDD/F. Analysis of sediment cores revealed that the contamination source area in Homebush Bay continues to have one of the highest levels of PCDD/F contamination in the world (5207 pg WHO-TEQ g−1) with >50% of the toxicity attributed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), the most toxic PCDD/F congener. Comparison of congener profiles at the contamination source area with surrounding bays and historical data provided evidence for the attenuation of 2,3,7,8-TCDD and other congeners at the source area. This finding was supported by the detection of di-, mono- and unchlorinated dibenzo-p-dioxin. Microbial community analysis of sediments by 16S rRNA amplicon sequencing revealed an abundance of lineages from the class Dehalococcoidia (up to 15% of the community), including the genus Dehalobium (up to 0.5%). Anaerobic seawater enrichment cultures using perchloroethene as more biologically available growth substrate enriched the Dehalobium population by more than six-fold. The enrichment culture then proved capable of reductively dechlorinating 2,3,7,8-TCDD to 2,3,7-TriCDD and octachlorodibenzo-p-dibenzodioxin (OCDD) to hepta and hexa congeners. This work is the first to show microbial reductive dehalogenation of 2,3,7,8-TCDD with a bacterium from outside the Dehalococcoides genus, and one of only a few that demonstrates PCDD/F dechlorination in a marine environment.

Heavy metals, PAHs and POPs in recycled polyethylene samples of agricultural, post-commercial, post-industrial and post-consumer origin

In the present work, recycled polyethylene (LDPE) samples of agricultural, post-commercial, post-industrial and post-consumer origin were selected and analysed. The analysis comprised the determination of different contaminants such as metals, polycyclic aromatic hydrocarbons (PAHs), dioxin-like biphenyl polychlorides (PCBs), and polychlorinated-dibenzo-p-dioxins and furans (PCDD/Fs). A comparison with one sample of virgin plastic (unrecycled) was performed. The study aimed at stressing the importance of this type of analysis in recycled plastics. Indeed, such an examination will determine the material’s final destination, and the possible origin of the pollutants analysed is investigated. Black post-industrial and post-consumer samples presented the highest concentration of PCBs and PCDD/Fs, attaining a maximum value of 2.40 pg WHO-TEQ/g, while the least toxic sample (post-commercial) presented a toxicity of 0.38 pg WHO-TEQ/g. PAHs content was also much higher in black samples, reaching 514.41 ng/g, while the lowest concentrations were obtained for the post-commercial plastic sample, which did not exceed 38.98 ng/g. The higher PAHs concentrations in the black samples were related to the carbon black content of the black samples, which was 2.00% for black post-industrial sample and 1.51% for post-consumer sample. The PCDD/Fs congener profile observed in almost all samples was very similar to the profile found in the literature on urban air samples, indicating that the plastic is mainly influenced by the environment. The presence of some metals (mainly copper) showed a slight correlation with PCDD/Fs content. The pollutants analysed were found to be significantly reduced during the cleaning processes that are generally carried out in recycling companies.

Emission levels and phase distributions of PCDD/Fs in a full-scale municipal solid waste incinerator: The impact of wet scrubber system

The emission of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) from municipal solid waste (MSW) incinerations will pose serious risk to ecological environment and human health. To further understand the memory effect of wet scrubber system (WSS) on PCDD/Fs emission and phase distribution characteristics, a field study was conducted in a full-scale (850 t d−1) MSW incinerator where a WSS was newly adopted. The four exhaust flue gas samples and the two scrubbing solution samples inside WSS were separately collected for PCDD/Fs analyzing. The results indicated that the memory effect of WSS obviously enhanced the I-TEQ concentration of PCDD/Fs from 0.007 to 0.033 ng I-TEQ Nm−3 after flue gas passed through WSS, owing to increasing the total mass concentration of PCDD/Fs and the proportion of low-chlorinated congeners. The gas-phase PCDD/Fs was dominant (62.5%–88.9%) in flue gas, among which the PCDD/Fs enriched in condensed water notably contributed to nonnegligible proportions of 25.0%–67.6%. The adsorption/desorption process of PCDD/Fs was considered as one of the reasonable mechanisms of memory effect, based on the PCDD/Fs phase distribution and the congeners profile inside the WSS. Besides, the I-TEQ concentration of PCDD/Fs determined in scrubbing solution was up to 50.2 pg I-TEQ L−1, which might be a potential source to cause the enhancement of PCDD/Fs emission. This study verified the enhancement impact of WSS on PCDD/Fs emission and inspired the optimal design of WSS, i.e., choosing more suitable filling materials and timely replacing them to reduce the negative impact of memory effect, keeping WSS operated in relatively stable and consistent conditions, and safely disposing the scrubbing solution to mitigate the secondary pollution of PCDD/Fs.

An experimental simulation study of conventional waste burning practices in India for the assessment and inventorisation of PCDD/F/dl-PCB emissions

The paper reports an update to the polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) annual emission inventory of India from open burning of municipal solid wastes (MSW) through the generation of nation-specific emission factors for air (EFair) and burned residue (EFland) vectors. The MSW characteristics and modes of disposal practiced in Indian cities exhibits subtle variations from that of developed nations due to differences in food habits, living standards and climatic conditions. The annual emission calculations based on EFs from hitherto studies simulating conditions prevailing in developed countries can lead to anomalous accounting of emission levels. It is the first experimental study reported from Indian subcontinent to determine EFs of dioxins and dl-PCBs from MSW open burning by simulated combustion experiments conducted in a custom fabricated Open Burning Test Facility (OBTF) - “Burn Hut”, using real dumpsite waste samples. Iso-kinetic sampling and coning and quartering methods were employed for the sampling of air and land emissions from combustion experiments. The PCDD/F's EFair ranged from 3 to 675 μg toxicity equivalence (TEQ)/ton of waste with a geometric mean (GMair) of 67.0 μgTEQ/ton and EFland ranged from 10 to 2531 μgTEQ/ton waste (GMland – 100.0 μgTEQ/ton). The EFair and EFland of dl-PCBs ranged from 0.5 to 46 μgTEQ/ton (GMair 7.0 μgTEQ/ton) and 0.5 to 96 μgTEQ/ton of waste (GMland 6.0 μgTEQ/ton) respectively. A detailed assessment of correlations between emission and MSW composition/combustion practices were conducted along with a comparative evaluation of EFpresent vis-à-vis EFs reported elsewhere.

Reevaluation on accumulation and depletion of dioxin-like compounds in eggs of laying hens: Quantification on dietary risk from feed to egg

Updated assessment on transfer of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) from feed to food is essential for understanding human exposure risk. A controlled feeding experiment was conducted for laying hens to reevaluate the transfer characteristics of dioxin-like compounds from feed to egg. Two fortified diets (1.17 and 5.13 pg TEQ g−1 dry weight), made by blending with fly ash, were fed to laying hens for 14 days, followed by 28-days depletion. Levels of ∑TEQPCDD/Fs+DL-PCBs in eggs rapidly increased once exposure started, reaching at 1.98 and 6.86 pg TEQ g−1 lw at the end of exposure for low- and high-exposure groups, respectively, and dropped to under the European legislation (maximum levels: 5.0 pg TEQ g−1 lw) after 28-days depletion. The quantitative depletions showed that the half-lives (T1/2) of ∑TEQPCDD/Fs in eggs were 23 and 14 days for low- and high-exposure groups, respectively. The depletion and accumulation rates of PCDD/Fs were in the range of 0.026–0.151 and 0.005–0.016 day−1, respectively, representing that the T1/2 of PCDD/Fs in eggs ranged from 5 to 27 days. The depletion kinetics of DL-PCBs was not significant in egg. The hens with higher laying rates exhibited shorter T1/2 of PCDD/Fs, implying that increasing laying rate could expedite the depletion of PCDD/Fs in egg. The T1/2 of PCDD/Fs in egg were negatively correlated with the chlorine number, indicating that lower chlorinated congeners tended to be retained in the egg. Transfer rates of PCDD/Fs were in the range of 4–19%, which were lower than the previous results. These results were attributed to short exposure time and low bioavailability of PCDD/Fs in fly ash. Estimations of dietary intake highlighted the dietary risk of PCDD/Fs from feed to egg, which would pose limited adverse effects on human health.

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

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

Combined sediment desorption and bioconcentration model to predict levels of dioxin-like chemicals in fish

Flooding and other sediment disturbances can lead to increases in sediment resuspension. In this context, it is of central importance to understand the kinetics of release from these sediments and the uptake of pollutants, such as polychlorinated biphenyls (PCBs) and polychlorinated dioxins and furans (PCDD/Fs), into aquatic organisms. In the present study, we parameterized a sediment desorption model based on experimentally determined rapidly-desorbing fractions of dioxin-like chemicals (DLCs). We coupled this desorption model with a physiologically-based toxicokinetic model for rainbow trout. This combined model was used to predict DLC concentrations in the muscle of exposed fish. The performance of this model was evaluated using a previously published dataset on DLC uptake from sediment suspensions during simulated re-suspension events. Predictions generally differed less than 10-fold from measured values, and the model showed a good global coefficient of determination (R2) of 0.95. The root mean squared error (RMSE) for PCBs was 0.31 log units and 0.53 log units for PCDD/Fs. The results of our study demonstrate that the prediction of bioconcentration and related risk to fish resulting from sediment resuspension can be accurately predicted using coupled desorption and toxicokinetic models.

Factors associated with partitioning behavior of persistent organic pollutants in a feto-maternal system: A multiple linear regression approach

Prenatal exposure to persistent organic pollutants (POPs) has been a matter of particular concern because such exposure can severely affect the health of the fetus. The mechanistic understanding of the partitioning behavior of POPs in the feto-maternal system and the associated factors, however, have rarely been studied. Here, we employed a new approach based on multiple linear regression (MLR) analysis to predict the feto-maternal ratio (FM-ratio) of POPs and to assess the factors associated with feto-maternal partitioning behavior. Two preliminary exploratory MLR models were built using physiological conditions of the participants, and molecular descriptors were calculated with a computational model. The FM-ratio was calculated from the concentrations of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), and polybrominated diphenyl ethers (PBDEs) in 20 pairs of maternal and cord blood. The models showed that the lipids and cholesterols in the maternal and cord blood and the placenta significantly influence the partitioning of POPs. The body mass index (BMI) change during pregnancy was also related to the FM-ratio. The physicochemical properties associated with lipophilicity and molecular size were also related to the FM-ratio. Even though the results should be interpreted with caution, the preliminary MLR models illustrate that feto-maternal partitioning is governed by transplacental transporting mechanisms, toxicokinetics, and the molecular physicochemical properties of POPs. Overall, the new approach used in this study can improve our understanding of the partitioning behavior in the feto-maternal system.

Polybrominated dibenzo-p-dioxins and furans (PBDD/Fs) in Italian food: Occurrence and dietary exposure

Human exposure to polychlorinated dioxins and furans (PCDD/Fs) through the dietary pathway is widely recognised and regulations in some regions of the world help to limit food contamination. Similar information on the analogous polybrominated dioxins and furans (PBDD/Fs) is scarce, partly due to the higher threshold to analytical access and unavailability of some standard materials. The analytical methodology developed here determined twelve planar PBDD/F congeners using 13Carbon labelled PBDD/F surrogates and high resolution mass spectrometric detection, and was extensively validated prior to the analysis of a range of commonly consumed Italian foods. The methodology also allowed simultaneous determination of PCDD/Fs and polychlorinated biphenyls (PCBs). The results show that PBDD/Fs occurred in different foods over a range of concentrations from <0.001 pg/g to 4.58 pg/g in fish. The dietary exposure (upper bound) of different Italian population groups, resulting from these occurrence levels was estimated using the toxic equivalency (TEQ) approach that is commonly used for dioxin-like contaminants and ranged from 0.17 to 0.42 pg TEQ/kg bodyweight/day (lower bound – 0.01 pg TEQ/kg bodyweight/day) depending on the population subgroup. Although precautionary, upper bound values may provide a more realistic estimate of toxicity as not all congeners and foods were measured. As expected, children were more highly exposed than adults due to lower body weight. These exposure levels were between a quarter and a third of that arising from the sum of PCDD/Fs and PCBs (0.61 to 1.38 pg WHO-TEQ/kg bodyweight/day), but they contribute to dioxin-like toxicity. If this data is considered in view of the revised tolerable dioxin-like dietary intake published by EFSA in 2018, it is evident that the tolerable weekly intake of 2 pg/kg bodyweight/week would be exceeded by some of the assessed population sub-groups, or all sub-groups if the cumulative intake is considered.

Effect of different air pollution control devices on the gas/solid-phase distribution of PCDD/F in a full-scale municipal solid waste incinerator

The emission of polychlorinated dibenzo-p-dioxins and -furans (PCDD/F) from full-scale municipal solid waste incinerators (MSWI) is harmful to human and environmental health. This study analyzes the effect of different units of an air pollution control devices (APCDs), i.e. the semi-dry scrubber, fabric filter (FF), selective catalytic reduction (SCR), and wet scrubber (WS), on the removal characteristics and gas- and solid-phase distributions of PCDD/F in MSWI flue gas. APCDs reduce PCDD/F concentrations from 24.9 ng Nm−3 to 0.979 ng Nm−3 (2.16 ng I-TEQ Nm−3 to 0.0607 ng I-TEQ Nm−3), with a total removal efficiency (RE) of 96.1% (97.2% I-TEQ). Specifically, APCDs remove more than 95% of both gas- and solid-phase PCDD/F. The FF coupled with active carbon injection (FF + ACI) substantially reduces both gas- and solid-phase PCDD/F concentrations with an RE of 97.2% (98.7% I-TEQ). Additionally, FF + ACI exhibits a better RE of PCDF (98.9%) than PCDD (94.6%) and leads to PCDD congeners dominating the gas-phase. Both desorption and destruction of PCDD/F occur in the SCR, which favors removal of gas-phase PCDD/F but increases solid-phase PCDD/F. Therefore, SCR only decreases PCDD/F with a low RE of 27.6% (16.9% I-TEQ). However, SCR reduces NOx with a high RE of 82.3%, which could inhibit the RE of PCDD/F because of their different reaction mechanisms. WS increases PCDD/F in both the gas and solid-phase by 1.95 times (2.57 times for I-TEQ) due to the memory effect, which typically increases the total mass concentration of PCDD/F and the proportions of lower-chlorinated gas-phase PCDD/F. Migration of gas- and solid-phase PCDD/F are also analyzed according to temperature. The results of this study can contribute to the optimized design of industrial APCDs for controlling PCDD/F emissions from MSWI.