Despite increasing waste-to-energy (WtE) capacities, there remain deficiencies in comprehension of 136 kinds of tetra- through octa-chlorinated dibenzo-p-dioxin and dibenzofurans (136 PCDD/Fs) originating from incineration sources. Samples from twenty typical WtE plants, encompassing coal-fired power plants (CPP), grate incinerators (GI), fluidized bed incinerators (FBI), and rotary kilns (RK), yielded extensive PCDD/F datasets. Research was conducted on fingerprint mapping, formation pathways, emission profiles, and diagnostic analysis of PCDD/Fs in WtE plants. Fingerprints revealed a prevalence of TCDF, followed by PeCDF, while CPP and RK respectively generated more PCDD and HxCDD. De novo synthesis was the predominant formation pathway except one plant, where CP-route dominated. DD/DF chlorination also facilitated PCDD/F formation, showing general trends of FBI > GI > CPP > RK. The PCDD/F emission intensities emitted in air pollution control system inlet (APCSI) and outlet (APCSO) followed the statistical sequence of RK > FBI > GI > CPP, with the average I-TEQ concentrations in APCSO reaching 0.18, 0.08, 0.11, and 0.04 ng I-TEQ·Nm-3. Emission spectrum were accordingly formed. Four clusters were segmented for diagnosis analysis, where PCDD/Fs in GI and FBI were similar, grouped as a single cluster. PCDD/Fs in CPP and RK demonstrated distinctive features in TCDD, HxCDD, and HxCDF. The WtE plants exceeding the limit value tended to generate and retain fewer TCDD and TCDF yet had higher fractions of HxCDD and HxCDF. The failure of APCS coupled with the intrinsic source strength of PCDD/Fs directly led to exceedance, highlighting safe operational practices. This study motivated source tracing and precise evaluation of 136 PCDD/Fs based on the revealed fingerprint profiles for WtE processes.

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 75.8 ng/Nm3 for PCDDs, 219 ng/Nm3 for PCDFs, and 763 ng/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.

Thermal treatment of municipal solid waste incineration (MSWI) fly ash (FA) allows heavy metals solidification, polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) decomposition, and environmentally stable materials production, but lacking advanced insights into PCDD/Fs dramatically limits its development. In this study, the decomposition and reformation of PCDD/Fs during thermal treatment of two typical fly ashes (loading 0.294 and 0.594 ng I-TEQ/g PCDD/Fs, respectively) are systematically investigated, under conditions of three heating temperature (500, 800, and 1100 °C) and two atmospheres (oxidative and inert). Over 95 % of PCDD/Fs in FA are effectively decomposed for all tests mainly via cyclic skeleton destruction accompanied by dechlorination, but reformation predominantly through de novo synthesis in off-gases significantly reduces the overall elimination efficiency. Moreover, both de novo synthesis and chlorination are enhanced as temperature increase promoting migrations of catalytic metals and chlorine, yet are weakened at the absence of oxygen, both of which are revealed by PCDD/F-signatures evolution. Catalytic metal is identified as the most critical factor accounting for PCDD/Fs reformation, which is also evidenced by kinetic models of de novo synthesis. Finally, the decomposition and reformation pathways during thermal treatment of fly ashes are proposed. The results pave the way for controlling PCDD/Fs reformation and improving the thermal treatment of fly ashes.

We have studied the feasibility of solid phase extraction of PCDDs/PCDFs and dioxin-like PCBs from oils and fats as the first step of a sample preparation procedure that would not involve the chemical decomposition of the matrix. A few experimental setups using dual-layer columns packed with various brands of active carbon were tested. The use of a dual-layer microcolumn with AX-21 and Carboxen 1000 carbons for dioxins extraction from animal fats, vegetable oils and powdered milk gave satisfactory recoveries which met the European Union Commission Regulation 2017/644 criteria for dioxin analysis. The developed method of solid phase extraction on a dual-layer carbon column requires lower amounts of solvents and sorbents, tolerates high amounts of fat and can be used in both manual and automated sample preparation procedures. The recoveries obtained for the most toxic congeners (2,3,7,8-TCDD, 1,2,3,7,8-PeCDD and 2,3,4,7,8-PeCDF) are within 79-119%.

The detoxification of municipal solid waste incinerator (MSWI) fly ash dioxins urgently requires an effective treatment technology. In this study, we adopted a single-mode microwave (MW)-based pyrolysis to treat MSWI fly ash under N2 atmosphere and further elucidated the main influencing factors, including the chemical inhibitor, for dioxin control. The results show that (1) the detoxification process was optimized with a mass ratio of fly ash to SiC of 1:9, 23.1% (wt%) urea addition and pyrolysis temperature of ˜ 480 °C; (2) the total polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) destruction efficiency and the bioassay-derived 2,3,7,8-TCDD toxic equivalent (Bio-TEQ) removal efficiency reached 98.5% and 97.9%, respectively, accompanied with ˜ 1.3% of the total amount of dioxin being submitted to exhaust gas; (3) the MW-based pyrolysis of urea (133˜300 °C) was favourable for the generation of hot spots as well as the PCDD/F rapid destruction in fly ash. In addition, the leaching toxicity of heavy metals was also partially reduced after MW pyrolysis reactions. To the best of our knowledge, this is the first report adopting a MW-based pyrolysis to eliminate dioxin in MSWI fly ash with the addition of urea, which is a promising alternative to current methods.

Metallurgical plants are important sources of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs). It is significant to evaluate the air levels and human risks of PCDD/Fs, PCBs and PCNs in metallurgical plants considering their adverse effects on human health and thousands of metallurgical plants being in operation in China. The estimated inhalation intakes of PCDD/Fs, PCBs, and PCNs together in eight iron ore sintering plants, three secondary copper plants, four secondary aluminum plants, and one secondary lead plant were 4.9-213.4, 21.4-4026.4, 28.7-630, and 11.7fgTEQkg-1day-1, respectively, and the corresponding cancer risks were estimated to be 8.7×10-7 to 3.8×10-5, 5.1×10-6 to 1.1×10-4, 3.8×10-6 to 7.1×10-4, and 2.1×10-6, respectively. The estimated cancer risk were higher than 100 per million people for three secondary aluminum and copper smelters among the sixteen metallurgical plants, indicating high cancer risks. Stack gas samples from metallurgical plants were also collected and analyzed for comparing their emission profiles with that of air samples. The comparison of PCDD/F, PCB and PCN profiles between air samples and stack gas samples by similarity calculation and principal component analysis suggested the influence of stack gas emissions from metallurgical plants on surrounding air. These results are helpful for understanding the exposure risk to PCDD/Fs, PCBs and PCNs in numerous metallurgical plants being operation in China.

We analyzed 17 polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and 12 dioxin-like polychlorinated biphenyls (DL-PCBs) in samples from various fish species available at food markets in nine Korean cities. The estimated dietary intake of these chemicals was calculated from the raw concentrations of PCDD/Fs and DL-PCBs in each sample and from the food consumption of the Korean general population, and a comparison was made with the provisional tolerable monthly intake (PTMI). The average daily dietary exposure and the 95th percentile of intake of PCDD/Fs and DL-PCBs were 0.21 and 0.49 pg WHO05-toxic equivalents (TEQ) kg(-1) body weight d(-1) representing 5.27% and 12.26%, respectively, of the Korean tolerable daily intake (TDI). We applied the monthly fish consumption limits to the evaluation of improved risk assessment and concluded that unlimited consumption of most fish species does not contribute to the elevated cancer risk. This investigation was the first such large-scale study in Korea, and incorporated 37 species, including a species of whale, and 480 samples. The major aims of this study were to demonstrate the health risks associated with fish intake and to ensure food safety through total analysis of PCDD/Fs and DL-PCBs using gas chromatography/high-resolution mass spectrometry (GC-HRMS).

Mercury and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) accumulate in organisms through food webs and exert potentially toxic effects on aquatic organisms and humans. This study examined the levels of mercury and PCDD/Fs in organisms and sediment samples collected from a saltwater pond at the An-Shun site, a chloralkali factory that shut down in Tainan City, Taiwan. It was also a pentachlorophenol production plant. After the factories were shut down in the 1980s, mercury and PCDD/Fs contamination remained, posing severe health hazards. The correlation between PCDD/Fs congener accumulation patterns in distinct fish organs and the sediment was evaluated. Mercury and PCDD/Fs levels in all the fish samples exceeded food safety limits, and the concentrations of mercury and PCDD/Fs in each species were closely correlated (n = 12, Spearman\'s rank correlation [R] = 0.811, p < 0.01). The mercury concentrations were positively but non-significantly correlated with the weight (n = 11, R = 0.741, p < 0.01) and length (n = 11, R = 0.618, p < 0.05) of the species. The fish likely accumulated the contaminants through ingestion of other organisms or the sediment. However, after the pollutants entered a fish, they exhibited distinct accumulation patterns because of their differing chemical properties. Specifically, the mercury concentration was correlated with organism weight and length, whereas the PCDD/Fs concentration was associated with organ lipid content. The study results are valuable for assessing the health risks associated with ingesting mercury- and PCFF/F-contaminated seafood from the study site.

The formation and environmental release of highly toxic organohalogen compounds associated with informal recycling of waste electric and electronic equipment (e-waste) is a growing problem at e-waste dumps/recycling sites (EWRSs) in many developing countries worldwide. We chose a cross-sectional study design to measure the internal exposure to polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) as well as polychlorinated biphenyls (PCBs) of individuals working on one of the largest EWRSs of Africa, located at Agbogbloshie, Accra, Ghana, and in controls from a suburb of Accra without direct exposure to EWRS activities. In whole blood samples of 21 age matched male exposed individuals (mean age: 24.7 years, SD 6.0) and 21 male controls (mean age: 24.4 years, SD 5.7) 17 PCDD/F congeners were determined. Moreover three indicator PCB congeners (#138, #153 and #180) were measured in blood of 39 exposed (mean age: 27.5 years, SD 11.7) and 19 non-exposed (mean age: 26.8 years, SD 9.7) patients. Besides a health examination, biometric and demographic data, residential and occupational history, occupational exposures and working conditions were recorded using a standardized questionnaire. In the exposed group, median PCDD/F-concentrations were 6.18 pg/g lipid base WHO2005-TEq (range: 2.1-42.7) and significantly higher compared to the control group with 4.60 pg/g lipid base WHO2005-TEq (range: 1.6-11.6). Concentrations were different for 2,3,7,8-TetraCDD, three HexaCDD and all 10 PCDF congeners, indicating a combustion pattern. Using a multivariate regression analysis exposure to EWRS activities was the most important determinant for PCDD/F exposure. Median PCB levels for the indicator congeners #138, #153 and #180 were 0.011, 0.019 and 0.008 μg/l whole blood (ranges: 0.002-0.18, 0.003-0.16, 0.002-0.078) in the exposed group and, surprisingly, significantly higher in the controls (0.037, 0.062 and 0.022; ranges: 0.005-0.46, 0.010-0.46, 0.004-0.21). In a multivariate regression approach e-waste related activities had no positive influence on internal PCB exposure, but rather the time living in Accra. The internal PCB exposure is in particular notable for a country where PCBs have historically never been produced or used. The impact of EWRS activities on organohalogen compound exposure of individuals working at and living in the surroundings of the Agbogbloshie EWRS, and the surprisingly high PCB exposure of people living in Accra not involved in e-waste activities require further investigation.

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were analyzed in 25 background and 80 agricultural soil samples collected from 21 sites in Beijing, China. The levels of PCDD/Fs in the north agricultural soils were low (0.15-0.58 ng international toxic equivalent quantity [I-TEQ]/kg), which were comparable with those of the background soils (0.091-0.35 ng I-TEQ/kg). In the southern agricultural soils, however, concentrations were several times higher (0.27-3.3 ng I-TEQ/kg). Comparison of PCDD/Fs congener compositions between possible sources and samples indicated that agricultural soils in Beijing had not been contaminated by the 3 main PCDD/F contamination sources in China--ferrous and nonferrous metal, waste incineration, and power generation. They had, however, been slightly contaminated by the impurities of some organochlorine pesticides, such as sodium pentachlorophenate, and by open burning of biomass, vehicle exhaust, atmospheric deposition, sediment, and sewage sludge. These results have been supported by the principal components analysis.