Distribution patterns of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in sediments of the Xiangjiang River, China

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.

A review of levels and profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans in different environmental media from China

This review provides a summary of the levels and profiles of PCDD/Fs throughout China, as reported in peer reviewed literatures since 1997. The literature shows that PCDD/Fs are widespread in various environmental media including air, water, sediment, and soil. PCDD/Fs concentrations in air were relatively low in most regions, with only a few areas considered polluted. Many studies reported seasonal trends, with higher and lower concentrations in winter and summer, respectively. We analyzed the factors affecting the concentrations of dioxins in air and summarized the causes of seasonal changes. As hydrophobic organic compounds, PCDD/Fs readily accumulate in sediments. The distribution of dioxins in sediment in Bohai Sea area was mainly introduced and the factors affecting concentrations of dioxins were studied. The levels of dioxins in soil in different regions varied greatly, with higher levels in areas close to pollution sources. We examined the dioxins concentrations in soil in places where the levels were very low (including the Tibet Plateau and other remote areas), contaminated areas, and other areas. Apart from the contaminated areas, the dioxins concentrations in soil were low. The results of the relatively low number of studies that have investigated PCDD/Fs in water have reported no obvious pollution in some waters, apart from Dongting Lake. PCDD/Fs levels across China are similar to those worldwide. Point sources, mainly related to local geographic, economic, and historical factors, were the most common source of contamination. E-waste dismantling and chemical production has the greatest impact on PCDD/Fs in different media.

Human and environmental exposure to PCDD/Fs and dioxin-like PCBs in Africa: A review

This paper reviews literature for the last two decades with emphasis on levels, toxic equivalencies and sources of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) in Africa. Further, we comprehensively analysed data, interpret differences and identify existing gaps with those from other continents. We observed that high levels of PCDD/Fs and dl-PCBs were reported in environmental and biological samples near densely populated urban and industrialised areas compared to those in rural settings. In general, the concentrations of PCDD/Fs and dl-PCBs in the blood samples from Africa were in the same range as those from Asia but lower than those from Europe. The concentrations of dioxins and dioxin-like compounds in the atmosphere in Africa were comparable to and/or higher than those in developed countries. The reported sources of PCDD/Fs and dl-PCBs in Africa were industrial emissions, obsolete pesticide stockpiles, household heating, recycling of electronic waste, and incineration and combustion of domestic waste. Regional and intercontinental transport of dioxins could not be confirmed because of the lack of sufficient literature on them. Further data about the levels and sources of PCDD/Fs and dl-PCBs in Africa need to be generated to complete the chemical inventories for the continent and to facilitate the implementation of the Stockholm Convention on persistent organic pollutants. The reviewed literature shows that most analyses have been carried out in laboratories outside Africa because of the limited institutional capacity in Africa. More support needs to be given to laboratories in Africa to develop the capacity to accurately quantify dioxins on routine basis.

PBDEs, PCBs and PCDD/Fs in the sediments from seven major river basins in China: Occurrence, congener profile and spatial tendency

Polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) were extensively investigated in the sediment samples collected from seven major river basins around China. The concentrations were in the range of 0.05-6.15 × 10(4) ng g(-1) dry weight (dw), 0.29-21.7 ng g(-1) dw and 0.01-6.49 ng g(-1) dw for PBDEs, PCBs and PCDD/Fs, respectively. The concentrations showed wide variations among different river basins, while the congener profiles in all the sediments were generally characterized by only a few compounds, such as BDE-209, -99 and -47, CB-11 and -28, OCDD and OCDF, etc. The spatial analysis identified a decreasing trend of these persistent organic pollutants (POPs) from south to north China, consistent with regional industrialization. However, relatively higher level of POPs was also observed in the upstream of Yellow River Basin. The present study gives insight into the spatial occurrence of the three POPs in the major river basins in China.

Polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and polybrominated diphenyl ethers in sediments and fish species from the Murchison Bay of Lake Victoria, Uganda

Polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) and polybrominated diphenyl ethers (PBDEs) were analyzed in sediments and fish from the Murchison Bay of Lake Victoria by high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS). Average concentrations of total (Σ) PCDD/Fs and ΣPBDEs in sediments ranged from 68.8 to 479 pg g(-1) dry weight (dw) and 60.8 to 179 pg g(-1) dw, respectively. Contamination levels of sedimentary PCDD/Fs and PBDEs were low to moderate compared to other urbanized regions worldwide. The concentrations in different fish species (Nile perch; Lates niloticus and Nile tilapia; Oreochromis niloticus) were 5.32 to 49.0 pg g(-1) wet weight (ww) for PCDD/Fs and 59.3 to 495 pg g(-1) ww for PBDEs. Higher concentrations of the pollutants were found in L. niloticus than O. niloticus, which could be attributed to species differences in feeding habits and lifestyles. World Health Organization-toxic equivalents (WHO2005-TEQs) for PCDD/Fs ranged from 0.08 to 0.33 pgTEQg(-1) dw and 0.001-0.14 pg TEQg(-1) ww in sediments and fish, respectively. The TEQ values were low compared to the data for fresh water fish reported in literature and within a permissible level of 3.5 pg g(-1) ww recommended by the European Commission. Based on the Commission set value and minimum risk level criteria formulated by the Agency for Toxic Substances and Disease Registry, the fish from the Murchison Bay was fit for human consumption.

Pollution characteristics and potential health risk of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in soil/sediment from Baiyin City, North West, China

In order to better understand the environmental behaviors of persistent organic pollutants, the characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were investigated in twenty-three soil/sediment samples from Baiying City, Northwest China, in 2008. The possible sources and potential health risk of PCDD/Fs were also discussed. The concentrations of PCDD/Fs in nineteen soil samples varied between 20.13 and 496.26 pg/g dry weight (dw.), with an average value of 125.59 pg/g dw. The highest International Toxic Equivalent (I-TEQ) of PCDD/Fs (8.34 pg/g dw.) in soil was found at sample S1 collected from proximity to a copper metallurgy plant. The concentrations of PCDD/Fs in four sediment samples ranged from 37.69 to 491.49 pg/g dw., with an average value of 169.95 pg/g dw. The highest I-TEQ of PCDD/Fs (8.56 pg/g dw.) in sediment was found at sample S12 collected from the East big ditch with waste water discharged into the Yellow River. The results indicated that PCDD/Fs contamination of soil/sediment is originated from three sources: chlorine-containing chemicals, non-ferrous metal industrial PCDD/Fs emission and coal burning. The health risk exposure to PCDD/Fs through soil, dust ingestion and dermal absorption ranged from 0.0006 to 0.0134 pg/kg/day Word Health Organization's toxic equivalent in 1998 (WHO1998-TEQ) with mean values 0.0032 pg WHO1998-TEQ for adults and varied between 0.0012 and 0.0256 pg/kg/day WHO1998-TEQ with mean values 0.006 pg/kg/day WHO1998-TEQ for children, respectively. These results indicated that health risk of PCDD/Fs for children should be paid more attention.

Dioxin levels in fertilizers from Belgium: determination and evaluation of the potential impact on soil contamination

Dioxins are harmful persistent organic pollutants (POPs) to which humans are exposed mostly via the consumption of animal products. They can enter the food chain at any stage, including crop fertilization. Fertilizers belong to several categories: synthetic chemicals providing the essential elements (mostly N, P and K) that are required by the crops but also organic fertilizers or amendments, liming materials, etc. Ninety-seven samples of fertilizers were taken in Belgium during the year 2011 and analyzed after a soft extraction procedure for polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (DL-PCBs) using GC-IDHRMS. Only small qualitative differences could be observed between the main fertilizer categories since the PCDD:PCDF:DL-PCB average ratio obtained with the results expressed in TEQ was often close to 30:30:40 (typically for sewage sludge) or 40:30:30 (typically for compost). The median dioxin levels determined were generally lower than recorded previously and were the highest for sewage sludge and compost (5.6 and 5.5 ng TEQ/kg dry weight (dw), respectively). The levels in other fertilizers were lower including manure for which the median value was only 0.2 ng TEQ/kg dw. Several fertilization scenarios relying on the use of those fertilizers were assessed taking into consideration the application conditions prevailing in Belgium. From this assessment it could be concluded that the contribution of fertilizers to the overall soil contamination will be low by comparison of other sources of contamination such as atmospheric depositions. At the field scale, intensive use of compost and sewage sludge will increase dramatically the dioxin inputs compared with other fertilization practices but this kind of emission to the soil will still be relatively low compared to the dioxin atmospheric depositions.

Severe pollution of PCDD/Fs and dioxin-like PCBs in sediments from Lake Shihwa, Korea: tracking the source

Concentrations of polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) were determined in surface sediments from Lake Shihwa and from creeks that discharge into this artificial lake. The toxic equivalents (TEQs) in sediments ranged from 1.0 to 1770 pg/g dry weight, which were some of the highest values ever reported so far for coastal sediments on a global basis. The concentrations of PCDD/Fs and DL-PCBs decreased with increasing distance from the creeks to offshore regions of the lake. Based on a multivariate statistical analysis and congener profiles, it was found that high contamination by PCDD/Fs in creek sediments collected around Lake Shihwa was associated with releases from chlor-alkali processes. Significant correlations were found for total organic carbon content and the concentrations of highly chlorinated PCDD/F congeners. This is the first report to document chlor-alkali processes as a significant source of PCDD/F contamination in Korean coastal waters.

Distribution patterns and major sources of dioxins in soils of the Changsha-Zhuzhou-Xiangtan urban agglomeration, China

Surface soils from an industrial base, the Changsha-Zhuzhou-Xiangtan urban agglomeration in central China were analyzed for 2378-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). The PCDD/F concentrations ranged from 268 to 7510 pg g(-1) dry weight (dw), 72% of which were above the U.S. guideline value (1000 pg g(-1)). It was found that octachlorodibenzo-p-dioxin (OCDD) was the most dominant congener accounting for 78.4-99.3% of the total PCDD/Fs, which was consistent with the PCDD/F profiles reported in other Asian countries. It is recommended that the four major sources of PCDD/Fs in the region can be diesel-fuel vehicles, open straw burning, mass burn-water wall (MB-WW), pentachlorophenate (PCP)/PCP-Na and boilers-hazardous waste incineration. This study is one of the few studies with a focus on the PCDD/F pollution in central China, providing evidences for establishing priorities in reduction of ecological risks posed by PCDD/Fs in central China and elsewhere.