Polychlorinated dibenzodioxins

Summary

Polychlorinated dibenzodioxins (PCDDs), or simply dioxins, are a group of long-lived polyhalogenated organic compounds that are primarily anthropogenic, and contribute toxic, persistent organic pollution in the environment. They are commonly but inaccurately referred to as dioxins for simplicity, because every PCDD molecule contains a dibenzo-1,4-dioxin skeletal structure, with 1,4-dioxin as the central ring. Members of the PCDD family bioaccumulate in humans and wildlife because of their lipophilic properties, and may cause developmental disturbances and cancer. Because dioxins can persist in the environment for more than 100 years, the majority of PCDD pollution today is not the result of recent emissions, but the cumulative result of synthetic processes undertaken since the beginning of the 20th century, including organochloride-related manufacturing, incineration of chlorine-containing substances such as polyvinyl chloride (PVC), and chlorine bleaching of paper. Forest fires and volcanic eruptions have also been cited as an airborne source, although their contribution to the current levels of PCDD accumulation are minor in comparison. Incidents of dioxin poisoning resulting from industrial emissions and accidents were first recorded as early as the mid 19th century during the Industrial Revolution. The word "dioxins" may also refer to other similarly acting chlorinated compounds (see Dioxins and dioxin-like compounds). The structure of dibenzo-1,4-dioxin consists of two benzene rings joined by two oxygen bridges. This makes the compound an aromatic diether. The name dioxin formally refers to the central dioxygenated ring, which is stabilized by the two flanking benzene rings. In PCDDs, chlorine atoms are attached to this structure at any of 8 different places on the molecule, at positions 1–4 and 6–9. There are 75 different PCDD congeners (that is, related dioxin compounds). The toxicity of PCDDs depends on the number and positions of the chlorine atoms. Congeners that have chlorine in the 2, 3, 7, and 8 positions have been found to be significantly toxic.

Official source

https://en.wikipedia.org/wiki/Polychlorinated_dibenzodioxins

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Organic pollutants in compost and digestate. Part 2. Polychlorinated dibenzo-p-dioxins, and -furans, dioxin-like polychlorinated biphenyls, brominated flame retardants, perfluorinated alkyl substances, pesticides, and other compounds

Joseph Tarradellas, Rahel Christine Brändli

Compost and digestate are important recycling fertilizers and have beneficial effects on soil parameters. However, they can contain significant amounts of organic pollutants. Here, the first comprehensive data set on dibenzo-p-dioxins and -furans ( PCDD/F), dioxin-like polychlorinated biphenyls ( DL-PCB), brominated flame retardants, perfluorinated alkyl substances ( PFAS), pesticides, phthalates, nonylphenol and chlorinated paraffins ( CP) in source-separated compost and digestate from Switzerland is presented ( n = 3-18). The median Sigma 17PCDD/ F and Sigma 12DL-PCB concentrations were at 3.2 ng I-TEQ kg(dry)(-1) (weight (dw)) and 3.0 ng WHO-TEQ kg(dw)(-1), respectively. Brominated diphenyl ether 209 ( BDE 209) accounted for 72% of the total polyBDE content ( 10 mu g kg(dw)(-1)). Hexabromocyclododecane ( HBCD) and tetrabromobisphenol A ( TBBPA) levels were at 100 and 0.51 mg kg(dw)(-1), respectively. PFAS were identified for the first time in compost and digestate ( median concentration 6.3 mu g kg(dw)(-1), P21compounds). Out of 269 pesticides analysed, 30 fungicides, 14 herbicides, eight insecticides and one acaricide were detected. Di( 2-ethylhexyl) phthalate ( DEHP) median concentration accounted for 280 mg kg(dw)(-1), and nonylphenol was below the detection limit of 1 mg kg(dw)(-1). The sum of short and medium chain CP was between 90 and 390 mg kg(dw)(-1.) The concentrations observed were at or above the levels found in background soils, which are the main recipient of compost and digestate. Where actually applied, compost can contribute considerably to the total input of organic pollutants to the soil. However, on a total Swiss agricultural area base, inputs seem to be limited.

Royal Society of Chemistry2007

Sources and fate of PCDDs and PCDFs in rural and urban ecosystem and food chain in southern Vietnam

Tuan Anh Mai

Problems related to Dioxins contamination in Southern Vietnam are until now still a hot newsreel and controversy subject in international conferences as well as in many articles. The adverse effects of Dioxins residue from chemicals used by U.S. Army during the Vietnam War (Ranch Hand Operation 1961 to 1971) have caused many consequences not only to Vietnamese ecosystem and people but also to the U.S army veterans that participated in the war at that period as reported in many scientific reports. In Vietnam, since 1980 many studies have been carried out in collaboration with overseas scientists and laboratories on Dioxin contamination levels as well as its influences on ecosystem and human health. However, regardless of many efforts, up to now the problem of Dioxin contamination and its consequences is not yet completely and appropriately solved. There is still relative high Dioxins residue in the areas named as "hot spot" in Southern Vietnam and its contamination is causing the adverse effects on local residents. Nowadays, studies on this subject are relatively difficult to perform due to many factors: over 30 years passed; land use disturbance; degradation and transfer of dioxin into biological food web; population emigration; etc.. In addition, a lack of related documents and military secrets also contributed to this. With the support of SDC in frame of a collaboration project between Vietnam and Switzerland, we have carried out the research named "Sources and Fate of PCDDs and PCDFs in rural and urban ecosystem and food chains of South-Vietnam". Our research has examined integratelly the PCDD/Fs sources with special regard on the PCDD/Fs source from the war, but also consider the others possible sources such industrial and municipal combustions, agricultural used chemicals, etc. The selected locations for our research have been set up based on collected document from Division 10-80 and Office 33 (two responsible organizations for Dioxins and related problems in Vietnam): CamLo District – QuangTri Province; DaNang City; MaDa Forest and BienHoa City (BienHoa Airforce Base and BienHung Lake) – DongNai Province; and industrial zone – Thu Duc – Hochiminh City. Seventeen 2,3,7,8-PCDD/Fs congeners have been chosen for our research due to their high toxicities. Soil, sediment, municipal waste incinerator (MWI) bottom ash, fish tissue, and human adipose are selected as the matrices to examine the PCDD/Fs residue. The result showed that even after more than 30 years, the PCDD/Fs concentration based on i-TEQ value (especially for 2,3,7,8-TCDD) is still higher than guideline values in some countries: very high i-TEQ value in cultivate soil of CamLo district and DaNang City. For the area named "hot spot" such BienHoa Airforce Base and BienHung Lake, the i-TEQ value and 2,3,7,8-TCDD concentration in soil and sediment are superior than values proposed by Agency for Toxic Substance and Disease Registry (ATSDR), Canadian Council of Ministers of the Environment (CCME) and U.S Environmental Protection Agency (U.S. EPA). The PCDD/Fs concentration in fish tissue of BienHung Lake (catfish and snake-head) is superior in comparison with European Council (EC) standard. The dioxin contamination risk for local resident health is very high due to the lack of information and inconsiderable attention of responsible organizations about this problem. As BienHoa was selected as a case-study for PCDD/Fs transfer in food chain, using statistic methods (cluster analysis and Principal Component Analysis - PCA), we have showed a high similarity of PCDD/Fs profiles pattern between BienHoa Airforce Base soils, BienHung Lake sediments and fish tissue. The similarity in PCDD/Fs relative i-TEQ profiles between MWIs bottom ash and soil of industrial zone ThuDuc proves that industrial and municipal combustions are responsible sources for PCDD/Fs in the soil of such these zones. However in comparison with the sites contaminated by Agent Orange (A.O)/Dioxin, the PCDD/Fs contamination level in the industrial soil is lower and mainly dominated by PCDFs than PCDDs. The result also showed comparables i-TEQ values in BienHoa residents with inhabitants of industrial countries, however Vietnam is only developing and agricultural country. Beside that, 2,3,7,8-TCDD has been detected in many tested cases. 2,3,7,8-TCDD is the most toxic compound and related to the A.O/Dioxins from the war, unfortunately we have not enough data to assess the relationship between A.O/Dioxin residue and these samples. To find out this relationship it is necessary an integrated large-scale investigation. Result of our research serves as a base for set-up a reference laboratory for PCDD/Fs and dioxin-liked compounds research in the South of Vietnam. At present time, a small laboratory for PCDD/Fs analysis has been installed in IER and serves as a member of VietNam Dioxin Research Network.

EPFL2006

Composting (aerobic treatment of organic wastes) and digestion (anaerobic treatment of organic wastes combined with biogas production) are important waste management strategies with increasing significance in the European Union and Switzerland. Most of the compost produced is applied to agricultural soils, which hereby recycles nutrients and influences soil properties beneficially. However, compost can contain pollutants that may be hazardous for the soil ecosystem. The problem related to heavy metals had been recognised and measures for reduction were taken. Regarding organic pollutants, the current knowledge is insufficient for quality control and risk assessment. This thesis provides a comprehensive overview on organic contaminates in compost, digestate, and presswater and describes factors that may influence them. In the beginning an extensive literature review was carried out to summarize the current data. Compound classes to be analysed in Swiss composts and digestates were prioritized and analytical methods established. Polychlorinated biphenyl concentrations (∑ of PCB 28, 52, 101, 118, 138, 153, 180) were significantly higher in urban (median: 30 μg/kgdry weight (dw), n=52) than in rural samples (median: 14 μg/kgdw, n=16), which points – together with low concentrations in general – to aerial deposition on feedstock material as major input pathway to compost. Median polycyclic aromatic hydrocarbon (PAH) concentration was 3010 μg/kgdw (∑ of 16 PAH defined by the US EPA except dibenzo[a,h]anthracene, n=69). PAH levels were influenced by the organic matter degradation process (higher levels in digestate than in compost), the season of input material collection (spring/summer>winter>autumn), the particle size (higher concentrations in unsieved or sieved >20mm than in sieved to ≤ 20mm products), and maturity (lower concentrations in more mature composts). One fourth of the samples exhibited PAH concentrations above the Swiss guide value for compost (Ordinance on the Reductions of Risks linked to Chemical Products). These elevated concentrations can lead to considerable input of PAH to soil by compost application. To assess the major contributors of PAH in compost, characteristic PAH ratios and some molecular markers were considered, which pointed mainly to combustion origin of these contaminants. Multifactor statistical analysis indicated traffic emission, straw combustion and some asphalt abrasion as potential additional sources. Concentrations of other organic pollutants determined (dibenzo-p-dioxins and -furans, dioxin-like PCB, brominated flame retardants (BFR), perfluorinated alkyl substances (PFAS), di(2-ethylhexyl)phthalate, nonylphenol and chlorinated paraffins) were mostly above levels found in background soil, except for nonylphenol, which was not detected. Out of 269 pesticides analysed, 30 fungicides, 14 herbicides, eight insecticides and one acaricide were detected. For the first time, the fate of organic pollutants during full-scale composting and digestion was assessed. Concentrations of low chlorinated PCB increased during composting (about 30 %), whereas a slight decrease was observed for the higher chlorinated congeners (about 10%). Enantiomeric ratios of atropisomeric PCB were close to racemic and did not change. Levels of low molecular weight PAH were reduced during composting (50 to 90% reduction), whereas heavier compounds remained stable. However, as indicated above, conventional composting does not reduce PAH concentrations sufficiently to comply with Swiss guide values (see above). Further research is needed to i) identify measures to reduce PAH concentrations in digestate and compost, ii) to monitor organic pollutants that are still increasing in other environmental matrices (e.g. BFR and PFAS) or identify new compounds which have not been detected in compost yet, iii) to evaluate potential risk of compost application to soil by assessing the bioavailable fractions of organic pollutants and iv) to examine possible new input materials and co-substrates for composting and digestion.

EPFL2006