Brominated dioxins (PBDD/Fs) and PBDEs in marine shellfish in the UK

The occurrence of brominated dioxins (PBDD/Fs) and polybrominated diphenyl ethers (PBDEs) was investigated in commonly consumed species of marine shellfish in the UK. Individual samples of Pacific oysters (Crassostrea gigas), native oysters (Ostrea edulis), mussels (Mytilus edulis), scallops (Pecten maximus), and cockles (Cerastoderma edule) were collected from different coastal regions between 2006 and 2007. Samples of a particular species from each site were composited and 60 samples were analysed. Polybrominated dibenzofurans (PBDFs) occurred more frequently and generally at a higher level than polybrominated dibenzodioxins (PBDDs), except for 237-TriBDD, which was the predominant PBDD/F congener in some species, notably oysters. This profile may reflect the environmental distribution of these compounds and the effects of removal mechanisms, such as degradation, selective uptake and metabolism. PBDEs were detected in all samples. The dominant congeners were BDEs 47, 49, 99 and 100 and, to a lesser extent, BDEs 66 and 154. The occurrence of BDE-209 was observed in most samples and appears to be species selective, with the highest values occurring almost exclusively in mussels and cockles. Among the species studied, oysters and mussels displayed relatively higher levels of both sets of contaminants; native oysters, in particular, showed elevated levels of 237-TriBDD (up to 14.5 ng/kg). In general, contaminant levels appeared to be consistent with the extent of local industrialisation with lower levels observed in more remote areas such as the north of Scotland. Polybrominated biphenyls (PBBs) were also measured, and PBBs 49, 52 and 77 were the most frequently detected, although levels were very low. Dietary intakes, estimated for PBDD/Fs, showed that 237-TriBDD from single portions of oysters constituted a high proportion of the total dietary intake of the congener but, otherwise, dietary intakes of PBDD/Fs from shellfish were relatively low.     

Polybrominated diphenylethers (PBDEs) and brominated dioxins (PBDD/Fs) in Irish food of animal origin

Brominated dioxins (PBDD/Fs) and 17 polybrominated diphenylether (PBDE) congeners including BDE-209 were analysed in 100 composite samples of commonly consumed foods of animal origin, prepared from ten to 40 individual subsamples of each type. These included 30 samples of milk from farms; eggs from chickens; fat from cows, pigs, sheep, and poultry; and liver from cows, pigs, sheep, horses, and poultry. The ISO 17025-accredited analytical methodology used, follows similar guidelines as given for chlorinated dioxins and polychlorinated biphenyls (PCBs) in European Commission Directive 2002/69/EC. Apart from some samples of milk, PBDD/Fs and PBDEs were detected in all food types. Concentrations ranged from 0.31 µg kg^?1 Σ17 PBDEs for a sample of milk to 37.5 µg kg^?1 Σ17 PBDEs for a sample of liver. The corresponding range for the PBDD/F toxicity (computed using analogous PCDD/F toxic equivalency factors (TEFs)) was 0.09 ng TEQ kg^?1 to approximately 3.5 ng TEQ kg^?1. The detection of these compounds, in particular PBDD/Fs, is consistent with the increased use and disposal of brominated organic compounds.     

Destruction of the World Trade Center and PCBs, PBDEs, PCDD/Fs, PBDD/Fs, and chlorinated biphenylenes in water, sediment, and sewage sludge

Ash-laden runoff samples collected near Ground Zero soon after the September 11, 2001 attack on the World Trade Center (WTC) and subsequent fire demonstrate the release of polychlorinated biphenyls (PCBs), polybrominated dipheyl ethers (PBDEs), polybrominated dibenzo-p-dioxins and polybrominated dibenzofurans (PBDD/Fs), polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs), and tetra- and pentachlorinated biphenylenes (PCBPs) from the incident. Relative abundances of PCDD/F congeners in the runoff water and post-disaster lower Manhattan dust samples were different from those seen in pre-disaster NYC combined sewer outfall (CSO) samples. The WTC-related samples showed a greater relative abundance of 2,3,4,7,8-PeCDF than usually seen in CSOs, sludges, and treated wastewaters. This congener may be associated with certain types of incineration. Comparison of sediment and water samples collected in the lower Hudson River before and shortly after September 11, 2001 (9/11) showed no changes in PCB or PCDD/F concentrations or homologue profiles determined down to the parts per quadrillion range. Comparisons of ambient water samples collected post-9/11 with archived samples suggest that the WTC disaster did not significantly impact ambient concentrations of the target chemicals. Ambient concentrations of PBDD/Fs in New York Harbor are similar to those of PCDD/Fs, suggesting that these contaminants deserve increased scrutiny with respect to toxicity, sources, and fate in the environment.     

UK dietary exposure to PCDD/Fs,PCBs, PBDD/Fs,PBBs and PBDEs: comparison of results from 24-h duplicate diets and total diet studies

ABSTRACT

Chemicals in food are monitored to check for compliance with regulatory limits and to evaluate trends in dietary exposures, among other reasons. This study compared two different methods for estimating human dietary exposure to lipophilic persistent organic pollutants (POPs) during 2011/12: (1) the 2012 Total Diet Study (TDS) conducted by the UK Food Standards Agency (FSA) and (2) a 24-h duplicate diet (DD) study of 20 adults from the North East of England. The equivalence of the two approaches was assessed; anything less than an order of magnitude could be considered reasonable and within three-fold (equivalent to 0.5 log) as good. Adult dietary exposure estimates derived from the DD study for both average and high-level (97.5th percentile) consumers compared well with those from the TDS. Estimates from the DD study when compared with those from the TDS were within 10% for P97.5 for total PCDD/F/PCB with divergence increasing to a factor of 3.4 for average BDE-209. Most estimates derived from the TDS were slightly higher than those derived from the DD. Comparison with earlier UK TDS data over the last 30 years or so confirmed a gradual decline in levels of PCDD/F/PCBs in food. Such comparisons also indicated peaks in dietary exposure to ∑PBDE (excluding BDE-209) between 2000 and 2005. Exposure estimates for all measured compounds using both TDS and DD data were found to be within recommended tolerable daily intakes where available or within acceptable margins of exposure.     

Characterization and inventory of PCDD/Fs and PBDD/Fs emissions from the incineration of waste printed circuit board

Many developing countries have not significantly changed their course with regard to electronic waste contamination, and they are still facing the specter of mountains of hazardous electronic waste, with serious consequences for both the environment and public health. An efficient and stable analytical method was developed to determine the inventory and emission factors of polybrominated dibenzo-p-dioxin and dibenzofurans (PBDD/Fs) and polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/Fs) formed from the incineration of scrap printed circuit boards (PCBs). Both PBDD/Fs and PCDD/Fs have been found in all experimental sections with a maximum formation rate at temperatures between 250 and 400 °C. The amounts tended first to increase and then began to decrease as the temperature rose. When subjected to a heating temperature of 325 °C, the total content of twelve 2,3,7,8-substituted PBDD/Fs congeners (tetra- through octabromo-) gathered from three outputs was the largest, at 19?000, 160?000, and 57 ng TEQ/kg in solid, liquid, and gaseous fractions, respectively; the total content of seventeen 2,3,7,8-substituted PCDD/Fs congeners (tetra- through octachloro-) was 820, 550, and 1.4 ng TEQ/kg. The formation of PCDD/Fs was remarkably less than that of PBDD/Fs because bromine concentrations considerably exceeded chlorine concentrations. The ingredients and conditions necessary to form PCDD/Fs or PBDD/Fs were definitely present, such as products of incomplete combustion, halogenides, an oxidizing atmosphere, and a catalyst-Cu salts being the most effective, significantly increasing the yields of PCDD/Fs and PBDD/Fs and decreasing the optimum temperature range.     

Mechanism and direct kinetics study on the homogeneous gas-phase formation of PBDD/Fs from 2-BP, 2,4-DBP, and 2,4,6-TBP as precursors

This study investigated the homogeneous gas-phase formation of polybrominated dibenzo-p-dioxin/dibenzofurans (PBDD/Fs) from 2-BP, 2,4-DBP, and 2,4,6-TBP as precursors. First, density functional theory (DFT) calculations were carried out for the formation mechanism. The geometries and frequencies of the stationary points were calculated at the MPWB1K/6-31+G(d,p) level, and the energetic parameters were further refined by the MPWB1K/6-311+G(3df,2p) method. Then, the formation mechanism of PBDD/Fs was compared and contrasted with the PCDD/F formation mechanism from 2-CP, 2,4-DCP, and 2,4,6-TCP as precursors. Finally, the rate constants of the crucial elementary reactions were evaluated by the canonical variational transition-state (CVT) theory with the small curvature tunneling (SCT) correction over a wide temperature range of 600-1200 K. Present results indicate that only BPs with bromine at the ortho position are capable of forming PBDDs. The study, together with works already published from our group, clearly shows an increased propensity for the dioxin formations from BPs over the analogous CPs. Multibromine substitutions suppress the PBDD/F formations.     

Emerging functional nanomaterials for the detection of food contaminants

Along with the progress in nanoscience, a variety of advanced functional nanomaterials were constructed to develop effective and innovative analytical techniques for food safety surveillance. In this review, we summarized the advanced analytical methods that have been developed based upon advanced functional nanomaterials, including plasmonic nanomaterial-based colorimetric methods, fluorescent nanomaterial-based fluorescent methods, advanced functional material-based molecular imprinting technology, advanced functional material-based chromatographic methods, plasmonic nanomaterial-based surface enhanced Raman scattering technology, and advanced functional material-based electrochemical methods. This review provides a progressive roadmap for further development of portable, rapid, and in situ detection technology to promote food safety surveillance from bench to market and eventually reduce the gap between research in the laboratory and industrial applications.     

PBDDs/Fs and PCDDs/Fs in the raw and clean flue gas during steady state and transient operation of a municipal waste combustor

Concentrations of polybrominated dibenzo-p-dioxins, and -dibenzofurans (PBDDs/Fs) and polychlorinated dibenzo-p-dioxins, and -dibenzofurans (PCDDs/Fs), were determined in the pre- and post-air pollution control system (APCS) flue gas of a municipal waste combustor (MWC). Operational transients of the combustor were found to considerably increase levels of PBDDs/Fs and PCDDs/Fs compared to steady state operation, both for the raw and clean flue gas; ΣPBDDs/Fs increased from 72.7 to 700 pg dscm(-1) in the raw, pre-APCS gas and from 1.45 to 9.53 pg dscm(-1) in the post-APCS flue gas; ΣPCDDs/Fs increased from 240 to 960 ng dscm(-1) in the pre-APCS flue gas, and from 1.52 to 16.0 ng dscm(-1) in the post-APCS flue gas. The homologue profile of PBDDs/Fs and PCDDs/Fs in the raw flue gas (steady state and transients) was dominated by hexa- and octa-isomers, while the clean flue gas homologue profile was enriched with tetra- and penta-isomers. The efficiency of the APCS for PBDD/F and PCDD/F removal was estimated as 98.5% and 98.7%, respectively. The cumulative TEQ(PCDD/F+PBDD/F) from the stack was dominated by PCDD/F: the TEQ of PBDD/F contributed less than 0.1% to total cumulative toxic equivalency of MWC stack emissions.     

Formation of PCDD/Fs in the sintering process: influence of the raw materials

The sintering process is among the major sources of PCDD/Fs in the environment. This research studies the influence of the raw materials in this type of industrial plant on the amounts of PCDD/Fs generated. Particular interest is given to coke, which constitutes the principal source of carbon for the de novo synthesis of PCDD/Fs, and to the dust collected in the electrostatic precipitator (E.S.P. dust), usually recycled in the raw materials. The de novo synthesis of PCDD/Fs is simulated at the laboratory scale by thermal treatments of the samples. The use of a particular coke as a fuel does not drastically reduce the formation of PCDD/Fs. Actually, the global amounts of PCDD/Fs generated from the graphite and the two cokes tested are very similar. Only modifications in the fingerprint are observed. On the other hand, the addition of 10 wt % dust collected in the electrostatic precipitator leads to the formation of amounts of PCDD/Fs multiplied by a factor larger than 10(3). These results imply caution against the recycling of this E.S.P. dust in the raw materials.     

Isotopic signature and impact of car catalysts on the anthropogenic osmium budget

Higher osmium concentrations and lower 187Os/188Os ratios in sediments from urban areas have been linked to anthropogenic osmium sources. Automobile catalytic converters that use platinum group metals (PGM) are a potential source for this Os pollution. We present the first direct Os concentrations and isotopic measurements of catalytic converters for major automobile brands to test the assumption that car catalysts release Os with a distinct signature in the environment. The analysis of four new catalytic converters yields similar low 187Os/188Os ratios (0.1-0.2), suggesting a similar source for the PGM. The Os concentrations measured are in the ppt range (6-228 ppt). From our results, the osmium contribution of the car catalysts to the environment through attrition (wearing and grinding down of the catalyst by friction) is predicted to be low, <0.2 pg Os/m2/year in highly urbanized environment. We show that Os loss from catalysts as volatile OsO4 is important at car catalyst operating temperatures. Moreover, we estimate that car catalysts may be responsible for up to approximately 120 pg Os/m2 deposited per year in urban areas and that part of it may be exported to sedimentary sinks. Car catalytic converters are thus an important anthropogenic osmium source in densely populated areas. The NIST car catalyst standard (SRM-2557, made from recycled used catalysts) yields higher concentrations (up to 721 ppt Os) and a more radiogenic isotopic composition (approximately 0.38), perhaps indicative of Os contamination during its preparation.     

Severe PCDD/F and PBDD/F pollution in air around an electronic waste dismantling area in China

The presence of chlorinated and brominated compounds in electronic waste (EW) results in the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) during the EW dismantling process. In this study, we investigated the dioxins present in ambient air around the EW dismantling area Guiyu in Guangdong, China. Atmospheric PCDD/F (tetra to octa) abundances and toxic equivalent (TEQ) values were 64.9-2365 pg/m3 and 0.909-48.9 pg of W-TEQ/m3, respectively; these are the highest documented values of these compounds found in ambient air in the world. PBDD/Fs (eight 2,3,7,8-substituted congeners) were also found at high pollution levels (concentrations of 8.124-61 pg/m3 and 1.6-2104 pg of I-TEQ/m3). Profiles of the 2,3,7,8-PCDD/F homologues in the air of Guiyu differed from typical urban air patterns reported in the literature, and the concentration of homologues increased with the chlorination degree of 2,3,7,8-PCDD/Fs except for OCDF. The severe dioxin pollution present in Guiyu substantially influences the adjacent area of Chendian, where atmospheric PCDD/F and 2,3,7,8-PBDD/F levels are higher than those of common urban areas in the world. Our tentative inhalation risk assessment showed that residents in Guiyu are at a high risk of exposure to dioxins. The total PCDD/F intake doses far exceed the WHO 1998 tolerable daily intake limit of 1-4 pg of W-TEQ kg(-1) day(-1).     

Thermodynamic modeling of PCDD/Fs formation in thermal processes

Three thermodynamic databases of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), derived using the Group Additivity approach and two computational molecular modeling methods, Modified Neglect of Diatomic Overlap (MNDO) and Parametrized Model 3 (PM3), respectively, combined with the Scientific Group Thermodata Europe (SGTE) database have been used to model the formation of PCDD/Fs in thermal processes, such as iron ore sintering process. The predictions using the three different databases are compared, and similar thermodynamic conditions of PCDD/Fs formation are found. The comparison of the calculated values with measured results obtained from industrial iron ore sinter plant indicates that the PCDDs and PCDFs found in practice are not in equilibrium with each other. While within each dioxin and furan homologue equilibrium between the isomers appears to be established in industrial processes, reactions between dioxins and furans seem to be kinetically inhibited. This view has been supported by assuming no reaction at all between PCDFs and PCDDs in the simulation. With this assumption, both PCDFs and PCDDs reached partial pressures between 600 and 800 K in the order of magnitude actually found in practice. Taking this restriction into account, the conditions for PCDD/Fs formation were calculated as a function of oxygen partial pressure; temperature; concentrations of carbon, hydrogen, and chlorine; and C/H ratio.     

食品中PCDD/Fs和dlPCBs的检测方法研究进展

二恶英化合物是典型的高毒性持久性有机污染物,可在食物链中不断累积,最终引发食品安全问题,严重威胁人类健康。近年来,食品中二恶英类化合物的分析筛选和监测控制等问题一直是人们研究的重点。本文综述了二恶英类化合物的致毒机制和几种用于分析检测二恶英类化合物方法的基本原理和优缺点,以及国内外分析检测的最新研究进展,并对我国开展二恶英分析监测提出了建议和展望。     

基于GC-MS/MS法测定鱼肉中二噁英和二噁英类多氯联苯

建立基于GC-MS/MS方法,采用稳定性同位素稀释法测定鱼肉中二噁英及二噁英类多氯联苯。样品经快速溶剂萃取仪提取3次,以酸化硅胶除脂,经多层硅胶柱、碱性氧化铝柱和活性炭柱净化,分别收集含PCDD/Fs和DL-PCBs组分,经浓缩复溶后供GC-MS/MS测定。结果表明:在净化步骤中,PCDD/Fs和DL-PCBs受洗脱液的体积以及收集步骤的影响较大,分开收集PCDD/Fs和DL-PCBs,先对PCDD/Fs的收集液进行测定,然后将其和DL-PCBs的收集液合并完成DL-PCBs的测定,从而对DL-PCBs进行准确定量。采用鱼肉为样品基质时,该方法PCDD/Fs和DL-PCBs的内标回收率为63.3%～106.8%,RSD为0.4%～9.6%;目标物的回收率为93.6%～114.5%,RSD为0.9%～9.2%,方法线性和检出限达到国家标准GB 5009.205的要求,适用于鱼肉样品中PCDD/Fs和DL-PCBs的测定。     

Emerging infectious diseases of crop plants in developing countries: impact on agriculture and socio-economic consequences

Emerging infectious diseases (EIDs) caused by plant pathogens can develop into unexpected and very serious epidemics, owing to the influence of various characteristics of the pathogen, host and environment. Devastating epidemics, having social implications by increasing the rate of urbanization, occurred in the past in Europe, and many other EIDs still occur with high frequency in developing countries. Although the ability to diagnose diseases and the technologies available for their control are far greater than in the past, EIDs are still able to cause tremendous crop losses, the economic and social impact of which, in developing countries, is often underestimated. In the present article, four of the most important EIDs in developing countries are considered from the standpoint of their origin, characteristics, symptoms, mode of spread, possible control strategies, economic impact and the socio-economic consequences of their dissemination. They are Cassava Mosaic Virus Disease, capable of reducing yields by 80–90% and causing the suspension of cassava cultivation in many areas of East Africa; Striga hermonthica, a parasitic weed affecting cereals in an area of at least 5 million hectares in Sub-Saharan Africa; Xanthomonas Wilt of Banana, a bacterial disease that caused around 50% yield losses at the beginning of 21st century in Uganda and is threatening the food security of about 70 million people owing to its impact on an important staple crop; and race Ug99 of the rust fungus Puccinia graminis f. sp. tritici, which is having a tremendous impact on wheat in Uganda, and is also threatening most of the wheat-growing countries of the world.     

Further evidence for the existence of PCDD/Fs in the environment prior to 1900

PCDD/Fs and PCBs have been analyzed in a series of archived soil samples collected from various depths during the 1800s and early 1900s. PCBs were not found in soil samples collected before 1900, whereas PCDD/Fs were present in concentrations between 43 and 110 pg/g in surface soils, and between 9 and 150 pg/g in soils collected from below the surface. The PCDD/F homologue patterns of all surface soils were consistent with each other. The homologue pattern of deeper soils altered with depth to one that was dominated by highly chlorinated PCDDs. The highest sigma(4-8)PCDD/F concentration (150 pg/g) was found in the deepest soil analyzed (230-250 cm below the surface). The cork from one of the storage bottles contained considerable quantities of both PCBs and PCDD/Fs. However, contamination of the soils, either by diffusion through the cork or by cork particles, was discounted on the basis that no PCBs were evident in the soil, and that the PCDD/F homologue pattern in the cork was very different to that found in the soil. Similar arguments were used to discount contamination of the soil by dust. A sample of ashed vegetation from the archive, that had no cork stopper, contained high concentrations of PCBs (78 ng/g), concentrations of mono- to tri-CDFs that were higher than in any of the soils (190 pg/g), but very low concentrations of sigma(4-8)PCDD/F (12 pg/g). This pattern of analytes was considered to be representative of contamination from store room air and was completely different from the pattern observed in the soils. Taken together these observations indicate that contamination during storage, or subsequent handling, is unlikely to have occurred in archived soil samples that were stored with cork and wax seal intact. The results imply surface soil sigma(4-8)PCDD/F concentrations of around 60 pg/g at Rothamsted (southeast England) in the late 1800s, compared with approximately 300 pg/g reported for rural UK soils in the 1990s.     

Secondary effects of catalytic diesel particulate filters: copper-induced formation of PCDD/Fs

Potential risks of a secondary formation of polychlorinated dibenzodioxins/furans (PCDD/Fs) were assessed for two cordierite-based, wall-through diesel particulate filters (DPFs) for which soot combustion was either catalyzed with an iron- or a copper-based fuel additive. A heavy duty diesel engine was used as test platform, applying the eight-stage ISO 8178/4 C1 cycle. DPF applications neither affected the engine performance, nor did they increase NO, NO2, CO, and CO2 emissions. The latter is a metric for fuel consumption. THC emissions decreased by about 40% when deploying DPFs. PCDD/F emissions, with a focus on tetra- to octachlorinated congeners, were compared under standard and worst case conditions (enhanced chlorine uptake). The iron-catalyzed DPF neither increased PCDD/F emissions, nor did it change the congener pattern, even when traces of chlorine became available. In case of copper, PCDD/F emissions increased by up to 3 orders of magnitude from 22 to 200 to 12 700 pg I-TEQ/L with fuels of < 2, 14, and 110 microg/g chlorine, respectively. Mainly lower chlorinated DD/Fs were formed. Based on these substantial effects on PCDD/F emissions, the copper-catalyzed DPF system was not approved for workplace applications, whereas the iron system fulfilled all the specifications of the Swiss procedures for DPF approval (VERT).     

Soot-carbon influenced distribution of PCDD/Fs in the marine environment of the Grenlandsfjords,Norway

The particle associations of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) were studied in both the water column and the surface sediments of a marine fiord system and were found to poorly obey expectations from the organic matter partitioning (OMP) paradigm. The field observations were instead consistent with the presence of a stronger sorbent subdomain such as pyrogenic soot-carbon (SC) playing an important role in affecting the environmental distribution and fate of PCDD/Fs. Solid-water distribution coefficients (Kd) of PCDD/ Fs actually observed in the water column were several orders of magnitude above predictions from a commonly used OMP model. Even when these elevated Kd values were normalized to the particulate organic carbon (POC) content (i.e., K(OC)), the variability in K(OC) for individual PCDD/ Fs at different fjord locations and seasons of factors 100-1,000 suggested that bulk organic matter was not the governing sorbent domain of the suspended particles. Further, POC-normalized particle concentrations of PCDD/ Fs (C(OC)) in a vertical profile (surface water-bottom water-surface sediment) revealed a strong increasing trend with depth. Factors of about 100 higher Coc for all PCDD/Fs in the sediment than in the surface water could not be explained by higher fugacity in the surrounding deep water nor with C:N or delta13C indexes of selective aging of the bulk organic matter. Instead this was hypothesized to reflect selective preservation of a more recalcitrant and highly sorbing, but minor, subdomain such as soot. The extent of enhanced PCDD/F sorption, above the OMP predictions, was positively correlated with the SC:POC ratio of the suspended particles in surface and deep waters. Finally, the geographical distribution of sedimentary PCDD/F concentrations were better explained by the SC content than by the bulk OC content of the sediment. Altogether, these field-based findings add to recent laboratory-based sorption studies to suggest that we need to consider both amorphous OC partitioning domains and SC particles as carriers of planar aromatic contaminants if we are to explain the environmental distribution and fate of pollutants such as PCDD/Fs.     

PCDD/Fs in Norwegian and U.K. soils: implications for sources and environmental cycling

This paper presents data on polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in a set of well-characterized, undisturbed surface (0-5 cm) and subsurface background soils from the U.K. and Norway. The soils have been used previously to investigate the latitudinal distribution, fractionation, cold condensation, and "hopping" of other classes of persistent organic pollutants (POPs). The mono- to octa-CDD/F homologues were quantified. Woodland soils contained higher concentrations (on a dry and soil organic matter (SOM)-basis) than grassland soils, consistent with previous studies. The absolute concentrations of all the PCDDs and most of the PCDFs significantly decreased with latitude, generally supporting the idea of a "southern source region" and a "remote/ receiving northern region". There was little evidence of "fractionation" and minimal influence of PCDD/F "hopping" on PCDD/F distribution. The %SOM content had a rather minor influence on soil PCDD/F composition. These findings contrast with the trends seen in these soils for hexachlorobenzene (HCB), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs). Possible reasons for these differences are discussed and may include influences of/proximity to diffusive combustion sources and/ or sources of variable homologue emissions, formation/ conversion processes for PCDD/Fs in soils, or strong soil-PCDD/F partitioning. These soils, from regionally remote/ background locations in Europe contained between 0.2 and 78 pg sigmaTEQ/g DW. Some therefore exceed recommended levels of contamination for certain land uses by some European countries. These recommendations seem unrealistic and prohibitively restrictive in light of the dataset presented here.