Search

Understanding the transfer of polychlorinated dibenzo- p -dioxins and dibenzofurans (PCDD/Fs) in farm animals is essential for ensuring food safety, but such information for suckler ewes ( Ovis aries ) has been lacking. This work quantifies the accumulation, tissue distribution, and depuration kinetics of PCDD/Fs in these animals. Six suckler ewes (EXP group) were exposed to PCDD/Fs through contaminated hay (2.3-12.7 ng toxic-equivalent kg -1 dry matter) and then allowed to depurate by switching to noncontaminated hay from 29 days of lactation. Four control ewes were fed continuously with noncontaminated hay. At different time points covering depuration, weaning and slaughter, PCDD/F analysis of milk (three time points), blood and sternal adipose tissue (five time points), Longissimus thoracis muscle, liver, and empty body homogenate at slaughter (188 days of depuration) was performed. A relevant PCDD/F bioaccumulation was observed from oral intake in milk and adipose tissue (biotransfer factors of 1.24 and 1.06 day kg -1 lipids for the sum toxic-equivalent, respectively) in the EXP ewes, especially for penta- and hexa-chlorinated congeners. The EXP ewes' adipose tissue started at 10-fold the EU maximum level (ML) and showed depuration below the ML after 130 days. Specific PCDD/F accumulation in the ewe liver was observed, especially for dibenzofurans. These toxicokinetic data can inform recommendations to ensure the chemical safety of sheep food products.

We report on two farms in Switzerland heavily contaminated by polychlorinated biphenyls (PCBs) and dioxins (PCDD/Fs), occurring in the first case from diffuse sources and in the second case from PCB-containing wall paint. Extensive measurements of PCBs and PCDD/Fs on site (soil, forage, and paint) and in cattle (blood, fat, and milk) allowed validation of our novel dynamic toxicokinetic model, which includes the transfer of contaminants from the mother cows to their suckling calf and the uptake of soil by grazing cattle. We show that for calves, the mother milk is the main uptake route of contaminants. For both cows and calves, ingestion of contaminated soil, although often overlooked, is an appreciable uptake path. The remediation of the contaminated stable lead to a 2-3 fold reduction of the PCB levels in animals within one year. The transfer of animals to an uncontaminated mountain site during summer proved to be an effective decontamination procedure with up to 50% reduction of the levels within three months. Our study calls for a rapid removal of PCB-containing materials in animal husbandry farms and shows that the diffuse contamination of soils will remain a source for PCBs and PCDD/Fs in our food chain for decades to come.

In previous studies, the incorporation of polychlorinated biphenyls (PCBs) has been quantified in the accumulation areas of Alpine glaciers. Here, we introduce a model framework that quantifies mass fluxes of PCBs in glaciers and apply it to the Silvretta glacier (Switzerland). The models include PCB incorporation into the entire surface of the glacier, downhill transport with the flow of the glacier ice, and chemical fate in the glacial lake. The models are run for the years 1900-2100 and validated by comparing modeled and measured PCB concentrations in an ice core, a lake sediment core, and the glacial streamwater. The incorporation and release fluxes, as well as the storage of PCBs in the glacier increase until the 1980s and decrease thereafter. After a temporary increase in the 2000s, the future PCB release and the PCB concentrations in the glacial stream are estimated to be small but persistent throughout the 21st century. This study quantifies all relevant PCB fluxes in and from a temperate Alpine glacier over two centuries, and concludes that Alpine glaciers are a small secondary source of PCBs, but that the aftermath of environmental pollution by persistent and toxic chemicals can endure for decades.

Semivolatile organic compounds (SVOCs) can be released from products and distributed in the indoor environment, including air and dust. However, the mechanisms and the extent of substance transfer into air and dust are not well understood. Therefore, in a small-scale field study the transfer of nine SVOCs was investigated: Four artificial consumer products were doped with eight deuterium-labeled plasticizers (phthalates and adipates) and installed in five homes to investigate the emission processes of evaporation, abrasion, and direct transfer. Intentional release was studied with a commercial spray containing a pyrethroid. During the 12 week study, indoor air and settled dust samples were collected and analyzed. On the basis of our measurement results, we conclude that the octanol-air partitioning coefficient Koa is a major determinant for the substance transfer into either air or dust: A high Koa implies that the substance is more likely to be found in dust than in air. The emission process also plays a role: For spraying, we found higher dust and air concentrations than for evaporation. In contrast, apartment parameters like air exchange rate or temperature had just a minor influence. Another important mechanistic finding was that although transfer from product to dust currently is postulated to be mostly mediated by air, direct transport from product to dust on the product surface was also observed.

Iron-catalyzed diesel particle filters (DPFs) are widely used for particle abatement. Active catalyst particles, so-called fuel-borne catalysts (FBCs), are formed in situ, in the engine, when combusting precursors, which were premixed with the fuel. The obtained iron oxide particles catalyze soot oxidation in filters. Iron-catalyzed DPFs are considered as safe with respect to their potential to form polychlorinated dibenzodioxins/furans (PCDD/Fs). We reported that a bimetallic potassium/iron FBC supported an intense PCDD/F formation in a DPF. Here, we discuss the impact of fatty acid methyl ester (FAME) biofuel on PCDD/F emissions. The iron-catalyzed DPF indeed supported a PCDD/F formation with biofuel but remained inactive with petroleum-derived diesel fuel. PCDD/F emissions (I-TEQ) increased 23-fold when comparing biofuel and diesel data. Emissions of 2,3,7,8-TCDD, the most toxic congener [toxicity equivalence factor (TEF) = 1.0], increased 90-fold, and those of 2,3,7,8-TCDF (TEF = 0.1) increased 170-fold. Congener patterns also changed, indicating a preferential formation of tetra- and penta-chlorodibenzofurans. Thus, an inactive iron-catalyzed DPF becomes active, supporting a PCDD/F formation, when operated with biofuel containing impurities of potassium. Alkali metals are inherent constituents of biofuels. According to the current European Union (EU) legislation, levels of 5 μg/g are accepted. We conclude that risks for a secondary PCDD/F formation in iron-catalyzed DPFs increase when combusting potassium-containing biofuels.

Persistent organic pollutants (POPs) are ubiquitous contaminants of environmental and human health relevance, but their emissions into the environment are still poorly known. In this study, concentrations of selected POPs were measured in ambient air in Zurich, Switzerland, and interpreted with a multimedia mass balance model. The aim of the combination of measurements and modeling was to back-calculate atmospheric emission rates of POPs. Measurements were performed in summer 2010 and winter 2011 and target analytes included polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Estimated emissions were higher in summer than in winter. Emission estimates for Zurich can be extrapolated to annual averages for Switzerland of 312 kg·a(-1) (39 mg·capita(-1)·a(-1)), 53 kg·a(-1) (7 mg·capita(-1)·a(-1)), and 3 kg·a(-1) (0.4 mg·capita(-1)·a(-1), 94 g WHO98-TEQ·a(-1), 65 g I-TEQ·a(-1)) for the six indicator PCBs (iPCBs), the twelve coplanar dioxin-like PCBs (dlPCBs), and the 17 2,3,7,8-chlorosubstituted PCDD/Fs, respectively. The emission rates of iPCBs are in agreement with existing emission inventories, whereas for PCDD/Fs the emissions are five times higher than the estimates from the Swiss national emission inventory. Emissions of dlPCBs in Switzerland are presented here for the first time. Our study also provides the first seasonally resolved emission rates of POPs, which were determined with our combined measurement and modeling approach. These findings highlight the relevance of ongoing sources of POPs, even decades after regulations aiming to reduce or eliminate sources were established.

Catalytic diesel particle filters (DPFs) have evolved to a powerful environmental technology. Several metal-based, fuel soluble catalysts, so-called fuel-borne catalysts (FBCs), were developed to catalyze soot combustion and support filter regeneration. Mainly iron- and cerium-based FBCs have been commercialized for passenger cars and heavy-duty vehicle applications. We investigated a new iron/potassium-based FBC used in combination with an uncoated silicon carbide filter and report effects on emissions of polychlorinated dibenzodioxins/furans (PCDD/Fs). The PCDD/F formation potential was assessed under best and worst case conditions, as required for filter approval under the VERT protocol. TEQ-weighted PCDD/F emissions remained low when using the Fe/K catalyst (37/7.5 μg/g) with the filter and commercial, low-sulfur fuel. The addition of chlorine (10 μg/g) immediately led to an intense PCDD/F formation in the Fe/K-DPF. TEQ-based emissions increased 51-fold from engine-out levels of 95 to 4800 pg I-TEQ/L after the DPF. Emissions of 2,3,7,8-TCDD, the most toxic congener (TEF = 1.0), increased 320-fold, those of 2,3,7,8-TCDF (TEF = 0.1) even 540-fold. Remarkable pattern changes were noticed, indicating a preferential formation of tetrachlorinated dibenzofurans. It has been shown that potassium acts as a structural promoter inducing the formation of magnetite (Fe3O4) rather than hematite (Fe2O3). This may alter the catalytic properties of iron. But the chemical nature of this new catalyst is yet unknown, and we are far from an established mechanism for this new pathway to PCDD/Fs. In conclusion, the iron/potassium-catalyzed DPF has a high PCDD/F formation potential, similar to the ones of copper-catalyzed filters, the latter are prohibited by Swiss legislation.

The impact of a combined diesel particle filter-deNO(x) system (DPN) on emissions of reactive nitrogen compounds (RNCs) was studied varying the urea feed factor (α), temperature, and residence time, which are key parameters of the deNO(x) process. The DPN consisted of a platinum-coated cordierite filter and a vanadia-based deNO(x) catalyst supporting selective catalytic reduction (SCR) chemistry. Ammonia (NH₃) is produced in situ from thermolysis of urea and hydrolysis of isocyanic acid (HNCO). HNCO and NH₃ are both toxic and highly reactive intermediates. The deNO(x) system was only part-time active in the ISO8178/4 C1cycle. Urea injection was stopped and restarted twice. Mean NO and NO₂ conversion efficiencies were 80%, 95%, 97% and 43%, 87%, 99%, respectively, for α = 0.8, 1.0, and 1.2. HNCO emissions increased from 0.028 g/h engine-out to 0.18, 0.25, and 0.26 g/h at α = 0.8, 1.0, and 1.2, whereas NH₃ emissions increased from <0.045 to 0.12, 1.82, and 12.8 g/h with maxima at highest temperatures and shortest residence times. Most HNCO is released at intermediate residence times (0.2-0.3 s) and temperatures (300-400 °C). Total RNC efficiencies are highest at α = 1.0, when comparable amounts of reduced and oxidized compounds are released. The DPN represents the most advanced system studied so far under the VERT protocol achieving high conversion efficiencies for particles, NO, NO₂, CO, and hydrocarbons. However, we observed a trade-off between deNO(x) efficiency and secondary emissions. Therefore, it is important to adopt such DPN technology to specific application conditions to take advantage of reduced NO(x) and particle emissions while avoiding NH₃ and HNCO slip.

Diesel exhaust contains several genotoxic compounds that may or may not penetrate diesel particulate filters (DPFs). Furthermore, the DPF-supported combustion of soot and adsorbed compounds may lead to the formation of additional pollutants. Herein, we compare the impact of 14 different DPFs on emissions of known genotoxic compounds. During a four year period, these DPFs were tested on a heavy duty diesel engine, operated in the ISO 8178/4 C1 cycle. Integral samples, including gas-phase and particle-bound matter were taken. All DPFs were efficient wall-flow filters with solid particulate number filtration efficiencies eta > 98%. On the basis of their CO, NO, and NO(2) emission characteristics, two different filter families were distinguished. DPFs with high oxidation potential (hox, n = 8) converted CO and NO besides hydrocarbons, whereas low oxidation potential DPFs (lox, n = 6) did not support CO and NO oxidation but still converted hydrocarbons. Lox-DPFs reduced NO(2) from 1.0 +/- 0.3 (engine-out) to 0.42 +/- 0.11 g/kWh (eta = 0.59), whereas hox-DPFs induced a NO(2) formation up to 3.3 +/- 0.7 g/kWh (eta = -2.16). Emissions of genotoxic PAHs decreased for both filter families. Conversion efficiencies varied for individual PAHs and were lower for lox- (eta = 0.31-0.87) than for hox-DPFs (eta = 0.75-0.98). Certain nitro-PAHs were formed indicating that nitration is an important step along PAH oxidation. For example, 1-nitronaphthalene emissions increased from 11 to 17 to 21 microg/L without, with lox-, and hox-DPFs respectively, whereas 2-nitronaphthalene emissions decreased from 25 to 19 to 4.7 microg/L. In contrast to our expectations, the nitration potential of lox-DPFs was higher than the one of hox-DPFs, despite the intense NO(2) formation of the latter. The filters converted most genotoxic PAHs and nitro-PAHs and most soot particles, acting as carriers for these compounds. Hox-DPF exhaust remains oxidizing and therefore is expected to support atmospheric oxidation reactions, whereas lox-DPF exhaust is reducing and consuming oxidants such as ozone, when mixed with ambient air.

In this study, the hypothesis that melting Alpine glaciers may represent a secondary source of persistent organic chemicals is investigated. To this end, a dated sediment core from a glacier-fed lake (Lake Oberaar, Switzerland) was analyzed for a wide range of persistent organic pollutants, organochlorine pesticides, and synthetic musk fragrances. Input fluxes of all organochlorines increased in the 1950s, peaked in the 1960s-1970s, and decreased again to low levels in the 1980s-1990s. This observation reflects the emission history of these compounds and technical improvements and regulations leading to reduced emissions some decades ago. The input of synthetic musks remained at a high level in the 1950s-1990s, which is consistent with their relatively constant production throughout the second half of the 20th century. Since the late 1990s, input of all compound classes into the high-Alpine Lake Oberaar has increased sharply. Currently, input fluxes of organochlorines are similar to or even higher than in the 1960s-1970s. This second peak supports the hypothesis that there is a relevant release of persistent organic chemicals from melting Alpine glaciers. Considering ongoing global warming and accelerated massive glacier melting predicted for the future, our study indicates the potential for dire environmental impacts due to pollutants delivered into pristine mountainous areas.

With the recent ban of pentabromodiphenyl ether (technical PentaBDE) and octabromodiphenyl ether (technical OctaBDE) mixtures in the European Union (EU) and in parts of the United States, decabromodiphenyl ether (technical DecaBDE) remains as the only polybrominated diphenyl ether (PBDE) based flame retardant available, today. The EU risk assessment report for DecaBDE identified a high level of uncertainty associated with the suitability of the current risk assessment approach for secondary poisoning by debromination of DecaBDE to toxic lower brominated diphenylethers. Addressing this still open question, we investigated concentrations and temporal trends of DecaBDE, NonaBDE, and OctaBDE congeners in the sediments of Greifensee, a small lake located in an urban area close to Zürich, Switzerland. PBDE appeared first in sediment layers corresponding to the mid 1970s. While total Tri-HeptaBDE (BDE-28, -47, -99, -100, -153, -154 and -183) concentrations leveled off in the mid 1990s to about 1.6 ng/g dw (dry weight), DecaBDE levels increased steadily to 7.4 ng/g dw in 2001 with a doubling time of 9 years. Hexabromocyclododecanes (HBCD) appeared in Greifensee sediments in the mid 1980s. They are an important class of flame retardants that are being used in increasing amounts, today. As was observed for DecaBDE, HBCD concentrations were continuously increasing to reach 2.5 ng/g dw in 2001. Next to DecaBDE, all 3 NonaBDE congeners (BDE-208, BDE-207, and BDE-206) and at least 7 out of the 12 possible OctaBDE congeners (BDE-202, BDE-201, BDE-197/204, BDE-198/203, BDE-196/200, BDE-205, and BDE-194) were detected in the sediments of Greifensee. Highest concentrations were found in the surface sediments with 7.2, 0.26, 0.14, and 1.6 ng/g dw for Deca-, Nona-, Octa-, and the sum of Tri-HeptaBDE, respectively. While DecaBDE and NonaBDE were found to increase rapidly, the increase of OctaBDE was slower. Congener patterns of Octa- and NonaBDE present in sediments of Greifensee did not change with time. Consequently, there was no evidence for sediment mediated long-term transformation of PBDE within the observed time span of almost 30 years. Despite the high persistence of DecaBDE, environmental debromination occurs, as shown by the detection of a shift in congener patterns of Octa- and NonaBDE in sediments, compared to the respective congener patterns in technical PBDE products. The OctaBDE congener BDE-202 was detected in sediments, representing a transformation product that is not reported in any of the technical PBDE products. Comparison of OctaBDE congener patterns in sediments with OctaBDE congener patterns from known sources reveals that (i) they were distinctively different from the congener patterns in technical PBDE products and (ii) that they were similar to the OctaBDE patterns in house dust and photodegradation products of DecaBDE, suggesting contributions from these sources.

Diesel particulate filters (DPFs) are a promising technology to detoxify diesel exhaust. However, the secondary combustion of diesel soot and associated compounds may also induce the formation of new pollutants. Diesel soot is rated as carcinogenic to humans and also acts as a carrier for a variety of genotoxic compounds such as certain polycyclic aromatic hydrocarbons (PAHs) or nitrated PAHs (nitro-PAHs). Furthermore, diesel exhaust contains considerable amounts of nitric oxide (NO), which can be converted to more powerful nitrating species like nitrogen dioxide (NO2), nitric acid (HNO3), and others. This mix of compounds may support nitration reactions in DPFs. Herein we report effects of two cordierite-based, monolithic, wall-flow DPFs on emissions of genotoxic PAHs and nitro-PAHs and compare these findings with those of a reporter gene bioassay sensitive to aryl hydrocarbons (AHs). Soot combustion was either catalyzed with an iron- or a copper/iron-based fuel additive (fuel-borne catalysts). A heavy duty diesel engine, operated according to the 8-stage ISO 8178/4 C1 cycle, was used as test platform. Emissions of all investigated 4- to 6-ring PAHs were reduced by about 40-90%, including those rated as carcinogenic. Emissions of 1- and 2-nitronaphthalene increased by about 20-100%. Among the 3-ring nitro-PAHs, emissions of 3-nitrophenanthrene decreased by about 30%, whereas 9-nitrophenanthrene and 9-nitroanthracene were found only after DPFs. In case of 4-ring nitro-PAHs, emissions of 3-nitrofluoranthene, 1-nitropyrene, and 4-nitropyrene decreased by about 40-60% with DPFs. Total AH-receptor (AHR) agonist concentrations of diesel exhaust were lowered by 80-90%, when using the iron- and copper-based DPFs. The tested PAHs accounted for < 1% of the total AHR-mediated response, indicating that considerable amounts of other aryl hydrocarbons must be present in filtered and unfiltered exhaust. We conclude that both DPFs detoxified diesel exhaust with respect to total aryl hydrocarbons, including the investigated carcinogenic PAHs, but we also noticed a secondary formation of selected nitro-PAHs. Nitration reactions were found to be stereoselective with a preferential substitution of hydrogen atoms at peri-positions. The stereoisomers obtained are related to combustion chemistry, but differ from those formed upon atmospheric nitration of PAHs.

Diesel exhaust contains numerous toxic substances that show different modes of action such as triggering aryl hydrocarbon receptor (AhR)-mediated pathways. We investigated AhR-mediated activity of exhaust generated by a heavy-duty diesel engine operated with or without iron- or copper/iron-catalyzed diesel particulate filters (DPFs). AhR agonists were quantified using the DR-CALUX reporter gene assay (exposure of cells for 24 h). We found 54-60 ng 2,3,7,8-tetrachlorodibenzo-p-dioxin CALUX equivalents (TCDD-CEQs) per m3 of exhaust in unfiltered samples and 6-16 ng TCDD-CEQ m3 in DPF-treated samples. DPF applications decreased TCDD-CEQ concentrations by almost 90%. Concentrations of known AhR agonists were determined with GC/HRMS and converted to TCDD-CEQ concentrations using compound-specific relative potency values. The analyzed nine polycyclic aromatic hydrocarbons (PAHs) and the 172,3,7,8-chlorinated dibenzodioxins/furans (23,7,8-PCDD/Fs) contributed only marginally (0.6-1.6%) to the total agonist concentration. However, both DPFs also decreased concentrations of individual PAHs by 7(0-80%. Variation of the assay exposure time (8, 24, 48,72, and 96 h) revealed that AhR-mediated activity decreased over time and reached a plateau after 72 h, which was most likely due to biotransformation of AhR agonists by the exposed H4IIE cells. At the plateau, we measured 1-2 ng TCDD-CEQ m(-3) in both an unfiltered and a filtered exhaust sample. Our findings show that DPFs are a promising technology to detoxify diesel exhaust regarding compounds with AhR-mediated activity.

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).

Brominated flame retardants (BFRs) are synthetic additives mainly used in electrical and electronic appliances and in construction materials. The properties of some BFRs are typical for persistent organic pollutants, and certain BFRs, in particular some polybrominated diphenyl ether (PBDE) congeners and hexabromocyclododecane (HBCD), are suspected to cause adverse health effects. Global consumption of the most demanded BFRs, i.e., penta-, octa-, and decaBDE, tetrabromobisphenol A (TBBPA), and HBCD, has doubled in the 1990s. Only limited and rather uncertain data are available regarding the occurrence of BFRs in consumer goods and waste fractions as well as regarding emissions during use and disposal. The knowledge of anthropogenic substance flows and stocks is essential for early recognition of environmental impacts and effective chemicals management. In this paper, actual levels of penta-, octa-, and decaBDE, TBBPA, and HBCD in waste electrical and electronic equipment (WEEE) as a major carrier of BFRs are presented. These BFRs have been determined in products of a modern Swiss recycling plant applying gas chromatography/electron capture detection and gas chromatography/mass spectrometry analysis. A substance flow analysis (SFA) technique has been used to characterize the flows of target substances in the recycling process from the bulk WEEE input into the output products. Average concentrations in small size WEEE, representing the relevant electric and electronic appliances in WEEE, sampled in 2003 amounted to 34 mg/kg for pentaBDE, 530 mg/kg for octaBDE, 510 mg/kg for decaBDE, 1420 mg/kg for TBBPA (as an additive), 17 mg/kg for HBCD, 5500 mg/kg for bromine, and 1700 mg/kg for antimony. In comparison to data that have been calculated by SFA for Switzerland from literature for the 1990s, these measured concentrations in small size WEEE were 7 times higher for pentaBDE, unexpectedly about 50% lower for decaBDE, and agreed fairly well for TBBPA (as an additive) and octaBDE. Roughly 60% of the total bromine input determined by SFA based on X-ray fluorescence analysis of the output materials of the recycling plant cannot be assigned to the selected BFRs. This is an indication for the presence of other brominated substances as substitutes for PBDEs in electrical and electronic equipment. The presence of BFRs, in particular PBDEs in the low grams per kilogram concentration range, in the fine dust fraction recovered in the off-gas purification system of the recycling plant reveals a high potential for BFR emissions from WEEE management and point out the importance for environmentally sound recycling and disposal technologies for BFR-containing residues.

In October 2000, joint sealants containing polychlorinated biphenyls (PCB) were discovered in various public buildings in Switzerland. Triggered by this event, a nationwide comprehensive study was initiated by the Swiss Agency for the Environment, Forests, and Landscape, and 1348 samples of joint sealants as well as 160 indoor air samples from concrete buildings erected between 1950 and 1980 were analyzed. Out of 1348 samples, 646 (48%) contained PCB. In 279 (21%) samples, PCB concentrations of 10 g/kg and more were detected, and concentrations of 100 g/kg of PCB or more were found in 129 (9.6%) samples. These data indicate that PCB were widely used as plasticizers in joint sealants in Switzerland. In buildings constructed between 1966 and 1971, one-third of all joint sealants investigated contained more than 10 g/kg of PCB. PCB concentrations exceeding the limit of 0.050 g/kg above which material is required to be treated as PCB bulk product waste were reached by 568 samples (42%). PCB with a chlorine content between 45 and 55%, corresponding to mixtures such as Clophen A50, Aroclor 1248, and Aroclor 1254, were encountered in 316 samples (70%). In 42 cases (26%) where joint sealants containing PCB were present, clearly elevated PCB indoor air concentrations above 1 microg/m3 were encountered. In eight cases (5%), levels were higher than 3 microg/m3. The Swiss tentative guideline value of 6 microg/m3 (based on a daily exposure of 8 h) for PCB in indoor air was exceeded in one case (0.6%). On the basis of this work, representing the first large-scale nationwide analysis of the issue of PCB-contaminated joint sealants, we estimate that there are still 50-150 t of PCB present in these materials, acting as diffuse sources. They are distributed over many hundreds of buildings all over the country and represent a significant but frequently overlooked inventory of PCB. In light of the Stockholm Convention on persistent organic pollutants that entered into force last year, reduction of the release of PCB from these widely used materials is an important issue to be addressed.

The environmental safety of decabromodiphenyl ether (BDE-209), a widely used flame retardant, has been the topic of controversial discussions during the past several years. Degradation of BDE-209 into lower brominated diphenyl ether congeners, exhibiting a higher bioaccumulation potential, has been a critical issue. Here, we report on the degradation of BDE-209 and the formation of octa- and nonabromodiphenyl ether congeners under anaerobic conditions. Sewage sludge collected from a mesophilic digester was used as the inoculum and incubated up to 238 days with and without a set of five primers. Following Soxhlet extraction and a liquid chromatography cleanup procedure, parent compounds and debromination products were analyzed by GC/HRMS. In experiments with primers, concentrations of BDE-209 decreased by 30% within 238 days. This corresponds to a pseudo-first-order degradation rate constant of 1 x 10(-3) d(-1). Without primers, the degradation rate constant was 50% lower. Formation of two nonabromodiphenyl ether and six octabromodiphenyl ether congeners proved that BDE-209 underwent reductive debromination in these experiments. Debromination occurred at the para and the meta positions, whereas debromination at the ortho position was not statistically significant. All three nonabromodiphenyl ether congeners (BDE-206, BDE-207, and BDE-208) were found to undergo reductive debromination as well. No significant change of the BDE-209 concentration and no formation of lower brominated congeners was observed in sterile control experiments. To our knowledge, this is the first report demonstrating microbially mediated reductive debromination of BDE-209 under anaerobic conditions.

Between 1997 and 1999, several cases of dioxin contaminations in foodstuffs of animal origin occurred in Europe due to feed contaminated by several independent sources: citrus pulp pellets, fat containing polychlorinated biphenyls (PCB), and kaolinitic clay as anti-caking agent in feedingstuffs. As a consequence of the latter, a survey on polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) in food of animal origin was initiated by the Swiss authorities to assess the extent of PCDD/F contamination and to document the efficiency of the measures taken to ensure the decontamination of the food supply. Investigation of a total of 128 samples of cow's milk, poultry, eggs, and meat revealed several cases of residue levels distinctly above the background exposure limit of approximately 2.5 ng of I-TEQ/kg (fat basis). Particularly, elevated concentrations were found in eggs (maximum 13 ng of I-TEQ/kg), poultry (maximum 3.9 ng of I-TEQ/kg), and pork (maximum 7.5 ng of I-TEQ/kg). On the basis of the observed PCDD/F congener pattern, the contamination could be attributed to PCDD/F-contaminated kaolin that was used as an anti-caking agent in particular feedstuffs.

Indoor air levels of coplanar polychlorinated biphenyls (mono- and non-ortho substituted PCB) of various buildings were determined. As a consequence of the presence of joint sealings containing PCB, total PCB concentrations in indoor air up to 4,200 ng/m3 were detected (data based on a survey including 29 sampling sites). In a PCB contaminated industrial building, total indoor air PCB levels up to 13,000 ng/m3 were measured. Typical PCB congeners in indoor air include PCB 28, PCB 52, and PCB 101. Concentrations of coplanar (dioxin-like) PCB have been determined for six different sites. The most abundant coplanar PCB congener in indoor air is PCB 118, followed by PCB 105, PCB 123, and PCB 77 in various order. Levels of coplanar PCB, expressed as toxicity equivalents (TEG), do correlate well with the total indoor air PCB concentration: a total PCB level of 1,000 ng/m3 corresponds to a concentration of coplanar PCB of 1.2 pg TEQ/m3. Based on this correlation and on an indoor air PCB level of 6,000 ng/m3 (tentative guideline value for PCB in indoor air in Switzerland based on a daily exposure of 8 h), the maximum daily intake of coplanar PCB via indoor air was estimated to be 0.6 pg TEQ/kg body weight.