Life cycle of PCBs and contamination of the environment and of food products from animal origin

This report gives a summary of the historic use, former management and current release of polychlorinated biphenyls (PCBs) in Germany and assesses the impact of the life cycle of PCBs on the contamination of the environment and of food products of animal origin. In Germany 60,000 t of PCBs were used in transformers, capacitors or as hydraulic oils. The use of PCB oils in these “closed applications”, has been banned in Germany in 2000. Thirty to 50% of these PCBs were not appropriately managed. In West Germany, 24,000 t of PCBs were used in open applications, mainly as additive (plasticiser, flame retardant) in sealants and paints in buildings and other construction. The continued use in open applications has not been banned, and in 2013, an estimated more than 12,000 t of PCBs were still present in buildings and other constructions. These open PCB applications continuously emit PCBs into the environment with an estimated release of 7–12 t per year. This amount is in agreement with deposition measurements (estimated to 18 t) and emission estimates for Switzerland. The atmospheric PCB releases still have an relevant impact on vegetation and livestock feed. In addition, PCBs in open applications on farms are still a sources of contamination for farmed animals. Furthermore, the historic production, use, recycling and disposal of PCBs have contaminated soils along the lifecycle. This legacy of contaminated soils and contaminated feed, individually or collectively, can lead to exceedance of maximum levels in food products from animals. In beef and chicken, soil levels of 5 ng PCB-TEQ/kg and for chicken with high soil exposure even 2 ng PCB-TEQ/kg can lead to exceedance of EU limits in meat and eggs. Areas at and around industries having produced or used or managed PCBs, or facilities and areas where PCBs were disposed need to be assessed in respect to potential contamination of food-producing animals. For a large share of impacted land, management measures applicable on farm level might be sufficient to continue with food production. Open PCB applications need to be inventoried and better managed. Other persistent and toxic chemicals used as alternatives to PCBs, e.g. short chain chlorinated paraffins (SCCPs), should be assessed in the life cycle for exposure of food-producing animals and humans.     

Effects of different vermicompost extracts of palm oil mill effluent and palm-pressed fiber mixture on seed germination of mung bean and its relative toxicity

Several treatment technologies are available for the treatment of palm oil mill wastes. Vermicomposting is widely recognized as efficient, eco-friendly methods for converting organic waste materials to valuable products. This study evaluates the effect of different vermicompost extracts obtained from palm oil mill effluent (POME) and palm-pressed fiber (PPF) mixtures on the germination, growth, relative toxicity, and photosynthetic pigments of mung beans (Vigna radiata) plant. POME contains valuable nutrients and can be used as a liquid fertilizer for fertigation. Mung bean seeds were sown in petri dishes irrigated with different dilutions of vermicomposted POME-PPF extracts, namely 50, 60, and 70% at varying dilutions. Results showed that at lower dilutions, the vermicompost extracts showed favorable effects on seed germination, seedling growth, and total chlorophyll content in mung bean seedlings, but at higher dilutions, they showed inhibitory effects. The carotenoid contents also decreased with increased dilutions of POME-PPF. This study recommends that the extracts could serve as a good source of fertilizer for the germination and growth enhancement of mung bean seedlings at the recommended dilutions.     

PCDD/PCDF formation in the chlor-alkali process—laboratory study and comparison with patterns from contaminated sites

Studies on the formation of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) during the electrolysis of sodium chloride solution (brine) using graphite or titanium electrodes were carried out at a laboratory scale. High concentrations of PCDFs but no PCDDs were formed in tests using graphite electrodes. With titanium electrodes, PCDFs were only formed when tar pitch was added and mainly originated from the dibenzofuran present in the tar. For the first time, a detailed assessment of the formation of mono- to octachlorinated PCDD/PCDF from tar pitch was investigated. The assessment included of the chlorination steps proved that PCDFs were formed by successive lateral chlorinated from dibenzofuran to MonoCDFs, DiCDFs, and TriCDFs to form the typical known “chlorine pattern” of TetraCDF to OctaCDF with a dominance of 1,2,7,8- and 2,3,7,8-TetraCDFs, 1,2,3,7,8-PentaCDF, and 1,2,3,4,7,8-HexaCDF as marker congeners. The final homologue distributions depended on reaction time and reaction temperature. In addition, electrolysis with non-chlorinated dibenzo-p-dioxins, dibenzofuran, and biphenyl was carried out. As a result, PCDDs, PCDFs, and PCB were formed at comparable yields. Congener patterns in soil samples from a PCDD/F-contaminated site where chlor-alkali electrolysis had been operated for decades in Japan had identical isomer distribution demonstrating the source and contamination potential and risk of these processes. Therefore, sites where in the past 120 years chlor-alkali electrolysis has been operated or where residues from chlor-alkali production or other chlorine using industries have been disposed should be assessed for their pollution level and exposure relevance. The assessment of total organohalogen content revealed that PCDF is only a small fraction of organohalogens in the contaminated soils. For an appropriate risk assessment, also other chlorinated aromatic compounds such as PCBs or PCNs need to be considered.     

Enhanced photocatalytic activity using GO/TiO<Subscript>2</Subscript> catalyst for the removal of DCA solutions

This work aimed to optimize high-performance photocatalysts based on graphene oxide/titanium dioxide (GO/TiO₂) nanocomposites for the effective degradation of aqueous pollutants. The catalytic activity was tested against the degradation of dichloroacetic acid (DCA), a by-product of disinfection processes that is present in many industrial wastewaters and effluents. GO/TiO₂ photocatalysts were prepared using three different methods, hydrothermal, solvothermal, and mechanical, and varying the GO/TiO₂ ratio in the range of 1 to 10%. Several techniques were applied to characterize the catalysts, and better coupling of GO and TiO₂ was observed in the thermally synthesized composites. Although the results obtained for DCA degradation showed a coupled influence of the composite preparation method and its composition, promising results were obtained with the photocatalysts compared to the limited activity of conventional TiO₂. In the best case, corresponding to the composite synthesized via hydrothermal method with 5% of GO/TiO₂ weight ratio, an enhancement of 2.5 times of the photocatalytic degradation yield of DCA was obtained compared to bare TiO₂, thus opening more efficient ways to promote the application of photocatalytic remediation technologies.     

Photocatalytic reduction of carbon dioxide over Cu/TiO<Subscript>2</Subscript> photocatalysts

The photocatalytic reduction of CO₂ with H₂O was investigated using Cu/TiO₂ photocatalysts in aqueous solution. For this purpose, Cu/TiO₂ photocatalysts (with 0.2, 0.9, 2, 4, and 6 wt.% of Cu) have been synthesized via sol-gel method. The photocatalysts were extensively characterized by means of inductively coupled plasma optical emission spectrometry (ICP-OES), N₂ physisorption (BET), XRD, UV-vis DRS, FT-IR, Raman spectroscopy, TEM-EDX, and photoelectrochemical measurements. The as-prepared photocatalysts contain anatase as a major crystalline phase with a crystallite size around 13 nm. By increasing the amount of Cu, specific surface area and band gap energy decreased in addition to the formation of large agglomeration of CuO. Results revealed that the photocatalytic reduction of CO₂ decreased in the presence of Cu/TiO₂ in comparison to pure TiO₂, which might be associated to the formation of CuO phase acting as a recombination center of generated electron-hole pair. Decreasing of photoactivity can also be connected with a very low position of conduction band of photocatalysts with high Cu content, which makes H₂ production necessary for CO₂ reduction more difficult.     

A mini review of fluoride-induced apoptotic pathways

Fluorine or fluoride can have toxic effects on bone tissue and soft tissue at high concentrations. These negative effects include but not limited to cytotoxicity, immunotoxicity, blood toxicity, and oxidative damage. Apoptosis plays an important role in fluoride-induced toxicity of kidney, liver, spleen, thymus, bursa of Fabricius, cecal tonsil, and cultured cells. Here, apoptosis activated by high level of fluoride has been systematically reviewed, focusing on three pathways: mitochondrion-mediated, endoplasmic reticulum (ER) stress-mediated, and death receptor-mediated pathways. However, very limited reports are focused on the death receptor-mediated apoptosis pathways in the fluoride-induced apoptosis. Therefore, understanding and discovery of more pathways and molecular mechanisms of fluoride-induced apoptosis may contribute to designing measures for preventing fluoride toxicity.     

Spatial distribution of metals within the liver acinus and their perturbation by PCB126

Animal studies show that exposure to the environmental pollutant 3,3′,4,4′,5-pentachlorobiphenyl (PCB126) causes alterations in hepatic metals as measured in acid-digested volume-adjusted tissue. These studies lack the detail of the spatial distribution within the liver. Here we use X-ray fluorescence microscopy (XFM) to assess the spatial distribution of trace elements within liver tissue. Liver samples from male Sprague Dawley rats, treated either with vehicle or PCB126, were formalin fixed and paraffin embedded. Serial sections were prepared for traditional H&E staining or placed on silicon nitride windows for XFM. With XFM, metal gradients between the portal triad and the central vein were seen, especially with copper and iron. These gradients change with exposure to PCB126, even reverse. This is the first report of how micronutrients vary spatially within the liver and how they change in response to toxicant exposure. In addition, high concentrations of zinc clusters were discovered in the extracellular space. PCB126 treatment did not affect their presence, but did alter their elemental makeup suggesting a more general biological function. Further work is needed to properly evaluate the gradients and their alterations as well as classify the zinc clusters to determine their role in liver function and zinc homeostasis.     

Trace metal (Cd,Cu, Pb,Zn) fractionation in urban-industrial soils of Ust-Kamenogorsk (Oskemen), Kazakhstan—implications for the assessment of environmental quality

Ust-Kamenogorsk is one of the largest cities and industrial centers in Kazakhstan. Non-ferrous metallurgy (Zn–Pb smelter) has acted as a predominating industrial branch in the city since late 1940s. The industrial plants are situated directly adjacent to the residential area of the city which creates grievous ecotoxicological hazard. In the present paper, we aimed at assessing the trace metal pollution of top soils in Ust-Kamenogorsk and its potential threats to the local population. The top soils were sampled at 10 sites throughout the city center. We determined the physical and chemical properties of soils as well as the contents of Cd, Cu, Pb, and Zn. In addition, the soil samples were subjected to a five-step sequential extraction to ascertain the fractionation of trace metals. On this basis, we calculated the geoaccumulation index (I_geo) and pollution load index (PLI) and assessed bioavailability of the elements. From our data, it emerged that the soils displayed a strong polymetallic pollution. PLI was as high as 33.4. Throughout the city, the trace metal contents exceeded the geochemical background and allowable values for residential, recreational, and institutional areas. The I_geo obtained were 3.7–6.5 for Cd, 1.5–4.7 for Cu, 2.8–5.7 for Pb, and 2.6–4.6 for Zn. The soils in Ust-Kamenogorsk displayed extremely high contamination with Cd, moderate to strong contamination with Pb and Zn, and low to moderate contamination with Cu. Cd and Pb were found to be the most bioavailable elements. The mobility of trace metals in the soils changed in the order Cd > Pb > Zn > Cu.