Synergistic increase in cell lethality by dieldrin and H2O2 in rat thymocytes: Effect of dieldrin on the cells exposed to oxidative stress

Dieldrin, one of persistent pesticides, is highly resistant to biotic and abiotic degradation. It is accumulated in organisms. Recent studies suggest that dieldrin exerts a potent cytotoxic action on cells exposed to oxidative stress. In this study, the effect of dieldrin on rat thymocytes exposed to hydrogen peroxide (H₂O₂)-induced oxidative stress was examined. Dieldrin at 5 μM and H₂O₂ at 300 μM slightly increased cell lethality from a control value of 5.4 ± 0.5% (mean ± standard deviation of four experiments) to 7.8 ± 1.3% and 9.0 ± 0.3%, respectively. Simultaneous application of dieldrin and H₂O₂ significantly increased cell lethality to 46.2 ± 1.8%. The synergistic increase in cell lethality was dependent on dieldrin concentration (0.3–5 μM) but not on H₂O₂ concentration (30–300 μM). Dieldrin accelerated H₂O₂-induced cell death, which was estimated with the help of annexin V-FITC and propidium iodide. Presence of either dieldrin or H₂O₂ decreased the cellular content of nonprotein thiol and increased intracellular Zn²⁺ concentration. The combination of dieldrin and H₂O₂ further pronounced these effects. TPEN, a chelator of intracellular Zn²⁺, significantly attenuated the synergistic increase in cell lethality induced by dieldrin and H₂O₂. It is, therefore, suggested that dieldrin augments the cytotoxicity of H₂O₂ in a Zn²⁺-dependent manner.     

Assessing the toxicity of sodium chloride to the glochidia of freshwater mussels: implications for salinization of surface waters

Chloride concentrations in surface waters have increased significantly, a rise attributed to road salt use. In Canada, this may be a concern for endangered freshwater mussels, many with ranges limited to southern Ontario, Canada’s most road-dense region. The acute toxicity of NaCl was determined for glochidia, the mussel’s larval stage. The 24 h EC50s of four (including two Canadian endangered) species ranged from 113-1430 mg Cl L⁻¹ (reconstituted water, 100 mg CaCO₃ L⁻¹). To determine how mussels would respond to a chloride pulse, natural river water (hardness 278-322 mg CaCO₃ L⁻¹) was augmented with salt. Lampsilis fasciola glochidia were significantly less sensitive to salt in natural water (EC50s 1265-1559 mg Cl L⁻¹) than in reconstituted water (EC50 285 mg L⁻¹). Chloride data from mussel habitats revealed chloride reaches levels acutely toxic to glochidia (1300 mg L⁻¹). The increased salinization of freshwater could negatively impact freshwater mussels, including numerous species at risk.     

Photocatalytic degradation with immobilised TiO(2) of three selected neonicotinoid insecticides: imidacloprid, thiamethoxam and clothianidin

This research focused on photocatalytic degradation of imidacloprid, thiamethoxam and clothianidin employing a tailor-made photoreactor with six polychromatic fluorescent UVA (broad maximum at 355 nm) lamps and immobilised titanium dioxide (TiO₂) on glass slides. The disappearance was followed by high pressure liquid chromatography (HPLC-DAD) analyses, wherein the efficiency of mineralization was monitored by measurements of total organic carbon (TOC). Within 2 h of photocatalysis, all three neonicotinoids were degraded following first order kinetics with rate constants k = 0.035 ± 0.001 min⁻¹ for imidacloprid, k = 0.019 ± 0.001 min⁻¹ for thiamethoxam and k = 0.021 ± 0.000 min⁻¹ for clothianidin. However, the rate of mineralization was low, i.e. 19.1 ± 0.2% for imidacloprid, 14.4 ± 2.9% for thiamethoxam and 14.1 ± 0.4% for clothianidin. This indicates that several transformation products were formed instead. Some of them were observed within HPLC-DAD analyses and structures were proposed according to the liquid chromatography-electro spray ionization tandem mass spectrometry analyses (LC-ESI-MS/MS). The formation of clothianidin, as thiamethoxam transformation product, was reported for the first time.     

Seasonal and spatial variations of Po and Pb activity concentrations in Mytilus galloprovincialis from Croatian coast of the Adriatic Sea

Results of 2 years monitoring of ²¹⁰Po and ²¹⁰Pb activity concentrations in soft tissue of the species Mytilus galloprovincialis from Croatian part of the Adriatic coast are presented. The samples were collected at thirteen coastal stations (some of which are also a part of the Mediterranean Mussel Watch Project) in spring and autumn of 2010 and 2011. The collected mussels were ranging between 4 cm and 6 cm in shell length. After sample pre-treatment lead and polonium were radiochemically separated on Sr resin. ²¹⁰Po was determined by alpha-particle spectrometry and ²¹⁰Pb was determined, via ²¹⁰Bi, by a low-level gas proportional counter. The results of ²¹⁰Po activity concentrations were found to vary between (104 ± 11) and (1421 ± 81) Bq kg⁻¹ dry weight while ²¹⁰Pb activity concentrations were much lower and in range (8.2 ± 5.3)–(94.1 ± 29.8) Bq kg⁻¹ dry weight. Higher ²¹⁰Po and ²¹⁰Pb activity concentrations were determined in spring period. The inter-site differences seen in their activity concentrations can be due to natural background levels of sites. The ²¹⁰Po/²¹⁰Pb activity concentration ratios in all cases exceeded unity for all mussel samples and ranged between 4.0 and 47.9.     

Evidence for changing the critical level for ammonia

The current critical level for ammonia (CLE_NH3) in Europe is set at 8 μg NH₃ m⁻³ as an annual average concentration. Recent evidence has shown specific effects of ammonia (NH₃) on plant community composition (a true ecological effect) at much smaller concentrations. The methods used in setting a CLE_NH3 are reviewed, and the available evidence collated, in proposing a new CLE_NH3 for different types of vegetation. For lichens and bryophytes, we propose a new CLE_NH3 of 1 μg NH₃ m⁻³ as a long-term (several year) average concentration; for higher plants, there is less evidence, but we propose a CLE_NH3 of 3 ± 1 μg NH₃ m⁻³ for herbaceous species. There is insufficient evidence to provide a separate CLE_NH3 for forest trees, but the value of 3 ± 1 μg NH₃ m⁻³ is likely to exceed the empirical critical load for N deposition for most forest ecosystems.     

Investigation of the role of biopolymer clusters in MBR membrane fouling using flash freezing and environmental scanning electron microscopy

The technique that employs flash freezing and environmental scanning electron microscopy (ESEM) was utilised for detailed investigation of the fouling materials in a membrane bioreactor (MBR). The method involves the flash freezing of a wet sample in liquid nitrogen for 10 s to preserve its structure for direct ESEM observation with a high image resolution. ESEM images show that the sludge cake formed by simple filtration of the MBR bulk sludge has a highly porous, sponge-like structure with a fairly low resistance. However, the fouling layer attached to the membrane surface contains a thin gel layer under the main body of the sponge-like sludge cake, which is similar to that formed by filtration of a dispersion of biopolymer clusters (BPCs). It is apparent that BPCs tend to accumulate on the membrane surface, and the gel layer is largely responsible for the high filtration resistance of the cake layer on the fouled membranes.     

Removal of dissolved organic matter in municipal effluent with ozonation, slow sand filtration and nanofiltration as high quality pre-treatment option for artificial groundwater recharge

In the paper the combination process of ozonation, slow sand filtration (SSF) and nanofiltration (NF) was investigated with respect to dissolved organic matter (DOM) removal as high quality pre-treatment option for artificial groundwater recharge. With the help of ozonation leading to breakdown of the large organic molecules, SSF preferentially removes soluble microbial by-product-like substances and DOM with molecular weight (MW) less than 1.0 kDa. NF, however, removes aromatic, humic acid-like and fulvic acid-like substances efficiently and specially removes DOM with MW above 1.0 kDa. The residual DOM of the membrane permeate is dominated by small organics with MW 500 Da, which can be further reduced by the aquifer treatment, despite of the very low concentration. Consequently, the O₃/SSF/NF system offers a complementary process in DOM removal. Dissolved organic carbon (DOC) and trihalomethane formation potential (THMFP) can be reduced from 6.5 ± 1.1 to 0.7 ± 0.3 mg L⁻¹ and from 267 ± 24 to 52 ± 6 μg L⁻¹, respectively. The very low DOC concentration of 0.6 ± 0.2 mg L⁻¹ and THMFP of 44 ± 4 μg L⁻¹ can be reached after the aquifer treatment.     

Organochlorine pesticide in fresh and pasteurized cow's milk from Kampala markets

Fresh and pasteurized milk samples from Kampala markets were analyzed for organochlorine pesticides using a gas chromatograph equipped with an electron capture detector. Five organochlorine pesticides, namely; aldrin, dieldrin, endosulfan, lindane, DDT and its metabolites were detected in the milk samples and confirmed with a gas chromatograph equipped with a mass spectrometer [GC-MS]. The mean values are expressed in mg kg⁻¹ milk fat (mf) basis. The mean concentration in the fresh milk (n = 54) were: 0.026 ± 0.003 mg kg⁻¹ mf; 0.002 ± 0.0003 mg kg⁻¹, below the detection limit; 0.007 ± 0.003 mg kg⁻¹, 0.009 ± 0.002 mg kg⁻¹ milk fat for lindane, endosulfan dieldrin and aldrin, respectively. The mean concentrations of p,p′-DDE; p,p′-DDT and o,p′-DDT were 0.009 ± 0.002 mg kg⁻¹; 0.033 ± 0.007 mg kg⁻¹ and 0.008 ± 0.001 mg kg⁻¹ mf, respectively in the fresh milk samples.In the pasteurized milk samples (n = 47), the mean concentrations recorded were: 0.008 ± 0.003 mg kg⁻¹, 0.025 ± 0.004 mg kg⁻¹, and 0.007 ± 0.001 mg kg⁻¹, respectively for p,p′-DDE; p,p′-DDT and o,p′-DDT.Alpha and beta-endosulfan recorded the concentration below the detection limit and the mean of 0.022 ± 0.001 mg kg⁻¹ mf, 0.005 ± 0.002 mg kg⁻¹ mf, and 0.006 ± 0.0002 mg kg⁻¹ mf, respectively for lindane, dieldrin and aldrin. Although, most of the residues detected were above the residue limits set by the FAO/WHO (2008), bioaccumulation of these residues is likely to pose health risks to the consumers of milk in Uganda.     

An aerosol flow tube study of the interaction of N2O5 with calcite, Arizona dust and quartz

The interaction of N₂O₅ with dispersed samples of Arizona Test Dust (ATD), Calcite (CaCO₃) and quartz (SiO₂) was investigated at varying relative humidity using an aerosol flow reactor. Reactive uptake coefficients, γ, obtained at close to zero relative humidity were (4.8 ± 0.7) × 10⁻³ for CaCO₃, (8.6 ± 0.6) × 10⁻³ for Quartz and (9.8 ± 1.0) × 10⁻³ for ATD. In the case of calcite, evidence was obtained for an enhanced rate of uptake at relative humidities above ≈ 50%. The results are compared to literature values obtained using bulk substrates and to previous aerosol uptake data on Saharan dust.     

Use of whole-body and subcellular Cu residues of Lumbriculus variegatus to predict waterborne Cu toxicity to both L. variegatus and Chironomus riparius in fresh water

We tested the use of whole-body and subcellular Cu residues (biologically-active (BAM) and inactive compartments (BIM)), of the oligochaete Lumbriculus variegatus to predict Cu toxicity in fresh water. The critical whole-body residue associated with 50% mortality (CBR₅₀) was constant (38.2-55.6 μg g⁻¹ fresh wt.) across water hardness (38-117 mg L⁻¹ as CaCO₃) and exposure times during the chronic exposure. The critical subcellular residue (CSR₅₀) in metal-rich granules (part of BIM) associated with 50% mortality was approximately 5 μg g⁻¹ fresh wt., indicating that Cu bioavailability is correlated with toxicity:subcellular residue is a better predictor of Cu toxicity than whole-body residue. There was a strong correlation between the whole-body residue of L. variegatus (biomonitor) and survival of Chironomus riparius (relatively sensitive species) in a hard water Cu co-exposure. The CBR₅₀ in L. variegatus for predicting mortality of C. riparius was 29.1-45.7 μg g⁻¹ fresh wt., which was consistent within the experimental period; therefore use of Cu residue in an accumulator species to predict bioavailability of Cu to a sensitive species is a promising approach.     

Thermodynamic and kinetic study of phenol degradation by a non-catalytic wet air oxidation process

This work is dedicated to an accurate evaluation of thermodynamic and kinetics aspects of phenol degradation using wet air oxidation process. Phenol is a well known polluting molecule and therefore it is important having data of its behaviour during this process. A view cell is used for the experimental study, with an internal volume of 150 mL, able to reach pressures up to 30 MPa and temperatures up to 350 °C. Concerning the thermodynamic phase equilibria, experimental and modelling results are obtained for different binary systems (water/nitrogen, water/air) and ternary system (water/nitrogen/phenol). The best model is the Predictive Soave Redlich Kwong one. This information is necessary to predict the composition of the gas phase during the process. It is also important for an implementation in a process simulation. The second part is dedicated to kinetics evaluation of the degradation of phenol. Different compounds have been detected using GC coupled with a MS. A kinetic scheme is deduced, taking into account the evolution of phenol, hydroquinones, catechol, resorcinol and acetic acid. The kinetic parameters are calculated for this scheme. These data are important to evaluate the evolution of the concentration of the different polluting molecules during the process. A simplified kinetic scheme, which can be easily implemented in a process simulation, is also determined for the direct degradation of phenol into H₂O and CO₂. The Arrhenius law data obtained for the phenol disappearance are the following: k = 1.8 × 10⁶ ± 3.9 × 10⁵ M⁻¹ s⁻¹ (pre-exponential factor) and E_a = 77 ± 8 kJ mol⁻¹ (activation energy).     

Conditioning of sewage sludge by Fenton's reagent combined with skeleton builders

Physical conditioners, often known as skeleton builders, are commonly used to improve the dewaterability of sewage sludge. This study evaluated a novel joint usage of Fenton’s reagent and skeleton builders, referred to as the F-S inorganic composite conditioner, focusing on their efficacies and the optimization of the major operational parameters. The results demonstrate that the F-S composite conditioner for conditioning sewage sludge is a viable alternative to conventional organic polymers, especially when ordinary Portland cement (OPC) and lime are used as the skeleton builders. Experimental investigations confirmed that Fenton reaction required sufficient time (80 min in this study) to degrade organics in the sludge. The optimal condition of this process was at pH = 5, Fe²⁺ = 40 mg g⁻¹ (dry solids), H₂O₂ = 32 mg g⁻¹, OPC = 300 mg g⁻¹ and lime = 400 mg g⁻¹, in which the specific resistance to filtration reduction efficiency of 95% was achieved.     

Toxicity of nanoparticulate and bulk ZnO, Al2O3 and TiO2 to the nematode Caenorhabditis elegans

Limited information is available on the environmental behavior and associated potential risk of manufactured oxide nanoparticles (NPs). In this research, toxicity of nanoparticulate and bulk ZnO, Al₂O₃ and TiO₂ were examined to the nematode Caenorhabditis elegans with Escherichia coli as a food source. Parallel experiments with dissolved metal ions from NPs were also conducted. The 24-h median lethal concentration (LC₅₀) and sublethal endpoints were assessed. Both NPs and their bulk counterparts were toxic, inhibiting growth and especially the reproductive capability of the nematode. The 24-h LC₅₀ for ZnO NPs (2.3 mg L⁻¹) and bulk ZnO was not significantly different, but significantly different between Al₂O₃ NPs (82 mg L⁻¹) and bulk Al₂O₃ (153 mg L⁻¹), and between TiO₂ NPs (80 mg L⁻¹) and bulk TiO₂ (136 mg L⁻¹). Oxide solubility influenced the toxicity of ZnO and Al₂O₃ NPs, but nanoparticle-dependent toxicity was indeed observed for the investigated NPs.     

混凝剂品种对混凝-超滤联合工艺膜污染的影响

本实验以工业化学合成聚合硫酸铁混凝剂和自制生物聚合硫酸铁为例,考察了铁系混凝剂品种对地表水浊度、TOC和UV254的去除效果,混凝剂品种对混凝-超滤联合工艺处理地表水过程中超滤膜污染的影响。混凝实验结果表明,在10 mg/L(以Fe3+计)最佳投加量下,两类混凝剂对浊度、TOC和UV254的去除率基本相同。超滤膜污染实验结果表明,生物聚合铁预处理水样通量衰减速度略大于化学聚合铁预处理水样;膜污染阻力分析结果显示,随着循环次数的增加,工业化学合成聚合铁预处理水样造成的不可逆污染阻力逐渐增加,而生物聚合铁预处理水样造成的不可逆污染阻力却略有下降;膜污染机理分析表明,2组过滤过程的膜污染类型基本相似,由最初的膜孔堵塞过渡到最终的滤饼层污染。SEM分析表明,生物聚合铁预处理水样的膜污染较为严重。     

Polychlorinated biphenyls (PCBs) in indoor air originating from sealants in contaminated and uncontaminated apartments within the same housing estate

Twenty-four congeners of polychlorinated biphenyls (PCBs) were measured in 83 air samples and 20 elastic sealants samples of apartments with PCB-containing sealants. In addition, PCBs were measured in 21 air samples from reference apartments located in an uncontaminated section of the same estate. The PCB_tot levels in the air of the contaminated section were 168-3843 ng m⁻³ (mean: 1030 ng m⁻³), while the mean levels in the reference apartments were 6.03 ng m⁻³. The sum of the 24 measured PCB congeners in sealants from the contaminated section was 187-221 680 mg kg⁻¹. Principal component analysis revealed four groups among the sealant samples with different congener compositions, only two of which were clearly similar to known PCB mixtures, while two were not. Significant correlations and intercorrelations were observed between the lower chlorinated congeners in air and sealant, e.g. for PCB 28_air and 28_seal (p = 0.04) and for PCB 28_air and 52_air, 52_seal. However, no correlation was observed between the lower chlorinated congeners and the sums of PCB (∑PCB₆ or ∑PCB₂₄) or the higher chlorinated congeners. Analysis of air concentrations in relation to questionnaire data indicated that the indoor air levels could be reduced by increased cleaning and airing frequencies.     

Air quality assessment by tree bark biomonitoring in urban, industrial and rural environments of the Rhine Valley: PCDD/Fs, PCBs and trace metal evidence

Tree barks were used as biomonitors to evaluate past atmospheric pollution within and around the industrial zones of Strasbourg (France) and Kehl (Germany) in the Rhine Valley. The here estimated residence time for trace metals, PCBs and PCDD/Fs in tree bark is >10 years. Thus, all pollution observed by tree bark biomonitoring can be older than 10 years. The PCB baseline concentration (sum of seven PCB indicators (Σ₇PCB_ind)) determined on tree barks from a remote area in the Vosges mountains is 4 ng g⁻¹ and corresponds to 0.36 × 10⁻³ ng toxic equivalent (TEQ) g⁻¹ for the dioxin-like PCBs (DL-PCBs). The northern Rhine harbor suffered especially from steel plant, waste incinerator and thermal power plant emissions. The polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/Fs) concentrations analyzed in tree barks from this industrial area range between 392 and 1420 ng kg⁻¹ dry-weight (dw) corresponding to 3.9 ng TEQ_PCDD/Fs kg⁻¹ to 17.8 ng TEQ_PCDD/Fs kg⁻¹, respectively. Highest PCDD/F values of 7.2 ng TEQ kg⁻¹ to 17.8 ng TEQ kg⁻¹ have been observed close to and at a distance of <2 km southwest of the chemical waste incinerator. However, very close to this incinerator lowest TEQ dioxin-like PCB (TEQ_DL-PCB) values of 0.006 ng TEQ g⁻¹ have been found. On the other hand close to and southwest and northeast of the steel plant the values are comparatively higher and range between 0.011 ng TEQ g⁻¹ and 0.026 ng TEQ g⁻¹. However, even stronger Σ₇PCB_ind enrichments have been observed at a few places in the city center of Kehl, where ΣDL-PCB values of up to 0.11 ng TEQ g⁻¹ have been detected. These enrichments, however, are the result of ancient pollutions since recent long-term measurements at the same sites indicate that the atmospheric PCB concentrations are close to baseline. Emissions from an old landfill of waste and/or great fires might have been the reasons of these PCB enrichments. Other urban environments of the cities of Kehl and Strasbourg show significantly lower Σ₇PCB_ind concentrations. They suffer especially from road and river traffic and have typically Σ₇PCB_ind concentrations ranging from 11 ng g⁻¹ to 29 ng g⁻¹. The PCB concentration of 29 ng g⁻¹ has been found in tree bark close to the railway station of Strasbourg. Nevertheless, the corresponding TEQ_DL-PCB are low and range between 0.2 × 10⁻³ ng TEQ g⁻¹ and 7 × 10⁻³ ng TEQ g⁻¹. Samples collected near road traffic are enriched in Fe, Sb, Sn and Pb. Cd enrichments were found close to almost all types of industries. Rural environments not far from industrial sites suffered from organic and inorganic pollution. In this case, TEQ_DL-PCB values may reach up to 58 × 10⁻³ ng TEQ g⁻¹ and the corresponding V, Cr, Co, Ni, and Cd concentrations are comparatively high.     

Wastewater treatment plants and landfills emit volatile methyl siloxanes (VMSs) to the atmosphere: investigations using a new passive air sampler

Volatile methyl siloxanes (VMSs) are a class of chemicals with an increasing range of applications and widespread distribution in the environment. Passive air samplers (PAS) comprising sorbent-impregnated polyurethane-foam (SIP) disks were first calibrated and then deployed around two wastewater treatment plants (WWTPs) and at two landfill sites to investigate inputs of VMSs to air. SIP-derived air concentrations for ΣVMSs (ng/m³) at background sites on the perimeter of the WWTP were 479 ± 82.3 and comparable to results for the upwind samples at the landfills (333 ± 194). Order of magnitude higher concentrations of ΣVMSs (ng/m³) were found for on-site samples at the WWTPs (3980 ± 2620) and landfills (4670 ± 3360). Yearly emissions (kg/yr) to air were estimated and ranged from 60-2100 and 80-250, respectively, for the cyclic VMSs. These findings demonstrate and quantify for the first time, waste sector emissions of VMSs to the atmosphere.     

The freshwater planarian Polycelis felina as a sensitive species to assess the long-term toxicity of ammonia

Behavioural endpoints are a good link between physiological and ecological effects. However long-term behavioural endpoints are not uniformly studied over all different organism groups. For example behaviour has been scarcely studied in planarians. Unionized ammonia (NH₃) is one of the most widespread pollutants in developed countries, and is known to alter animal behaviour. In this study a long-term (30 d) bioassay was conducted to assess the effect of this pollutant on survival and behavioural activity (e.g. locomotion activity) of the freshwater planarian Polycelis felina. One control and three environmentally-realistic concentrations of unionized ammonia (treatments of 0.02, 0.05, and 0.09 mg N-NH₃ L⁻¹) were used in quintuplicate. The behaviour of planarians was measured after 0, 10, 20 and 30 d of ammonia exposure. Mortality was recorded every 2 d. Unionized ammonia increased mortality in the two highest NH₃ concentrations and the locomotory activity was depressed in all treatments after 20 d of exposure. Behavioural effect was observed at concentrations 20 times lower than the short-term LC50 for this species. Previous studies proposed safe concentrations of unionized ammonia of 0.01-0.10 mg N-NH₃ L⁻¹ to aquatic ecosystems, but our study has shown that these concentrations will affect planarians. Because planarians play a key role in streams (as predator/scavenger), safe concentrations should be below 0.02 mg N-NH₃ L⁻¹ to protect this species in the freshwater community. Our results can contribute to improve the knowledge about ammonia toxicity to freshwater ecosystems, we recommend that safe concentrations of unionized ammonia should be based on very sensitive species.     

Effects of salinity, DOM and metals on the fate and microbial toxicology of propetamphos formulations in river and estuarine sediment

Toxicity studies tend to use pure pesticides with single organisms. However, natural systems are complex and biological communities diverse. The organophosphate pesticide propetamphos (PPT) has been found exceeding regulatory limits (100 ng L⁻¹) in rivers. We address whether solution properties affect the fate of Analar (Analar-PPT) or industrial PPT (PPT-Ind) propetamphos formulations and whether propetamphos and metal toxicant effects are additive, antagonistic or synergistic? The sorption, desorption, biodegradation and microbial toxicology of Analar-PPT and PPT-Ind were investigated in Conwy River and estuary sediment. Results showed elevated salinity enhanced PPT sorption, while higher salinities increased PPT-Ind retention. Higher dissolved organic matter (DOM) and low salinity slowed Analar-PPT biodegradation (1.9 × 10⁻³ h⁻¹). Analar-PPT and PPT-Ind biodegradation was further reduced by low salinity, high DOM and dissolved Zn and Pb (6.3 × 10⁻⁴ h⁻¹, 1100 h t_½ for Analar-PPT; 7.5 × 10⁻⁴ h⁻¹, 924 h t_½ for PPT-Ind). Toxicity effects of PPT, Zn and Pb in equitoxic ratio were higher for PPT-Ind (4.7 μg PPT-Ind g⁻¹; 581 μg Zn g⁻¹; 395 μg Pb g⁻¹) than for Analar-PPT (34.6 μg PPT g⁻¹; 312 μg Zn g⁻¹; 212 μg Pb g⁻¹) whilst a toxicant ratio 1:100:10 suggested small quantities of Analar-PPT (EC₁₀ = 0.06 μg g⁻¹) affected microbial communities. The combined toxicity effect was more than additive. Thus, industrial formulations and pollutant mixtures should be considered when assessing environmental toxicity.     

The impact of production type and region on polychlorinated biphenyl (PCB), polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) concentrations in Canadian chicken egg yolks

Chicken eggs from five different production types (conventional, omega-3 enriched, free range, organic and free run) were collected, when available, from three regions (west, central and east) of Canada to determine persistent organic pollutant (POP) concentrations. Total polychlorinated biphenyl (PCB) concentrations (∑37 congeners) in yolks from the eggs ranged from 0.162 ng g⁻¹ lipid to 24.8 ng g⁻¹ lipid (median 1.25 ng g⁻¹ lipid) while the concentration of the sum of the 6 indicator PCBs ranged from 0.100 ng g⁻¹ lipid to 9.33 ng g⁻¹ lipid (median 0.495 ng g⁻¹ lipid). Total polychlorinated dibenzo-p-dioxin/dibenzofuran (PCDD/F) concentrations ranged from 2.37 pg g⁻¹ lipid to 382 pg g⁻¹ lipid (median 9.53 pg g⁻¹ lipid). The 2005 WHO toxic equivalency (TEQ) ranged from 0.089 pg TEQ_{PCDD/F+dioxin-like[DL]-PCB} g⁻¹ lipid to 12.8 pg TEQ_{PCDD/F+DL-PCB} g⁻¹ lipid (median 0.342 pg TEQ_{PCDD/F+DL-PCB} g⁻¹ lipid). PCB and PCDD/F concentrations were significantly different (p < 0.001) in egg yolks from different regions of collection. In contrast to observations in Europe, PCB and PCDD/F concentrations in Canadian egg yolks were not impacted solely by the production type (e.g., conventional, free range, organic, etc.) used to maintain the laying chickens. Additionally, only one Canadian free range yolk from western Canada (12.8 pg TEQ_{PCDD/F+DL-PCB} g⁻¹ lipid) exceeded the European toxic equivalent concentration limits for eggs (5 pg TEQ_{PCDD/F+DL-PCB} g⁻¹ lipid). This differs from observations in Europe where free range/home produced eggs frequently have higher POP concentrations than eggs from other production types. Median PCB dietary intake estimates based on consumption of eggs were less than 10 ng d⁻¹ while median PCDD/F intakes were less than 45 pg d⁻¹.