Laboratory tests of ammonium and barley straw extract as agents to suppress abundance of the harmful alga Prymnesium parvum and its toxicity to fish

Prymnesium parvum is a harmful alga whose blooms can cause fish kills in brackish waters. Two potential suppressants of this alga were tested, ammonium and barley straw extract (BSE), at temperatures of 10, 20 and 30 degrees C. Laboratory batch cultures were grown for 3 weeks at each temperature, with weekly doses of ammonium or BSE at either low or high levels, or a no-dose control treatment. The growth rate of P. parvum during exponential phase was highest at 20 degrees C and lowest at 10 degrees C, and was stimulated by the highest ammonium dose. Only cultures grown at 20 degrees C were toxic to fish. The highest ammonium dose abolished such toxicity and reduced the endpoint population density of P. parvum. BSE did not reduce the exponential growth rate, endpoint density, or toxicity to fish of P. parvum. The results support the use of ammonium additions, but not BSE, to suppress harmful blooms of P. parvum in those circumstances where the possible disadvantages can be managed.     

The combined toxic effects of nonpolar narcotic chemicals to Pseudokirchneriella subcapitata

This paper presents the toxicity data of 10 nonpolar narcotic chemicals on Pseudokirchneriella subcapitata (green algae) assessed by a new algal toxicity testing technique conducted under air-tight environment. Based on DO production, median effective concentration (EC50) varies from 1.73 mg/L (1-octanol) to 8,040 mg/L (2-propanol). The endpoint of algal growth rate reveals similar sensitivity as that from DO production. Compared to literature data, Pseudokirchneriella subcapitata and Nitrosomonas are apparently more sensitive to nonpolar narcotics than other organisms such as minnow, daphnia, and Tetrahymena pyriformis. Furthermore, good correlations between toxic effects observed from Pseudokirchneriella subcapitata and other aquatic organisms were found. Hence, algal toxicity test can be considered as a surrogate test for estimating the toxicity of nonpolar chemicals to fathead minnow, Microtox, activated sludge, Daphina magna, and Tetrahymena pyriformis. The combined effects of 13 binary mixtures of nonpolar chemicals were investigated using both additive-index method and isobologram analysis. Overall speaking, the joint actions between these chemicals are strictly additive. Model analyses indicate that these compounds act on identical reaction sites or receptors, which verify that these chemicals are of the same toxicity mechanism (narcosis).     

Analysis of toxicity tests on fish growth

We present a statistical analysis of bioassays for fish growth, such as the routine toxicity test that is described in the OECD guideline 210. The analysis is based on the Dynamic Energy Budget theory and a one-compartment kinetics for the toxic compound. It is fully process oriented. We compare a formulation in terms of direct effects on growth with indirect effects via assimilation and maintenance. All formulations characterize the effects by a no-effect concentration, a tolerance concentration and the elimination rate. Simplified formulations are obtained for very small and very large elimination rates. The accuracy of estimates for the no-effect concentration is judged with the profile likelihood function. The method is illustrated with applications to several data-sets for body size versus concentration of toxicant.     

Contribution for tier 1 of the ecological risk assessment of Cunha Baixa uranium mine (Central Portugal): II. soil ecotoxicological screening

This study presents the first ecotoxicological data concerning the soils of the area surrounding the Cunha Baixa uranium mine. Our main goal was to categorise soils from the area based on their toxicity profiles using a battery of cost- and time-effective bioassays (elutriate approach - Microtox and Daphnia acute tests; whole-soil approach - Microtox and avoidance assays with Eisenia andrei), as a part of tier 1 of an ongoing Environmental Risk Assessment. No acute toxicity was found for any of the 10 sites/soils using Microtox or Daphnia. On the contrary, the behavioural response of E. andrei was found to be an extremely sensitive endpoint, allowing the discrimination of highly to moderately toxic soils based on their toxicity profiles (as a function of soil concentration). Soils exhibiting highest toxicity corresponded to areas subjected to runoffs or sludge deposition from the aquatic effluent, while non-toxic soils were farthest to the mine. Data obtained in avoidance assays strengthen the previous evaluation of risks based on chemical data and supported decisions about proceeding for tier 2.     

高海拔隧道施工环境CO浓度控制标准研究

为研究高海拔隧道施工环境CO浓度对人体毒性的影响及CO浓度控制标准,本文基于人体碳氧血红蛋白(COHb)模型对不同海拔高度隧道施工环境CO浓度对人体毒性的影响进行了计算分析。结果表明,相同CO浓度下,仅改变呼吸量不会导致CO对人体毒性影响程度的改变;相反,随着海拔高度的增大,CO对人体毒性的作用显著增强,且CO浓度较低时,随着海拔高度增加人体COHb比值增大越明显,其毒性增长程度也更突出。基于隧道施工人员连续工作8 h体内COHb不高于2.5%为基准,建立了不同海拔高度隧道施工CO浓度控制标准模型。     

In vitro evaluation of the cytotoxicity of iron oxide nanoparticles with different coatings and different sizes in A3 human T lymphocytes

The ever expanding use of engineered nanoscaled materials has brought about a commensurate growth in concern about their potential risks to human and environmental health. Toxicity of nanoparticles could vary with their physicochemical parameters. The dependence of cytotoxicity on particle size and surface coating of iron oxide nanoparticles was investigated in this in vitro study using the A3 human T lymphocyte as a model. Two different sizes (10 nm and 50 nm) and two different surface coatings (amine and carboxyl groups) of iron oxide (IO) nanoparticles were tested with fluorescein diacetate (FDA) assay and WST-1 assay. In the 1-h FDA assay with PBS, IO nanoparticles did not show size-dependent toxicity to A3 cells in terms of mass concentration; however, in terms of the number of particles per well and the total surface area, they did exhibit size-dependent toxicity. Fifty nanometer IO nanoparticles are more toxic than the 10 nm counterparts. The results of both the 24-h FDA and WST-1 assays in a complete growth medium indicate size- and surface coating-dependent toxicity to A3 cells in terms of mass concentration. IO nanoparticles of the smaller size are more toxic than those of the larger size. IO nanoparticles with the carboxyl group have a higher toxicity than those with the amine group. However, in the 24-h FDA assay, in terms of the number of particles per well and the resultant total surface area per well, the 50 nm IO nanoparticles are more toxic than those of size 10 nm. In terms of mass concentration, the number of particles per well and the total surface area, both of the 24-h assays showed the consistent results that IO nanoparticles with the carboxyl group have a higher toxicity than those with the amine group.     

Analysis of toxicity tests on Daphnia survival and reproduction

We present a statistical analysis of bioassays for Daphnia survival and reproduction, such as the routine toxicity test that is described in the OECD guideline 202. The analysis is based on the Dynamic Energy Budget theory and a one-compartment kinetics for the toxic compound. It is fully process oriented. We compare a formulation in terms of effects on survival during oogenesis to various direct and indirect effects on the energetics of reproduction. All formulations characterize the effects by a no-effect concentration, a tolerance concentration and the elimination rate. We conclude that all options lead to similar no-effect levels. We compare the analysis to the standard NOEC/EC50 analysis and conclude that our analysis is both simpler and more effective.     

Combined effect of copper, cadmium, and lead upon Cucumis sativus growth and bioaccumulation

Cucumis sativus (cucumber) was tested to assess an ecotoxicity in soils contaminated by the heavy metals copper (Cu), cadmium (Cd), and lead (Pb) separately and in combinations. The toxicity endpoint was plant growth, which was measured as shoot and root lengths after 5 day exposure. Sum of toxic unit (TU) at 50% inhibition for the mixture (EC50mix) was calculated from the dose (TU-based)-response relationships by the Trimmed Spearman-Karber method. Binary metal combinations of Cu+Cd, Cu+Pb, and Cd+Pb produced all three types of interactions; concentration additive (EC50mix=1TU), synergistic (EC50mix<1TU), and antagonistic (EC50mix>1TU) responses. Ternary combination of Cu+Cd+Pb produced an antagonistic response for the growth of Cucumis sativus. Bioaccumulations of Cu, Cd, and Pb were observed in Cucumis sativus and the bioaccumulation of one metal was influenced by the presence of other metals in metal mixtures. In general, antagonistic and/or synergistic responses reflected bioaccumulation patterns in some binary combinations, but the patterns in mixtures were not always consistent with toxicity data. This study indicated that TU approach appears to be a good model to estimate the combined effect of metals in plant systems, and mixture toxicity may be closely-related to the bioaccumulation pattern within plants. Combined effects of mixtures have to be taken into account to ecological risk assessment.     

Alkalinity measurements within natural waters: towards a standardised approach

A discussion on the measurement of alkalinity in bicarbonate bearing and acidic waters is presented as a move towards developing a standardised approach within the aquatic sciences. The discussion is based on theoretical and practical considerations. Practical illustrations are provided from measurements of calcium bicarbonate bearing waters (River Thames) and acidic to near neutral waters from acidic soil systems with calcium bearing groundwater sources (the mid-Wales region and the Scottish Dee basin). A comparison of single endpoint and Gran procedures is made and the various error terms assessed. It is concluded that single endpoint and Gran methodologies are applicable in the standard pH titration used in aquatic research (pH 4.5-4.0). However, analytical errors increase, particularly for the single endpoint titration, the lower the endpoint/endpoint-range in pH. For the Thames, the value of a single endpoint over a Gran procedure is illustrated. The Thames results show that some buffering components may still be titrated out within the Gran titration range used: this leads to an underestimate in the alkalinity. Indeed, by making a comparison between single endpoint and Gran alkalinity measurements, the Thames results indicated the presence of unexpected buffering components: the interrogative nature of this type of analysis is highlighted. A standardised approach is outlined.     

Toxic effects of cupric,chromate and chromic ions on biological oxidation

Using a completely mixed, continuously operated, lightly loaded, laboratory activated sludge system, the toxic effects of cupric, chromic and chromate ions under conditions of shock loading were observed. These were determined with the aid of a total carbon analyzer and simple mass balance techniques in terms of conversion of the organic nutrient fed. The distribution of the metal ion between aqueous solution and suspended solids was measured using atomic absorption spectrophotometry. Toxic effects were in the order: Cu²⁺ > CrO₄^2? > Cr³⁺ while the reductions in conversion were 90, 50 and 20 per cent, respectively, for concentrations of 5 ppm metal ion. Cupric ion toxicity was directly proportional to the weight of copper absorbed per unit mass of suspended matter within the total copper concentration range (0–5.5 ppm) studied. This toxicity decreased markedly with increased suspended solids concentration: an 80 per cent decrease in conversion at 210 ppm suspended solids was reduced to a negligible quantity (3 per cent) by increasing the suspended solids to 4000 ppm. At 210 ppm suspended solids, 34 per cent of the added copper was removed by the sludge in 7 h.The results of this work suggest that the toxic effect of metal ions on a sewage plant activated sludge system could be reduced by rapidly increasing the suspended solids concentration, possibly by the addition of dried sludge. It is also implied that the effect on dilute systems such as lagoons would be much greater because of the low suspended solids.This work supports a mechanism involving rapid adsorption of the cupric ion by both viable and dead sludge followed by a slower rate determining step resulting in the toxic effect. The first order rate constant for substrate utilization was found to be (1.07 ± 0.6) h^?1.     

Toxicity of the 13 priority pollutant metals to Vibrio fisheri in the Microtox chronic toxicity test

The Microtox Acute Toxicity Test has been successfully used to measure the toxicity of metals and other pollutants at high concentrations (ppm) in selected environmental samples. However, metals and other toxicants are often found in much lower concentrations (ppb) in many municipal wastewaters and receiving waters. In order to assess the toxicity of these pollutants in these samples, a more sensitive toxicity assay is needed. The Microtox chronic toxicity test has been developed to measure the sublethal effect of toxicants over multiple generations of the test species, Vibrio fisheri. In this study, the toxicity of the 13 priority pollutant metals [i.e. As, Se, Cd, Cr (III and VI), Cu, Pb, Sb, Ag, Tl, Zn, Be, Hg and Ni] to V. fisheri was evaluated using the Microtox chronic toxicity test. In this test, the inhibitory concentration (IC), lowest observable effect concentration (LOEC), and no observable effect concentration (NOEC) were obtained after 22-h of incubation at 27+/-1 degrees C, by comparing the light output of the control to that of the test sample. Among the 13 priority pollutant metals, beryllium (Be) was found to be the most toxic in the test (LOEC=0.742-1.49 microg/l) while thallium (Tl) was the least toxic (LOEC=3840-15300 microg/l). The LOECs for copper (as Cu) and lead (Pb) in reagent (ASTM Type I) water were 6.78-13.6 microg/l and 626-1251 microg/l, respectively. The toxicity of copper sulfate (as Cu) in reagent water was shown and significantly reduced with the addition of natural organic matter (fulvic acid) or EDTA to the sample. The LOEC values for the 13 priority pollutant metals in this test were comparable to or lower than those reported for commonly used aquatic toxicity tests, such as the Ceriodaphnia dubia assay.     

Analysis of bioassays with time-varying concentrations

In the analysis of ecotoxicological bioassays the concentration of the test compounds is assumed to be constant. In many situations this assumption is questionable, as various processes may cause a substantial decline in the concentration during exposure. This leads to difficulties in the estimation of parameters that characterise the toxicity of the test compound. As a solution to this problem, time-varying concentrations are often replaced by their mean values for the estimation of toxicity parameters. However, Monte-Carlo simulations show that this approach results in biased estimates of the toxicity parameters. As an alternative approach, we propose models to estimate one important toxicity parameter, the no effect concentration, in situations where the concentration of the compound varies in time. These models are extensions of the DEBtox model (Kooijman and Bedaux, 1996) which is based on biological assumptions about toxicokinetics and toxic effects. We also propose a new approach for the estimation of toxicity parameters for strongly accumulating non-metabolisable compounds. This approach does not require any kinetics assumption. Computer simulation and experimental data confirm the relevance of the different proposals.     

Acute and early life stage toxicity of industrial effluent on Japanese medaka (Oryzias latipes)

To develop the whole effluent toxicity testing methods (WET), embryo larval stage toxicity test using Japanese medaka (Oryzias latipes) was conducted to evaluate an effluent from a banknote printing plant (BPP). The method is based on acute toxicity using endpoint of 96-h larval morality and on chronic toxicity using endpoints such as the time to hatch, hatching success, deformity, growth rate, swim-up failure, accumulative mortality and sexual ratio. In test for 96-h larval mortality, LC50 (the concentration was lethal to 50% of newly hatching medaka larvae) was 72.9%. In chronic toxicity test, newly fertilized embryos (<5-h old) were exposed to 1%, 6.25%, 12.5%, 25%, 50% effluent concentrations and to 200 mug/l BPA in a 24-h static renewal system at 25+/-1 degrees C until 15 day post-hatch. The results showed that all chronic endpoints were significantly different from the control at 50% dilution (p < 0.01). Embryos began to show lesions on 4th day at higher concentrations (12.5%, 25%, 50% BPP effluent concentrations). Treatment group of 25% dilution showed delayed time to hatch. A reduction in body weight was observed at 25% dilutions for males and females, respectively. Deformities were observed in newly hatched larvae at 25% and 50% BPP effluent concentrations. At 25% dilution, sex ratio of larvae was alternated and there was feminization phenomenon. We conclude that embryo larval stage test using medaka is feasible to evaluate both acute and chronic toxicities and potential endocrine disrupting activity of industrial effluents.     

Urban diffuse pollution: key data information approaches for the Water Framework Directive

The Water Framework Directive (WFD) provides a coherent structure within which the problems of diffuse urban pollution can be effectively tackled and managed. The context of impermeable surface water quality within the terms of the Directive are outlined, and the pollutant sources and loadings associated with various urban land uses are identified. Stormwater flows and quality are sufficient to prejudice any ‘good’ ecological potential, particularly in terms of chronic receiving water sediment toxicity. A simple volume–concentration method for the prediction of pollutant loadings and impact assessment on a subcatchment scale is described and discussed.     

Modeling the ecological impact of heavy metals on aquatic ecosystems: a framework for the development of an ecological model

In this paper, an ecological model is proposed to predict the effects of heavy metals on aquatic ecosystems. The bioavailable concentration of metals and a concept of toxicity strength (TS) are combined. The integrated ecological model relates the transport, distribution and speciation of heavy metals and their toxicity, and the effect of environmental variability on metal toxicity. It also emphasizes the link between physical and chemical processes of heavy metals in rivers and ecological effects. Based on the data obtained from research in the CERP project (Co-operative Ecological Research Project), the ecological impact of heavy metals on the aquatic ecosystem of the Le An River (polluted by heavy metals from a copper mine) was predicted. The results show that the estimated values of toxicity strength for surface water are in agreement with the percentage inhibition for the test organism (P. phosphoreum) and that the predicted ecological effect of polluted sediment is consistent with natural variability in aquatic ecosystems.     

Sublethal toxicity and biotransformation of pyrene in Lumbriculus variegatus (Oligochaeta)

The aim of this work was to study the toxicity and biotransformation of polyaromatic hydrocarbon (PAH) pyrene in the oligochaete aquatic worm, Lumbriculus variegatus. PAHs are ubiquitous environmental pollutants that pose a hazard to aquatic organisms, and metabolizing capability is poorly known in the case of many invertebrate species. To study the toxicity and biotransformation of pyrene, the worm was exposed for 15 days to various concentrations of water-borne pyrene. The dorsal blood vessel pulse rate was used as a sublethal endpoint. Pyrene biotransformation by L. variegatus was studied and the critical body residues (CBR) were estimated for pyrene toxicity. The toxicokinetics of pyrene uptake was evaluated. A combination of radiolabeled (¹⁴C) and nonlabeled pyrene was used in the exposures, and liquid scintillation counting (LSC) and high-pressure liquid chromatography were employed in both water and tissue residue analyses. The results showed that L. variegatus was moderately able to metabolize pyrene to 1-hydroxypyrene (1-HP), thus demonstrating that the phase-I-like oxidizing enzyme system metabolizes pyrene in L. variegatus. The amount of the 1-HP was 1-2% of the amount of pyrene in the worm tissues. The exposure to pyrene reduced the blood vessel pulse rate significantly (p < 0.05), showing that pyrene had a narcotic effect. The estimated CBRs remained constant during the exposure time, varying from 0.120 to 0.174 mmol pyrene/kg worm wet weight. The bioconcentration factors (BCF) decreased as exposure concentration increased. It was suggested that the increased toxicity of pyrene accounted for the decrease in BCFs by lowering the activity of the organism.     

Concentrations of polybrominated diphenyl ethers, polychlorinated dibenzo-p-dioxins and dibenzofurans, and polychlorinated biphenyls in human blood samples from Korea

Analysis of blood samples is an effective way of evaluating contamination by persistent pollutants such as polybrominated diphenyl ethers (PBDEs), polychlorinated dibenzo-p-dioxin/furans (PCDD/Fs), and polychlorinated biphenyls (PCBs) in human population. Concentrations of PBDEs, PCDD/Fs and PCBs were measured in the blood of laborers (n = 13) working full time in two different municipal waste incinerator (MWI) plants and residents from the general population (n = 22) living in areas near MWIs in Korea. The concentrations of PBDEs were found to be slightly higher in the blood of incineration workers (8.61-46.05 ng/g lipid; mean, 19.33 ng/g lipid; median, 15.94 ng/g lipid) in comparison to that of residents from the general population (7.24-28.89 ng/g lipid; mean, 15.06 ng/g lipid; median, 14.34 ng/g lipid). The total average PCDD/Fs and PCB TEQ concentration was 20.11 pg/g lipid, averaged over incineration workers (17.73 pg/g lipid) and the general population (21.52 pg/g lipid). In addition, the average total crude concentration of PCDD/Fs was 7.40 ng/g lipids, which was 4.1 times greater than for PBDEs. Congener specific analysis confirmed that BDE 47 was a predictive indicator for total PBDE concentration (correlation coefficient r = 0.912), and that PCB 153 was a predictive indicator for total PCB concentration (r = 0.967). The PBDE levels in human blood in Korea are much higher than those reported in other countries. The presence of the BDE 183 congener was characteristic in the blood of workers from an electronic dismantling facility in MWIs.     

Toxicity of metals and metal mixtures: analysis of concentration and time dependence for zinc and copper

The toxic effects of heavy metals, zinc and copper, in unary and binary solutions were studied using the Microtox acute toxicity test which relies upon the attenuation of light intensity emitted by Vibrio fischeri. The toxic effect Gamma (ratio of the light intensity lost at time t to the light intensity remaining at time t) of zinc could be related to its concentration [X] by a two-parameter equation Gamma=a(1-exp(-b[X])), where parameter a was a function of time and b equal to 0.88L/mg. The toxic effect of zinc asymptotically approached a maximum with respect of to concentration at all times. The toxic effect of copper was fundamentally different from that of zinc, and increased exponentially with concentration without any limiting maximum value. It could also be described by a two-parameter equation, however, the equation had the form Gamma=aexp(b[X]), where parameter a was a constant and b a function of time. The different functional dependencies (of the toxic effect on the metal concentration) of zinc and copper indicate that different toxicity/inhibition mechanisms were possibly responsible for the attenuation of light intensity for the two metals. The toxic effects of binary mixtures were substantially higher than those expected on the basis of additivity of individual metals. No simple correlations were obtained that could relate the toxic effect of binary mixture to those of individual metals. A better understanding of metal-microbe interactions is needed for achieving predictive capability for toxic effect of mixtures.     

Oxidative stress responses of Daphnia magna exposed to TiO2 nanoparticles according to size fraction

Size is one of important factors determining titanium dioxide nanoparticle (TiO₂ NP) toxicity since penetration is eased with decreasing particle size and bioavailability is increased. The effect of particle size on oxidative stress against titanium dioxide nanoparticle (TiO₂ NP) exposure to Daphnia magna was investigated with both acute and chronic toxicity tests. Experiments on biochemical responses, repeatedly performed after size fractionation of the NPs using filtration, focused on the activities of four antioxidant enzymes: catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPX), and glutathione-S-transferase (GST). In the chronic bioassay, the mortality was significantly increased at TiO₂ NP concentrations of 5 and 10 mg/L; however, no reduction of the reproduction ability was observed. Biochemical measurements showed that TiO₂ NP exposure significantly increased the antioxidant enzyme activities in D. magna. CAT, GPX and GST, but not SOD, showed a concentration-dependent increase. In terms of size fraction, particles ranging from 400 to 800 nm exhibited an increase of antioxidant enzyme activities in GST and GPX. These biochemical level observations suggested that TiO₂ NP toxicity was mediated by reactive oxygen species (ROS) generation via oxidative stress in D. magna. The increased mortality at the concentration of 5 mg/L in the chronic bioassay was attributed to accumulated TiO₂ NPs in the intestine of D. magna, which might induce effects such as oxidative stress relating to the induction of antioxidant enzymes.