Sensitivity evaluation of the Daphtoxkit and Thamnotoxkit microbiotests on blind samples

At the Oregon State University Workshop we utilized two "culture/maintenance-free" microbiotests, the Thamnotoxkit F with the anostracan crustacean Thamnocephalus platyurus and the Daphtoxkit F magna with the cladoceran crustacean Daphnia magna, to determine the toxicity of water samples in a blind format. The Thamnotoxkit was applied to 7 samples and the Daphtoxkit to 12 samples. The chemical composition of the water samples to which the Toxkit microbiotests had been applied was disclosed a posteriori by the organizers and appeared to contain chlordimeform, colchicine, phosdrin, mercuric chloride, sodium arsenite, metham sodium, sodium cyanide, trimethylol propane phosphate, p-chlorophenol and a natural sediment sample containing mercury. Three of the water samples were blanks that had not been spiked with chemicals. No false positives were obtained with the two Toxkits and all the toxic waters were earmarked as such by the microbiotests, except trimethylol propane phosphate, which was not found to induce acute effects in Daphnia magna in the non-diluted water sample containing 100 mg l(-1) of this compound.     

Toxicity assessment of wastewaters, river waters, and sediments in Austria using cost-effective microbiotests

The toxicity and chemical quality of surface water and sediment in the River Traun in Austria were studied because of recurrent fish mortality in some alpine rivers over the last few years. The analyses were carried out on samples collected during winter and summer upstream and downstream of two municipal wastewater treatment plants (WWTPs) and on effluents taken at the points of discharge of these two plants. Toxicity tests were performed on 20 samples of surface water, effluent, and sediment pore water. The test battery was composed of microbiotests with protozoans (Protoxkit F), microalgae (Algaltoxkit F), crustaceans (Daphtoxkit F magna and Thamnotoxkit F), and a higher plant (seed germination and root elongation assay on cress). Direct contact tests were performed on whole sediment with crustaceans (Ostracodtoxkit F). The physical-chemical characteristics of the surface water, effluent, and sediment pore water samples analyzed were conductivity, total hardness, pH, O(2), BOD(5), TOC, DOC, AOX, NH(4), NH(3), NO(2), PO(4)--P, Cd, Pb, Cu, and Zn. The toxicity data were expressed as percentage mortality or percentage inhibition, depending on the effect criterion of the respective assay. None of the water samples collected upstream and downstream of the WWTPs showed any significant (short-term) toxicity in either winter or in summer, but the effluents of the first municipal wastewater treatment plant were toxic to some of the test biota. All the sediment pore water samples induced serious inhibition of root growth of cress, and several pore waters were toxic to other test biota as well, particularly at the outlets of the WWTPs. The toxic character of some sediments was confirmed by direct contact tests with the ostracod crustacean. The chemical analyses did not reveal particularly high concentrations of any chemical that is very toxic. As a result no direct causal relationship could be established between the detected toxic effects and the chemical composition of the surface waters or sediment pore waters. The outcome of this preliminary study again highlights the need to complement chemical analyses with toxicity tests to determine the toxic hazard to aquatic environments that may be threatened by contamination. Furthermore, the investigations also confirmed the need to apply a battery of tests for an ecologically meaningful evaluation of the hazards of waters, sediments, and wastewaters. Finally, the results of the 360 bioassays performed show that culture-independent microbiotests are practical and reliable tools for low-cost toxicity monitoring of aquatic environments.     

Assessment of toxicity and genotoxicity of hydrophobic organic compounds in wastewater

This review highlights and discusses current state of the art and limitations in evaluation and assessment of potential (geno)toxic impact of particle-bound hydrophobic organic compounds (HOCs) in wastewaters on receiving ecosystems. Despite extensive work on whole effluent toxicity testing and concomitant development of protocols for identifying chemical toxicants, little has been done to develop procedures and protocols to identify (geno)toxicity of the particle phase from industrial or municipal wastewaters. Some studies, however, have shown that particulate matter is of considerable importance in the delivery of genotoxins to receiving waters. Further, it has been suggested that such particle-bound HOCs deposited in receiving waters often result in long-term environmental impact. As a consequence, particle-bound HOCs (geno)toxins should be recognized as an important potential hazard. The sparsity of work leads to suggestion of further research to improve understanding of the contribution of these particle-bound pollutants from liquid wastes and their specific role in aquatic ecosystems. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 241–247, 1999     

Application of a sediment quality triad and different statistical approaches (Hasse diagrams and fuzzy logic) for the comparative evaluation of small streams

In order to evaluate the ecotoxicological contamination of 12 aquatic sites in streams within the catch ment area of the Neckar River, a sediment quality triad (SQT) approach was applied. In contrast to Chapman's original triad approach, not only sediments, but also surface waters were examined. In brief, to obtain a com prehensive insight into the potential ecotoxicological hazard, both acute toxicity and more specific effects such as mutagenic, genotoxic, teratogenic, dioxin- and estrogen-like responses were recorded. Different statistical methods (ranking, cluster analyses, Hasse diagram techniques, and fuzzy logic) for the evaluation and presentation of the SQT data were compared with respect to the needs of environmental decision-making. Results document advan tages and disadvantages of the methods applied for the evaluation and classification of data within the complex data matrixes. The ranking procedure presented as well as the Hasse diagram technique seem to be suitable tools to elucidate the pattern of the ecotoxicological load. However, these classification methods require expert knowledge to interpret the ranking results with respect to decision-making in environmental sciences and policy. In contrast, fuzzy logic allows both to develop site-specific expert systems in order to assess the ecotoxicological burden and to give insight into the pattern of the contamination.     

Interlaboratory comparison studies of the luminescent bacteria toxicity bioassay

This article presents results and conclusions obtained from the interlaboratory comparison studies of the luminescent bacteria toxicity assay performed during three consecutive years. This assay is one of the recommended bioassays used in the current Spanish and Catalonian regulations for toxicity assessment of industrial discharges. It is used routinely to assess the level of contamination of industrial wastewaters, and to calculate a levy related to volume and contaminant load of industrial wastewater discharges. The objective of these exercises was to evaluate the repeatability of results obtained using this bioassay when used to assess toxicity of diverse wastewaters. Differences in bacterial sensitivity toward chemical substances, storage conditions, reagents, and sample handling, and minute differences in test procedure, may result in increased deviations when testing identical samples in different laboratories. A discussion on experimental conditions and test variables that may affect variability of results of this bioassay is provided. Studies were performed yearly from 1993 to 1995, using four series of five samples in each exercise. Samples tested included standard solutions of pure compounds, and effluents collected either from industrial or municipal discharges. The number of participants increased steadily (11 in 1993, 19 in 1994, 24 in 1995), which indicates increasing awareness of private and public laboratories in this type of quality assurance exercise. Overall, the relative standard deviations were respectively 48.8, 42.2, and 35.5%, which indicates not only a better knowledge of the nature of the assay, but also a trend of improvement in experimental procedures and quality assurance programs within each laboratory. © 1997 John Wiley & Sons, Inc. Environ Toxicol Water Qual 12 : 283–294, 1997     

Use of health hazard criteria for estimating the hazard potential of chemicals to water in case of a spill

Accidental spills resulting in severe pollution can occur during transportation or handling of large volumes of chemicals. To address this problem, chemicals are classified according to the level of hazard to man and the environment in order to then define graduated technical standards. Three regulatory examples (enforced or drafted for transport and industrial installations in Europe) covering aspects of limnic as well as sea water are discussed in regard to health aspects of pollution. Whereas for the safety of seagoing tankships an exposure orientated combination of health and environmental aspects is used, for industrial plants in Germany a scoring system based on the European Union's Risk Phrase system is applied. The health-related parameters primarily used for hazard classification are repeated-dose toxicity and acute oral and dermal toxicity. Acute oral toxicity is most widely used because of the ready availability of data. Carcinogenicity is treated as the most important hazard. The report discusses the importance of dermal exposure, aspiration, and endocrine disruption as parameters as well as the importance of health criteria for the protection of aquatic organisms.     

Cyst-based toxicity tests XIV--application of the ostracod solid-phase microbiotest for toxicity monitoring of river sediments in Flanders (Belgium)

In view of the need for rapid and low-cost solid-phase assays for contaminated sediments, a new 6-day "culture/maintenance-free" microbiotest has been developed with the freshwater ostracod crustacean Heterocypris incongruens at the Laboratory for Biological Research in Aquatic Pollution at the Ghent University in Belgium. The sensitivity of the Ostracodtoxkit F has been compared with that of the 10-day sediment contact test with the amphipod crustacean Hyalella azteca and the two pore water assays (on the anostracan crustacean Thamnocephalus platyurus and the microalgae Raphidocelis subcapitata) selected by the Flemish Environmental Agency for initial hazard assessment of contaminated sediments. The exercise was performed on 26 sediments collected at random from various rivers of the Flemish hydrographic basin in Belgium. The toxicity data ranged from nontoxic to highly toxic for the solid-phase assays and showed that the mortality of the two test biota varied from "nearly identical" to "substantially different," depending on the sediment. The correlation coefficient for the data pairs was weakly positive (r = 0.60), mainly because of 5 samples for which a low mortality had been noted with the ostracod versus a much higher mortality for the amphipod. However, for 4 out of the 5 samples of concern, a substantial growth inhibition was recorded for H. incongruens, showing that this assay eventually performed as did the amphipod test in detecting the toxic character of the sediments. The comparison of toxicity data of the two solid-phase assays with those of the two pore water tests again confirmed that both types of bioassay provided complementary (nonredundant) information. On the basis of its various advantages (independence of stock culturing/maintenance, user-friendliness, precision, and time and cost savings) the new ostracod microbiotest appears to be a promising tool for routine toxicity assessment of contaminated sediments.     

Cyst-based toxicity tests XV--application of ostracod solid-phase microbiotest for toxicity monitoring of contaminated soils

A new "culture/maintenance-free" microbiotest has recently been developed for "direct-contact" toxicity determination of contaminated sediments. The 6-day Ostracodtoxkit F makes use of the neonates of the ostracod crustacean Heterocypris incongruens hatched from dormant eggs (cysts). The new low-cost assay has already been applied in three studies on river sediment from Flanders (Belgium) and from Canada and was found to perform comparably to the 10-day Hyalella azteca and Chironomus riparius tests in detecting and quantifying sediment toxicity. Taking into account that sediments are in fact underwater soils, the ostracod microbiotest was tentatively applied on 15 contaminated soils from Flanders (Belgium), and its sensitivity (based on mortality as the test criterion) was evaluated in comparison to the 28-day reproduction inhibition assay with the springtail Folsomia candida. The results revealed that the ostracod test species was as sensitive as or, in several samples, even more sensitive than the springtails. Leachate experiments on the same soil samples also showed that in most cases ostracod mortality was a result of the (nonsoluble) toxicants bound to the solid-phase particles, rather than of those that had dissolved in the water phase. Providing confirmation of these first findings through additional studies, the new culture/maintenance-free ostracod microbiotest seems to have good potential as a low-cost and user-friendly tool for routine toxicity monitoring of contaminated soils.     

Application of Toxkit microbiotests for toxicity assessment in soil and compost

The potential of Toxkit microbiotests to detect and analyze pollution in agricultural soil and the quality of compost was studied. The toxicity tests used included seed germination biotests using cress salad (Lepidum sativum L.), tomato (Lycopersicum esculentum L.), and cucumber (Cucumis sativus L.), and the Toxkit microbiotests included those with microalgae (Selenastrum capricornutum), protozoa (Tetrahymena thermophila), crustaceans (Daphnia magna, Thamnocephalus platyurus, and Heterocypris incongruens), and rotifers (Brachionus calyciflorus). Experiments on compost were undertaken in a modified solid-state fermentation system (SSF) and under field conditions (in a windrow). To promote the composting process, two strains of Trichoderma (Trichoderma lignorum and Trichoderma viride), as well as a nitrification association that regulated the nitrogen-ammonification and nitrification processes were applied.     

Tests for the toxicity assessment of cyanobacterial bloom samples

Cyanobacterial (blue-green algal) blooms are one of the common consequences of the increasing eutrophication of surface waters. The production of cyanobacterial toxins and their presence in drinking and recreational waters represents a growing danger to human and animal health. Due to a lack of toxin standards and to resource limitations on the wide-scale use of analytical methods (e.g., high-performance liquid chromatography, enzyme-linked immunosorbent assay (ELISA)) in cyanobacterial toxin monitoring, it is necessary to assess and to develop additional methods for their detection and estimation. Microbiotests using invertebrates offer a possible approach for the inexpensive and straightforward detection and assessment of cyanobacterial bloom toxicity. Three microbiotests with: Thamnocephalus platyurus, Daphnia magna, and Spirostomum ambiguum were examined with bloom samples containing hepatotoxic microcystin-LR and up to five additional microcystin variants. Two kinds of cyanobacterial bloom sample preparations were tested: crude extracts (CE) and purified extracts (PE). The highest toxicity was found when CE was used for microbiotests. The sensitivity of microorganisms decreased from S. ambiguum to T. platyurus and to D. magna. A statistically significant correlation was found between microcystin concentration and T. platyurus biotest, and between mouse bioassay and S. ambiguum results. Addition of Me2SO (1%, v/v) is a possible method to increase the sensitivity of the microorganisms for microcystin-LR.     

Bioassays and biochemical biomarkers for assessing olive mill and citrus processing wastewater toxicity

The toxicity and the biochemical effects of olive mill wastewater and citrus processing wastewater were evaluated using acute toxicity bioassays (Gammarus pulex and Hydropsyche peristerica) and biochemical biomarkers (acetylcholinesterase [AChE] and glutathione S‐transferase [GST]). The bioassays indicated toxic properties of olive mill and citrus processing wastewaters. The 24 h LC₅₀ values of olive mill wastewater ranged from 2.64% to 3.36% for G. pulex and 3.62% to 3.88% for H. peristerica, while the LC₅₀ of citrus processing wastewater was 25.26% for G. pulex and 17.16% for H. peristerica. Based on a five‐class hazard classification system applied for wastewaters discharged into the aquatic environment, olive mill wastewater and citrus processing wastewater were classified as highly toxic and toxic, respectively. Results of the biochemical biomarkers showed that both agroindustrial effluents at increasing sublethal wastewater concentrations could cause inhibition of the AChE and induction of the GST activities. These first results showed that both species as well as their AChE and GST activities have the potential to be used as indicators and biomarkers for assessing olive mill and citrus processing wastewaters quality. © 2010 Wiley Periodicals, Inc. Environ Toxicol, 2011.     

A proposal to improve clarity and communication in the EU Classification process for chemicals for carcinogenicity and reproductive and developmental toxicity

There is an issue in the EU classification of substances for carcinogenicity and for reproductive or developmental toxicity which has brought difficulties to those involved in the process. The issue lies in the inability of the classification system to distinguish between carcinogens and reproductive toxicants with different levels of concern. This has its origins in the early years of toxicology when it was thought that a relatively small number of chemicals would be either carcinogens or reproductive toxicants, but this has turned out not to be the case. This can cause problems in communicating to the users of chemicals, including the public, the nature of the hazard presented by chemicals. Processes have been developed within the classification system for setting specific concentration limits which assess the degree of hazard for carcinogens and reproductive toxicants as high, medium or low. However these categories are not otherwise used in classification. It is proposed that their wider use would bring the advantages of transparency, clarity of communication, certainty of the process and would allow chemicals with a high degree of hazard to be identified and managed in an appropriate way. Copyright © 2014. The Authors. Journal of Applied Toxicology Published by John Wiley & Sons Ltd.     

Incorporating potency into EU classification for carcinogenicity and reproductive toxicity

Although risk assessment, assessing the potential harm of each particular exposure of a substance, is desirable, it is not feasible in many situations. Risk assessment uses a process of hazard identification, hazard characterisation, and exposure assessment as its components. In the absence of risk assessment, the purpose of classification is to give broad guidance (through the label) on the suitability of a chemical in a range of use situations. Hazard classification in the EU is a process involving identification of the hazards of a substance, followed by comparison of those hazards (including degree of hazard) with defined criteria. Classification should therefore give guidance on degree of hazard as well as hazard identification. Potency is the most important indicator of degree of hazard and should therefore be included in classification. This is done for acute lethality and general toxicity by classifying on dose required to cause the effect. The classification in the EU for carcinogenicity and reproductive toxicity does not discriminate across the wide range of potencies seen (6 orders of magnitude) for carcinogenicity and for developmental toxicity and fertility. Therefore potency should be included in the classification process. The methodology in the EU guidelines for classification for deriving specific concentration limits is a rigorous process for assigning substances which cause tumours or developmental toxicity and infertility in experimental animals to high, medium or low degree of hazard categories by incorporating potency. Methods are suggested on how the degree of hazard so derived could be used in the EU classification process to improve hazard communication and in downstream risk management.     

ISTA13--international interlaboratory comparative evaluation of microbial assay for risk assessment (MARA)

The microbial assay for risk assessment (MARA) is an innovative system based on an array of 11 different microbial species freeze-dried in a 96-well micro-titer plate. Developed for testing the toxicity of chemicals, mixtures, and environmental samples, the assay employs species of a taxonomically diverse range. In addition to 10 prokaryotic species, a eukaryote (yeast) is included in the range. The MARA's innate scope of a multi-dimensional test allows determination of toxicity based on a unique assay fingerprint or index, numerically expressed as the mean microbial toxic concentration (MTC). The most significant potential of the test is in the additional inference that can be conveyed to the toxicity evaluation because of the presence of each of the constituent species. The performance of MARA was evaluated to ascertain its capability and potential scope in an intralaboratory trial. Sensitivity to toxicants and different environmental samples was assessed. Evaluation included comparison with other tests; namely Microtox, invertebrate (Daphnia magna and Thamnocephalus platyurus) microbiotests, and respiration- and nitrification-inhibition tests. MARA's performance was further assessed with the implementation of an international interlaboratory trial. This involved the participation of 13 laboratories ranging from academic establishments to regulatory agencies. The results of the testing will be presented with assessment of the extent of variability and specific assay components. The trial evaluation indicated that performance of the assay was satisfactory and the results were within the acceptable range. MARA is a robust multispecies assay offering scope for toxicity assessment of a diverse range of samples.     

Toxicity analysis of leachates from hazardous wastes via microtox and daphnia magna

One of the most common ways of surface and ground water contamination from hazardous wastes is through its leachates. Toxicity is a meaningful parameter allowing an integrated evaluation of the potential danger of leachates. Two bioassays were considered for measuring toxicity: Microtox and Daphnia magna. The toxicity was measured on leachates obtained, using different leaching procedures, from wastes of a pesticide manufacturing industry and sludge from electroplating wastewater. Twenty-two tests were carried out, measuring IC50 for D. magna and EC50 for Microtox. Both bioassays were compared using three toxicity criteria. The first criterium is classification on toxic/non-toxic at 25 and 50% leachate concentration. The second criterium is classification on percent ranks, and the third on log ranks. Considering these criteria, the agreement between both bioassays is within a 75–85%. It is shown that both, Microtox and D. magna assays could be used as toxicity indicators for the wastes considered. The sensitivity of the bioassays is different depending on leachate composition. In all samples, the leachate concentration of chemicals was measured.     

Development of a base set of toxicity tests using ultrafine TiO2 particles as a component of nanoparticle risk management

The development of a risk management system for nanoscale or ultrafine particle-types requires a base set of hazard data. Assessing risk is a function of hazard and exposure data. Previously, we have suggested "parallel tracks" as a strategy for conducting nanoparticle research. On the one hand, mechanistic studies on "representative" nanoparticles could be supported by governmental agencies. Alternatively, with regard to commercial nanoparticles, the environmental, health and safety (EHS) framework would include a minimum base set of toxicity studies which should be supported by the companies that are developing nano-based products. The minimum base set could include the following criteria: substantial particle characterization, pulmonary toxicity studies, acute dermal toxicity and sensitization studies, acute oral and ocular toxicity studies, along with screening type genotoxicity, and aquatic toxicity studies. We report here the toxicity results of a base set of hazard tests on a set of newly developed, well-characterized, ultrafine TiO(2) (uf-TiO(2)) particle-types. In vivo pulmonary toxicity studies in rats demonstrated low inflammatory potential and lung tissue toxicity. Acute dermal irritation studies in rabbits and local lymph node assay results in mice indicated that uf-TiO(2) was not a skin irritant or dermal sensitizer. Acute oral toxicity studies demonstrated very low toxicity and uf-TiO(2) produced short-term and reversible ocular conjunctival redness in rabbits. Genotoxicity tests demonstrated that uf-TiO(2) was negative in both the bacterial reverse mutation test and in an in vitro mammalian chromosome aberration test with Chinese hamster ovary cells. The results of aquatic toxicity screening studies demonstrated that uf-TiO(2) exhibited low concern for aquatic hazard in unaerated, 48h, static acute tests using the water flea, Daphnia magna; exhibited low concern for aquatic hazard in unaerated, 96h, static acute tests using the rainbow trout, Oncorhynchus mykiss; and exhibited medium concern in a 72h acute test using the green algae Pseudokirchneriella subcapitata. To summarize the findings, the results of most of the studies demonstrated low hazard potential in mammals or aquatic species following acute exposures to the ultrafine TiO(2) particle-types tested in this program.     

Towards more efficient testing strategies--analyzing the efficiency of toxicity data requirements in relation to the criteria for classification and labelling

This contribution is based on the assumption that the aim of toxicity testing as required by chemicals legislation is to identify as many chemicals of concern to human health and the environment as possible, given a limited amount of resources allocated to testing. Based on this assumption we propose a method for the optimization of test systems for industrial chemicals, based on the calculation of efficiency ratios for tests and test systems. The efficiency ratio of a toxicity test depends on the monetary cost of performing the test and the probability that the test will identify a chemical of concern, as estimated by the rules for classification and warning labelling. Efficiency ratios are estimated based on the results of basic standardized toxicity testing for acute toxicity, subacute toxicity, irritation and sensitization of 1409 industrial chemicals notified in the European Union between 1994 and 2004. This careful evaluation of the regulatory consequences of testing indicated that many of these substances are classified based on short-term testing of acute toxicity, irritation and sensitization and that most of the substances classified due to a 28-day study were also classified based on short-term testing. These results indicate that, within the classification and labelling system, it is currently more efficient to perform short-term testing of a larger number of substances rather than to perform subacute toxicity studies on substances already tested for acute toxicity.     

A rapid microbiotest for the detection of cyanobacterial toxins

Cyanobacteria occur widely in lakes, reservoirs, ponds, and slow flowing rivers. Many species are known to produce toxins (cyanotoxins), a number of which are of concern for health. Cyanotoxins vary in chemical structure and may be found intracellular or released into water. There is not only a wide variation in the toxicity of known cyanotoxins but a substantial number of toxins have to date not been identified chemically. Chemical analysis of cyanotoxins is nowadays not used for routine monitoring because it is time consuming, it requires specialized equipment and expertise, and is hence expensive. There is hence an urgent need for rapid tests in surface waters to detect cyanobacterial toxins because of the need for safe drinking water and safe natural bathing waters, which may be burdened by cyanobacterial blooms or scums. Previous investigations have already shown that larvae of the anostracan crustacean Thamnocephalus platyurus are quite sensitive to neurotoxic and hepatotoxic cyanotoxins. The present paper reports on the sensitivity comparison of the (1 h) Rapidtoxkit (based on a sublethal endpoint) and the (24 h) Thamnotoxkit microbiotest (based on mortality). Both assays make use of larvae of T. platyurus. The Rapidtoxkit is a new microbiotest that determines the decrease of ingestion of colored particles by the crustacean larvae, which are stressed by a short exposure to toxicants. Fifteen cyanobacterial samples composed of laboratory strains and natural bloom samples were tested by both microbiotests. All samples were also analyzed concurrently by HPLC for microcystins and cylindrospermopsin. The correlation coefficient between the two microbiotests (r = 0.82) showed the very good correspondence between the sublethal and the lethal effects. No known toxins could be detected in some samples, although the latter were found highly toxic to the test organisms in both bioassays. These results point to the presence of unknown toxin(s) produced by some cyanobacteria such as e.g., the Cylindrospermopsis raciborskii strain isolated from Lake Balaton in Hungary. This comparative study clearly showed that the 1 h Rapidtoxkit is an attractive rapid alternative to the Thamnotoxkit microbiotest.     

Exposure assessment within a Total Diet Study: A comparison of the use of the pan-European classification system FoodEx-1 with national food classification systems

A Total Diet Study (TDS) consists of selecting, collecting and preparing commonly consumed foods purchased at retail level and analysing them for harmful and/or beneficial chemical substances. A food classification system is needed to link food consumption data with the contaminant concentration data obtained in the TDS for the exposure assessment. In this study a comparison was made between the use of a national food classification systems and the use of FoodEx-1, developed and recommended by the European Food Safety Authority (EFSA). The work was performed using data of six European countries: Belgium, Czech Republic, France, The Netherlands, Spain and the UK. For each population, exposure to contaminant A (organic compounds) and/or contaminant B (inorganic compound) was assessed by the Monte Carlo Risk Assessment (MCRA) software using the national classification system and FoodEx-1 for food consumption data and for TDS laboratory results. Minimal differences between both approaches were observed. This observation applied for both contaminant A and contaminant B. In general risk assessment will be similar for both approaches; however, this is not guaranteed. FoodEx-1 proved to be a valuable hierarchic classification system in order to harmonise exposure assessment based on existing TDS results throughout Europe.     

Chemical composition and toxicity of waste dump leachates using Selenastrum capricornutum Printz (Chlorococcales,Chlorophyta)

Chemical composition and toxicity of leachates from a municipal waste dump in Buenos Aires Province were analyzed. Three sets of samples, obtained in 1996 and 1997, were compared. Levels of nitrogen, phosphorus, and organics (expressed as COD) were distinctly lower in 1997. Such differences were mainly attributed to higher rainfall in that year. The Selenastrum capricornutum assay showed a high sensitivity to heavy metals (Cd=0.049 mg L⁻¹; Cr hexavalent=0.247 mg L⁻¹ and Zn=0.037 mg L⁻¹). Cu, Zn, and Pb concentrations were toxic to algae in leachate samples of the first year, while the EC₅₀ leachates were slightly toxic (86.6 and 99.31%). Most likely, high levels of organics (COD=4640 and 3470 mg L⁻¹) form complex mixtures with metals reducing their toxicity. The EC₅₀ leachate=48.5% in the last year may be explained by high concentrations of Pb and Cu. © 2000 John Wiley & Sons, Inc. Environ Toxicol 15: 76–80, 2000