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Various types of toxicity classification systems have been elaborated by scientists in different countries, with the aim of attributing a hazard score to polluted environments or toxic wastewaters or of ranking them in accordance with increasing levels of toxicity. All these systems are based on batteries of standard acute toxicity tests (several of them including chronic assays as well) and are therefore dependent on the culturing and maintenance of live stocks of test organisms. Most systems require performance of the bioassays on dilution series of the original samples, for subsequent calculation of L(E)C50 or threshold toxicity values. Given the complexity and costs of these toxicity measurements, they can only be applied in well-equipped and highly specialized laboratories, and none of the classification methods so far has found general acceptance at the international level. The development of microbiotests that are independent of continuous culturing of live organisms has stimulated international collaboration. Coordinated at Ghent University, Belgium, collaboration by research groups from 10 countries in central and eastern Europe resulted in an alternative toxicity classification system that was easier to apply and substantially more cost effective than any of the earlier methods. This new system was developed and applied in the framework of a cooperation agreement between the Flemish community in Belgium and central and eastern Europe. The toxicity classification system is based on a battery of (culture-independent) microbiotests and is particularly suited for routine monitoring. It indeed only requires testing on undiluted samples of natural waters or wastewaters discharged into the aquatic environment, except for wastewaters that demonstrate more than 50% effect. The scoring system ranks the waters or wastewaters in 5 classes of increasing hazard/toxicity, with calculation of a weight factor for the concerned hazard/toxicity class. The new classification system was applied during 2000 by the participating laboratories on samples of river water, groundwaters, drinking waters, mine waters, sediment pore waters, industrial effluents, soil leachates, and waste dump leachates and was found to be easy to apply and reliable.

Lake Velencei is a shallow lake in Hungary. The first cyanobacterial bloom of Microcystis aeruginosa appeared in the lake in 1991. This cyanobacterial species was also found earlier but blooms were not recorded. The toxins of M. aeruginosa were studied in Lake Velencei in 1992. The present study deals with the toxicity of a M. aeruginosa biomass of different origin detected by intraperitoneal (ip.) mouse assay, Thamnotoxkit F microbiotest, and toxin analysis by high-performance liquid chromatography (HPLC). The biomass was collected by plankton net and the isolated strains were cultured from sediments and from bloom material. Minimal lethal doses (MLD) by ip. mouse assay ranged from 20 to 50 mg/kg -1 . Comparing the results from 1992 and 1997-1998, no change in the toxicity of M. aeruginosa was detected. According to the HPLC analysis the combination of microcystins varied in a narrow range with microcystin-LR found in each sample. The cyanobacterial blooms caused by M. aeruginosa in Lake Velencei considerably decreased, though it remained in the sediment with the same toxicity. The Thamnotoxkit F microbiotest was an alternative method for detecting the cyanotoxins.

The Thamnotoxkit F was evaluated for detecting cyanobacterial toxins. This is a 24 hour bioassay using, as test organisms larvae of the freshwater anostracan crustacean Thamnocephalus platyurus hatched from cysts. Freeze-dried Microcystis aeruginosa samples from freshwaters throughout Hungary were tested. Good correlation was obtained between the results of intraperitoneal mouse bioassays and Thamnotoxkit F assays. The LC 50 's for purified microcystins- LR, -RR, and -YR ranged from 0.1 to 2.27 μg per mL, respectively in the Thamnotoxkit assay. The LC 50 of laboratory cultures of Cylindrospermopsis raciborskii isolated from samples from Lake Balaton, was 0.574 mg lyophilized material per mL, in a four-laboratory trial. Although not developed originally for detecting cyanobacterial toxins, the Thamnotoxkit F has good potential as an initial screening procedure for toxicity assessment of cyanobacterial scums and blooms in freshwaters.

The aim of this study is to compare the responses of two different ecotoxicological methods for the determination of the toxic hazard of river or creek sediments in Hungary. Since water quality is intrinsically linked to sediment quality, the ecotoxicological control of sediments is also very important in the water quality policy. The 2000/60 EC Water Framework Directive aims at achieving a good qualitative and quantitative status of all water bodies by 2015. Fifteen sediments and four sludges were collected at different sites in Hungary, which are contaminated by industrial sewage. The first assay is the acute toxicity test with the crustacean Daphnia magna Straus (OECD 202) using larvae less than 1 day old, and an exposure time of 2 days. The second assay is the Ostracodtoxkit F with freshly hatched larvae of the crustacean Heterocypris incongruens and an exposure time of 6 days. The Ostracodtoxkit F test is a "direct sediment contact" bioassay, in which the test organisms are in continuous contact with the sediments. The Daphnia tests were applied on water extracts of the sediment without any contact of the test organisms with the contaminated sediment. The same 1:4 water/sediment ratio has been applied to both tests. The results showed higher toxic effects of the sediments to H. incongruens than to D. magna confirming the need to complement "water only" tests with "solid phase" assays for a meaningful evaluation of the toxic hazard of aquatic environments. The sensitivity of H. incongruens is similar to that of the other test species which are currently used for solid-phase assays. The growth inhibition of H. incongruens is a very sensitive endpoint for sediment toxicity testing. The sediment toxicity tested by ostracods showed strong correlation with concentration of total chromium, lead, and cadmium together.

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.

Many studies have been published on the human health effects of cyanobacterial toxicity. As a public health concern, we have to mention that the development of contact dermatitis, asthmalike symptoms, and symptoms resembling hay fever during bathing in cyanobacterial blooms have been also described. Microcystis aeruginosa, Anabaena flos-aquae, Aphanizomenon flos-aquae, and Cylindrospermopsis raciborskii are the most common species found in Hungarian freshwaters. A sensitization test on albino guinea pigs, and intradermal reactivity, and occular irritation test on albino rabbits were carried out with freeze-dried algal suspension in physiological salt solution. The sensitivity of guinea pigs is similar to that of humans. Microcystis, Anabaena, Cylindrospermopsis, and Aphanizomenon bloom and strain samples were examined in sensitization and irritation tests and no correlation was found between the toxin content and the allergenic character. The most toxic one (Microcystis aeruginosa) was not the most allergenic sample, but the nontoxic Aphanizomenon was the most allergenic one. The axenic strains were not allergenic at all. The pure microcystin LR was only slightly allergenic even in high concentration (1.5 mg/ml). Water and lipid soluble fractions were obtained by water and chloroform extraction of lyophilized algal suspensions. The chloroform fraction was bound on C18 cartridges and eluted by methanol in nine fractions. Only one of the lipid soluble fractions was skin irritative whereas the strongest irritative effect was shown by the water soluble fraction.