Lowest Observed Effect Concentration Values Research Articles

Acute toxicity of peroxy sulfonated oleic acids (PSOA) to freshwater aquatic species and sludge microflora as observed in laboratory environments.

BackgroundPeroxy sulfonated oleic acids (PSOA) is a novel surfactant peracid. The commercial applications of PSOA result in the chemical primarily being disposed of via industrial waste water effluent. Given this manner of disposal, it is important to understand the aquatic hazards of the chemical to better assess the risk posed to aqueous environments. Acute aquatic toxicity laboratory experiments were performed to evaluate aquatic hazards and were conducted according to standard OECD test guidelines with rainbow trout (Oncorhynchus mykiss), water fleas (Daphnia magna) and algae (Pseudokirchneriella subcapitata). In addition, microbial toxicity was evaluated in activated sludge obtained from a domestic sewage treatment facility.Results Lethal concentration in 50 % of test species (LC50) and effect concentration in 50 % of test species (EC50) values for PSOA ranged from 0.75 to 5.44 mg/L, representing a relatively small range spanning less than an order of magnitude. No observed effect concentration (NOEC) and lowest observed effect concentration (LOEC) ranges were also relatively small, with ranges of 0.25–1.66 and 0.5–3.6 mg/L, respectively. The EC50, LOEC and NOEC values for microbial toxicity were 216, 60 and 20 mg/L, respectively. Predicted no effect concentrations (PNEC) for aqueous media were based on the 96-h LC50 (0.75 mg/L) for O. mykiss, the organism displaying the greatest sensitivity to PSOA. These values were derived for freshwater, marine water and intermittent releases to water and ranged from 7.5 × 10−5 to 7.5 × 10−3 mg/L. A sewage treatment plant PNEC of 2 mg/L was derived based on an activated sludge 3-h NOEC of 20 mg/L.ConclusionThese values, along with the anticipated environmental fate and transport for PSOA, were considered in assessing the overall aquatic risk posed by this chemical. Despite the relatively high acute aquatic hazards for PSOA, environmental modeling suggests the overall risk of PSOA to aqueous environments is low based on its anticipated uses. This conclusion is consistent with the significant processing of industrial wastewater by onsite or municipal wastewater treatment facilities prior to release to the environment.

Environmental safety level of lead (Pb) pertaining to toxic effects on grey mullet (Mugil cephalus) and tiger perch (Terapon jarbua).

Acute and chronic bioassay toxicity test of Lead (Pb) in Grey Mullet (Mugil cephalus), and Tiger perch (Terapon jarbua) was conducted. LC50 values (Lethal Concentration) from acute tests and chronic values were calculated by the geometric mean of the No-Observed-Effect Concentration (NOEC) and the Lowest-Observed-Effect Concentration (LOEC) in a study period of 30 days. This research was conducted to evaluate the quantitative relationship between toxicity test statistics and correlation between toxicant and the organisms exposed. Three test average LC50 was analyzed for 24, 48, 72, and 96 h and the 96 h average LC50 of M. cephalus and T. jarbua is 2.57 ± 0.47 and 2.99 ± 0.23 mg/L of Pb, respectively. Significant correlation is observed with the increased time duration and exposure concentration. The NOEC and LOEC values were calculated based on survival of test organisms for M. cephalus and T. jarbua and the values are 0.014 and 0.029 and 0.011 and 0.022 mg/L, respectively. The chronic value is found to be 0.011 mg/L for M. cephalus and 0.021 mg/L for T. jarbua. The intensity of biochemical and histological alterations increased gradually with increased Pb concentration and the exposure time. Toxicity testing is the primary step to determine the water quality safe limit on marine organisms. The outcome of the study indicates that the sensitivity of juvenile organisms to Pb, persistence of toxic effects and biomarkers as a tool capable of revealing the toxic effects of heavy metals on the environment and aquatic biota.

Chronic toxicity of parabens and their chlorinated by‐products in Ceriodaphnia dubia

The chronic toxicity of 12 compounds of parabens and their chlorinated by-products was investigated using 7-day Ceriodaphnia dubia test under static renewal condition in order to generate information on how to disinfect by-products of preservatives that are discharged in aquatic systems. The mortality and inhibition of reproduction tended to increase with increasing hydrophobicity and decreased with the degree of chlorination of parabens. The EC50 values for mortality, offspring number, and first brood production ranged between 0.30-3.1, 0.047-12, and 1.3-6.3 mg L(-1) , respectively. For the number of neonates, the most sensitive endpoint, the no-observed-effect concentration (NOEC) and lowest-observed-effect concentration (LOEC) values ranged from 0.63 to 10 mg L(-1) and from 1.2 to 19 mg L(-1) , respectively. Methylparaben (MP), benzylparaben (BnP), and dichlorinated BnP (Cl2 BnP) elicited a significant decrease in offspring numbers even at their lowest concentration tested; the NOEC for these compounds was determined to be less than the lowest test concentration (1.3, 0.04, and 0.63 mg L(-1) for MP, BnP, and Cl2 BnP, respectively). Propylparaben (PP), chlorinated PP, isopropylparaben (iPP), and chlorinated iPP exhibited nonmonotonic concentration-dependent response; their NOEC and LOEC values could not be determined. The multivariate approach involving principal component analysis and hierarchical cluster analysis revealed four groups that corresponded to the toxicological profiles of parabens. Our results suggested that disinfection of parabens by chlorination could reduce aquatic toxicity of original compounds. The findings obtained in our study together with the data available on paraben concentrations in aquatic systems can be used to perform preliminary risk assessment by comparing the predicted environmental concentration (PEC) with the predicted no-effect concentration (PNEC) for the marine aquatic environment. The calculated PEC/PNEC ratios ranged from 0.0012 to 0.2, with the highest value observed in MP. This suggested that there are negligible environmental risks for aquatic organisms at current use levels.

Biochemical and genotoxic response of naphthalene to fingerlings of milkfish Chanos chanos

The present study investigated the acute toxicity, sub-lethal toxicity and biochemical response of naphthalene in fingerlings of milkfish Chanos chanos. The 96 h acute toxicity LC50 values for C. chanos exposed to naphthalene was 5.18 μg l(-1). The estimated no observed effect concentration and lowest observed effect concentration values for naphthalene in C. chanos were 0.42 and 0.69 μg l(-1) respectively for 30 days. The estimated maximum allowable toxicant concentration for naphthalene was 0.53 μg l(-1). Biochemical enzyme markers such as lipid peroxidation, catalase, glutathione S transferase and reduced glutathione were measured in gills and liver tissues of C. chanos exposed to sub-lethal concentrations of naphthalene. Fluctuation in lipid peroxidation and catalase level suggests that naphthalene concentrations play a vital role in induction of oxidative stress in fish. Induction of reduced glutathione level and inhibition of glutathione S-transferase level was observed in naphthalene exposed C. chanos suggesting that there may be enhanced oxidative damage due to free radicals. Increasing concentration increases in number of nuclear abnormalities. The formation of micronuclei and binucleated micronuclei induction by naphthalene confirm its genotoxic potential. The highest levels of DNA damage (% tail length) were observed at 1.24 μg l(-1) of naphthalene. The study suggests that biochemical enzymes, nuclear abnormalities and DNA damage index can serve as a biological marker for naphthalene contamination.

Arsenate (As V) in water: Quantitative sensitivity relationships among biomarker, ecotoxicity and genotoxicity endpoints

It is useful to test ecotoxicity and genotoxicity endpoints in the environmental impact assessment. Here, we compare and discuss ecotoxicity and genotoxicity effects in organisms in response to exposure to arsenate (As V) in solution. Eco(geno)toxicity responses in Aliivibrio fischeri, Lytechinus variegatus, Daphnia magna, Skeletonema costatum and Vicia faba were analyzed by assessing different endpoints: biomass growth, peroxidase activity, mitotic index, micronucleus frequency, and lethality in accordance with the international protocols. Quantitative sensitivity relationships (QSR) between these endpoints were established in order to rank endpoint sensitivity. The results for the QSR values based on the lowest observed effect concentration (LOEC) ratios varied from 2 (for ratio of root peroxidase activity to leaf peroxidase activity) to 2286 (for ratio of higher plant biomass growth to root peroxidase activity). The QSR values allowed the following sensitivity ranking to be established: higher plant enzymatic activity>daphnids≈echinoderms>bacteria≈algae>higher plant biomass growth. The LOEC values for the mitotic index and micronucleus frequency (LOEC=0.25mgAsL−1) were similar to the lowest LOEC values observed in aquatic organisms. This approach to the QSR of different endpoints could form the basis for monitoring and predicting early effects of pollutants before they give rise to significant changes in natural community structures.

Acute and chronic toxic effect of lead (Pb) and zinc (Zn) on biomarker response in post larvae of Penaeus monodon (Fabricus, 1798)

Metal pollution produces damage to marine organisms at the cellular level possibly leading to ecological imbalance. The present investigation focused on the acute and chronic toxicity of lead (Pb) and zinc (Zn) by examining the effects of biomarker enzymes in post-larvae of Penaeus monodon (Tiger prawn). Antioxidant biomarker responses such as lipid peroxidation (LPO) and catalase (CAT) activity for Pb and Zn were determined following chronic exposure. Acute Lethal Concentration 50 (LC50) values observed in the study at 96 h for Pb and Zn at 5.77 ± 0.32 mg L−1 and 3.02 ± 0.82 mg L−1, respectively. The estimated No Observed Effect Concentration and Lowest Observed Effect Concentration values for Pb were 0.014 and 0.029 mg L−1 and that recorded for Zn was 0.011 and 0.022 mg L−1, respectively. Among the two metals studied, toxicity of Zn was found to be greater to P. monodon than Pb. The activities of antioxidant defense enzymes and total protein content differed significantly from control following exposure to both metals. Overall, the biomarker studies demonstrated that alterations in antioxidant enzymes and induction of LPO reflect the consequences of heavy metal exposure in P. monodon.

Effects of the anti-androgen, bicalutamide, in a reduced life-cycle study with the fathead minnow (Pimephales promelas)

In support of the environmental risk assessment (ERA) of the non-steroidal anti-androgen bicalutamide, a reduced fish full life-cycle (FFLC) was conducted. The traditional FFLC is deemed to be the “gold standard” for evaluating the potential environmental impact of human pharmaceuticals, covering all life-stages and measuring long term effects. However, such studies require large numbers of animals and take considerable effort and time. The reduced FFLC, employed here, used fewer animals and was shorter in duration, yet still included sensitive life-stages and measured long term effects to provide robust information in support of the ERA for an endocrine disrupting chemical. Fathead minnows (Pimephales promelas) were held in breeding pairs and their reproductive performance assessed over 28 days. Embryos from at least two pairs per treatment were subsequently grown up until 85 days post hatch and a subset allowed to spawn to assess the developmental and reproductive effects of the parental exposure on this F1 generation. Fish were exposed in a flow-through system, at 25±1°C. Nominal (mean measured) test concentrations of bicalutamide were 0.01 (0.055), 0.10 (0.10), 1.0 (0.9), 10 (9.2) and 100 (92.1)μgL−1. There were no significant effects on F0 fecundity or growth (wet weight and standard length), but a significant decrease in nuptial tubercle prominence (a secondary sexual characteristic, SSC) was observed in male fish exposed to 100μgL−1. In the F1 generation, there were no treatment-related effects on hatching success or SSC, but survival was significantly decreased in fish exposed to the top concentration (100μgL−1). In female fish, wet weight and standard length were also significantly increased at this concentration. Gonadal histopathology revealed no treatment related effects on sex ratio, sexual differentiation or sexual development. However, there was a concentration related effect on gonad lesion severity in female fish exposed to 100μgL−1 and reproduction (number of eggs spawned) was also significantly reduced in breeding groups exposed to this concentration. Taking into account these data, the overall no observed effect concentration and lowest observed effect concentration values for bicalutamide were 10 and 100μgL−1, respectively.

Accuracy assessment of time–concentration–effect models in predicting chronic lethality from acute toxicity data

Acute-to-chronic (ACE) models (accelerated life testing, ALT; linear regression analysis, LRA) are used to estimate chemical concentrations resulting in low levels of chronic mortality from acute toxicity data, thereby greatly increasing the inferential value of acute data. We applied the ACE models to test data from 72 chemicals and 14 aquatic species (131 acute and 97 chronic tests) and then compared the results with reported chronic no observed effect concentrations (NOEC) and lowest observed effect concentrations (LOEC), as determined by traditional analysis of variance techniques. Acute-to-chronic models produced highly accurate chronic lethality estimates compared with reported chronic NOEC and LOEC values. Lethality estimates fell within two times reported NOEC-LOEC values 71% of the time and within five times 98% of the time. Therefore, ACE models are very appropriate for estimating chronic lethality from acute toxicity data when chronic data are absent and have high applicability in probability-based hazard and risk assessments.

Evaluation of the toxicity of Streptomyces aburaviensis (R9) extract towards various agricultural pests

The dichloromethane extract of culture filtrate from Streptomyces aburaviensis R9 was evaluated using various rapid bioassays to determine potential inhibitory effects towards phytopathogenic fungi (Colletotrichum acutatum, C. fragariae, C. gloeosoprioids, Botrytis cinerea, Fusarium oxysporum, Phomopsis viticola and P. obscurans), fish bacterial pathogens (Edwardsiella ictaluri and Flavobacterium columnare), a green alga (Selenastrum capricornutum), plant seeds [Bent grass (Agrostis sp.) monocot and lettuce (Lactuca sativa) dicot] and 2-methylisoborneol (MIB)-producing cyanobacteria (Planktothrix perornata and Pseudanabaena sp.). The dichloromethane extract showed selective inhibition against the cyanobacterium P. perornata, with a lowest-complete-inhibition concentration (LCIC) of 10 mg/L and lowest-observed-effect concentration (LOEC) of 10 mg/L while LCIC and LOEC values were 100 mg/L when tested against S. capricornutum. This extract also showed slight meristematic cytogenic necrosis at 200 mg/L towards germinated seeds of both test plants. The compounds were not very toxic towards the channel catfish (Ictalurus punctatus) pathogenic bacteria E. ictaluri and F. columnare. Preliminary evaluation of the extract toward C. acutatum, C. fragariae and C. gloeosoprioids using TLC bioautography revealed moderate activity. However, further evaluation of the extract using a microtiter plate bioassay determined that inhibition was strongest against C. acutatum and C. fragariae, though this inhibitory activity diminished at 72 hours and was moderately less active than the commercial fungicides azoxystrobin and captan when comparing 1 - 100 mg/L levels at 48 hours.

Developmental toxicity of benzotriazole in the protochordate Ciona intestinalis (Chordata, Ascidiae)

Benzotriazoles (BT) are applied as anticorrosive and de-icing agents and have been detected in a variety of aquatic ecosystems and municipal wastewater effluents. We have assessed the developmental effects of benzotriazole (CAS number 95-14-7) to the marine invertebrate Ciona intestinalis (Chordata, Ascidiae). At 15 +/- 1 degrees C, the 24 h No-Observed Effect Concentration (NOEC) and Lowest Observed Effect Concentration (LOEC) values based on embryo morphological development were 100 and >100 mg L(-1), respectively (nominal concentration under static conditions). After 48 h, the NOEC and LOEC values were 10 and 32 mg L(-1), respectively. Light and electron microscopy studies on benzotriazole-exposed larva indicated that the primary target cells were the extra-embryonic test cells, which are known to play a significant apoptotic role during ascidian metamorphosis. The visible decline of test cells in benzotriazole-exposed larvae raises the possibility that the compound interferes with the regulation of embryo development in protochordates such as C. intestinalis. Further research is warranted to assess the potential longer term sublethal impacts of benzotriazole in aquatic organisms.

Seawater ecotoxicity of monoethanolamine, diethanolamine and triethanolamine

Monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) are compounds with potential acute, sub-chronic and chronic toxicity effects towards aquatic species. A literature review highlighted the existence of a gap in the knowledge on their toxicity with saltwater testing species. A battery of toxicity tests including the alga Phaeodactylum tricornutum Bohlin, the bivalve molluscs Crassostrea gigas (Thunberg) and Mytilus galloprovincialis (Lmk), and the crustacean Artemia franciscana, was considered to update and improve the existing ecotoxicological information. Data were provided as the Effective Concentration that induces a 50% effect in the observed population (EC50), Lowest Observed Effect Concentration (LOEC) and No Observed Effect Concentration (NOEC). EC50, LOEC and NOEC values were compared with a reviewed database containing the existing ecotoxicological data from saltwater organisms.

Gene expression analysis in zebrafish embryos: A potential approach to predict effect concentrations in the fish early life stage test

Based on the hypothesis that analysis of gene expression could be used to predict chronic fish toxicity, the zebrafish (Danio rerio) embryo test (DarT), developed as a replacement method for the acute fish test, was expanded to a gene expression D. rerio embryo test (Gene-DarT). The effects of 14 substances on lethal and sublethal endpoints of the DarT and on expression of potential marker genes were investigated: the aryl hydrocarbon receptor 2, cytochrome P450 1A (cypla), heat shock protein 70, fizzy-related protein 1, the transcription factors v-maf musculoaponeurotic fibrosarcoma oncogene family protein g (avian) 1 and NF-E2-p45-related factor, and heme oxygenase 1 (hmox1). After exposure of zebrafish embryos for 48 h, differential gene expression was evaluated using reverse transcriptase-polymerase chain reaction, gel electrophoresis, and densitometric analysis of the gels. All tested compounds significantly affected the expression of at least one potential marker gene, with cyp1a and hmox1 being most sensitive. Lowest-observed-effect concentrations (LOECs) for gene expression were below concentrations resulting in 10% lethal effects in the DarT. For 10 (3,4- and 3,5-dichloroaniline, 1,4-dichlorobenzene, 2,4-dinitrophenol, atrazine, parathion-ethyl, chlorotoluron, genistein, 4-nitroquinoline-1-oxide, and cadmium) out of the 14 tested substances, LOEC values derived with the Gene-DarT differ by a factor of less than 10 from LOEC values of fish early life stage tests with zebrafish. For pentachloroaniline and pentachlorobenzene, the Gene-DarT showed a 23- and 153-fold higher sensitivity, respectively, while for lindane, it showed a 13-fold lower sensitivity. For ivermectin, the Gene-DarT was by a factor of more than 1,000 less sensitive than the acute fish test. The results of the present study indicate that gene expression analysis in zebrafish embryos could principally be used to predict effect concentrations in the fish early life stage test.

Acute and Chronic Toxicity of Imidacloprid to the Aquatic Invertebrates Chironomus tentans and Hyalella azteca under Constant- and Pulse-Exposure Conditions

The toxicity of imidacloprid, a nicotinic mimic insecticide, to the aquatic invertebrates Chironomus tentans and Hyalella azteca, was first evaluated in static 96-hour tests using both technical material (99.2% pure) and Admire, a commercially available formulated product (240 g a.i. L(-1)). The 96-h lethal concentration (LC)50 values for technical imidacloprid and Admire were 65.43 and 17.44 microg/L, respectively, for H. azteca, and 5.75 and 5.40 microg/L, respectively, for C. tentans. Admire was subsequently used in 28-day chronic tests with both species. Exposure scenarios consisted of a constant- and a pulse-exposure regime. The pulse exposure lasted for four days, after which time the animals were transferred to clean water for the remaining 24 days of the study. Assessments were made on both day 10 and day 28. In the C. tentans under constant exposure, larval growth on day 10 was significantly reduced at 3.57 microg/L imidacloprid, the lowest-observed-effect concentration (LOEC). The no-observed-effect concentration (NOEC) and LOEC for the 28-day exposure duration (adult survival and emergence) were 1.14 and greater than 1.14 mug/L, respectively; the associated LC50 and LC25 were 0.91 and 0.59 microg/L, respectively. The LOEC for the pulse treatment was greater than 3.47 microg/L, but the day 10 LC25 was 3.03 microg/L. In the H. azteca tests, the day 10 and 28 constant exposure, as well as the day 28 pulse exposure, LOEC (survival) values were similar at 11.95, 11.46, and 11.93 microg/L, respectively. The day 10 and 28 constant exposure effective concentration (EC)25s (dry weight) were also similar, at 6.22 and 8.72 microg/L, respectively, but were higher than the pulse-exposure day 10 LOEC and EC25 (dry weight) values of 3.53 and 2.22 microg/L, respectively. Overall, C. tentans was more sensitive to acute and chronic imidacloprid exposure, but less sensitive to a single pulse, than H. azteca. Chronic, low-level exposure to imidacloprid may therefore reduce invertebrate survival and growth, but organisms are able to recover from short-term pulse exposure to similar imidacloprid concentrations if the stressor is removed after four days.

Applying weight gain in Pomacea lineata (Spix 1824) (Mollusca: Prosobranchia) as a measure of herbicide toxicity

Pomacea lineata, an extremely ubiquitous snail and pest to rice farmers throughout Asia, holds promise as a valuable resource for monitoring water quality in northeast Brazil. In this paper, we present data demonstrating the rate of weight gain in P. lineata neonates as a consistent measure of the stress imposed by sublethal concentrations of the herbicides Paraquat and Round-up. Our secondary agenda is to demonstrate the feasibility of incorporating bioassay into the standard municipal and state procedure of monitoring water quality. Growth data to assess chronic toxicity were generated in experiments of four and four, eight, twelve and sixteen days for Paraquat and Round-up, respectively. We estimated a 96 h no observed effect concentration (NOEC) and lowest observed effect concentration (LOEC) for Paraquat of 0.12 and 0.25 mg/L. The 96 h Round-up data yielded NOEC and LOEC values, respectively, of 0.25 and 0.5 mg/L. All concentrations of Round-up tested for the 192 h exposure yielded significantly lower growth than the control. Consequently, no NOEC could be derived. The LOEC was < 0.12 mg/L. Furthermore, there was no mortality during the test. At the lowest concentrations of Paraquat tested (0.005 mg/L) there was a significant increase in growth compared with the controls, suggesting a hormetic effect.

Isolation and Identification of Antifungal and Antialgal Alkaloids fromHaplophyllum sieversii

Bioassay-guided fractionation of the hexane/ethyl acetate/water (H/EtOAc/H2O) crude extract of the aerial parts of Haplophyllum sieversii was performed because of preliminary screening data that indicated the presence of growth inhibitory components against Colletotrichum fragariae, Colletotrichum gloeosporioides, and Colletotrichum acutatum. Fractionation was directed using bioautographical methods resulting in the isolation of the bioactive alkaloids flindersine, anhydroevoxine, haplamine, and a lignan eudesmin. These four compounds were evaluated for activity against C. fragariae, C. gloeosporioides, C. acutatum, Botrytis cinerea, Fusarium oxysporum, and Phomopsis obscurans in a dose-response growth-inhibitory bioassay at 50.0, 100.0, and 150.0 microM. Of the four compounds tested, flindersine demonstrated the highest level of antifungal activity. Additionally, flindersine, eudesmin, and haplamine were screened against the freshwater phytoplanktons Oscillatoria perornata, Oscillatoria agardhii, Selenastrum capricornutum, and Pseudanabaena sp. (strain LW397). Haplamine demonstrated selective inhibition against the odor-producing cyanobacterium O. perornata compared to the activity against the green alga S. capricornutum, with lowest observed effect concentration values of 1.0 and 10.0 microM, respectively.

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 °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 μg/l) while thallium (Tl) was the least toxic (LOEC=3840–15 300 μg/l). The LOECs for copper (as Cu) and lead (Pb) in reagent (ASTM Type I) water were 6.78–13.6 μg/l and 626–1251 μg/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.

Impact of perfluorooctanoic acid on the structure of the zooplankton community in indoor microcosms

There is presently, a substantial amount of information being gathered concerning the environmental risk associated with the perfluorooctanoic acid (PFOA) compound. The aim of this paper was to determine a 35 day community no observable effect concentration (NOEC community) or lowest observable effect concentration (LOEC) for freshwater zooplankton exposed to PFOA during a study in 30 l indoor aquatic microcosms. Some significant ( P<0.01) temporal fluctuations in zooplankton abundance were observed, however, a NOEC community could not be calculated. LOEC for various species varied between 10 and 70 mg l −1. According to LOEC values, the tentative order of descriptors sensitivity was as follows: Daphnia magna>richness≥ Cyclops canthocamptus staphylinus> Cyclops diaptomus>total zooplankton≥ Rotifera sp. The long term ecological significance of these temporal fluctuations could not be determined in this study, however, the overall study cessation analysis showed that the structure of the ecosystem was changed from a more diverse community dominated by larger species towards a less diverse community dominated by smaller more and robust species ( P<0.05). Additional chronic toxicity testing should also be addressed since these compounds are so persistent and recalcitrant.

Chromatography-mass spectrometry and toxicity evaluation of selected contaminants in seawater

In the present work a combined analytical study involving gas and liquid-chromatography and toxicity studies were developed for the determination of various contaminants typically present in sea water samples. The compounds investigated were Diuron, Chlorothalonil, Dichlofluanid, TCMTB (2-thiocyanomethylthiobenzothiazole), lrgarol 1051, Sea nine 211 and MTBE (methyl-tert-butyl ether). The selected compounds are additives of boat paints and gasoline and they can release into the aquatic environment in considerable amounts in areas with intense shipping traffic. The developed analytical protocol consisted on the use of a solid phase extraction procedure with Oasis™ HLB cartridges followed by GC-El/NCI-MS and LC-ES-MS both in SIM mode. Average recoveries, loading 600 mL of samples with pH=3, varied from 40 to 95% and the detection limits ranged from 1–25 ng L−1. The developed method was applied to real samples from various marinas of Andalusia (Spain).Daphnia magna, Vibrio fischeri andSelenastrum capricornotum toxicity bioassays on individual and mixtures of selected compounds were applied to evaluate EC50 (effective concentration) and LOEC (lowest observable effect concentration) values. Resulting values were in the range of 0.001–720 mg L−1 for EC50 and 0.8.10−9–30 mg L−1 for LOEC for all contaminants except for MTBE where no toxic effect were found up to 680 mg L−1 onDaphnia magna. Toxicity effects of binary mixtures of the selected compounds showed synergistic effects in the majority of the cases (47.6%) and antagonistic in the lower of the cases (9.5%). Levels of the contaminants found in the seawater samples showed around a 30% of inhibition on tested species, during the summer months considering mixture lrgarol 1051-Diuron. Accelerated toxicity processes were observed in mixtures MTBE-Diuron and MTBE-Dichlofluanid.

POPULATION-LEVEL EFFECTS OF THE NEEM INSECTICIDE, NEEMIX, ON DAPHNIA PULEX

Although natural insecticides from the neem tree are generally perceived as less harmful to the environment than synthetic insecticides, new evidence indicates that these products may pose a risk to certain nontarget organisms. In this paper, acute and chronic effects of commercial neem insecticides on the aquatic invertebrate, Daphnia pulex were examined. The acute toxicity of two commercial neem insecticides, Neemix, Azatin and the experimental insecticide, RH-9999 to D. pulex was investigated using traditional 48 hr concentration-mortality estimates. Neemix and Azatin were equitoxic with LC50's of 0.68 and 0.57 ppm; RH-9999 was significantly less toxic with an LC50 of 13 ppm. A 10 d population growth study was conducted for Neemix and a Neemix formulation blank (Neemix devoid of the active ingredients) to determine whether the active ingredients of Neemix and/or components of the formulation were responsible for toxicity. D. pulex populations went to extinction after exposure to a Neemix concentration of 0.45 ppm azadirachtin (equivalent to the acute LC7). Neemix No Observable Effect Concentration (NOEC) and Lowest Observable Effect Concentration (LOEC) values for population growth were 0.045 and 0.15 ppm azadirachtin, respectively. The mean number of offspring per surviving female (Ro) declined in a concentration-dependent manner after exposure to Neemix with no offspring being produced after exposure to 0.45 ppm. Neemix NOEC and LOEC values for reproduction were 0.045 and 0.15 ppm, respectively. The formulation blank caused no mortality in the individuals used to start the population growth study but reduced reproduction and population growth accounting for 47% of the toxicity caused by Neemix at a concentration of 0.15 ppm. Thus, the formulation contributes substantially to the toxicity of Neemix but neem components are also toxic to D. pulex. Because the NOEC for population growth and reproduction were higher than the estimated environmental concentration of 0.035 ppm (a measure developed for forest pest mananagement), Neemix should pose little risk to populations of D. pulex.

Effects of Copper Sulfate on Typha latifolia Seed Germination and Early Seedling Growth in Aqueous and Sediment Exposures

The vascular macrophyte Typha latifolia Linnaeus (common cattail) may be a sentinel for evaluating potential phytotoxicity to rooted aquatic macrophytes in aquatic systems. To further evaluate the potential utility of this species, T. latifolia seed germination, shoot growth, and root elongation were measured in 7-day aqueous exposures using mean measured aqueous copper concentrations of 10.0, 23, 41, 62, 174, and 402 microg Cu/L, which were > or = 62% of nominal concentrations. Seed germination and seedling shoot growth were not significantly affected by any of these copper concentrations as compared to controls. Mean measured no-observed-effect-concentration (NOEC) and lowest-observed-effect-concentration (LOEC) for root elongation were 18.6 microg Cu/L and 35.0 microg Cu/L, respectively. Seven-day sediment tests were conducted by amending uncontaminated sediments with copper sulfate to mean measured concentrations of 7.9, 17.1, 21.0, 51.2, 89.5, and 173.5 mg Cu/kg, which were > or = 84% of nominal concentrations. Seed germination was not significantly different from controls. Mean measured NOEC and LOEC values for seedling shoot growth were 89.5 mg Cu/kg and 173.5 mg Cu/kg, respectively, and mean measured NOEC and LOEC values for root growth were 14.0 mg Cu/kg and 19.7 mg Cu/kg, respectively. These results demonstrate that T. latifolia early seedling growth can be utilized for assessing aqueous and sediment toxicity of copper.