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H LC50 (h + lc50)
Terms modified by H LC50 Selected AbstractsComparing the relative toxicity of malathion and malaoxon in blue catfish Ictalurus furcatusENVIRONMENTAL TOXICOLOGY, Issue 4 2008Winfred G. Aker Abstract Malathion inhibits the critical body enzyme, acetylcholinesterase (AChE). This capability requires that malathion should first be converted to malaoxon to become an active anticholinesterase agent. Conversion can be caused by oxidation in mammals, insects, plants, and in sunlight. In this study, the effects of malathion and malaoxon on catfish Ictalurus furcatus were evaluated. After 96-h exposures, the LC50 (concentration that causes 50% mortality) and IC50 (concentration that causes 50% enzyme inhibition) for malaoxon were lower than corresponding values for malathion. The overall mean 96-h LC50 is 17.0 ppm for malathion and 3.1 ppm for malaoxon. IC50 values for malathion are 8.5 ppm for brain, 10.3 ppm for liver, and 16.6 ppm for muscle. Corresponding values for malaoxon are 2.3, 3.7, and 6.8 ppm, respectively. All the AChE activities in malathion- and malaoxon-exposed catfish brain showed significant inhibition. The oxidation product malaoxon demonstrated higher inhibition on AChE activity than did malathion. Moreover, malaoxon showed significant inhibition on butyrylcholinesterase (BChE) in the liver if the concentrations were increased to more than 1 ppm. Malathion showed no difference between treatment group and control group. Compared with malathion, malaoxon showed higher inhibition on monoamine activity than that of malathion. The results indicated that the oxidative product malaoxon is more toxic than the parent compound malathion. AChE, BChE, and monoamine activities are confirmed as bioindicators of malathion exposure in blue catfish, I. furcatus. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008. [source] Toxicity reduction of metal pyrithiones by near ultraviolet irradiationENVIRONMENTAL TOXICOLOGY, Issue 4 2006Hideo Okamura Abstract Zinc pyrithione (ZnPT) or copper pyrithione (CuPT) have been effectively used as ship-antifouling agents, as an alternative to organotin compounds. Because of their instability in light and a lack of suitable analytical procedures, there is little data on their residue levels in environmental matrices. It is possible to investigate the fate of such compounds by toxicity alteration with certain treatments. The purpose of this study was to evaluate the degradation of pyrithiones through toxicity reduction by near ultraviolet (UV-A) irradiation. Metal pyrithiones dissolved in acetonitrile were irradiated with a UV-A lamp for 0, 0.5, 1, and 2 h, and were subjected to UV spectral measurement and toxicity evaluation using both sea urchin and freshwater rotifer bioassays. For the bioassays, photolyzed samples were dissolved in dimethyl sulfoxide after evaporation of the acetonitrile. The changes in UV spectra of photolyzed ZnPT or CuPT showed a time-dependent degradation, and the UV spectra at 2 h irradiation suggested substantial decomposition. Toxicities of ZnPT and CuPT were 12 and 5 ,g/L as 24 h LC50 to the survival of rotifers and 10,6 ng/L and 2.3 ng/L as 27 h EC50 to normal pluteus formation, respectively. By evaporation of the acetonitrile, the EC50 of ZnPT was 2.2 ng/L, which was the same as that of CuPT. The EC50s of ZnPT or CuPT for both species increased with longer irradiation times. Photolyzed ZnPT or CuPT demonstrated substantial degradation in the UV spectra, but possessed marked toxicity, which is probably due to toxic degradation products. One reason why photolyzed CuPT was toxic to rotifers was explained by the high toxicity of copper ions formed by UV-A irradiation. © 2006 Wiley Periodicals, Inc. Environ Toxicol 21: 305,309, 2006. [source] Cadmium tolerance in the Nile tilapia (Oreochromis niloticus) following acute exposure: Assessment of some ionoregulatory parametersENVIRONMENTAL TOXICOLOGY, Issue 1 2006Sofia Garcia-Santos Abstract The Nile tilapia (Oreochromis niloticus) can tolerate very high levels of waterborne cadmium. It has one of the highest 96 h LC50 recorded for a freshwater teleost fish (14.8 mg/L Cd; hardness 50 mg/L CaCO3). Cadmium is known to perturb ion balance in teleost fishes. However, in an acute time course experiment, plasma Na+ concentrations were unaffected, and plasma Ca2+ values only decreased after 96 h exposure in a dose-independent manner. Branchial Na+/K+ -ATPase activity and ,-subunit protein level expression in crude gill homogenates were not affected by Cd exposure during this period. Branchial chloride cell numbers, identified as Na+/K+ -ATPase immunoreactive cells using immunohistochemistry, decreased 24 h after exposure but recovered thereafter. Histopathological changes did not follow a consistent pattern of variation with exposure time, and the alterations noted in gill epithelium were basically nonspecific to cadmium. Because of its tolerance, it can be concluded that the tilapia O. niloticus would not be a suitable test organism to evaluate sublethal toxicity of cadmium and the realistic impact of this pollutant in the environment. However, it certainly could contribute significantly to our understanding of the toxic mechanism of cadmium exposure in aquatic organisms. This is the first work to investigate the effect of waterborne pollutants on Na+/K+ -ATPase ,-subunit protein expression in fish gills. © 2006 Wiley Periodicals, Inc. Environ Toxicol 21: 33,46, 2006. [source] Effects of insecticide exposure on feeding inhibition in mayflies and oligochaetesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2007Alexa C. Alexander Abstract The present study examined the effects of pulse exposures of the insecticide imidacloprid on the mayfly, Epeorus longimanus Eaton (Family Heptageniidae), and on an aquatic oligochaete, Lumbriculus variegatus Müller (Family Lumbriculidae). Pulse exposures of imidacloprid are particularly relevant for examination, because this insecticide is relatively soluble (510 mg/L) and is most likely to be at effect concentrations during runoff events. Experiments examined the recovery of organisms after a 24-h pulse exposure to imidacloprid over an environmentally realistic range of concentrations (0, 0.1, 0.5, 1, 5, and 10 ,g/L). Effects on feeding were measured by quantifying the algal biomass consumed by mayflies or foodstuffs egested by oligochaetes. Imidacloprid was highly toxic, with low 24-h median lethal concentrations (LC50s) in early mayfly instars (24-h LC50, 2.1 ± 0.8 ,g/L) and larger, later mayfly instars (24-h LC50, 2.1 ± 0.5 ,g/L; 96-h LC50, 0.65 ± 0.15 ,g/L). Short (24-h) pulses of imidacloprid in excess of 1 ,g/L caused feeding inhibition, whereas recovery (4 d) varied, depending on the number of days after contaminant exposure. In contrast to mayflies, oligochaetes were relatively insensitive to imidacloprid during the short (24-h) pulse; however, immobility of oligochaetes was observed during a 4-d, continuous-exposure experiment, with 96-h median effective concentrations of 6.2 ± 1.4 ,g/L. Overall, imidacloprid reduced the survivorship, feeding, and egestion of mayflies and oligochaetes at concentrations greater than 0.5 but less than 10 ,g/L. Inhibited feeding and egestion indicate physiological and behavioral responses to this insecticide. [source] Acute and chronic toxicity of five selective serotonin reuptake inhibitors in Ceriodaphnia dubiaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2004Theodore B. Henry Abstract Contamination of surface waters by pharmaceutical chemicals has raised concern among environmental scientists because of the potential for negative effects on aquatic organisms. Of particular importance are pharmaceutical compounds that affect the nervous or endocrine systems because effects on aquatic organisms are possible at low environmental concentrations. Selective serotonin reuptake inhibitors (SSRIs) are drugs used to treat clinical depression in humans, and have been detected in low concentrations in surface waters. In this investigation, the acute and chronic toxicity of five SSRIs (fluoxetine, Prozac®; fluvoxamine, Luvox®; paroxetine, Paxil®; citalopram, Celexa®; and sertraline, Zoloft®) were evaluated in the daphnid Ceriodaphnia dubia. For each SSRI, the 48-h median lethal concentration (LC50) was determined in three static tests with neonate C. dubia, and chronic (8-d) tests were conducted to determine no-observable-effect concentrations (NOEC) and lowest-observable-effect concentrations (LOEC) for reproduction endpoints. The 48-h LC50 for the SSRIs ranged from 0.12 to 3.90 mg/L and the order of toxicity of the compounds was (lowest to highest): Citalopram, fluvoxamine, paroxetine, fluoxetine, sertraline. Mortality data for the 8-d chronic tests were similar to the 48-h acute data. The SSRIs negatively affected C. dubia reproduction by reducing the number of neonates per female, and for some SSRIs, by reducing the number of broods per female. For sertraline, the most toxic SSRI, the LOEC for the number of neonates per female was 0.045 mg/L and the NOEC was 0.009 mg/L. Results indicate that SSRIs can impact survival and reproduction of C. dubia; however, only at concentrations that are considerably higher than those expected in the environment. [source] Wastewater treatment polymers identified as the toxic component of a diamond mine effluentENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2004Simone J. C. de Rosemond Abstract The EkatiÔ Diamond Mine, located approximately 300 km northeast of Yellowknife in Canada's Northwest Territories, uses mechanical crushing and washing processes to extract diamonds from kimberlite ore. The processing plant's effluent contains kimberlite ore particles (,0.5 mm), wastewater, and two wastewater treatment polymers, a cationic polydiallydimethylammonium chloride (DADMAC) polymer and an anionic sodium acrylate polyacrylamide (PAM) polymer. A series of acute (48-h) and chronic (7-d) toxicity tests determined the processed kimberlite effluent (PKE) was chronically, but not acutely, toxic to Ceriodaphnia dubia. Reproduction of C. dubia was inhibited significantly at concentrations as low as 12.5% PKE. Toxicity identification evaluations (TIE) were initiated to identify the toxic component of PKE. Ethylenediaminetetraacetic acid (EDTA), sodium thiosulfate, aeration, and solid phase extraction with C-18 manipulations failed to reduce PKE toxicity. Toxicity was reduced significantly by pH adjustments to pH 3 or 11 followed by filtration. Toxicity testing with C. dubia determined that the cationic DADMAC polymer had a 48-h median lethal concentration (LC50) of 0.32 mg/L and 7-d median effective concentration (EC50) of 0.014 mg/L. The anionic PAM polymer had a 48-h LC50 of 218 mg/L. A weight-of-evidence approach, using the data obtained from the TIE, the polymer toxicity experiments, the estimated concentration of the cationic polymer in the kimberlite effluent, and the behavior of kimberlite minerals in pH-adjusted solutions provided sufficient evidence to identify the cationic DADMAC polymer as the toxic component of the diamond mine PKE. [source] Influence of water quality and age on nickel toxicity to fathead minnows (Pimephales promelas)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2004Tham Chung Hoang Abstract This research characterized the effects of water quality and organism age on the toxicity of nickel (Ni)to fathead minnows (Pimephales promelas) to facilitate the accurate development of site-specific water-quality criteria. Nickel sulfate hexa-hydrate (NiSO4·6H2O) was used as the Ni source for performing acute toxicity tests (median lethal concentration after 96-h exposure [96-h LC50]) with <1-d-old and 28-d-old P. promelas under varying regimes of hardness, pH, alkalinity, and natural organic matter (NOM). The toxicity of Ni was inversely related to water hardness between hardness values of 20 and 150 mg/L (as CaCO3). Below 30 mg/L alkalinity, Ni toxicity was related to alkalinity. The effect of pH was confounded by hardness and the presence of NOM. In the absence of NOM, the toxicity of Ni increased as pH increased at high hardness and alkalinity. In general, 28-d-old fish were less sensitive than <1-d-old fish to Ni. This lower sensitivity ranged from 12-fold at low hardness and alkalinity (20 and 4 mg/L, respectively) to 5-fold at high hardness and alkalinity (100 and 400 mg/L, respectively). The presence of NOM (10 mg/L as dissolved organic carbon [DOC]) reduced Ni toxicity by up to 50%, but this effect appeared to be saturated above DOC at 5 mg/L. Incubating Ni with the NOM solution from 1 to 17 days had no effect on Ni toxicity. When using multivariate analysis, the 96-h LC50 for Ni was a function offish age, alkalinity, hardness, and NOM (96-h LC50 = ,0.642 + 0.270(fish age) + 0.005(alkalinity) + 0.018(hardness) + 0.138(DOC)). When using this model, we found a strong relationship between measured and predicted 96-h LC50 values (r2 = 0.94) throughout the treatment water qualities. The biotic ligand model (BLM) did not accurately predict Ni toxicity at high or low levels of alkalinity. Results of our research suggest that the BLM could be improved by considering NiCO3 to be bioavailable. [source] Acute and chronic toxicity of nickel to marine organisms: Implications for water quality criteriaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2002John W. Hunt Abstract Acute and chronic toxicity tests were conducted to determine the effects of nickel on three U.S. west coast marine species: a fish (the topsmelt, Atherinops affinis), a mollusk (the red abalone, Haliotis rufescens), and a crustacean (the mysid, Mysidopsis intii). The 96-h median lethal concentration (LC50) for topsmelt was 26,560 mg/L, and the chronic value for the most sensitive endpoint in a 40-d exposure was 4,270 mg/L. The median effective concentration (EC50) for 48-h abalone larval development was 145.5 ,g/L, and the chronic value for juvenile growth in a 22-d exposure through larval metamorphosis was 26.43 mg/L. The mysid 96-h LC50 was 148.6 ,g/L, and the chronic value for the most sensitive endpoint in a 28-d, whole life-cycle exposure was 22.09 ,g/L. The abalone and mysid acute values were lower than other values available in the literature. Acute-tochronic ratios for nickel toxicity to the three species were 6.220, 5.505, and 6.727, respectively, which were similar to the only other available saltwater value of 5.478 (for Americamysis [Mysidopsis] bahia) and significantly lower than the existing values of 35.58 and 29.86 for freshwater organisms. Incorporation of data from the present study into calculations for water quality criteria would lower the criterion maximum concentration and raise the criterion continuous concentration for nickel. [source] Acute and chronic toxicity of nitrate to fathead minnows (Pimephales promelas), ceriodaphnia dubia, and Daphnia magnaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2000George Scott Abstract Increasing concentrations of nitrate in surface water and groundwater are becoming a worldwide concern, yet little information has been published on toxicity of nitrate to common organisms used for toxicity testing. The acute and chronic toxicity of nitrate (NO3 -N) to Ceriodaphnia dubia, Daphnia magna, and Pimephales promelas was investigated in 48-h to 17-d laboratory exposures. The 48-h median lethal concentration (LC50) of nitrate to C. dubia and D. magna neonates was 374 mg/L NO3 -N and 462 mg/L NO3 -N. The no-observed-effect concentration (NOEC) and the lowest-observed-effect concentration (LOEC) for neonate production in C. dubia were 21.3 and 42.6 mg/L NO3 -N, respectively. The NOEC and LOEC values for neonate production in D. magna were 358 and 717 mg/L NO3 -N, respectively. The 96-h LC50 for larval fathead minnows (P. promelas) was 1, 341 mg/L NO3 -N. The NOEC and LOEC for 7-d larval and 11-d embryo-larval growth tests were 358 and 717 mg/L NO3 -N, respectively. Additional exposure of breeding P. promelas and their fertilized eggs to nitrate did not increase susceptibility further. The LC50 values for all species tested were above ambient concentrations of nitrate reported for surface water. However, the LOEC for C. dubia was within the range of concentrations that could be found in streams draining areas under extensive agricultural cultivation. [source] Developmental toxicity of estrogenic alkylphenols in killifish (Fundulus heteroclitus)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2000Sue A. Kelly Abstract Estrogenic alkylphenols have been identified in the aquatic environment, and concern has arisen over the ability of these compounds to interact with and potentially disrupt vertebrate endocrine systems. Here we report that waterborne nonylphenol (NP) and 4- tert -octylphenol (4- t -OP) are toxic to the embryos and larvae of Fundulus heteroclitus, an estuarine teleost, causing both lethal and sublethal developmental abnormalities. Hatch success in surviving embryos is also adversely affected by alkylphenol exposure. Correlation analysis has indicated that decreased hatch success is strongly correlated to deformities in the torso/abdomen and tail of embryos. Larval exposure to the alkylphenols demonstrates that NP and 4- t -OP are lethal at concentrations an order of magnitude less than those lethal to embryos (NP larval 96-h LC50 = 0.95 ,M [204 ,g/L]; NP embryo 96-h LC50 = 24 ,M [5 mg/L]). In evaluating the role of estrogenicity in developmental toxicity of the alkylphenols, we have found that tamoxifen, an estrogen receptor antagonist, can prevent embryo-lethality for NP and 4- t -OP While these embryos survive, some sublethal abnormalities are still evident, particularly in the torso and tail. The results of these studies suggest that the alkylphenols have the potential to cause developmental toxicity in aquatic organisms and that this may occur through disruption of estrogen-based signals. [source] Transgenic strains of the nematode Caenorhabditis elegans as biomonitors of metal contaminationENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2000L. K. Cioci Abstract Transition metal contamination poses a serious environmental and human health threat. The bioavailability of transition metals in environmental samples can best be assessed with living organisms. A transgenic strain of the free-living soil nematode Caenorhabditis elegans has been engineered for monitoring the bioavailability of metals. A reporter transgene consisting of a fragment of the promoter from the C. elegans metallothionein-2 gene (mtl-2) that controls the transcription of a ,-galactosidase reporter (lacZ) has been integrated into the genome of this organism. By using these transgenic C. elegans, the toxicological response to metals in samples can be quickly measured with a simple histochemical staining assay. The C. elegans that contain the mtl-2:lacZ transgene provide a more sensitive assay of exposure to cadmium, mercury, zinc, and nickel than 24-h LC50 assays or those using nematodes with heat-shock protein,based reporter transgenes. This study demonstrates that C. elegans that contain mtl-2:lacZ transgenes can function as sensitive toxicological indicators of metals. [source] Ammonia in estuaries and effects on fishJOURNAL OF FISH BIOLOGY, Issue 6 2005F. B. Eddy This review aims to explore the biological responses of fish in estuaries to increased levels of environmental ammonia. Results from laboratory and field studies on responses of fish to varying salinity and their responses increased ammonia will be evaluated, although studies which examine responses to ammonia, in relation to varying salinity, pH and temperature together are rare. In a survey of British estuaries the continuous measurement of total ammonia showed values that ranged from background levels increasing up to c. 10 mg N l,1 although higher values have been noted sporadically. In outer estuaries pH values tended to stabilize towards sea water values (e.g. c. pH 8). Upper reaches of estuaries are influenced by the quality of their fresh waters sources which can show a wide range of pH and water quality values depending on geological, climatic and pollution conditions. In general the ammonia toxicity (96 h LC50) to marine species (e.g. 0·09,3·35 mg l,1 NH3) appears to be roughly similar to freshwater species (e.g. 0·068,2·0 mg l,1 NH3). Ammonia toxicity is related to differences between species and pH rather than to the comparatively minor influences of salinity and temperature. In the marine environment the toxicity of ionized ammonia should be considered. The water quality standard for freshwater salmonids of 21 ,g l,1 NH3,N was considered to be protective for most marine fish and estuarine fish although the influence of cyclical changes in pH, salinity and temperature were not considered. During ammonia exposures, whether chronic or episodic, estuarine fish may be most at risk as larvae or juveniles, at elevated temperatures, if salinity is near the seawater value and if the pH value of the water is decreased. They are also likely to be at risk from ammonia intoxication in waters of low salinity, high pH and high ammonia levels. These conditions are likely to promote ammonia transfer from the environment into the fish, both as ionized and unionized ammonia, as well as promoting ammonia retention by the fish. Fish are more likely to be prone to ammonia toxicity if they are not feeding, are stressed and if they are active and swimming. Episodic or cycling exposures should also be considered in relation to the rate at which the animal is able to accumulate and excrete ammonia and the physiological processes involved in the transfer of ammonia. In the complex environment of an estuary, evaluation of ammonia as a pollutant will involve field and laboratory experiments to determine the responses of fish to ammonia as salinity and temperature vary over a period of time. It will also be necessary to evaluate the responses of a variety of species including estuarine residents and migrants. [source] Effect of binary combination of some plant-derived molluscicides with MGK-264 or piperonyl butoxide on the reproduction of the snail Lymnaea acuminataPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 2 2005Priyamvada Singh Abstract The effects of sub-lethal treatments (20 and 60% of 24-h LC50) with plant-derived molluscicides Annona squamosa, acetogenins, Argemone mexicana seed and protopine, in combination (1 + 5) with MGK-264 (ENT 8184) or piperonyl butoxide on the reproduction of Lymnaea acuminata has been studied. The plant-derived molluscicides and their active molluscicidal components, protopine and acetogenins, in combination with ENT 8184 or piperonyl butoxide caused a significant reduction in the fecundity, hatchability and survival of young snails. Combination of A squamosa seed powder with piperonyl butoxide was very effective as it caused a complete arrest of snail fecundity within 24 h of treatment. Removal of the snails to fresh water after the 96-h treatments caused a significant recovery in the fecundity of L acuminata. Copyright © 2004 Society of Chemical Industry [source] Efficacy of tricaine methanesulphonate and clove oil as anaesthetics for juvenile cobia Rachycentron canadumAQUACULTURE RESEARCH, Issue 7 2009Mariel Gullian Abstract Six experiments were designed to determine the optimal anaesthetic dosage of tricaine methanesulphonate (TMS) and clove oil that could be used safely on juvenile cobia Rachycentron canadum of two sizes [G1=4.9±0.8 g; G2=13.9±3.1 g]. We documented the stage of anaesthesia and the acute toxicity as 96 h LC50 (lethal concentration 50% population) at various exposure times of the two anaesthetics. At 10 min induction time, the TMS 96 h LC50 was 93.9 mg L,1 in G1 and 97.0 mg L,1 in G2. Compared with clove oil, the 96 h LC50 was 60.0 mg L,1 in G1 and 69.8 mg L,1 in G2. The difference between the two groups (G1, G2) did not influence anaesthesia safety (P>0.05). Rachycentron canadum achieved stage 3 anaesthesia more rapidly at a lower clove oil concentration level (40 mg L,1, 10 min) than TMS (60 mg L,1, 10 min), but the recovery period of clove oil, was significantly longer. Clove oil was the most effective in reducing the short-term stress induced by routine biometry (20 mg L,1, 10 min) and also by transporting (1 mg L,1, 8 h). Whereas, for long-term exposure, 40 mg L,1 TMS was found to be safe. [source] Toxicity of chlorine to different sizes of black tiger shrimp (Penaeus monodon) in low-salinity shrimp pond waterAQUACULTURE RESEARCH, Issue 14 2002Husnah Abstract An experiment was conducted, in a dark room with controlled temperature (27.3,28.4 °C), to determine the acute toxicity of chlorine concentration to black tiger shrimp (Penaeus monodon fabicus) of sizes 0.02 g, 2.75 g, 8.47 g and 23.65 g. Toxicity tests on each of these shrimp sizes were run in triplicate in glass jars under static conditions without media renewal. The concentration of active chlorine that killed 50% of the shrimp of each size after 24-h exposure (LC50 -24 h) was used as an indicator of acute toxicity. Chlorine concentrations applied in the shrimp toxicity test ranged from 2.0 to 14.5 mg L,1 in shrimp pond water. As the test water contained total suspended solids of 22.0,85.0 mg L,1 and total ammonia nitrogen of 0.18,0.40 mg L,1, the resultant concentrations of combined residual chlorine ranged from 0.6 to 3.5 mg L,1, which were the effective doses causing shrimp mortality. The test results showed that 24-h LC50 for average shrimp size at 0.02, 2.75, 8.47 and 23.65 g occurred in water containing combined residual chlorine at a concentration of 0.91, 1.39, 1.74 and 1.98 mg L,1, for which the original application doses were 6.96, 2.05 11.50 and 13.34 mg L,1 respectively. [source] | ||||||||||