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Acute Toxicity Tests (acute + toxicity_test)
Selected AbstractsSmooth muscle contraction induced by Indigofera dendroides leaf extracts may involve calcium mobilization via potential sensitive channelsPHYTOTHERAPY RESEARCH, Issue 7 2003S. Amos Abstract The contractile effects of the aqueous extract of the leaves of Indigofera dendroides (ID) were studied on the gastrointestinal motility in mice and isolated smooth muscle preparations obtained from rats and guinea pigs. The contractile effects of 10,6 M acetylcholine, 80 mM KCl and 1.6 mg/ml ID were measured on the rat ileal smooth muscle exposed to calcium-free buffer or physiological solution, to determine the calcium pools mobilized by extract for activation of contraction. Acute toxicity test (LD50) was also carried out in mice. The result showed that ID (0.05,3.2 mg/ml) produced a concentration-dependent contraction of the guinea pig and rat ileum. These responses were not blocked by mepyramine (2.49 × 10,9 M), verapamil (8.14 × 10,9 M), or pirenzepine (4.7 × 10,7 M), but were blocked completely by atropine (2.92 × 10,9 M). A signi.cant increase in propulsion of gastrointestinal motility was observed. Acetylcholine, KCl and ID produced contractions in Ca2+ free media. The phasic components of the contractile responses to Ach as well as the tonic component of K+ and ID-induced contractions were relatively resistant to short periods of calcium-free exposure. Ach, K+ and ID still caused contractions in the presence of verapamil. The data revealed that ID-induced contractions were not mediated by histaminergic receptors, calcium channels, M1 muscarinic receptors. It also suggests that Ach mobilize Ca from some tightly bound or intracellular pool, whereas high K+ and ID may mobilize Ca from some superficial or loosely-bound pool. Copyright © 2003 John Wiley & Sons, Ltd. [source] QSARs for aromatic hydrocarbons at several trophic levelsENVIRONMENTAL TOXICOLOGY, Issue 2 2006Walter Di Marzio Abstract Quantitative structure,activity relationships (QSARs) with aromatic hydrocarbons were obtained. Biological response was measured by acute toxicity of several aquatic trophic levels. The chemicals assayed were benzene, toluene, ethylbenzene, o -xylene, m -xylene, p -xylene, isopropylbenzene, n -propylbenzene, and butylbenzene. Acute toxicity tests were carried out with Scenedesmus quadricauda, as representative of primary producers; Daphnia spinulata, a zooplanctonic cladoceran; Hyalella curvispina, a benthic macroinvertebrate; and Bryconamericus iheringii, an omnivorous native fish. The EC50 or LC50 was calculated from analytical determinations of aromatic hydrocarbons. Nonlinear regression analysis between the logarithm of the octanol,water partition coefficient (log Kow) of each compounds and the toxicity end points was performed. QSARs were positively related to increases in log Kow at all trophic levels. Intertaxonomic differences were found in comparisons of algae with animals and of invertebrates with vertebrates. We observed that these differences were not significant with a log Kow higher than 3 for all organisms. Aromatic hydrocarbons with log Kow values of less than 3 showed different toxicity responses, with algae more resistant than fish and invertebrates. We concluded that this was a result of the narcotic mode of action related to liposolubility and the ability of the compound to reach its target site in the cell. The bioconcentration factor (BCF) achieved to start nonpolar narcosis fell almost 1 order of magnitude below the BCF expected from the log Kow. Predicted critical body residues for nonpolar narcosis ranged between 2 and 1 mM. © 2006 Wiley Periodicals, Inc. Environ Toxicol 21: 118,124, 2006. [source] Early signs of lethal effects in Daphnia magna (Branchiopoda, Cladocera) exposed to the insecticide cypermethrin and the fungicide azoxystrobinENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2010Ursula Friberg-Jensen Abstract This study presents the effects of sublethal concentrations of pesticides cypermethrin and azoxystrobin on the activity of several physiological parameters of egg-carrying Daphnia magna studied using a video-image technique. Single tethered daphnids were continuously recorded for 24,h of pesticide exposure, and the activity of the heart, the filtering limbs, the mandibles, and the focal spine were subsequently analyzed. Acute toxicity tests based on the criteria of immobilization were performed on egg-carrying D. magna, and sublethal concentrations of 0.1, 1.0, and 10,µg/L cypermethrin and 0.5, 1.0, and 2.0,mg/L azoxystrobin were established. At a concentration as low as 0.1,µg/L cypermethrin, the 5% effective concentration after 24,h of exposure (EC5,24h), the activity of the focal spine increased and the filtering limb activity decreased. The activity of the mandibles was reduced by exposure to 1.0 (EC18,24,h) and 10,µg/L (EC41,24,h) cypermethrin, whereas heart activity increased at a concentration of 10,µg/L (EC41,24,h). With regard to azoxystrobin, the activity of all response parameters except the focal spine decreased by exposure to 0.5,mg/L (EC4,24h) azoxystrobin. The focal spine was not affected by azoxystrobin. The results show that physiological mechanisms important for ingestion of food in D. magna may be impaired by low concentrations of commonly used pesticides. Environ. Toxicol. Chem. 2010;29:2371,2378. © 2010 SETAC [source] Alternative approaches can greatly reduce the number of fish used for acute toxicity testingENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2006Conny C. Hoekzema Abstract Acute toxicity tests with algae, daphnids, and fish are required for the classification and environmental risk assessment of chemicals. The degree of risk is determined by the lowest of these acute toxicity values. Many ecotoxicological programs are seeking to reduce the numbers of fish used in acute toxicity testing. The acute threshold test is a recently proposed strategy that uses, on average, only 10 (instead of 54) fish per chemical. We examined the consequences of reducing the number of fish used in toxicity testing on the ultimate outcome of risk assessments. We evaluated toxicity data sets for 507 compounds, including agrochemicals, industrial chemicals, and pharmaceuticals from our internal database. Theoretical applications of the acute threshold test gave similar results to those obtained with the standard fish median lethal concentration (LC50) test but required only 12% as many fish (3,195 instead of 27,324 fish used for all compounds in the database). In 188 (90%) of the 208 cases for which a complete data set was available, the median effect concentration for algae or daphnids was lower than the LC50 for fish. These results show that replacement of the standard fish LC50 test by the acute threshold test would greatly reduce the number of fish needed for acute ecotoxicity testing without any loss of reliability. [source] Source of toxicity in storm water: Zinc from commonly used paintENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2004Lynn Adams Kszos Abstract A Department of Energy site in Paducah, Kentucky (USA), stores thousands of cylinders of depleted uranium hexa-fluoride. Breaches of the cylinders could result in the release of uranium and hydrogen fluoride. Beginning in 1996, a program was begun to paint the cylinders in order to prevent corrosion of the cylinders and the surfaces of the storage yards were converted to concrete. In 1998, storm water from the cylinder storage yards was found to be toxic to Ceriodaphnia, at concentrations exceeding limits in the site's discharge permit. A six-month study was conducted to identify the source of the toxicity in the storm water. Ceriodaphnia toxicity tests with the storm water resulted in 48-h median lethal concentrations (LC50) ranging from 12 to 94%; zinc concentrations in the storm water ranged from 0.08 to 0.54 mg/L. Acute toxicity tests with zinc and linear regression identified that zinc concentrations in the storm water were sufficient to account for the toxicity observed. By tracking the sources to the discharge point, newly painted cylinders were identified as the source of the zinc in the storm water. Rainwater collected directly from the painted cylinders contained up to 13 mg Zn/L. Laboratory and field tests showed that topcoating the cylinders would reduce the amount of zinc in the runoff from the cylinders. [source] Preparation and application of a novel environmentally friendly organic seed coating for riceJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 13 2009Defang Zeng Abstract BACKGROUND: Traditional rice seed coating techniques involve the use of chemical pesticides, which can damage the seed in the process and cause possible physical and environmental damage. Increasing knowledge and concern about the traditional applications have brought new attention to the industry and the search for a novel coating agent that is effective, safe and environmentally friendly. A new type of organic rice seed coating agent was developed using liquid-based polymeric adhesives. By using chitosan as the main raw material, modified with sodium hydroxide and polymerised with plant growth regulators and other additives, the novel seed coating agent is a safer, cheaper and more environmentally friendly alternative. RESULTS: The novel seed coating agent significantly enhanced sprout growth over traditional agents. We found it has obvious biological advantages: it stimulates the seedling growth of rice, advances the growth of root, improves root activity and increases the crop yield in the germination test and field trial. Compared with the traditional rice seed coating agent, the crop yield of seeds coated by the novel seed coating agent was increased by 5%, and at 25% less cost. The fungal inhibition test of the novel seed coating agent and acute toxicity test on fish showed that it has an obvious fungal inhibitory effect and a higher safety index during usage and disposal. CONCLUSION: This result suggests that treating seeds with the novel seed coating agent has significant agricultural implications through the enhanced seed vigour as reflected in growth. It is efficient and effective, resulting in better seed and crop protection. The novel seed coating agent demonstrates unique characteristics with great economic and environmental benefits. Copyright © 2009 Society of Chemical Industry [source] Hydrogenated castor oil nanoparticles as carriers for the subcutaneous administration of tilmicosin: in vitro and in vivo studiesJOURNAL OF VETERINARY PHARMACOLOGY & THERAPEUTICS, Issue 2 2009C. HAN Tilmicosin-loaded solid lipid nanoparticles (SLN) were prepared with hydrogenated castor oil (HCO) by o/w emulsion,solvent evaporation technique. The nanoparticle diameters, surface charges, drug loadings and encapsulation efficiencies of different formulations were 90,230 nm, ,6.5,,12.5 mV, 40.3,59.2% and 5.7,11.7% (w/w), respectively. In vitro release studies of the tilmicosin-loaded nanoparticles showed a sustained release and the released tilmicosin had the same antibacterial activity as that of the free drug. Pharmacokinetics study after subcutaneous administration to Balb/c mice demonstrated that a single dose of tilmicosin-loaded nanoparticles resulted in sustained serum drug levels (>0.1 ,g/mL) for 8 days, as compared with only 5 h for the same amount of tilmicosin phosphate solution. The time to maximum concentration (Tmax), half-life of absorption (T½ ab) and half-life of elimination (T½ el) of tilmicosin-loaded nanoparticles were much longer than those of tilmicosin phosphate solution. Tissue section showed that drug-loaded nanoparticles caused no inflammation at the injection site. Cytotoxicity study in cell culture and acute toxicity test in mice demonstrated that the nanoparticles had little or no toxicity. The results of this exploratory study suggest that the HCO,SLN could be a useful system for the delivery of tilmicosin by subcutaneous administration. [source] The hepatoprotective effects of Limonium sinense against carbon tetrachloride and , -D-galactosamine intoxication in ratsPHYTOTHERAPY RESEARCH, Issue 7 2003Shang-Shing Chaung Abstract In the present study, the hepatoprotective action of Limonium sinense (Plumbaginaceae) was evident after carbon tetrachloride (CCl4) and , -D-galactosamine (D-GalN), respectively, challenge in rats. The plant materials were divided into two parts: (1) the roots extracted with water (WRE) and (2) the leaves extracted with methanol and fractionated with chloroform (CLE). Both WRE and CLE were extremely ,avonoid-enriched extracts. In an CCl4 -induced acute liver damage study, pretreatment with WRE at 300 mg/kg i.p. and CLE at 100 mg/kg i.p. signi,cantly reduced the amino-transaminases levels of SGOT (p < 0.01) and SGPT (p < 0.01) previously increased by CCl4 intoxication. In D-GalN-induced acute liver damage study, administration of WRE (300 and 500 mg/kg) or CLE (100 mg/kg) p.o. also signi,cantly reduced the SGOT (p < 0.01) and SGPT (p < 0.01) levels previously increased by D-GalN intoxication. Furthermore, the serum triglyceride level was increased after pretreatment with WRE or CLE previously reduced by D-GalN intoxication. All of the liver function pro,les were con,rmed to have improvement of liver lesion in histopathological obsvervation. In an acute toxicity test on ICR mice, the LD50 of WRE was 777.6 mg/kg i.p. An in vitro study showed that CLE possessed a more potent cytotoxicity to human hepatocellular carcinoma cells (Hep3B) (EC50 = 43.1 µg/mL) than the other organic fractions, which were fractionated from methanol extracts of the leaves of L. sinense. The present results conclude that L. sinense possesses a hepatoprotective ef,cacy, and is relatively safe in rats. Copyright © 2003 John Wiley & Sons, Ltd. [source] Microbiological and Toxicological Effects of Perla Black Bean (Phaseolus vulgaris L.) Extracts: In Vitro and In Vivo StudiesBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 2 2009Víctor Javier Lara-Díaz Three different solvents were used to obtain Perla black bean extracts. All three Perla black bean extracts were tested for antibacterial and antiparasitic activity and further analysed for intrinsic cytotoxicity (IC50). Methanol Perla black bean extract was used for acute toxicity test in rats, with the up-and-down doping method. All Perla black bean extracts inhibited bacterial growth. Pseudomonas aeruginosa, Proteus vulgaris, Klebsiella oxytoca, Enterococcus faecalis, Staphylococcus aureus, Staphylococcus epidermidis and Listeria monocytogenes showed inhibition, while Escherichia coli and Enterobacter aerogenes did not. Acidified water and acetic acid Perla black bean extract were tested in parasites. The best IC50 was observed for Giardia lamblia, while higher concentrations were active against Entamoeba histolytica and Trichomonas vaginalis. The Vero cells toxicity levels (IC50) for methanol, acidified water and acetic acid Perla black bean extract were [mean ± S.D. (95% CI)]: 275 ± 6.2 (267.9,282.0), 390 ± 4.6 (384.8,395.2) and 209 ± 3.39 (205.6,212.4) µg/ml, respectively. In vivo acute toxicity assays did not show changes in absolute organ weights, gross and histological examinations of selected tissues or functional tests. The acetic acid and methanol Perla black bean extract proved to exhibit strong antibacterial activity and the acidified water Perla black bean extract exerted parasiticidal effects against Giardia lamblia, Entamoeba hystolitica and Trichomonas vaginalis. The three Perla black bean extracts assayed over Vero cells showed very low toxicity and the methanol Perla black bean extract in vivo did not cause toxicity. [source] Difference in the sensitivity to chemical compounds between female and male neonates of Daphnia magnaENVIRONMENTAL TOXICOLOGY, Issue 5 2008Erika Ikuno Abstract Daphnia magna usually produce female offspring by parthenogenesis, and thus only female neonates are used to evaluate the environmental toxicity to chemicals. Additionally, it is known that male daphnids are induced by exposure to a juvenile hormone, methyl farnesoate, during late ovarian development. In this study, we investigated the concentration of methyl farnesoate in a 24-h exposure producing 100% males, and the difference in sensitivity to chemical compounds, potassium dichromate, pentachlorophenol, and paraquat, between females and males, referring to OECD Test Guideline 202. The results show that the minimum concentration for 100%-male induction of methyl farnesoate in adult females was 50 ,g/L. In addition, acute toxicity tests (immobility test) with the other chemicals showed that male neonates have higher tolerance to potassium dichromate and pentachlorophenol than females for at least 24 h after birth, while no sex difference was observed in the sensitivity to paraquat. The differences in the median effective concentrations in these compounds between female and male neonates suggest two different overall modes of action. Using female daphnids for environmentally toxicity testing seems reasonable, since the females are more sensitive to chemicals than males. Furthermore, the method of male induction established in this study could be used for screening of endocrine disruptors. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008. [source] Toxicity tests to assess pollutants removal during wastewater treatment and the quality of receiving waters in ArgentinaENVIRONMENTAL TOXICOLOGY, Issue 3 2001Carlos E. Gómez Abstract In Argentina, legislation to control adverse impacts of effluent discharges and the quality of receiving waters is scant and relies mainly on the physicochemical characteristics of the effluents and receiving waters. Objectives of this study were to use standardized acute toxicity tests to assess treatment of petrochemical industry effluents and the toxicity of various treated industrial effluents in the Buenos Aires metropolitan area and their receiving waters. Tests for the first objective used Daphnia magna and Ceriodaphnia dubia; those for the second used D. magna, Spirillum volutans, and Scenedesmus spinosus. Chemical analyses demonstrated that the removal of aromatic hydrocarbon compounds (benzene, toluene, ethylbenzene, xylene, styrene, and naphthalene) from the petrochemical effluents ranged between 77 and 93%, but toxicity removal was significantly lower: untreated effluents were very toxic and treated effluents were very toxic to toxic [acute toxicity units (TUa)>3]. Physicochemical parameters measured according to current Argentinian regulations indicated that industrial effluents (e.g., from textile and paper industries) were within established guidelines, but 25% of the samples were moderately to highly toxic (TUa>1.33). However, for the receiving waters, toxicity tests were moderate to very toxic. The results show the need of including tests for toxicity of discharged effluents, and their effects on receiving waters of Argentina, especially for regulatory purposes. © 2001 John Wiley & Sons, Inc. Environ Toxicol 16: 217,224, 2001 [source] Technical basis for polar and nonpolar narcotic chemicals and polycyclic aromatic hydrocarbon criteria.ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2009Abstract A method is presented for extending the target lipid model (TLM) of narcotic toxicity to polar narcotic chemicals. The proposed polyparameter TLM extends the applicability of the TLM by including polar compounds and removing explicit chemical class corrections. The validity of the model is tested using a data set of 1,687 acute toxicity tests for 42 aquatic species, including fish, amphibians, arthropods, mollusks, polychaetes, coelenterates, protozoans, and algae, and 398 chemicals. The target lipid-water partition coefficient is computed using the Abraham polyparameter model. This replaces use of the octanol-water partition coefficient so that the partitioning of polar narcotic chemicals can be described correctly. The model predicts the log median lethal concentration with a root mean square error of 0.460 for nonpolar and polar chemicals and 0.501 for only polar chemicals. [source] Acute and chronic toxicity of mercury to early life stages of the rainbow mussel, Villosa iris (Bivalvia: Unionidae)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2005Theodore W. Valenti Abstract Mercury (Hg) contamination is receiving increased attention globally because of human health and environmental concerns. Few laboratory studies have examined the toxicity of Hg on early life stages of freshwater mussels, despite evidence that glochidia and juvenile life stages are more sensitive to contaminants than adults. Three bioassays (72-h acute glochidia, 96-h acute juvenile, and 21-d chronic juvenile toxicity tests) were conducted by exposing Villosa iris to mercuric chloride salt (HgCl2). Glochidia were more sensitive to acute exposure than were juvenile mussels, as 24-, 48-, and 72-h median lethal concentration values (LC50) for glochidia were >107, 39, and 14 ,g Hg/L, respectively. The 24-, 48-, 72-, and 96-h values for juveniles were 162, 135, 114, and 99 ,g Hg/L, respectively. In the chronic test, juveniles exposed to Hg treatments ,8 ,g/L grew significantly less than did control organisms. The substantial difference in juvenile test endpoints emphasizes the importance of assessing chronic exposure and sublethal effects. Overall, our study supports the use of glochidia as a surrogate life stage for juveniles in acute toxicity tests. However, as glochidia may be used only in short-term tests, it is imperative that an integrated approach be taken when assessing risk to freshwater mussels, as their unique life history is atypical of standard test organisms. Therefore, we strongly advocate the use of both glochidia and juvenile life stages for risk assessment. [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] In vitro and in vivo estrogenicity and toxicity of o -, m -, and p -dichlorobenzeneENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2003Bram J. Versonnen Abstract The estrogenicity of o -, m -, and p -dichlorobenzene (DCB) was evaluated with a yeast estrogen screen (YES) and zebrafish (Danio rerio) vitellogenin (VTG) assays. With the YES, p -DCB and m -DCB were found to be estrogenic in a concentration-responsive manner. The relative potency measured with the YES (relative to 17,-estradiol) was 2.2 × 10,7 for p -DCB and 1.04 × 10,8 for m -DCB. Following acute toxicity tests with the zebrafish, plasma VTG production was measured to examine the in vivo estrogenic activity of the three compounds after a 14-d exposure. Adult zebrafish were exposed to different concentrations of o -, m - and p -DCB, ranging from 0.1 to 32 mg/L; ethynylestradiol ([EE2]; 5 ng/L, 10 ng/L, 50 ng/L, and 100 ng/L) was used as a positive control. After exposure, blood samples were taken and protein electrophoresis was performed to determine the relative VTG content. Gonadosomatic indices (GSI) and condition factors (CF) were also calculated. Elevated VTG levels and decreased female GSIs were found in fish exposed to ,5 ng EE2/L and in fish exposed to ,10 mg p -DCB/L. Low GSIs coincided with high levels of VTG in the blood of female zebrafish. This relation was not only found in fish exposed to EE2 but also in controls and fish exposed to DCB. Therefore, a direct or indirect effect of VTG on the GSI is suggested rather than a direct toxic effect of the tested compounds on the gonads. [source] Discrepancy between acute and chronic toxicity induced by imidacloprid and its metabolites in Apis melliferaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2001Séverine Suchail Abstract Imidaclopridi a systemic nitroguanidine insecticide that belongs to theneonicotinoid family. As an agonist of the acetylcholine receptor, it attacks the insect nervous system and is extremely effective against various sucking and mining pests. Oral acute and chronic toxicity of imidacloprid and its main metabolites (5-hydroxyimidacloprid, 4,5-dihydroxyimidacloprid, desnitroimidacloprid, 6-chloronicotinic acid, olefin, and urea derivative) were investigated in Apis mellifera. Acute intoxication by imidacloprid or its metabolites resulted in the rapid appearance of neurotoxicity symptoms, such as hyperresponsiveness, hyperactivity, and trembling and led to hyporesponsiveness and hypoactivity. For acute toxicity tests, bees were treated with doses of toxic compounds ranging from 1 to 1,000 ng/bee (10,10,000 ,g/kg). Acute toxicity (LD50) values of imidacloprid were about 60 ng/bee (600 ,g/kg) at 48 h and about 40 ng/bee (400 ,g/kg) at 72 and 96 h. Out of the six imidacloprid metabolites tested, only two (5-hydroxyimidacloprid and olefin) exhibited a toxicity close to that of imidacloprid. Olefin LD50 values were lower than those of imidacloprid. The 5-hydroxyimidacloprid showed a lower toxicity than imidacloprid with a LD50 four to six times higher than that of imidacloprid. Urea also appeared as a compound of nonnegligible toxicity by eliciting close to 40% mortality at 1,000 ng/bee (10,000 ,g/kg). However, no significant toxicity was observed with 4,5-dihydroxyimidacloprid, 6-chloronicotinic acid, and desnitroimidacloprid in the range of doses tested. To test chronic toxicity, worker bees were fed sucrose solutions containing 0.1, 1, and 10 ,g/L of imidacloprid and its metabolites for 10 d. Fifty percent mortality was reached at approximately 8 d. Hence, considering that sucrose syrup was consumed at the mean rate of 12 ,l/d and per bee, after an 8-d period the cumulated doses were approximately 0.01, 0.1, and 1 ng/bee (0.1, 1, and 10 ,g/kg). Thus, all tested compounds were toxic at doses 30 to 3,000 (olefin), 60 to 6,000 (imidacloprid), 200 to 20,000 (5-OH-imidacloprid), and >1,000 to 100,000 (remaining metabolites) times lower than those required to produce the same effect in acute intoxication studies. For all products tested, bee mortality was induced only 72 h after the onset of intoxication. [source] Site-specific marine water-quality criterion for cyanideENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2000Kevin V. Brix Abstract A site-specific marine water,quality criterion for cyanide was developed for Puget Sound, Washington, USA. The U.S. Environmental Protection Agency (U.S. EPA) national cyanide water-quality criterion is driven by toxicity data for the eastern rock crab, Cancer irroratus, a species not resident to the U.S. western coast (West Coast). The reported LC50 for C. irroratus is six times lower than any other marine species tested. Cyanide acute toxicity tests were conducted using first stage zoeae of all four species of Cancer spp. resident to Puget Sound to develop a site-specific criterion for this water body. Testing with Puget Sound Cancer spp. reveals sensitivities 24 times less, on average, than C. irroratus. Recalculation of the Puget Sound water-quality criterion for cyanide, by substituting the new Cancer spp. data for the C. irroratus data, results in water-quality criterion protecting marine life against acute and chronic toxicity of 9.4 and 2.9 ,g/L cyanide, compared to the U.S. EPA national value of 1.0 ,g/L for both acute and chronic toxicity. [source] | ||||||||||