Toxicity and mutagenicity of the molluscicidal plant Ambrosia maritima L.

The acute and subchronic toxicity of the molluscicidal plant, Ambrosia maritima L., has been tested on rats. No toxic signs could be detected neither after oral administration of 5 g/kg of dried leaves of the plant as a powder or as a methanolic extract, nor after the incorporation of 50,000 ppm powdered leaves in the feed during 4 weeks. Using an aqueous extract of the plant material of A. maritima or using ambrosin, one of the active molluscicidal components of the plant, no mutagenic activity could be detected in the S. typhimurium strains TA97, TA 98, TA1538, TA100 and TA1535.     

Anacardic acid: molluscicide in cashew nut shell liquid

The components of anacardic acid, (a mixture of 6-n-C (15) alkylsalicylic acids whose side chains vary in degrees of unsaturation) have been isolated by high pressure liquid chromatography from a crude extract of cashew nut shell, ANACARDIUM OCCIDENTALE, and tested for toxicity to fresh water snails, BIOMPHALARIA GLABRATA. The triene component is the most toxic form (LC (50) 0.35 ppm), the diene and monoene components are less toxic (LC (50) 0.9 and 1.4 ppm), and the saturated component is relatively nontoxic (LC (50) > 5 ppm). Since decarboxylated anacardic acid (cardanol) and salicylic acid do not kill snails at concentrations up to 5 ppm, it appears that both, carboxyl group and unsaturated side chain are absolutely required for molluscicidal activity. The mechanism of toxicity of anacardic acid to snails is unknown.     

Inhalation toxicity of dibutylhexamethylenediamine in rats

Dibutylhexamethylenediamine (DBHMD), a polymer intermediate, is strongly alkaline and is corrosive to eyes and skin. Its inhalation toxicity was defined in rats in both acute and subchronic studies. A 4-hr LC50 of 0.22 mg/litre was obtained for DBHMD of either 80.6 or 98.25% purity. Clinical signs of irritation were apparent during and immediately following exposure and no delayed deaths occurred. The mortality dose-response line was relatively steep. Reduction of exposure times to 5 min produced an LC50 of 51 mg/litre, with similar clinical signs and a steep dose-response line. These data suggest that the product of concentration and time (Ct) is constant for exposure times ranging from 5 min to 4 hr. Repeated (ten) exposures to 0.0125 mg/litre caused no signs of adverse response in rats. A concentration of 0.0234 mg/litre caused some mortality, mucous-membrane irritation, changes in haematological parameters (including erythrocyte counts, haemoglobin, concentration and total and differential leucocyte counts) and an increased acidity and decreased volume of urine. Death at this exposure level was attributed to cardiac failure secondary to pulmonary oedema and congestion, with evidence of hepatic congestion, diffuse cardiac myocytolysis and oedema, and thymic atrophy and congestion. Changes in the heart and thymus were seen in one of two rats killed after the tenth exposure. Clinical and pathological changes observed after the ten exposures were absent after a 14-day recovery period. DBHMD is highly toxic following acute inhalation and produces a steep dose-response following either single or multiple exposures.     

Toxicity of perfluorooctane sulfonate and perfluorooctanoic acid to plants and aquatic invertebrates

Acute toxicities of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) were tested on four freshwater species and three plant species. PFOS was more toxic than PFOA for all species tested in this study. Similar time-response patterns of PFOS and PFOA toxicity were observed for each tested species. Values of the 48-h LC(50) of PFOS for all test species ranged from 27 to 233 mg/L and values of the 96-h LC(50) for three of the species ranged from 10 to 178 mg/L. Values of the 48-h LC(50) of PFOA for all test species ranged from 181 to 732 mg/L and values of the 96-h LC(50) for three of the species ranged from 337 to 672 mg/L. The most sensitive freshwater species to PFOS was green neon shrimp (Neocaridina denticulate) with a 96-h LC(50) of 10 mg/L. Of the aquatic organisms tested, the aquatic snail (Physa acuta) always has the highest resistance to PFOS or PFOA toxicity over each exposure period. Both PFOS and PFOA had no obvious adverse effect on seed germination for all three plant species. Five-day EC(50) of root elongation was more sensitive to LC(50) of seed germination in this study. Based on EC(10), EC(50), and NOECs, the 5-day root elongation sensitivity of test plants to both PFOS and PFOA was in the order of lettuce (Lactuca sativa) > pakchoi (Brassica rapa chinensis) > cucumber (Cucumis sativus). Based on the results of this study and other published literature, it is suggested that current PFOS and PFOA levels in freshwater may have no acute harmful ecological impact on the aquatic environment. However, more research on the long-term ecological effects of PFOS and PFOA on aquatic fauna are needed to provide important information to adequately assess ecological risk of PFOS and PFOA.     

The influence of microcystin-LR and hepatotoxic cyanobacterial extract on the water plant Spirodela oligorrhiza

The eutrophication of the Sulejów Reservoir dam in Poland is related to toxicity from cyanobacterial blooms. The main species responsible for hepatotoxic bloom formation is Microcystis aeruginosa. The aim of this study was to evaluate the influence of toxic cyanobacterial extract on the growth and morphology of the water plant Spirodela oligorrhiza, compared with commercial-grade microcystin-LR (MC-LR). It was found that after 96 h of incubation the highest concentration of cyanobacterial extract, containing 0.344 mg MC-LR/L, reduced the number of fronds by about 50% in comparison with the control. The extract effected a reduction in the frond mass and a decrease in chlorophyll (a + b) concentration. A reduction in the number of fronds was also observed after the first 24 h of incubation in the presence of 0.2 and 0.1 microg/L of commercial-grade MC-LR. Changes in activity of constitutive acid phosphatase and RNase after 7 days of incubation with commercial-grade MC-LR were observed. The results confirm the toxicity of cyanobacterial hepatotoxins to Spirodela oligorrhiza, which can be used as a sensitive bioindicator.     

Molluscicidal and larvicidal activities and essential oil composition of Cymbopogon winterianus

Abstract

Context. Cymbopogon winterianus Jowitt ex Bor (Poaceae), known as citronella grass, is an aromatic herbaceous plant and the essential oil extracted from this grass is used in cosmetics, perfumes, hygiene and cleanliness products worldwide.

Objective: This study investigated the composition and molluscicidal and larvicidal activities of the essential oil of C. winterianus cultivated in North Brazil.

Materials and methods: The oil was obtained by hydrodistillation, analyzed by gas chromatography (GC) and GC-mass spectrometry and then its molluscicidal and larvicidal activities against snails (Biomphalaria glabrata) and hatched larvae of Artemia salina, respectively, were evaluated at concentrations from 10 to 1000?mg/L.

Results: The main constituents of oil were citronellal (26.5%), geraniol (16.2%), elemol (14.5%) and citronellol (7.3%). The molluscicidal test revealed significant lethal concentration (LC) values (LC₉₀?=?97.0?mg/L, LC₅₀?=?54.0?mg/L and LC₂₀?=?22.0?mg/L), indicating the presence of molluscicidal compounds in the oil. In addition, the oil showed moderate larvicidal activity (LC₅₀?=?181.0?mg/L) against the larvae of A. salina, which could justify its use in the aquatic environment without affecting other living organisms.

Discussion and conclusion: The results suggest that the oil of C. winterianus could be an effective alternative to control schistosomiasis, with an average margin of safety to other living organisms that coexist with snails.     

Piscicidal and anti-acetylcholinesterase activity of Euphorbia royleana stem bark extracts against freshwater common predatory fish Channa punctatus

The present paper deals with the piscicidal activity of different solvent extracts of Euphorbia royleana stem bark against freshwater predatory fish Channa punctatus, which is commonly present in shrimp and carp culture ponds. The rank of order of toxicity of different solvent extract was: diethyl ether (LC(50) (96h) 31.76mg DW/L) > chloroform (LC(50) (96h) 56.26mg DW/L) > methanol (LC(50) (96h) 56.80mg DW/L) > acetone (LC(50) (96h) 65.77mg DW/L). There was a significant (P < 0.05) negative correlation between LC values and exposure periods, thus increase in exposure time. The LC(50) values of diethyl ether extract of E. royleana stem bark decrease from 81.78mg DW/L (24h) to 31.76mg DW/L (96h). Similar trend were also observed in case of chloroform, methanol and acetone extracts. Exposure of sub-lethal doses (40% and 80% of LC(50)) of the diethyl ether extract for 24h or 96h caused significant inhibition in the activity of enzyme acetylcholinesterase (AChE) in liver and muscle tissue of fish C. punctatus. There was a significant recovery observed in the activity of enzyme acetylcholinesterase in both the tissues of fish after 7th day of the withdrawal of treatment. Thus, the diethyl ether extract of E. royleana stem bark can be used for control of unwanted predatory fish C. punctatus from fish culture ponds. Their toxicological action is due to their anti-acetylcholinesterase enzyme activity, reversibility in their action is advantageous factor for their use as environmentally safe piscicide in aquatic bodies.     

Toxicities of triclosan, phenol, and copper sulfate in activated sludge

The effect of toxicants on the BOD degradation rate constant was used to quantitatively establish the toxicity of triclosan, phenol, and copper (II) against activated sludge microorganisms. Toxicities were tested over the following ranges of concentrations: 0-450 mg/L for phenol, 0-2 mg/L for triclosan, and 0-35 mg/L for copper sulfate (pentahydrate). According to the EC(50) values, triclosan was the most toxic compound tested (EC(50) = 1.82 +/- 0.1 mg/L), copper (II) had intermediate toxicity (EC(50) = 18.3 +/- 0.37 mg/L), and phenol was the least toxic (EC(50) = 270 +/- 0.26 mg/L). The presence of 0.2% DMSO had no toxic effect on the activated sludge. The toxicity evaluation method used was simple, reproducible, and directly relevant to activated sludge wastewater treatment processes.     

Toxicity of methanol to fish, crustacean, oligochaete worm, and aquatic ecosystem

Static renewal bioassays were conducted in the laboratory and in outdoor artificial enclosures to evaluate toxic effects of methanol to one teleost fish and two aquatic invertebrates and to limnological variables of aquatic ecosystem. Ninety-six-hour acute toxicity tests revealed cladoceran crustacea Moina micrura as the most sensitive to methanol (LC50, 4.82 g/L), followed by freshwater teleost Oreochromis mossambicus (LC50, 15.32 g/L) and oligochaete worm Branchiura sowerbyi (LC50, 54.89 g/L). The fish, when exposed to lethal concentrations of methanol, showed difficulties in respiration and swimming. The oligochaete body wrinkled and fragmented under lethal exposure of methanol. Effects of five sublethal concentrations of methanol (0, 23.75, 47.49, 736.10, and 1527.60 mg/L) on the feeding rate of the fish and on its growth and reproduction were evaluated by separate bioassays. Ninety-six-hour bioassays in the laboratory showed significant reduction in the appetite of fish when exposed to 736.10 mg/L or higher concentrations of methanol. Chronic toxicity bioassays (90 days) in outdoor enclosures showed a reduction in growth, maturity index and fecundity of fish at 47.49 mg/L or higher concentrations of methanol. Primary productivity, phytoplankton population, and alkalinity of water were also reduced at these concentrations. Chronic exposure to 1527.60 mg/L methanol resulted in damages of the epithelium of primary and secondary gill lamellae of the fish. The results revealed 23.75 mg/L as the no-observed-effect concentration (NOEC) of methanol to freshwater aquatic ecosystem.     

Molluscicidal activity of Solanum elaeagnifolium seeds against Galba truncatula intermediate host of Fasciola hepatica: Identification of β-solamarine

Context: The persistence of fascioliasis in many developing countries urges the search for simple, cheap, and effective substances. In this view, plants provide interesting molluscicidal activities thanks to the secondary metabolites they produce. The genus Solanum is known for its potent effect on vector snails.

Objective: The molluscicidal activity of Solanum elaeagnifolium Cav. (Solanaceae) seeds against Galba truncatula Müll. (Lymnaeidae), intermediate host of Fasciola hepatica L. (Fasciolidae), was evaluated.

Materials and methods: Solanum elaeagnifolium seeds were powdered and successively extracted using n-hexane, methylene chloride, acetone, and methanol, for 20?h each. After filtration, solvents were evaporated. An acid–base treatment was conducted on seed methanolic extract to isolate total alkaloids and β-solamarine. Total saponins fraction was obtained after successive macerations and evaporations. The molluscicidal activity was evaluated by subjecting snails, in groups of 10, for 48?h to 500?mL of extracts, fractions, and pure product aqueous solutions, each containing amounts, ranging from 1 to 50?mg of plant material in 5?mg increments.

Results: The methanolic extract of seeds, β-solamarine isolated for the first time from this plant and total saponins fraction showed very potent activities on snails, giving respective median lethal concentrations (LC₅₀) of 1.18, 0.49, and 0.94?mg/L. Total alkaloids fraction obtained from the methanolic extract was less active giving an LC₅₀ value of 14.67?mg/L.

Discussion and conclusion: This study emphasizes that glycoalkaloids and saponins of Solanum elaeagnifolium are potent molluscicidal agents. Seed methanolic extract, β-solamarine, and total saponins fraction may be used as molluscicides.     

Comparison of R-metalaxyl and rac-metalaxyl in acute, chronic, and sublethal effect on aquatic organisms: Daphnia magna, Scenedesmus quadricanda, and Danio rerio

Chiral pesticides are used widely in the world, and at present, older racemic products are being replaced by enantiopure products because of accelerated development of asymmetry synthesis techniques. Pesticides as xenobiotic released into environment impose a great stress on nontarget organisms. Although it is a necessary procedure for pesticides to have a registration based on toxicological data from nontarget organism, until now ecological risk assessment about metalaxyl only depend on racemic products. Hence, we investigated the acute, chronic, and sublethal toxicity of R-metalaxy and rac-metalaxyl on aquatic organisms such as D. magna (Daphnia magna), algae (Scenedesmus quadricanda), and adult zebrafish (Danio rerio). The results showed a significant difference in toxicity between R-metalaxyl and rac-metalaxyl. R-Metalaxy was about 20-fold more toxic to algae than rac-metalaxyl with IC(50) of 222.89 +/- 1.18 mg/L and 19.95 +/- 1.12 mg/L, respectively. Similarly, R-metalaxyl was about fourfold toxic to D. magna than rac-metalaxyl according to the individual 24-h-LC(50) values, and sixfold toxic than rac-metalaxyl based on 24-h-EC(50) values. In the light of 48-h-LC(50) and EC(50), this difference in toxicity was more significant. As for adult zebrafish, there was no pronounced difference in acute toxicity, in addition, at sublethal level a different pattern in inducing Na(+),K(+)-ATPase activity between them was found. In general, R-metalaxyl seemed more toxic to aquatic organisms than rac-metalaxyl.     

Acute toxicity of Phytolacca dodecandra (Endod-S) and Niclosamide to snails,Schistosoma mansoni cercaria,Tilapia fish,and soil microorganisms

The acute toxicity of two molluscicides, the extract of the plant Phytolacca dodecandra (Endod-S) and Niclosamide, was determined using the following test species: The snails Biomphalaria glabrata (albino) and Biomphalaria pfeifferi, Schistosoma mansoni cercaria, and Tilapia nilotica fish. Endod-S showed a 24-h LC₅₀ of 2.57 and 5.37 mg/L for B. glabrata (albino) and B. pfeifferi respectively. Niclosamide produced a 24-h LC₅₀ of 0.063 mg/L and 0.049 mg/L for B. glabrata (albino) and B. pfeifferi, respectively. The 4-h LC₅₀ for S. mansoni cercaria was 2.92 mg/L for Endod-S and 0.0008 mg/L for Niclosamide. The 24-h LC₅₀ for Tilapia nilotica was 1.82 mg/L for Endod-S and 0.21 mg/L for Niclosamide. The toxicity of Endod-S and Niclosamide to a mixed population of soil microorganisms was measured using oxygen uptake and growth as measured by turbidity. Endod-S was not toxic to the microorganisms. The average Niclosamide toxic end point (IC₅₀) for these bacteria was 450 mg/L.     

Study on the toxicity of sodium bromide to different freshwater organisms

The toxicity of sodium bromide for freshwater organisms was tested using algae (Scenedesmus pannonicus), crustaceans (Daphnia magna) and fish (Poecilia reticulata and Oryzias latipes). Depending on the species tested, the acute toxicity varied from 44 to 5800 mg Br-/litre (EC50 values) and the No Observed Effect Concentrations (NOEC values) in the long-term tests varied from 7.8 to 250 mg Br-/litre. Bromide ion markedly impaired reproduction in both crustaceans and fish. Histologically no effects were observed in the long-term test with Oryzias, but in the reproduction test with Poecilia, hyperplasia of the thyroid, atrophy and degeneration of the musculature and regressive changes in the female reproductive tract were observed. As a criterion of water quality, 1 mg Br-/litre has been proposed, on the basis of reproductive performance in the Poecilia test. The concentrations found in surface water frequently exceed this value and sometimes reach levels at which acute effects on water organisms can be expected.     

Acute toxicity, behavioral changes, and histopathological effects of deltamethrin on tissues (gills, liver, brain, spleen, kidney, muscle, skin) of Nile tilapia (Oreochromis niloticus L.) fingerlings

Deltamethrin, a synthetic pyrethroid contaminating aquatic ecosystems as a potential toxic pollutant, was investigated in the present study for acute toxicity. The purpose of this study was to evaluate LC(50) values of deltamethrin on Nile tilapia (Oreochromis niloticus L.) fingerlings and investigate histopathological responses of fish exposed to deltamethrin. The 48 h LC(50) value for Nile tilapia fingerlings was estimated as 4.85 microg/L using static test system. In addition, behavioral changes at each deltamethrin concentration were observed closely. All fish, exposed to 5 microg/L deltamethrin revealed severe morphological alterations in the gills and liver. In the gills hyperemia, fusion of secondary lamellae and telangiectasis were observed; whereas hydropic degenerations in liver were observed in all examined fish. The results are significant for reporting acute deltamethrin toxicity in terms of behavioral and histopathological changes: Deltamethrin is highly toxic to fingerlings.     

Acute inhalation toxicity of cetylpyridinium chloride

Cetylpyridinium chloride (CPC) is a quaternary ammonium salt and cationic surfactant. It has been used as a biocide in personal hygiene products and a charge control additive in some reprographic toners. CPC is orally toxic to rats, mice and rabbits and can cause severe eye irritation. Acute inhalation toxicity studies of CPC and other quaternary ammonium salts have not, however, been reported. Groups of five rats per sex were exposed to aerosols containing 0 (control), 0.05, 0.07, 0.13 and 0.29 mg CPC/litre for 4 hr and observed for toxicity and ocular effects for 14 days thereafter. All animals were subjected to autopsy and the eyes were examined microscopically. The LC₅₀ (sexes combined) of CPC was 0.09 mg/litre with upper and lower 95% confidence limits of 0.13 and 0.07 mg/litre, respectively. Clinical signs of toxicity included weight loss, nasal discharge, chromodacryorrhoea, respiratory difficulty and eye irritation, and all these non-lethal effects were reversible. Acute inflammation of the cornea, iris and/or aqueous humour were found in one, seven and four of 10 rats exposed to 0.07, 0.13 and 0.29 mg CPC/litre, respectively. Corneal epithelial hyalinization, without evidence of ongoing inflammation, was found in three additional rats among the 10 exposed to 0.29 mg CPC/litre.     

Acute toxicity of seeds of the sapodilla (Achras sapota L.)

An aqueous extract of the sapodilla seed (Achras sapota L.) was acutely toxic to mice and rats (i.p. LD50 = 190 and 250 mg/kg, respectively) with symptoms of dyspnoea, apnoea and convulsions. Soxhlet extraction and chromatographic separation of the seed constituents yielded a brown amorphous solid containing saponin. This was heat-stable and toxic by the i.p. route (LD50 = 30-50 mg/kg) but non-toxic by the oral route in mice and rats. It is proposed that the toxicity of the sapodilla seed is due mainly to the saponin content.     

Ambrosia maritima L.: study of molluscicidal properties of several generations originating in Egypt and cultivated in Senegal

The authors experiment molluscicidal properties of Ambrosia maritima L. from Egypt and cultivated in Senegal. Four generations are tested. Six plants, on eight tested, had same molluscicidal activity as the strain in Egypt.     

A new approach for the assessment of acrylamide toxicity using a green paramecium.

Exposure to acrylamide induces neurotoxic effects in humans. In addition, it induces genotoxic, reproductive and carcinogenic effects in laboratory animals. However, no convenient bioassay system for assessing acrylamide toxicity to animal and plant cells has been proposed to date. The present study aims to evaluate acrylamide toxicity to a green paramecium, Paramecium bursaria, bearing many endosymbiotic algae, because some chemicals are highly toxic to paramecia or microalgae, and some protozoa are already used for evaluation of environmental contaminations. Results showed that high acrylamide concentrations (> or = 1500 mg/l) have a lethal effect on P. bursaria. Although low acrylamide concentrations (< or = 150 mg/l) induced less change on the paramecium growth, the number of endosymbiotically growing algal cells drastically decreased. The acrylamide concentration required to induce a 50% decrease in the cell number (IC(50)) was determined to be 7.8 mg/l for endosymbiotic algae, indicating that the algal sensitivity to acrylamide was 7 and 15 times higher than that of Syrian hamster embryo (SHE) cells and the host cells, respectively. Here, we propose the use of P. bursaria being a convenient and sensitive bioindicator as a new approach for the assessment of acrylamide toxicity.     

Acute toxicities of trace metals and common xenobiotics to the marine copepod Tigriopus japonicus: Evaluation of its use as a benchmark species for routine ecotoxicity tests in Western Pacific coastal regions

Marine copepods have recently been recognized as important organisms in ecotoxicity testing for regulatory purposes. The harpacticoid copepod Tigriopus japonicus has a wide geographical distribution along the coast in the Western Pacific including Japan, South Korea, Taiwan, and Hong Kong. This study evaluated the acute toxicity sensitivity profile of Tigriopus japonicus against 12 common toxic substances including six endocrine disrupting chemicals (EDCs), three biocides and three trace metals. Through standard acute toxicity test procedures, toxicity endpoints LC(50), LC(10), and no observed effect concentration (NOEC) of each chemical were obtained. Although T. japonicus depicted different sensitivities towards different chemicals, a dose-response relationship was consistent in all cases. T. japonicus was particularly sensitive to most of the EDCs, but relatively less sensitive to molinate (a thiocarbate herbicide). Across all tested chemicals, tributyltin (TBT) was the most toxic to the copepod with the LC(50), LC(10), and NOEC of 0.05, 0.03, and 0.02 mg/L, respectively. A comparison made with available data on acute toxicities of these chemicals to other marine copepod species revealed that T. japonicus is generally more sensitive to EDCs and in particular to TBT. We, therefore, strongly advocate that T. japonicus shall be adopted as a benchmark marine species for routine ecotoxicity testing and ecotoxicological studies in Western Pacific coasts.     

Acute toxicity to freshwater organisms of antiparasitic drugs for veterinary use

The acute toxicity of five antiparasitic drugs used in the veterinary field-amprolium hydrochloride (APH), bithionol (BT), levamisole hydrochloride (LVH), pyrimethamine (PYM) and trichlorfon (TRC)-to the aquatic organisms Oryzias latipes, Daphnia magna, and Brachionus calyciflorus was examined. The toxicity test with O. latipes was conducted in accordance with the OECD Guidelines for the Testing of Chemicals (1993) to determine the 24-, 48-, 72-, and 96-h LC(50) values. In addition, 24- and 48-h EC(50) values for D. magna and a 24-h EC(50) for B. calyciflorus were determined with the DAPHTOXKIT F(trade mark) magna (Creasel, Belgium) and the ROTOXKIT F(trade mark) (Creasel, Belgium), respectively. High-performance liquid chromatographic analysis revealed that APH, LVH, and PYM were stable in water, but BT was unstable, decreasing by 84% on average at 24 h. TRC rapidly decomposed, with only 0.7% of the initial concentration remaining after 96 h, forming dichlorvos. The toxicity of TRC to O. latipes was determined in two ways: exposure to the same medicated water for 96 h (static test) and exposure to medicated water replaced every 24 h (semistatic test). AMP, LVM, and PYM were tested in the static condition, and BT was tested in the semistatic condition. BT was most toxic to O. latipes, with a 96-h LC(50) of 0.24 mg L(-1), followed by PYM, with a 96-h LC(50) of 5.6 mg L(-1). The 24-, 48-, 72-, and 96-h LC(50) values of TRC in the static test were 92.0, 45.2, 29.5, and 17.6 mg L(-1), respectively, which tended to be lower than those in the semistatic test, especially late in the observation period. D. magna was the most susceptible to TRC, with a 48-h EC(50) as low as 0.00026 mg L(-1). The 48-h EC(50) values of BT, PYM, and LVH for D. magna were 0.3, 5.2, and 64.0 mg L(-1), respectively. B. calyciflorus was the most susceptible to BT, with an EC(50) of 0.063 mg L(-1), followed by PYM, with an EC(50) of 15.0 mg L(-1). Among the test compounds, APH was the least toxic to all the freshwater organisms tested, with a 96-h LC(50) of >600 mg L(-1) for O. latipes, a 48-h EC(50) of 227 mg L(-1) for D. magna, and an EC(50) of 403 mg L(-1) for B. calyciflorus.