Influence of salinity on metal toxicity to Ulva pertusa

The present study was undertaken to establish the effect of salinity on the toxicity of cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) to Ulva pertusa, with inhibition of spore release used as the endpoint. The optimal salinity for maximal spore release for U. pertusa was found to be between 20 and 40 psu. Comparisons between toxicity of metals, as measured by EC₅₀, was shown to be in the descending order of Cu>Cd>Pb=Zn, which is similar to the toxicity of metals to algae, in general. When salinity was decreased from 30 to 20 psu, the EC₅₀ values for Cd toxicity to the inhibition of spore release in U. pertusa decreased from 261 to 103 g·L^?1, whereas increased salinity from 30 to 40 psu increased the EC₅₀ from 261 to 801 g·L^?1. Similarly, EC₅₀ values for Cu toxicity were 52 g·L^?1 at 20 psu, 99 g·L^?1 at 30 psu, and 225 g·L^?1 at 40 psu, and for Zn toxicity were 720 g·L^?1, 1,074 g·L^?1 and 1,520 g·L^?1, at 20, 30 and 40 psu, respectively. In contrast, no salinity dependent change in EC₅₀ values was apparent for Pb, with no significant differences in EC₅₀ values at under the three different salinity regimes. In general, lower salinity (20 psu) induced a significant decrease in percent spore release of U. pertusa as estimated by a decrease in EC₅₀ values, while higher salinity (40 psu) reduced the toxicity of metals as shown by an increase EC₅₀ values. These findings enable one to predict that any additional increase in pollution status would result in a pronounced reduction in the distribution of U. pertusa in brackish and estuarine waters.     

Individual and combined effects of cadmium and copper on the growth response of Chlorella vulgaris

The individual and combined effects of cadmium and copper on the growth response of the green alga, Chlorella vulgaris, were examined. The effects of pH alone, and in combination with copper were also evaluated. An increase in cadmium and copper concentrations caused a significant reduction in the growth of C. vulgaris cells, and the corresponding EC₅₀ values were 1.02 and 4.01 mg L⁻¹, respectively. For a pH range of 2–7, the inhibitory effect due to increased copper concentrations (coupled with the resulting drop in pH) was significantly higher than the impact due to increased acidity (by addition of HCl) alone. At lower metal concentrations (5 mg L⁻¹ Cu + < 2 mg L⁻¹ Cd or 2.5 mg L⁻¹ Cd + < 4 mg L⁻¹ Cu), a combination of copper and cadmium appeared to have a stronger inhibitory effect on cell growth than that of a single metal. In contrast, at higher metal concentrations (5 mg L⁻¹ Cu + > 2 mg L⁻¹ Cd or 2.5 mg L⁻¹ Cd + > 4 mg L⁻¹ Cu), the effect of a single metal exhibited a significantly stronger effect compared to a combination of the two metals. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 347–353, 1999     

Effect of heavy metals on the antioxidant enzymes in the marine ciliate Euplotes crassus

A single-cell eukaryote, Euplotes crassus is considered as a suitable model species to evaluate the effect of environmental contaminants particularly in sedimentary aquatic environments. Here, we investigated the effect of heavy metals (Cu, Pb and Zn) on the population growth and the gene expression of antioxidant enzyme coding genes (Ec-GR, Ec-GPx, and Ec-GSTtheta) in E. crassus. As a result, heavy metals negatively affected population growth measured as the 48-h EC₅₀ values as 1.58 mg/L for Cu, 4.13 mg/L for Pb, and 4.97 mg/L for Zn. Copper and zinc significantly increased the expression of Ec-GR, Ec-GPx, and Ec-GST-theta, suggesting that these genes may be involved in protection mechanisms against oxidative stress induced by Cu and Zn. Interestingly, Pb exposure inhibited the expression of all genes, indicating that these genes may be effective molecular biomarkers to evaluate toxic effects of heavy metals in this species.     

Preliminary toxicity tests using the green alga,Ankistrodesmus falcatus

The freshwater green alga Ankistrodesmus falcatus was cultured in increasing concentrations of Cr, Hg, Cd, Zn, and Al to evaluate the effect of these cations on its growth. Algal growth was estimated by absorbance at 750 nm. Potassium dichromate was used as reference for test reproducibility. The EC₅₀ for 3 tests was 1.890 mg L⁻¹ with a coefficient of variation of 40.25%. The 96 h static EC₅₀'s for heavy metals (in mg L⁻¹ of nominal concentrations) were as follows: Cr⁶⁺/K₂Cr₂O₇, 1.050; Hg²⁺/Hg(SCN)₂, 0.162; Hg²⁺/HgCl₂, 0.074; Cd²⁺/CdCl₂ · H₂O, 0.292; Zn²⁺/ZnSO₄ · ZH₂O, 2.432; and Al³⁺/Al₂(SO⁴)₀ · 18H₂O, 0.904. Thus yielding a toxicity series such that Hg > Cd > Al > Cr > Zn. These preliminary results suggest that bioassays using A. falcatus could be suitable for evaluating the toxicity of heavy metals in freshwaters. © 1997 by John Wiley & Sons, Inc. Environ Toxicol Water Qual 12: 11–14, 1997     

Ecotoxicity of losartan potassium in aquatic organisms of different trophic levels

The intensive use of the antihypertensive losartan potassium (LOS) has culminated in its high occurrence in aquatic environments. However, insufficient studies had investigated its effects in non-target organisms. In this study, ecotoxicity of LOS was assessed in aquatic organisms from distinct trophic levels (Desmodesmus subspicatus, Daphnia magna, and Astyanax altiparanae). Genotoxicity was assessed by the comet assay in D. magna and A. altiparanae, and biochemical biomarkers for the fish. LOS was more toxic to D. subspicatus (EC_50(72h) = 27.93 mg L⁻¹) than D. magna (EC₅₀ = 303.69 mg L⁻¹). Subsequently, this drug showed to induce more DNA damage in D. magna than A. altiparanae, when exposed to 2.5 mg L⁻¹. No significant stress responses were observed by the fish biomarkers, suggesting that higher trophic levels organisms are more tolerant to LOS toxicity. LOS showed relatively low toxic potential for a short period of exposure, but with different patterns of toxicity for the organisms from distinct trophic levels, contributing to further risk assessment of LOS.     

Adapting an enzymatic toxicity test to allow comparative evaluation of natural freshwater biofilms’ tolerance to metals

A simple, low-cost and non-radioactive short-term toxicity test was developed to study the effects of urban metals on natural freshwater periphytic communities. β-glucosidase activity of natural freshwater biofilms collected in situ was chosen as an endpoint. Metals (Cd, Cu, Ni, Pb, and Zn) successfully inhibited bacterial enzymatic activity after a 1-h exposure enabling the calculation of EC₅₀. The EC₅₀ value of a biofilm sample varied with the Total Suspended Solids concentration (TSS) of the biofilm suspension, showing that EC₅₀ values (expressed as total added metal concentrations) are not representative of the bioavailable metal concentration during the toxicity test. For Cu, Cd, Ni, Zn and Pb, the EC₅₀ values increased linearly with the TSS concentration leading us to define a normalized EC₅₀: the value of the EC₅₀ divided by the corresponding TSS concentration. Normalized EC₅₀ proved to be a robust, reliable way to assess metal tolerance of a biofilm for Cd, Cu, Ni, Zn and Pb. Normalized EC₅₀ obtained, expressed as kg_metal/g_TSS, varied between 0.2 to 7.6 for Cu, 1 to 8 for Cd, 1.8 to 92.3 for Ni, 1.8 to 76.6 for Zn and 25 to 189 for Pb.     

Acute toxicity of chlorinated organic chemicals to the embryos and larvae of the marine worm Platynereis dumerilii (Polychaeta: Nereidae)

The acute toxicity of a range of organic reference chemicals has been evaluated using the embryo-larval stages of the marine polychaete Platynereis dumerilii (Audouin and Milne-Edwards). After exposure under static conditions at 20±1°C, EC₅₀ values were calculated based upon reductions in normal embryo development. After exposure of 7 day old larvae under the same conditions, LC₅₀ values were calculated based on larval survival. The embryo development 48 h EC₅₀ and larval 48 h LC₅₀ values were, respectively, 6.39 and 8.94 mg L⁻¹ for 3,4-dichloroaniline, 122 and 104 mg L⁻¹ for phenol, 23.6 and 14.4 mg L⁻¹ for 4-chlorophenol, 4.24 and 3.20 mg L⁻¹ for 3,5-dichlorophenol, 2.55 and 4.24 mg L⁻¹ for 2,4,5-trichlorophenol, and 0.52 and 1.33 mg L⁻¹ for sodium pentachlorophenate (all based on nominal values). Comparison of these data with other published values suggest that, for these reference toxicants, the embryo–larval stages of P. dumerilii are of similar sensitivity to the early life stages of several other marine invertebrate species. These observations add to the refinement of a suite of bioassay techniques using P. dumerilii which, linked to previous studies, can be used to evaluate the developmental toxicity, cytotoxicity, and genotoxicity of marine contaminants. © 1998 John Wiley & Sons, Inc. Environ Toxicol Water Qual 13: 149–155, 1998     

Comparative assessment of herbicide phytotoxicity to Selenastrum capricornutum using microplate and flask bioassay procedures

Four reference toxicants (Cr⁶⁺, Cu²⁺, Zn²⁺, phenol) and 9 herbicides (imazamethabenz, 2,4-dichlorophenoxyacetic acid, picloram, glyphosate, bromoxynil, metolachlor, diquat dibromide, hexazinone, cyanazine) were appraised using both the microplate and flask assay Ninety-six hour EC₅₀s determined with Selenastrum capricornutum as the indicator species essentially demonstrated good intermethodological data concordance for all chemicals, with the exception of diquat dibromide, whose phytotoxicity in the microplate assay (EC₅₀ = 4.9 μg · L^?1) was nearly 7 times that of the flask assay (EC₅₀ = 34.2 μg · L^?1). Comparisons with other data in the scientific literature relating to similar herbicides with the same or different green algal indicator species appeared to corroborate the overall data obtained in our study. More than 4 orders of magnitude separated the most toxic (cyanazine, flask, and microplate EC₅₀s of 17.6 and 16.9 μg · L^?1, respectively) and the least toxic (imazamethabenz, flask, and microplate EC₅₀s of 89.1 and 91.1 mg · L^?1, respectively) herbicides. The biprocedural phytotoxicity comparison described in this work suggests that the simpler algal microplate assay can be an appropriate alternative to the flask technique to evaluate the algal growth inhibition effects of herbicides.     

Toxicity tests using the kelp <Emphasis Type="Italic">Undaria pinnatifida</Emphasis> for heavy metal risk assessment

The toxicity of six metals (Cd, Cu, Hg, Ni, Pb and Zn) to the early life stages of the brown seaweed Undaria pinnatifida were tested using two endpoints: spore germination and germ tube elongation. The optimal test conditions determined for photon irradiance, pH, salinity and temperature were darkness, pH 8, 35‰ and 15°C, respectively. The EC₅₀ values could be determined only for Hg and Cu and were 27 μg · L^-1 and 186 μg · L^-1, respectively, for germination and 16 μg · L^-1 and 45 μg · L^-1, respectively, for germ tube elongation. The variability of our U. pinnatifida test in response to the metal toxicants, as estimated from the coefficient of variation of the mean EC₅₀ values, was less than 28%. When tested against two different wastewater samples (PCB manufacturer and TV & communication equipment manufacturer), U. pinnatifida exhibited an EC₅₀ of 66.09-80.73% for germination and 24.98-62.62% for germ tube elongation with the CV (Coefficient of variation) range for both germination and germ tube elongation between 1.24 and 13.18%. The novel aspect of the present method is that the testing procedure requires no lighting or photoperiodic control. Additionally, the response of Undaria to the toxicity of Hg and Cu is very similar to that reported for other very sensitive macroalgal species. Because of its ecological and economic importance, the evaluation of toxicity using early stages of U. pinnatifida will provide useful scientific information, and we propose that this represents a valid bioassay within the battery of aquatic bioassays for the assessment of anthropogenic impacts on coastal ecosystems and commercial cultivation areas in nearshore environments.     

Sediment contaminants and microtox toxicity tested in a direct contact exposure test

Limnic and brackish water sediments were tested in a modified contact exposure bioluminescence test, the Microtox test. A variety of chemical constituents were analyzed in the sediments such as metals, chlorinated pesticides, and polychlorinated biphenyls. Sulfur in the common elemental form and pore water hydrogen sulfide were also analyzed. The measured effect in the Microtox toxicity test was correlated with the various chemical parameters to determine the origin of the toxic effect. Based on multivariate data anlaysis, a group of metals including Cu, Zn, Pb, and Cd were correlated positively with the Microtox toxicity tested in the direct contact test. Similarly, but to a lesser extent sulfur, hydrogen sulfide, and the pesticides p,p′-DDT and p,p′-DDD were also correlated. Other pesticides and all the analyzed polychlorinated biphenyls were poorly, if at all, correlated with the toxicity of the samples. In a comparison with the Microtox toxicity of the pure compounds, it was found that, of the analyzed and tested compounds, Zn, Pb, Cu, and elemental sulfur were present in amounts high enough to produce an effect in the test system. This calculation was, however, based on the assumption (unrealistic) that the total amount of a compound in the sediment was available in the test. On the other hand, the metals Cd, Cr, and Ni were found at concentrations of a few percent or less of their EC₅₀ concentrations in the Microtox test of the sediment, γ-Hexachlorocyclohexane and p,p′-DDT were also far less than the concentration required to give an effect in the test system. The pore water content of hydrogen sulfide was also too small to affect the test organism at the EC₅₀ dilution and, similarly, the fraction of the toxicant in the remaining aqueous phase in the sediment after separation of the pore water. Thus only the three metals Zn, Pb, and Cu, and elemental sulfur, were found in concentrations that would give an effect in the test system (0.68–398 times the effect), provided that the substances were available for the organisms. Consequently, elemental sulfur, Zn, Pb, and Cu were indicated as causing the effect in the Microtox test of sediments and not a series of other metal ions, nor tested chloropesticides or chlorinated biphenyls. © 1996 by John Wiley & Sons, Inc.     

Canadian water quality guidelines for deltamethrin

Canadian Water Quality Guidelines (CWQG) are numerical or narrative limits that protect designated water uses. Development of CWQG is based on review of deltamethrin's properties, uses, fate in the environment, ambient levels, accumulation in biota, and toxicity. Deltamethrin is a synthetic pyrethroid insecticide used against agricultural pests. Concentrations of deltamethrin in Canadian agricultural areas range between 10 and 1000 ng m⁻³ in air, 0.04 and 24.0 μg L⁻¹ in water, 3 and 5 ng g⁻¹ in sediments, 281 and 1375 ng g⁻¹ in plants, and 3.0 and 50.0 ng g⁻¹ in animals. In nature, deltamethrin can undergo volatilization, isomerization, and hydrolysis. Estimates of toxicity of deltamethrin to freshwater life range from 0.0001 μg L⁻¹ (48- and 96-h EC₀ for immobilization of Daphnia magna) to 1700 mg L⁻¹ (EC₅₀ for photoinhibition of Selanastrum capricornutum). Terrestrial life is affected by concentrations of deltamethrin ranging from 1.0 mg kg⁻¹ (retardation of fetus development in mice) to 5000 mg kg⁻¹ (LD₅₀ for a rat). A full guideline of 0.4 μg L⁻¹ is recommended for the protection of freshwater life. A full guideline of 2.5 μg L⁻¹ is recommended for water used for livestock production. There were insufficient data to derive guidelines for recreation, irrigation, and industrial applications. © 1998 John Wiley & Sons, Inc. Environ Toxicol Water Qual 13: 175–210, 1998     

Sensitivity of spore germination and germ tube elongation of Saccharina japonica to metal exposure

The sensitivity of early life stages of the brown seaweed Saccharina japonica to six metals (Cd, Cu, Hg, Ni, Pb, Zn) and two waste-water samples were investigated and a new toxicity bioassay developed. The two endpoints used were spore germination and germ tube elongation with an exposure time of 24 h. Optimal test conditions determined for photon irradiance, pH, salinity and temperature were darkness, pH 8, 35‰ and 15°C, respectively. The toxicity ranking of five metals was: Hg (EC₅₀ of 41 and 42 μg l⁻¹) > Cu (120 and 81 μg l⁻¹) > Ni (2,009 and 1,360 μg l⁻¹) > Zn (3,024 and 3,897 μg l⁻¹) > Pb (4,760 and 4,429 μg l⁻¹) > Cd (15,052 and 7,541 μg l⁻¹) for germination and germ tube elongation, respectively. The sensitivities to Cd, Cu and Ni were greater in germ tube elongation than in germination process. When tested against two different waste-water samples (processed animal and printed circuit board waste-water) values of EC₅₀ were between 21.29 and 32.02% for germination and between 5.33 and 8.98% for germ tube elongation. Despite differences in their chemical composition, the toxic effects of waste-water samples, as indicated by EC₅₀ values, did not differ significantly for the same endpoints. The CV range for both germination and germ tube elongation was between 4.61 and 37.69%, indicating high levels of precision of the tests. The results compare favourably with those from more established test procedures employing micro- and macroalgae. The advantages and potential limitations of the bioassay for the assessment of anthropogenic impacts on coastal ecosystems and commercial cultivation areas in near-shore environments are discussed.     

Oxidative damage induced in A549 cells by physically and chemically characterized air particulate matter (PM2.5) collected in Abidjan,Côte d'Ivoire

Exposure to high levels of air pollution particulate matter (PM) is strongly associated with increased pulmonary morbidity and mortality. However, the underlying mechanisms of action whereby PM cause adverse health effects are still unclear. In developing countries, like in the sub‐Saharian region of Africa, people are often exposed to high PM levels. Hence, three PM_2.5 samples were collected in the District of Abidjan (Côte d'Ivoire), under rural, urban or industrial influences. Their most toxicologically relevant physical and chemical characteristics were determined – thereby showing that most of them were equal or smaller than 2.5 µm – and the influence of both natural (Ca, Na, Mg, Ti, etc.) and anthropic (Al, Fe, Mn, Cr, Pb, Zn, Cu, Ni, benzene and its derivatives, paraffins, etc.) emission sources. The toxicity induced by the three PM samples was studied through 5‐bromodeoxyuridine incorporation to DNA, mitochondrial dehydrogenase activity and extracellular lactate dehydrogenase activity. Hence, effect concentrations at 10 and 50% (EC₁₀ and EC₅₀, respectively) were as follows: (i) rural PM – EC₁₀ = 5.91 µg cm^?2 and EC₅₀ = 29.55 µg cm^?2; (ii) urban PM – EC₁₀ = 5.45 µg cm^?2 and EC₅₀ = 27.23 µg cm^?2; and (iii) industrial PM – EC₁₀ = 6.86 µg cm^?2 and EC₅₀ = 34.29 µg cm^?2. Moreover, PM‐induced oxidative damage in A549 cells was observed through the induction of lipid peroxidation, the alteration of superoxide dismutase activity, and the disruption of glutathione status. Both the transition metals and the organic chemicals within the three collected PM samples under study might be involved in the oxidative damage and, therefore, the toxicity they induced in A549 cells. Copyright © 2009 John Wiley & Sons, Ltd.     

Distribution and ecological assessment of heavy metals in surface sediments of the East Lake, China

Concentrations and risk assessment of chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), lead (Pb), cadmium (Cd) and mercury (Hg) were investigated in 106 samples of surface sediments from the East Lake, China in this study. The mean concentration of Zn was highest among the eight heavy metals (225 mg kg^?1), followed by As (191 mg kg^?1), Cr (145 mg kg^?1), Cu (55 mg kg^?1), Ni (27.1 mg kg^?1), Pb (7.93 mg kg^?1), Cd (0.94 mg kg^?1) and Hg (0.21 mg kg^?1). Niuchao Hu was less polluted by heavy metals compare to the other four lakelets of the East Lake. The correlations among these heavy metals and the results of principal component analysis indicated that the distribution of Cd, Pb and Hg was related to anthropogenic activities, whereas Cu, As and Cr were affected by the parent rocks. Zinc and Ni were influenced both by anthropogenic activities and parent rocks. Based on the Sediment Quality Guidelines, the results of toxicity assessment indicated that adverse effects caused by Cr and As would be expected frequently. Nickel, Zn, Cd and Hg may cause adverse effects occasionally and Cu and Pb may cause toxicity infrequently. Arsenic was found to have the highest acute toxicity by toxic units (TUs), followed by Cr, Ni, Zn, Hg, Cu, Cd and Pb. The potential ecological risk index analysis indicated that As, Cd and Hg had considerable or high ecological risk, whereas Cr, Ni, Cu, Zn and Pb had low ecological risk. The potential ecological risk index (RI) of the heavy metals in the surface sediments of East Lake was 483, indicating considerable ecological risk. Close attention should be paid to pollution of the heavy metals in East Lake, China.     

Ecotoxicological effects of alpha-cypermethrin on freshwater alga Chlorella sp.: Growth inhibition and oxidative stress studies

Alpha-cypermethrin (ACy) is a synthetic pyrethroid insecticide commonly used in agricultural practices for controlling a broad range of insect pests particularly belonging to the order Lepidoptera and Coleoptera. The present study aims to evaluate the toxic effect of ACy on microalgae by studying its influence on Chlorella sp. According to our knowledge, this is the first detailed study of ACy toxicity on microalgae. Significant growth inhibition of Chlorella sp. was observed at high ACy concentration (6−48 mg L⁻¹) during the entire 96 h bioassay. The 96 h median effective concentration (EC₅₀) of ACy was estimated to be 11.00 mg L⁻¹. Flow cytometry analysis showed an enhanced generation of reactive oxygen species (ROS) and intracellular lipid accumulation after 96 h exposure to 11.00 mg L^-1 of ACy. Further, the same ACy concentration showed a significant decrease in photosynthetic pigment content and an increase in antioxidant enzyme activity and malondialdehyde (MDA) content in Chlorella sp.     

Evaluation of trace metals concentration and human health implication by indigenous edible fish species consumption from Meghna River in Bangladesh

This study is focused on the determination of trace metals (Cr, Cu, Zn, As, Pb, and Cd) concentrations of nine different indigenous fish species of Meghna River in Bangladesh to know the possible risk in human consumption. Fishes' wet muscles samples were analyzed to evaluate the level of trace metal concentrations. The concentrations (mg kg⁻¹ w/w) of the six selected trace metals were in the order Zn (1.42 ± 0.12) > Cr (1.31 ± 0.08) > Cu (0.92 ± 0.09) > Pb (0.54 ± 0.07) > Cd (0.51 ± 0.07) > As (0.47 ± 0.02). The results revealed that all the selected trace metals were below the maximum permissible limits recommended by the reference standards. The fish species may pose no risk with respect to the Estimated Daily Intake (EDI). Target hazard quotient (THQ) values for Cr, Cu, Zn, Pb, and Cd in all the fish species were <1.0, except for As which is dominantly organic in fishes. Both adults and children are vulnerable to carcinogenic health threat due to Cd exposure.     

A comparison of techniques used to extract solid samples prior to acute toxicity analysis using the microtox test

To date, there has been no widely accepted or standardized procedure for preparing leachates of solid samples for acute toxicity bioassays such as Microtox. Leaching procedures reported in the literature were evaluated for use with nonspecific environmental sample submissions. Using toxic environmental samples, two experiments were conducted to compare the effect that varying selected parameters would have on the effectiveness of the leaching procedure in removing toxicants from a solid sample matrix. Parameters that were varied included the type of toxicant, aqueous solvent system used to leach the sample, ratio of solid:liquid, type of mixing action, length of extraction time, and method of removing suspended solids from the leachate. Results from these experiments demonstrated that unacceptable variations of measured toxicity of a solid sample occurs with simple modifications of the method. The most dramatic shifts in 15 min EC₅₀ values were observed between vacuum filtering (EC₅₀ mean = 55.8%) and centrifuging (EC₅₀ mean = 22.3%) samples to clarify leachates. This and other significant interactions, between sample contaminant and aqueous system, suggest that no standard procedure will give readily interpretable results for different types of contamination. Investigators should carefully consider the application of the assay (e.g., the detection of toxicants using a sensitive method, or modeling the leaching of toxicants under specific environmental conditions) before selecting a leaching procedure. © 1996 by John Wiley & Sons, Inc.     

Eprinomectin antiparasitic affects survival,reproduction and behavior of Folsomia candida biomarker,and its toxicity depends on the type of soil

The objective of this study was to evaluate the toxicity of the antiparasitic agent eprinomectin in two subtropical soils, using ecotoxicological lethality, reproduction and avoidance behavior tests with springtails (Folsomia candida). Eprinomectin concentrations were 0 (control), 0.5, 1, 2, 4, 8, 12, 16 and 20 mg kg⁻¹ of dry soil combined with either Entisol or Oxisol soils. Statistically significant toxic effects of eprinomectin on springtails were observed in both soils. Eprinomectin was lethal starting at 8 mg kg^-1 of dry soil in Entisol, and 20 mg kg⁻¹ of dry soil in Oxisol, with effects less than 50% at lethal concentrations. Reductions in the reproduction rate of the springtails were also observed starting at 8 mg kg⁻¹ of dry soil in Entisol, and 0.5 mg kg⁻¹ of dry soil in Oxisol. EC_repr50 value calculated for Entisol was 4.38 ± 0.62 mg kg^-1 of dry soil; for Oxisol the EC_repr50 was above the highest tested concentration. For avoidance behavior, the effect occurred from 0.5 mg kg^-1 of dry soil for both soils. In Entisol, all concentrations caused avoidance of more than 95%, and in Oxisol the EC_avoi50 value was 1.33 ± 0.83 mg kg^-1 of dry soil. We conclude that eprinomectin affected survival, reproduction and caused avoidance behavior of F. candida in both soils. The toxic effects were greater as the concentration in the soils increased. The effects in Oxisol were less intense than those in Entisol with respect to the affected springtails. This discrepancy may be attributed to the different physicochemical characteristics of the soils that determine the retention capacity for eprinomectin; in particular, there are greater contents of clay, organic matter and cation exchange capacity in Oxisol.     

Influence of hormonal status in relaxant effect of diethylstilbestrol and nifedipine on isolated rat uterus contraction

• 1.1. The effects of diethylstilbestrol (DES, 10⁻⁷-10⁻⁵ M) and nifedipine (10⁻¹⁰-10⁻⁷ M) on KCl (60 mM)-induced tonic contraction in the uterus of ovariectomized and 17β-estradiol (0.1 mg/kg/day, s.c.)-, 17α-estradiol (0.1 mg/kg/day, s.c.)-, or progesterone (2 mg/kg/day, s.c.)-treated rats have been assayed.
• 2.2. The dose-dependent relaxation produced by nifedipine in ovariectomized rats (EC₅₀ = 5.59 ± 1.25 × 10⁻⁹ M) is potentiated in uterus of rats treated with 17β-estradiol and progesterone (EC₅₀ = 0.59 ± 0.1 and 0.49 ± 0.1 × 10⁻⁹ M, respectively) but not in the 17α-estradiol-treated rats (3.01 ± 0.6 × 10⁻⁹ M).
• 3.3. The relaxation produced by DES on ovariectomized rats (EC₅₀ = 0.84 ± 0.14 × 10⁻⁶ M) is reduced when the rats are treated with 17β-estradiol (EC₅₀ = 2.22 ± 0.2 × 10⁻⁶ M) or progesterone (EC₅₀ = 1.24 ± 0.08 × 10⁻⁶ M), but unmodified by 17α-estradiol (EC₅₀ = 0.58 ± 0.01 × 10⁻⁶ M).
• 4.4. The nifedipine-induced relaxation is reversed with Bay K 8644 (10⁻¹⁰-10⁻⁶ M) in all experimental conditions. However, Bay K 8644 counteracted the relaxation of DES at 45.7% on ovariectomized rats but this was lower than 30% in the other groups.
• 5.5. Our results suggest that in ovariectomized rats the effects of both nifedipine and DES are similar, but 17β-estradiol and progesterone produce a contrary effect on the relaxation induced by nifedipine and DES (by increasing the nifedipine and decreasing the DES effects).
• 6.6. The modifications produced by 17α-estradiol are similar to those produced by the ovariectomy and this suggests that 17α-estradiol is a drug lacking estrogenic activity.

     

Joint Toxicity of Copper and Zinc to a Terrestrial Nematode Community in an Acid Sandy Soil

Heavy metal toxicity to an indigenous nematode community was examined following the addition of Cu and Zn, alone or in combination, to agricultural soil. The dissolved Cu or Zn concentrations measured after equilibrating soil samples with a 0.01 M solution of CaCl₂ showed that the metal concentrations found in soils with combined metal additions were not significantly different from those with single metal additions. After an exposure period of six months, many nematode community parameters and individual nematode taxa were significantly affected by increasing concentrations of Cu and Zn up to 200 mg kg^–1. Some nematode taxa, such as Thonus, Alaimus and Aporcelaimellus were very sensitive and disappeared at Cu and Zn concentrations exceeding 50 mg kg^–1. For several nematode community parameters and nematode taxa, EC₅₀ values for single metal exposures were used to calculate TU₅₀ values for the joint toxicity of Cu and Zn. Based on these calculations, it is concluded that the effects of a combined exposure to Cu and Zn were additive or less than additive. Before this conclusion can be generalised, however, more data are needed on other types of soil, other pH values and other combinations of pollutants.