Toxic effects of combined stressors onDaphnia pulex: Interactions between diazinon, 4-nonylphenol, and wastewater effluent (original) (raw)
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Environmental toxicology and chemistry / SETAC, 2015
Contaminant exposure in aqueous systems typically involve complex chemical mixtures. Given the large number of compounds present in the environment, it is critical to rapidly identify hazardous chemical interactions. This study utilizes a prototype for a novel high throughput assay to quantify behavioral changes over time to identify chemical interactions that affect toxicity. The independent and combined effects of two chemicals, diazinon (an insecticide) and 4-nonylphenol (a detergent metabolite) on the swimming behavior of the freshwater crustacean, Daphnia pulex were examined. Cumulative distance and change in direction were measured repeatedly via optical tracking over 90-minutes. Exposure to low concentrations of diazinon (0.125 to 2 µM) or 4-nonylphenol (0.25 to 4µM) elicited significant concentration- and time-dependent effects on swimming behavior. Exposure to 0.5 µM 4-nonylphenol alone did not significantly alter mean cumulative distance, but did elicit a small, significan...
Susceptibility of five nontarget organisms to aqueous diazinon exposure
2000
MATERIALS AND METHODS In this research, the sensitivity of five freshwater aquatic organisms to diazinon was determined in aqueous laboratory exposures. A range of species was used to determine differential exposure responses (survival) for crustaceans, insects, and vertebrates. The experimental organisms were Ceriodaphnia dubia (waterflea),
An example of the identification of diazinon as a primary toxicant in an effluent
Environmental Toxicology and Chemistry, 1992
A toxicity identification evaluation (TIE) conducted on a municipal wastewater discharge from the southeast United States was part of a research project aimed at developing U.S. Environmental Protection Agency (EPA) TIE methods for acutely toxic effluents. The effluent consistently exhibited acute toxicity to Ceriodaphnia dubia but not to fathead minnows (Pirnephales promelus). Toxicity characterization procedures revealed that the primary toxicant was a nonpolar organic. Toxicity was recovered through C,8 solid-phase extraction and concentration steps. Gas chromatography-mass spectroscopy of these concentrates revealed the presence of diazinon (0,O-diethyl 0-[6-methyl-2-( 1 -methylethyl)-4-pyrimidinyl] phosphorothioate). Diazinon concentrations in whole effluent, determined by GC analyses, correlated well with the toxicity measurements of each sample. Relative species sensitivity also implicated diazinon as the primary toxicant. This study illustrates the successful application of EPA TIE methodologies for identifying a nonpolar organic toxicant in a complex effluent. The significance of detecting diazinon at acutely toxic concentrations in municipal wastewater may indicate a more widespread problem in this region of the United States. This toxicity problem may be attributed to the chemical characteristics of diazinon and its applications.
2018
In the present study, acute toxicity of the organophosphate pesticide, diazinon, was evaluated under experimental condition to adult Heteropneustes fossilis. The 96 h LC50 with 95% confidence limits of Heteropneustes fossilis is 16.56 (14.32-18.04) mg/l. None of the unexposed control fish died during the experiment. Mortality rate between each dose and mortality rate between 24-96 h depending on time was correlated. In the fish, significant relationship (p<0.05) was recorded between mortality rate and exposure times (24, 48, 72 and 96 h) at all concentrations of diazinon. Significant variation was observed between mortality rate of fish at all the exposure concentrations at all the exposure times (p<0.01). Effects of the toxicant on the behavioral changes of the fish were directly proportional to the increasing concentration of diazinon.
Diazinon is an extensively applied organo-phosphate pesticide, and nonylphenol is one of the major degradation products of nonylphenol polyethoxylates which are commonly used as surfactant in pesticide formulations. Both pollutants are widely distributed and often coexist in agroecosystems, where they might cause toxic effects to wild biota. This study assessed single and joint toxicity of binary mixtures of these organic compounds on the early development of Rhinella arenarum by means of a standardized test. Joint toxicity of diazinon/nonylphenol mixtures were assessed in embryos and larvae exposed to three different proportions at different exposure times. Embryo and larval toxicity was time-dependent, and larvae were significantly more sensitive than embryos to both compounds. For both embryos and larvae, nonylphenol was between 11 and 18 times more toxic than diazinon. Joint toxicity of the chemicals showed a tendency to be significantly higher than the predicted by additivity effects highlighting the threat that diazinon/ nonylphenol mixtures represent for Rhinella arenarum populations.
Mixture toxicity of three toxicants with similar and dissimilar modes of action to Daphnia magna
Ecotoxicology and Environmental Safety, 2008
Ecotoxicological studies are primarily conducted with single toxicant experiments. Natural ecosystems are however not exposed to single toxicants, but to a broad variety of anthropogenic and natural toxicants. Models which can predict the toxicity of mixtures of toxicants could be an important tool for use in risk assessment. The present study was conducted to investigate whether joint effects of three toxicants are predictable on the basis of single substance toxicity. Concentration Addition (CA) and Independent Action (IA), which assume that the toxicants have similar and dissimilar modes of action respectively, are generally accepted as reference models for the prediction of mixture toxicity. We investigated whether these models could predict the toxicity of three chemicals tested singly and in binary and ternary mixtures. Two insecticides (dimethoate and pirimicarb) with a similar mode of action (inhibition of acetylcholinesterase) and the detergent linear alkylbenzene sulphonate (LAS) with a different mode of action (interacts with plasma membrane) were used for this purpose. Mixtures were tested as fractions of equivalent effect concentrations in accordance with the isobolographic method. We hypothesized that, due to interaction with the plasma membrane, LAS would influence the permeability of the plasma membrane and thus facilitate the uptake of the insecticides resulting in increased toxicity yielding a synergistic effect. The isobole method provides important information about interactions among toxicants in mixtures and can detect antagonistic or synergistic effects. All experiments were conducted with the Cladoceran Daphnia magna in the OECD standardized Acute Immobilisation Test (48h.). Isoeffective concentrations were determined at the toxicants' individual EC 50 . To test whether mixture toxicity studies conducted at high toxicant concentrations can be used to predict mixture toxicity at lower concentrations the mixtures were evaluated at EC 10 or EC 25 as well as at EC 50 using isobolograms. Binary mixtures in accordance with CA were tested statistically using a non-linear regression model which can describe deviations from CA and provide a measure of the degree of synergism or antagonism. The results show that reference models (CA and IA) provide rather good estimates of mixture toxicity regardless of the modes of action. The IA results underestimated the ternary mixture of the three toxicants. However predictions were within a factor 2 of experimental results, which is likely to be acceptable in a risk assessment context. However several authors have shown that CA has the strongest predictive power and furthermore is known to be the more conservative of the two models. Thus, CA is recommended as a default reference model with regard to predicting mixture toxicity effects base d on single toxicity data. As expected the binary mixture of pirimicarb and dimethoate did not deviate from CA, hence no synergistic or antagonistic effects were observed. The binary mixture of LAS and the two pesticides appeared to be synergistic according to IA at the EC 50 -level, however at lower levels (EC 10 ) the synergistic effect was diminished. These results are based on the assumption of IA (dissimilar mode of action). However the toxicants may not elicit a different mode of action at all times, since mode of action could change with varying exposure concentrations, and further research is needed to determine the relationship between mode of action and exposure concentration.
Environmental toxicology and chemistry / SETAC, 2015
Behavior is increasingly reported as a sensitive and early indicator of toxicant stress in aquatic organisms. However, the systematic understanding of behavioral effects and comparisons between effect profiles is hampered because the available studies are limited to few chemicals and differ in the exposure conditions and effect parameters examined. The aims of this study were (i) to explore behavioral responses of Daphnia magna exposed to different toxicants, (ii) to compare behavioral effect profiles with regard to chemical modes of action and (iii) to determine the sensitivity and response time of behavioral parameters in a new multi-cell exposure system named "Multi-DaphTrack" compared to currently utilized tests. Twelve compounds covering different modes of toxic action were selected to sample a wide range of potential effect profiles. Acute standard immobilization tests and 48 h of behavioral tracking were performed in the customized "Multi-DaphTrack" system...