Combined toxicity effects of MTBE and pesticides measured with Vibrio fischeri and Daphnia magna bioassays

Toxicity of substituted p-phenylenediamine antioxidants and their derived novel quinones on aquatic bacterium: Acute effects and mechanistic insights

Substituted para-phenylenediamines (PPDs) are synthetic chemicals used globally for rubber antioxidation, with their quinone derivatives (PPD-Qs) raising particular environmental concerns due to their severe toxicity to aquatic organisms. Emerging research has identified a variety of novel PPD-Qs ubiquitously detected in the environment, yet experimental proof for the toxicity of PPD-Qs has not been forthcoming due to the unavailability of bulk standards, leaving substantial gaps in the prioritization and mechanistic investigation of such novel pollutants. Here, we use synthesized chemical standards to study the acute toxicity and underlying mechanism of 18 PPD-Qs and PPDs to the aquatic bacterium V. fischeri. Bioluminescence inhibition EC50 of PPD-Qs ranged from 1.76-15.6 mg/L, with several emerging PPD-Qs demonstrating significantly higher toxicity than the well-studied 6PPD-Q. This finding suggests a broad toxicological threat PPD-Qs pose to the aquatic bacterium, other than 6PPD-Q. Biological response assays revealed that PPD-Qs can reduce the esterase activity, cause cell membrane damage and intracellular oxidative stress. Molecular docking unveiled multiple interactions of PPD-Qs with the luciferase in V. fischeri, suggesting their potential functional impacts on proteins through competitive binding. Our results provided crucial toxicity benchmarks for PPD-Qs, prioritized these novel pollutants and shed light on the potential toxicological mechanisms.

Toxicity of representative organophosphate, organochlorine, phenylurea, dinitroaniline, carbamate, and viologen pesticides to the growth and survival of H. vulgaris, L. minor, and C. elegans

Pesticides are commonly found in the environment and pose a risk to target and non-target species; therefore, employing a set of bioassays to rapidly assess the toxicity of these chemicals to diverse species is crucial. The toxicity of nine individual pesticides from organophosphate, organochlorine, phenylurea, dinitroaniline, carbamate, and viologen chemical classes and a mixture of all the compounds were tested in three bioassays (Hydra vulgaris, Lemna minor, and Caenorhabditis elegans) that represent plant, aquatic, and soil-dwelling species, respectively. Multiple endpoints related to growth and survival were measured for each model, and EC10 and EC50 values were derived for each endpoint to identify sensitivity patterns according to chemical classes and target organisms. L. minor had the lowest EC10 and EC50 values for seven and five of the individual pesticides, respectively. L. minor was also one to two orders of magnitude more sensitive to the mixture compared to H. vulgaris and C. elegans, where EC50 values were calculated to be 0.00042, 0.0014, and 0.038 mM, respectively. H. vulgaris was the most sensitive species to the remaining individual pesticides, and C. elegans consistently ranked the least sensitive to all tested compounds. When comparing the EC50 values across all pesticides, the endpoints of L. minor were correlated with each other while the endpoints measured in H. vulgaris and C. elegans were clustered together. While there was no apparent relationship between the chemical class of pesticide and toxicity, the compounds were more closely clustered based on target organisms (herbicide vs insecticide). The results of this study demonstrate that the combination of these plant, soil, and aquatic specie can serve as representative indicators of pesticide pollution in environmental samples.

The toxicity effects of the individual and combined exposure of methyl tert-butyl ether (MTBE) and tire rubber powder (RP) on Nile tilapia fish (Oreochromis niloticus)

Methyl tert-butyl ether (MTBE) is soluble in water and can contaminate water sources when it spills during transportation or leaks from underground storage tanks. Incomplete combustion releases MTBE as exhaust fumes that can be deposited on urban surfaces. Meanwhile, car tires erosion emits of large amounts of rubber dust (RP), easily transported to water bodies. Therefore, this study has the objective of assessing the toxicity of varying concentrations of MTBE (0, 2.5, 5.0 μL L-1) and RP (0, 5.0, 10.0 mg L-1 RP), both individually and in combination, over a period of 28 days on Nile tilapia (Oreochromis niloticus). MTBE and PR decreased fish growth performance. Blood biochemical analytes indicated that MTBE and RP led to increasing Aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and creatinine phosphokinase (CPK), alkaline phosphatase and gamma-glutamyl transferase (GGT) activities. Alterations related to glucose, triglycerides, cholesterol, and creatinine, plasma contents, were also observed. Increased antioxidant biomarkers, including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), glutathione reductase (GR), and malondialdehyde (MDA), was observed. Exposure fish to MTBE and PR changed metabolic profile of muscle tissue. Moreover, results showed that MTBE, its metabolites, and PR could accumulate in the muscle tissue of fish. Results suggest that MTBE and RP can impact fish health, both individually and when combined. The presence of MTBE enhances the toxicity of RP, indicating a synergistic effect. Nevertheless, further studies are needed to understand the impact of toxic compounds on aquatic environments and organisms' health.

Individual and binary exposure to nanoscales of silver, titanium dioxide, and silicon dioxide alters viability, growth, and reproductive system: Hidden indices to re-establish artemia as a toxicological model in saline waters

This study evaluated and compared the individual and combined toxicity of AgNPs, TiO₂NPs, and SiO₂NPs to life cycle of A. salina. To this end, both stability and toxicity of AgNPs were determined in the presence of TiO₂NPs and SiO₂NPs. The colloidal stability of AgNPs decreased in the presence of the other two NPs, especially SiO₂NPs. AgNPs displayed acute toxicity to A. salina, whereas SiO₂NPs and TiO₂NPs chronically induced toxicity in a concentration- and time-dependent manner during 28-day exposure. The experimental NPs significantly decreased the weight and length of A. salina and induced reproductive toxicity through perturbation in first brood timespan, sexual maturity, egg development time, egg pouch area, offspring quality, and fecundity. Exposure to AgNPs shifted the mode of reproduction in brine shrimp from ovoviviparity to oviparity, and also co-presence of AgNPs with SiO₂NPs or TiO₂NPs caused infertility. Generally, their individual toxicity was in order of AgNPs > TiO₂NPs > SiO₂NPs, and binary exposure to AgNPs-SiO₂NPs appear to be more threatening than AgNPs-TiO₂NPs to A. salina. Together, this study highlights that these nanoparticles could disrupt reproductive health of A. salina and lead to alterations in population dynamics and aquatic ecosystem balance.

Development of portable whole-cell biosensing platform with lyophilized bacteria and its application for rapid on-site detection of heavy metal toxicity without pre-resuscitation

The high toxicity of heavy metals necessitates monitoring technology that allows rapid adaptation and deployment. Microbial whole-cell biosensors have become a priority because of their excellent performance. However, traditional methods have several limitations, including long assay time, poor portability, and the lack of ready-to-use on-site devices. In this study, a novel portable whole-cell biosensing platform was developed by integrating a simple handheld fiber-optic dissolve oxygen sensor and bacterial culture or lyophilized bacteria. Based on the oxygen consumption inhibition mechanism, this platform achieved rapid acute toxicity measurement of heavy metal ions through inhibit Escherichia coli (E.coli) respiration. Under the optimal conditions, the limit of detection and IC50 of Hg²⁺ using E. coli culture were 5.62 μM and 11.64 μM, respectively. Interestingly, the lyophilized E. coli could be directly applied for Hg²⁺ toxicity detection without pre-resuscitation, where an IC50 of 31.28 μM was obtained, and the whole detection process was only 18 min. The lyophilized E. coli could be stored long-term at -80 °C without significant loss of activity and detection performance. The portable whole-cell biosensing platform demonstrated a high potential for rapid on-demand toxicity detection in real water samples. The developed strategy is not only fast, portable, and easily storable, but also highly suited for on-site ready-to-use, and high-frequency toxicity detection of heavy metal ions in the field.

Pathogens and predators impacting commercial production of microalgae and cyanobacteria

Production of phytoplankton (microalgae and cyanobacteria) in commercial raceway ponds and other systems is adversely impacted by phytoplankton pathogens, including bacteria, fungi and viruses. In addition, cultures are susceptible to productivity loss, or crash, through grazing by contaminating zooplankton such as protozoa, rotifers and copepods. Productivity loss and product contamination are also caused by otherwise innocuous invading phytoplankton that consume resources in competition with the species being cultured. This review is focused on phytoplankton competitors, pathogens and grazers of significance in commercial culture of microalgae and cyanobacteria. Detection and identification of these biological contaminants are discussed. Operational protocols for minimizing contamination, and methods of managing it, are discussed.

Protective effect of the Spirulina platensis against toxicity induced by Diuron exposure in Mytilus galloprovincialis

Diuron herbicide is widely used for weeds control in many kinds of cultivations. It reaches the waterbodies through various fate routes and can adversely threaten non-target organism. The current study was carried out to evaluate the antioxidant activity of Spirulina as feed additive against the toxicity of Diuron concentrations (40 and 80 µg/L) on the edible mollusk Mytilus galloprovincialis during seven days of exposure. Oxidative stress biomarkers were applied on mussel gills and digestive gland, investigating changes in enzymes activities such as catalase (CAT), Glutathione-S-transferase (GST) and Acetylcholinesterase (AChE) and the Malondialdehyde level (MDA). The obtained results show that diuron altered oxidative stress biomarkers in both organs, gills and digestive gland. Performed principle component analysis (PCA) highlighted relationship between biomarkers involved in functional response. Spirulina platensis supplemented diet (1 mg/L), completely ameliorated diuron-induced oxidative stress in mussel tissues. Thus, Spirulina seems to be a promising microalgae and eco-friendly tool helping the health recovery of aquatic animals subjected to environmental stressors.

Deep-Sea Actinobacteria Mitigate Salinity Stress in Tomato Seedlings and Their Biosafety Testing

Soil salinity is an enormous problem affecting global agricultural productivity. Deep-sea actinobacteria are interesting due to their salt tolerance mechanisms. In the present study, we aim to determine the ability of deep-sea Dermacoccus (D. barathri MT2.1^T and D. profundi MT2.2^T) to promote tomato seedlings under 150 mM NaCl compared with the terrestrial strain D. nishinomiyaensis DSM20448^T. All strains exhibit in vitro plant growth-promoting traits of indole-3-acetic acid production, phosphate solubilization, and siderophore production. Tomato seedlings inoculated with D. barathri MT2.1^T showed higher growth parameters (shoot and root length, dry weight, and chlorophyll content) than non-inoculated tomato and the terrestrial strain under 150 mM NaCl. In addition, hydrogen peroxide (H₂O₂) in leaves of tomatoes inoculated with deep-sea Dermacoccus was lower than the control seedlings. This observation suggested that deep-sea Dermacoccus mitigated salt stress by reducing oxidative stress caused by hydrogen peroxide. D. barathri MT2.1^T showed no harmful effects on Caenorhabditis elegans, Daphnia magna, Eisenia foetida, and Escherichia coli MC4100 in biosafety tests. This evidence suggests that D. barathri MT2.1^T would be safe for use in the environment. Our results highlight the potential of deep-sea Dermacoccus as a plant growth promoter for tomatoes under salinity stress.

Mathematical Modeling Approaches for Assessing the Joint Toxicity of Chemical Mixtures Based on Luminescent Bacteria: A Systematic Review

Developments in industrial applications inevitably accelerate the discharge of enormous substances into the environment, whereas multi-component mixtures commonly cause joint toxicity which is distinct from the simple sum of independent effect. Thus, ecotoxicological assessment, by luminescent bioassays has recently brought increasing attention to overcome the environmental risks. Based on the above viewpoint, this review included a brief introduction to the occurrence and characteristics of toxic bioassay based on the luminescent bacteria. In order to assess the environmental risk of mixtures, a series of models for the prediction of the joint effect of multi-component mixtures have been summarized and discussed in-depth. Among them, Quantitative Structure-Activity Relationship (QSAR) method which was widely applied in silico has been described in detail. Furthermore, the reported potential mechanisms of joint toxicity on the luminescent bacteria were also overviewed, including the Trojan-horse type mechanism, funnel hypothesis, and fishing hypothesis. The future perspectives toward the development and application of toxicity assessment based on luminescent bacteria were proposed.

Identifying alternative solvents for C60 manufacturing using singular and combined toxicity assessments

Linseed oil, olive oil, and sunflower oil were selected based on green chemistry principles and C₆₀ solubility as alternative solvents to replace 1,2,4-trimethylbenzene (TMB) for C₆₀ manufacturing. Singular acute toxicity experiments of C₆₀ and the four solvents was performed using Daphnia magna to identify the solvent with the lowest toxicity and estimate the toxicity of C₆₀. The EC₅₀ for C₆₀ was estimated to be higher than 176 ppm. The toxicity of the solvents increased from sunflower oil to olive oil, linseed oil, and TMB. Combined toxicity tests were conducted to investigate the interaction between C₆₀ and the solvent since essential oils can be nanocarriers and facilitate the transport of C₆₀ into the cell membranes, which would increase its toxicity. Various concentrations of C₆₀ (0, 11, 22, 44, 88, and 176 mg/L) were mixed with solvents at their EC₅₀ concentrations. The toxicity of linseed oil increased with increasing C₆₀ concentrations. For olive and sunflower oil, the toxicity was lowered with low concentrations of C₆₀. Olive oil was determined to be a suitable solvent for C₆₀ manufacturing based on singular and combined toxicity assessments. This study showed the importance of considering combined toxicity for solvent selection.

Preconcentration and Analytical Methods for Determination of Methyl Tert-Butyl Ether and Other Fuel Oxygenates and Their Degradation Products in Environment: A Review

Fuel oxygenates (FOs) are mainly ethers or alcohols which are added to gasoline either to boost the octane number or to make the fuel burning process more "cleaner" with increasing the oxygen content, or to obtain a combination of both effects. FOs are water soluble with high mobility in the environment which presence even at very low concentrations lower the quality of water making it unsafe or unpleasant due to their objectionable taste and/or odor. Thus, their determination at trace in environmental samples is of high importance because of their sparingly biodegradability and their biological hazards. Instruments such as gas chromatography, Fourier transform infrared spectroscopy and ion mobility spectrometry are mainly used for the determination of FOs. However, the main challenge for determination of such oxygenates relates to proper sample preparation. Dilute or complex samples often demand a specific treatment to ensure effective enrichment of FOs before their detection. The main techniques used for this purpose are purge and trap, membrane extraction, and solid phase microextraction. This review presents a comprehensive evaluation of extraction/preconcentration techniques and analytical methods for determination of FOs in environmental samples. Advantages and disadvantages of each method are discussed in details along with critical evaluation of currently available methods.

An environmentally realistic pesticide and copper mixture impacts embryonic development and DNA integrity of the Pacific oyster, Crassostrea gigas

Frequent occurrences of pesticides in the environment have raised concerns that combined exposure to these chemicals may result in enhanced toxicity through additive or synergistic interaction between compounds. Spermatozoa and embryos of the Pacific oyster, Crassostrea gigas, were exposed to different concentrations of a pesticide mixture with and without copper, mimicking the cocktail of pollutants occurring in the oyster culture area of Arcachon Bay. For the 1× exposure condition, measured concentration corresponds to a total concentration of 1.083 μg L^-1 for the mixture of 14 pesticides and to 6.330 μg L^-1 for copper (Cu). Several endpoints including larval abnormalities, DNA damage to spermatozoa and embryo and gene expression in D-larvae were investigated. Results demonstrated that pesticide mixtures in combination with or without copper induced a dose-dependent increase in embryotoxic and genotoxic effects on D-larvae from the lowest tested dose of 0.1×. Transcription of genes involved in anti-oxidative stress (cat), respiratory chain (coxI), metal detoxification (mt1 and mt2), and cell cycle arrest and apoptosis (p53) was found to be significantly downregulated while the xenobiotic biotransformation gene gst was significantly upregulated in embryos exposed to pesticide mixture with and without Cu. These findings raise the question of the possible impacts of mixtures of pesticides and metals on wild or farmed oyster populations from polluted coastal marine areas.

Acute and chronic toxicity of herbicides and their mixtures measured by Aliivibrio fischeri ecotoxicological assay

The purpose of our work was to determine the acute and chronic toxicity of three of the EU's most common herbicides - mesotrione, S-metolachlor, terbuthylazine - and their mixtures by Aliivibrio fischeri ecotoxicological assays. While comparing the sensitivity of the acute (30 min) Microtox® standard assay with the chronic (25 h) test adapted to microtiter plate, joint effects (antagonism, additive effect and synergism) to the bioluminescence inhibition (consequently the metabolic damage) in A. fischeri were also determined by Combination Index (CI) method. 30 min of exposure to mesotrione and S-metolachlor resulted in a relatively low acute toxicity (EC₅₀ values were 118 and 265 mg/L), while terbuthylazine did not cause bioluminescence inhibition at all. Results showed that the chronic toxicity of S-metolachlor and terbuthylazine to A. fischeri (EC₅₀^10h = 59.2 and 4.9 mg/L and EC₅₀^15h = 54.0 and 9.6 mg/L, respectively) is larger by at least one order of magnitude than that after 30 min of contact time. Considering mesotrione no significant difference was experienced in toxicity. Regarding the EC₅₀ values, all of the mixtures had synergistic joint effects in the acute assay. However, in the chronic test all the mixtures showed antagonistic responses with the exception of mesotrione and S-metolachlor (ratio 1:1) combination, which also had additive and synergistic effects after 10 and 15 h of exposure, similarly to the short-term test. This is also the first report of the joint effects of these herbicides. The chronic test is a more sensitive indicator to the active ingredients; both acute and chronic assays supply valuable data of the toxic properties of the pesticides. Moreover, the short- and long-term joint effects of their mixtures supporting a more accurate and reliable risk assessment.

Nanosized titanium dioxide UV filter increases mixture toxicity when combined with parabens

To address the concern about the environmental impact of engineered nanoparticles frequently used in the recently marketed personal care and hygiene products (PCPs), we conducted a toxicity assessment and determined the EC₅₀ values of the nanosized inorganic UV filter TiO₂ (nano-TiO₂), as well as those of the organic UV filter oxybenzone (BP3) and three parabens (methyl, propyl, and benzylparaben) present in most PCPs formulation. The bioassays were carried out through standardized toxicity bioassays on two environmentally relevant aquatic species i.e. Daphnia magna and Phaeodactylum tricornutum. For nano-TiO₂ 48 h EC₅₀ on D. magna was 3.09 mgL^-1 and for parabens ranged from 32.52 to 1.35 mgL^-1. The two most toxic compounds on D. magna, nano-TiO₂ and benzylparaben (BzP), were further tested with the algae. For nano-TiO₂ 72 h EC₅₀ value was 2.27 mgL^-1 and for BzP it was 10.61 mgL^-1. In addition, D. magna was exposed to selected binary mixtures of the target compounds i.e. nano-TiO₂+BP3, nano-TiO₂+BzP and BP3+BzP On the endpoint of 48 h, a synergistic action was observed for nano-TiO₂+BP3 and nano-TiO₂+BzP, but an antagonistic effect occurred in the mixture BP3+BzP. These findings suggest that nano-TiO₂ can increase the toxicity of the mixture when combined with other compounds.

The involvement of McpB chemoreceptor from Pseudomonas aeruginosa PAO1 in virulence

Pseudomonas aeruginosa is an opportunistic human pathogen causing infections in a variety of plant and animal hosts. The gene mcpB, part of the chemosensory gene cluster II, encodes a soluble chemoreceptor whose function remains unknown. Previous studies show that the cheB2 gene, also located in the chemosensory cluster II, is involved in a specific response during infection and it is required for full pathogenicity of P. aeruginosa. To determine whether the McpB (or Aer2) chemoreceptor is involved in virulence processes, we generated a mcpB mutant and tested its phenotype using a virulence-measuring system. This system was developed by our group and is based on different bioassays using organisms living at different soil trophic levels, including microbial, nematode, arthropod, annelid, and plant model systems. The deletion of mcpB resulted in an attenuation of bacterial virulence in different infection models, and wild-type virulence was restored following genetic complementation of the mutant strain. Our study indicates that the McpB chemoreceptor is linked to virulence processes and may constitute the basis for the development of alternative strategies against this pathogen.

Establishment of an EC50 database of pesticides using a Vibrio fischeri bioluminescence method

An EC₅₀ database was established to assess the acute toxicity of 16 PESTANAL pesticide standards and of seven pesticide commercial formulations using a Vibrio fischeri bioluminescence method. Half maximal effective concentration (EC₅₀ ) is defined as the concentration of pollutant (in this case, pesticide) destroying 50% of the bacteria population and causing 50% bioluminescence inhibition, after a specified exposure time. Linear curves of bioluminescence inhibition versus pesticide concentration and EC₅₀ values were obtained for exposure times (t) of 5 or 15 min for these pesticides. The EC₅₀ values ranged from 6.90 × 10^-4 to 0.83 mg/ml (t = 5 min), and from 9.00 × 10^-4 to 0.37 mg/ml (t = 15 min) for pesticide standards, plus from 0.0077 to 0.74 mg/ml (t = 5 min), and from 0.0076 and 0.57 mg/ml (t = 15 min) for pesticide commercial formulations. The EC₅₀ database allowed classification of the pesticides under study into three categories according to their toxicity: very toxic, toxic and moderately toxic. These results demonstrated that the establishment of an EC₅₀ database and of linear curves of bioluminescence inhibition versus the pesticide concentration resulted in very important and irreplaceable tools to estimate the global and individual toxicity of pesticides present in environmental samples.

Antifouling processes and toxicity effects of antifouling paints on marine environment. A review

The production infrastructure in aquaculture invariably is a complex assortment of submerged components with cages, nets, floats and ropes. Cages are generally made from polyamide or high density polyethylene (PEHD). All of these structures serve as surfaces for biofouling. However, cage nets and supporting infrastructure offer fouling organisms thousands of square meters of multifilament netting. That's why, before immersing them in seawater, they should be coated with an antifouling agent. It helps to prevent net occlusion and to increase its lifespan. Biofouling in marine aquaculture is a specific problem and has three main negative effects. It causes net occlusion and so restricts water and oxygen exchange. Besides, the low dissolved oxygen levels from poor water exchange increases the stress levels of fish, lowers immunity and increases vulnerability to disease. Also, the extra weight imposed by fouling causes cage deformation and structural fatigue. The maintenance and loss of equipment cause the increase of production costs for the industry. Biocides are chemical substances that can prohibit or kill microorganisms responsible for biofouling. The expansion of the aquaculture industry requires the use of more drugs, disinfectants and antifoulant compounds (biocides) to eliminate the microorganisms in the aquaculture facilities. Unfortunately, the use of biocides in the aquatic environment has proved to be harmful as it has toxic effects on the marine environment. The most commonly used biocides in antifouling paints are Tributyltin (TBT), Chlorothalonil, Dichlofluanid, Sea-Nine 211, Diuron, Irgarol 1051 and Zinc Pyrithione. Restrictions were imposed on the use of TBT, that's why organic booster biocides were recently introduced. The replacement products are generally based on copper metal oxides and organic biocides. This paper provides an overview of the effects of antifouling biocides on aquatic organisms. It will focus on the eight booster biocides in common use, despite little data are available for some of them. Toxicity values and effects of these antifoulants will also be mentioned for different species of fish, crustaceans, invertebrates and algae.

Environmentally relevant concentrations of herbicides impact non-target species at multiple sublethal endpoints

There is concern over herbicide exposure effects on aquatic primary production and zooplankton as herbicides are found in aquatic ecosystems at concentrations potentially toxic to phytoplankton. We first aimed to determine the effect concentrations (growth inhibition) and mixture interactions of the herbicides diuron (0.5 to 50μg/L) and hexazinone (0.5 to 40μg/L) on the green algae Pseudokirchneriella subcapitata. Secondly, we evaluated chronic effects on Daphnia magna that were periodically fed on P. subcapitata that had been exposed to low, medium, and high concentrations. We hypothesized that based on the mode of action of the herbicides we would observe additive growth inhibition in algae, and sublethal effects on D. magna. Growth inhibition in P. subcapitata following mixture exposure was most consistent with the concentration addition (CA) concept; while the independent action (IA) model underestimated the combined effect. The lowest observed effect concentrations (LOEC) were 1.50μg/L hexazinone, 1.18μg/L diuron, and 0.125 TU (0.30μg/L diuron×0.12μg/L hexazinone) in the single and binary mixture exposures, respectively. High hexazinone exposure decreased D. magna survival (80% vs. 55.6%). Neonate number was reduced by 13.9% in high mixture and 23.5% in high hexazinone treatments. Gravid body length was reduced by 9.5% following exposure to the high mixture. Herbicide exposure decreased neonate size, especially in later broods. Herbicides decreased the phototaxic responses of neonates in most treatments. Herbicide exposure effects were detected at environmentally relevant concentrations, levels considered to be safe according to current USEPA aquatic life benchmarks, suggesting that these benchmarks need to be updated to improve ecological risk assessment. As herbicides are some of the most applied pesticides worldwide, sublethal endpoints can serve as sensitive early warning tools to indicate their presence and can support regulatory assessments and monitoring to protect aquatic life.

An assessment of direct and indirect effects of two herbicides on aquatic communities

Herbicides are often detected in watersheds at concentrations that are toxic to phytoplankton, potentially causing indirect effects on higher trophic organisms. The long-term effects of 5 applications over 30 d of binary mixtures of the herbicides diuron and hexazinone were assessed at "low" and "high" concentrations typically found in the environment, using mesocosms. Sixteen of 95 phytoplankton taxa, 3 of 18 zooplankton taxa, and 6 of 14 macroinvertebrate taxa responded negatively to contaminant exposures. Herbicide applications altered the phytoplankton community structure. Relative abundance of Cyanophyceae decreased following 5 applications from 52.1% in the control to 37.3% in the low treatment and to 25.9% in the high treatment, while Chlorophyceae increased to 50.6% in the low treatment and to 61.7% in the high treatment compared with the control (39.7%). Chlorophyceae had the greatest number of affected species (8), whereas 1 species within the Cyanophyceae was negatively affected on more than 1 sampling day. Further, chlorophyll a was reduced on 4 and 5 d out of the 8 total sampling days in the low and high treatments, respectively, compared with the control. These results highlight that integrating multiple taxa and contaminants with long-term exposures in ecological risk assessments of herbicides can facilitate the ability to make predictive and mechanistic generalizations about the role of herbicides in shaping patterns of species abundance in natural systems. Environ Toxicol Chem 2017;36:2234-2244. © 2017 SETAC.

Hydractinia echinata test-system. IV. Toxic synergism of human pharmaceuticals in mixtures with iodoform

The structure-toxicity relationships for a series of singular human stomatological pharmaceuticals preparations and in mixture with Iodoform on Hydractinia echinata were obtained and their synergism was analyzed through the Metamorphosis Reduction Concentration (MRC50) within the "Köln model". The differences manifested between the total and individual components of the samples and mixtures, associated with toxic versus non-toxic synergism, are dependent on three essential factors of synthesis (the nature, the concentration and the number) besides manifested isotoxicity of the given components. The method represents a practical alternative useful for the reduction of experimental tests on animal to the lowest possible level, in accordance to the '3Rs' (reduce, reuse and recycle) integrative concept.

Risk assessment of selected priority pollutants coming from boating activities

In this work, we evaluated the risk posed to aquatic organisms in the coastal waters of Albania and Apulia (Italy) by two priority pollutants (PPs), Irgarol 1051 and Diuron, used as biocides in antifouling paints on boat hulls. With this aim, we carried out an extensive 3-year monitoring in ports and marinas along the coasts of both countries, which showed a widespread occurrence of both PPs, with Irgarol 1051 concentrations usually being lower than the Diuron ones. The measured concentrations were compared with regulatory Environmental Quality Standards (EQS) (Directive 2008/105/EC) and used to perform a probabilistic Ecological Risk Assessment (ERA), for a thorough evaluation of the potential adverse effects upon marine ecosystem. Irgarol 1051 amounts above the Annual Average Concentration (AA-EQS, 2.5 ng/L) were often detected in Apulia and, less frequently, in Albania. Moreover, in Apulia, sometimes the Maximum Allowable Concentrations (MAC-EQS, 16 ng/L) was exceeded. In Apulia, where levels exceeded MAC/AA-EQS, ERA found not negligible probabilities of exceeding the toxicity level (6-18 %). A less critical situation was observed for Diuron whose levels were always below the MAC-EQS (1800 ng/L) in both countries and, in Albania, also below the AA-EQS (200 ng/L). On the other hand, in Apulia, this limit was exceeded in some locations. Correspondingly, ERA determined a not negligible risk in these sites (probability of exceedance 4-7 %).

Biosafety Test for Plant Growth-Promoting Bacteria: Proposed Environmental and Human Safety Index (EHSI) Protocol

Plant growth-promoting bacteria (PGPB) colonize plants and enhance their growth by different mechanisms. Some of these microorganisms may represent a potential threat to human, animal or plant health; however, their use might be approved in parts of Europe if they have been recommended as plant growth enhancers. The current regulatory framework has resulted in a fragmented, contradictory system, and there is an urgent need to establish harmonized protocols for the predictability, efficiency, consistency and especially the safety of PGPB for human and animal health and for the environment. In response to current efforts to update biosafety policies and provide alternative methods to replace the use of vertebrate animals, we propose a panel of tests and an evaluation system to reliably determine the biosafety of bacterial strains used as PGPB. Based on the results of different tests, we propose a scoring system to evaluate the safety of candidates for PGPB within the limitations of the assays used.

Assessment of toxicity and biodegradability on activated sludge of priority and emerging pollutants

Several methods for evaluating the toxicity and biodegradability of hazardous pollutants (chlorinated compounds, chemical additives and pharmaceuticals) have been studied in this work. Different bioassays using representative bacteria of marine and terrestrial ecosystems such as Vibrio fischeri and Pseudomonas putida have been used to assess the ecotoxicity. Activated sludge was used to analyse the effect of those pollutants in a biological reactor of a sewage treatment plant (STP). The results demonstrate that none of the compounds is toxic to activated sludge, except ofloxacin to P. putida. The additives tested can be considered moderately toxic according to the more sensitive V. fischeri assays, whereas the EC50 values of the pharmaceuticals depend on the specific microorganism used in each test. Regarding the biodegradability, respirometric measurements were carried out for fast biodegradability assessment and the Zahn-Wellens test for inherent biodegradability. The evolution of the specific oxygen uptake rate (SOUR) showed that only diethyl phthalate was easily biodegradable and acetylsalicylic acid was partially biodegradable (98% and 65% degradation, respectively). The persistence of dichloromethane, ofloxacin and hidrochlorothiazide was confirmed along the 28 days of the Zahn-Wellens test whereas 1,1,1-trichloroethane showed inherent biodegradability (74% removal). Most of the chlorinated compounds, pharmaceuticals, bisphenol A and ethylenediaminetetraacetic acid were partially degraded in 28 d with total organic carbon (TOC) reduction ranging from 21% to 51%. Sulphamethoxazole showed certain biodegradation (50% removal) with TOC decrease around 31%, which indicates the formation of non-biodegradable by-products.

Combined toxicities of methyl tert-butyl ether and its metabolite tert-butyl alcohol on earthworms via different exposure routes

Methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA) are among the major soil contaminants that threaten the health of soil ecosystems. Many MTBE-contaminated sites accumulate TBA, because TBA is the intermediate of MTBE biodegradation. To access the risk of MTBE and TBA in soil, we investigated the combined toxicities of MTBE and TBA using two earthworm species, Perionyx excavatus and Eisenia andrei, as well as the toxic effects via different exposure routes. The combined toxicity showed weak antagonistic effects (LC50mix values were slightly greater than 1.0), and sensitivity toward same pollutants differed in the two earthworm species. Moreover, the toxicity of MTBE and TBA was also affected by the exposure route; both filter paper and artificial soil tests showed that dermal-only exposure to MTBE had an even greater toxic effect than combined dermal and oral exposure. Thus, we suggest that diverse environmental factors including organic materials, the physicochemical properties of the contact media, and the exposure routes of the organism, should be taken into consideration when assessing the effects of pollutants on organisms in diverse environmental systems.

Microbial toxicity of methyl tert-butyl ether (MTBE) determined with fluorescent and luminescent bioassays

The inhibitory effects of the fuel additive methyl tert-butyl ether (MTBE) and potential degradation products tert-butanol (TBA) and formaldehyde was examined using mixed microbial biomass, and six strains of bioluminescent bacteria and yeast. The purpose was to assess microbial toxicity with quantitative bioluminescent and fluorescent endpoints, and to identify sensitive proxies suitable for monitoring MTBE contamination. Bioluminescent Aliivibrio fischeri DSM 7151 (formerly Vibrio fischeri) appeared highly sensitive to MTBE exposure, and was a superior test organisms compared to lux-tagged Escherichia coli DH5α, Pseudomonas fluorescens DF57-40E7 and Saccharomyces cerevisiae BLYR. EC10 and EC50 for acute MTBE toxicity in A. fischeri were 1.1 and 10.9 mg L(-1), respectively. Long term (24h) MTBE exposure resulted in EC10 values of 0.01 mg L(-1). TBA was significantly less toxic with EC10 and EC50 for acute and chronic toxicity >1000 mg L(-1). Inhibition of bioluminescence was generally a more sensitive endpoint for MTBE toxicity than measuring intracellular ATP levels and heterotrophic CO2 assimilation. A weak estrogenic response was detected for MTBE at concentrations ⩾ 3.7 g L(-1) using an estrogen inducible bioluminescent yeast strain (S. cerevisiae BLYES). Microbial hydrolytic enzyme activity in groundwater was affected by MTBE with EC10 values of 0.5-787 mg L(-1), and EC50 values of 59-3073 for alkaline phosphatase, arylsulfatase, beta-1,4-glucanase, N-acetyl-beta-d-glucosaminidase, and leucine-aminopeptidase. Microbial alkaline phosphatase and beta-1,4-glucanase activity were most sensitive to MTBE exposure with EC50 ⩽ 64.8 mg L(-1). The study suggests that bioassays with luminescent A. fischeri, and fluorescent assays targeting hydrolytic enzyme activity are good candidates for monitoring microbial MTBE toxicity in contaminated water.

Assessing single and joint toxicity of three phenylurea herbicides using Lemna minor and Vibrio fischeri bioassays

Single and joint toxicity of three substituted urea herbicides, namely monolinuron [3-(4-chlorophenyl)-1-methoxy-1-methylurea], linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea] and diuron [1-(3,4 dichlorophenyl)-3,3 dimethyl urea], were studied. The duckweed Lemna minor and the luminescent bacterium Vibrio fischeri were used for the toxicity assessment and they were exposed to various concentrations of the herbicides, individually and in binary mixtures. The exposure time was 7d for the duckweed and 30 min for the bacterium. Estimation of EC50 values was performed by frond counting and reduction in light output for Lemna minor and Vibrio fischeri, respectively. Lemna minor was found to be much more sensitive than Vibrio fischeri to target compounds. The toxicity of the three herbicides applied solely was estimated to be in decreasing order: diuron (EC50=28.3 μg L(-1))≈linuron (EC50=30.5 μg L(-1))>monolinuron (EC50=300 μg L(-1)) for the duckweed and linuron (EC50=8.2 mg L(-1))>diuron (EC50=9.2 mg L(-1))>monolinuron (EC50=11.2 mg L(-1)) for the bacterium. Based on the environmental concentrations reported in the literature and EC50 values obtained from Lemna minor experiments, Risk Quotients (RQ) much higher than 1 were calculated for diuron and linuron. In Lemna minor experiments, combination of target compounds resulted to additive effects due to their same mode of phenylurea action on photosynthetic organisms. Regarding Vibrio fischeri, synergistic, additive and antagonistic effects were observed, which varied according to the concentrations of target compounds.

The life-table demographic response of freshwater rotifer Brachionus calyciflorus to multi-metal (Cu, Zn, Cd, Cr, and Mn) mixture interaction

The effects of multi-metal mixtures on the life-table demography of rotifers are not well known. In this study, the freshwater rotifer Brachionus calyciflorus was exposed to mixture of Cu, Zn, Cd, Cr, and Mn, and the life-table demographic parameters including net reproductive rate, generation time, life expectancy at hatching, and intrinsic rate of population increase were calculated. The results showed that interactions between a given element concentration, except Mn, and the other four elements mixture concentration affected the intrinsic rate of population increase (p < 0.01). Interactions between Zn concentration, as well as Mn, and the other four elements mixture concentration affected the net reproductive rate and the life expectancy at hatching, respectively (p < 0.05). The variation of parameters with the rise of the other four elements mixture concentrations from 0 to high was mainly attributed to the difference of interaction among the five metals mixture with different ratio of concentrations.

Application of enzyme bioluminescence in ecology

: This review examines the general principles of bioluminescent enzymatic toxicity bioassays and describes the applications of these methods and the implementation in commercial biosensors. Bioluminescent enzyme system technology (BEST) has been proposed in the bacterial coupled enzyme system, wherein NADH:FMN-oxidoreductase-luciferase substitutes for living organisms. BEST was introduced to facilitate and accelerate the development of cost-competitive enzymatic systems for use in biosensors for medical, environmental, and industrial applications. For widespread use of BEST, the multicomponent reagent "Enzymolum" has been developed, which contains the bacterial luciferase, NADH:FMN-oxidoreductase, and their substrates, co-immobilized in starch or gelatin gel. Enzymolum is the central part of Portable Laboratory for Toxicity Detection (PLTD), which consists of a biodetector module, a sampling module, a sample preparation module, and a reagent module. PLTD instantly signals chemical-biological hazards and allows us to detect a wide range of toxic substances. Enzymolum can be integrated as a biological module into the portable biodetector-biosensor originally constructed for personal use. Based on the example of Enzymolum and the algorithm for creating new enzyme biotests with tailored characteristics, a new approach was demonstrated in biotechnological design and construction. The examples of biotechnological design of various bioluminescent methods for ecological monitoring were provided. Possible applications of enzyme bioassays are seen in the examples for medical diagnostics, assessment of the effect of physical load on sportsmen, analysis of food additives, and in practical courses for higher educational institutions and schools. The advantages of enzymatic assays are their rapidity (the period of time required does not exceed 3-5 min), high sensitivity, simplicity and safety of procedure, and possibility of automation of ecological monitoring; the required luminometer is easily available.

Assessment of toxicity in waters due to heavy metals derived from atmospheric deposition using Vibrio fischeri

Water toxicity originating from the atmospheric deposition of six heavy metals (Cd, Cr, Cu, Ni, Pb, Zn) was investigated on Vibrio fischeri activity in Izmir, Turkey. A LUMIStox® test was applied to dry and wet deposition samples and metal solutions. The inhibition levels and effective toxicity concentrations of these samples and solutions were determined. Interactive toxicity effects among the metals were investigated. When the impacts of the synthetic single heavy metal solutions were compared with each other, a toxicity ranking of Cr>Cd>Pb>Cu>Zn>Ni was obtained in order of decreasing severity. The total effective concentrations of these six metals were in the ranges of 0.074-0.221 mg/L and 0.071-0.225 mg/L for receiving aqueous solutions of dry and wet atmospheric depositions, respectively. The toxicity data showed that the wet deposition samples were 15% more toxic than the dry deposition samples. The interactive toxicity effects of the heavy metals in both dry and wet deposition samples were classified as antagonistic. High levels of heavy metals deposited in dissolved form may constitute an important input in the biochemical cycle and may have significant impacts.

Influences of two antibiotic contaminants on the production, release and toxicity of microcystins

The influences of spiramycin and amoxicillin on the algal growth, production and release of target microcystins (MCs), MC-LR, MC-RR and MC-YR, in Microcystis aeruginosa were investigated through the seven-day exposure test. Spiramycin were more toxic to M. aeruginosa than amoxicillin according to their 50 percent effective concentrations (EC(50)) in algal growth, which were 1.15 and 8.03 μg/l, respectively. At environmentally relevant concentrations of 100 ng/l-1 μg/l, spiramycin reduced the total MC content per algal cell and inhibited the algal growth, while exposure to amoxicillin led to increases in the total MC content per algal cell and the percentage of extracellular MCs, without affecting the algal growth. Toxicity of MCs in combination with each antibiotic was assessed in the luminescent bacteria test using the toxic unit (TU) approach. The 50 percent effective concentrations for the mixtures (EC(50mix)) were 0.56 TU and 0.48 TU for MCs in combination with spiramycin and amoxicillin, respectively, indicating a synergistic interaction between MCs and each antibiotic (EC(50mix)<1TU). After seven-day exposure to 100 ng/l-1 μg/l of antibiotics, spiramycin-treated algal media and amoxicillin-treated algal media showed significantly lower (p<0.05) and higher (p<0.05) inhibition on the luminescence of Photobacterium phosphoreum, respectively, compared with the untreated algal medium. These results indicated that the toxicity of MCs were alleviated by spiramycin and enhanced by amoxicillin, and the latter effect would increase threats to the aquatic environment.

Fuel derived pollutants and boating activity patterns in the Sea of Galilee

MTBE (Methyl tert-Butyl Ether) is a fuel additive that replaced lead as an antiknock compound in internal combustion motors. Few years after its introduction, detectable levels of MTBE were found in various water bodies. MTBE has a very low taste and odor threshold and is a potential carcinogen. Another group of fuel derived toxic compounds that has been detected in water bodies is BTEX (Benzene, Toluene, Ethylbenzene and Xylene). Boating activity and allochthonous contributions from watersheds are the major sources of fuel derived pollutants in lakes. Their concentrations in lakes thus vary as a function of boating activity intensity, lake surface area and depth, weather and wind regime, land-use in the watershed, etc. The Sea of Galilee (Lake Kinneret) is the only recreational lake in Israel and an important freshwater source. In the current study, a sampling campaign was conducted in order to quantify MTBE and BTEX concentrations in Lake Kinneret, its marinas and its main contributing streams. In addition, a boating-use survey was performed in order to estimate MTBE and BTEX contribution of recreational boating. The sampling campaign revealed that, as expected, MTBE concentrations were higher than BTEX, and that near shore (i.e., marina) concentrations were higher than in-lake concentrations. Despite the clear contribution from boating, high MTBE concentrations were found following a major inflow event in winter, indicating the importance of the allochthonous contribution. The contribution from boating during summer, as measured indirectly by in-lake concentrations, is likely underestimated due to enhanced MTBE volatilization due to strong winds and high temperatures. May-September was found to be the main recreational boating season, with continued boating year round. On average, a single boat is active 23 d/y, with 84% of the watercrafts being active only during weekends and holidays. The survey further indicated that boats stay in the lake for 4.5 h on average, which conforms to the unique winds regime that limits afternoon activity due to high winds, and have an average fuel consumption of 14 L/h. The annual load of MTBE and BTEX from recreational boating in Lake Kinneret was estimated at 4430 and 6220 kg/y respectively.

Hydractinia echinata test system. II. SAR toxicity study of some anilide derivatives of Naphthol-AS type

In this paper, a toxicity study for a series of anilides of Naphthol-AS type is presented. The toxicity of the model compounds was determined by using the Hydractinia echinata (Hydrozoa) test system. Conformational analysis of Naphthol-AS derivatives was performed to elucidate the possible enzymatic hydrolysis mechanism of these compounds. This mechanism occurs with different rates and always leads to a stoichiometric mixture of reaction products, consisting in the substituted amine and the corresponding α-hydroxy-carboxylic acid. With one exception, the toxicities of the reaction products are subadditive. Quite similar measured toxicity values, log(1/MRC₅₀), led to their average calculated values, and thus to the establishment of class isotoxicity. This method represents a practical alternative useful for the reduction of experimental tests on animals to the lowest possible level, in accordance to the '3Rs' (reduction, refinement and replacement) concept.

Cadmium, lead and their mixtures with copper: Paracentrotus lividus embryotoxicity assessment, prediction, and offspring quality evaluation

The aim of this research was to assess the combined effects of three heavy metals (copper, lead, cadmium) on the fertilization and offspring quality of the sea urchin Paracentrotus lividus at EC50, NOEL, and EC1 concentrations. The observed data were compared with the predictions derived from approaches of Concentration Addition (CA) and Independent Action (IA) in order to evaluate the proper prediction of the observed mixture toxic effect. The P. lividus embryotoxicity of trace metals decreases as follows: Cu > Pb > Cd at all toxicity concentration tested. EC50 mixture revealed less toxic only than Cu; EC50 was 0.80 (± 0.07) mg/l, the offspring malformations were mainly P1 type (skeletal alterations) up to 20% mixture concentration, and P2 type from 70% concentration. The NOEL and EC1 mixtures evidenced that all compounds contribute to the overall toxicity, even if present at low concentrations: the former EC50 was 0.532 (± 0.058) mg/l and the latter was 1.081 (± 0.240) mg/l. The developmental defects observed were mainly P1 type in both mixtures. Both CA and IA models did not accurately predict mixture toxicity for EC50 and NOEL mixtures. Instead, EC1 mixture effects seemed well represented by the IA model. The protective action of the CA model, although quite accurate when applied to simple biological systems like algae and bacteria, but failed to represent the worst-case in this study with more complex organisms. It would be useful to introduce in the models one or more factors that take into account the complexity of these biological systems.

Effect-directed investigation and interactive effect of organic toxicants in landfill leachates combining Microtox test with RP-HPLC fractionation and GC/MS analysis

Landfill leachates contain a large amount of unknown harmful compounds derived from domestic and industrial sources. A toxicity effect-directed approach was used to identify biologically active compounds in three landfill leachate samples (S1-S3) by combining the Microtox test with reverse-phase high performance liquid chromatography (RP-HPLC) fractionation and gas chromatography/mass spectrometry (GC/MS) analysis. Organic toxicants were recovered from coarse fractions only in S1 and in S2. Fine fractionation exhibited a somewhat different toxicity pattern in S1 and S2. GC/MS analysis positively identified Bisphenol A (BPA) and 4-t-butylphenol (4-t-BP) in both samples, N-ethyltoluenesulfoneamide (NETSA) was detected only in S1. However, their concentrations were not high enough to be responsible for the observed toxicity in original samples. A synergistic effect among detected organic compounds (BPA, NETSA, and 4-t-BP) was demonstrated. Each compound present at 1/7 of its individual EC(50), might lead to undesirable mixture toxicity, which indicated that interactive effects may, to a certain extent, play a role in landfill leachates with complex matrices. The results from further hydrophobicity analysis and estrogen receptor (ER) competitive binding assays of fraction 13 of both samples gave evidence that some possible toxicants that failed to be identified by GC/MS might be endocrine disrupting chemical(s) (EDC) with a log K (ow) range of 3.5-3.7 in both samples.

Toxicological profiling of chemical and environmental samples using panels of test organisms and optical oxygen respirometry

A simple and versatile methodology for high throughput toxicological assessment of chemical and environmental samples is presented. It uses panels of test organisms ranging from prokaryotic (E. coli, V. fischeri) and eukaryotic (Jurkat) cells to invertebrate (Artemia salina) and vertebrate (Danio rerio) organisms, to analyze alterations in their oxygen consumption by optical oxygen respirometry. All the assays are carried out in a convenient microtiter plate format using commercial reagents (phosphorescent oxygen probe, microplates) and detection on a standard fluorescent plate reader. Simple experimental set-up and mix-and-measure procedure allow parallel assessment of up to 96 samples (or assay points) in 2 h, easy generation of dose- and time-dependent responses, and EC(50) values. The methodology was demonstrated with several different classes of chemicals including heavy metal ions, PAHs, pesticides, their mixtures, and also validated with complex environmental samples such as wastewater from a wastewater treatment plant. It has been shown to provide high sensitivity, sample throughput and information content, flexibility and general robustness. It allows ranking and profiling of samples, compares favorably with alternative methods such as MicroTox and mortality tests with animal models, and is well suited for large-scale monitoring programs such as CWA and WFD.

Ecological effects of the herbicide linuron in tropical freshwater microcosms

Effects of a single application of the photosynthesis-inhibiting herbicide linuron (0, 15, 50, 150, and 500 microg/L) on the ecology of outdoor plankton-dominated microcosms were studied in Thailand. As a result of the decreased photosynthesis, DO and pH decreased while EC, alkalinity and nutrient concentrations increased. Chlorophytes belonging to the genera Scenedesmus, Coelastrum and Pediastrum were the most sensitive taxa, whereas several other chlorophytes, diatoms, and cryptophytes increased in abundance. Tolerant taxa appeared to be less digestable for several zooplankton taxa, which subsequently decreased in abundances. Chamaesiphon sp. (Cyanobacteria) was the most susceptible periphyton species. As a consequence of functional redundancy, effects of the herbicide on the chlorophyll-a content of periphyton and especially phytoplankton did not always reflect the effects noted on community level.

Sensitivity of green and blue-green algae to methyl tert-butyl ether

The toxicity of methyl tert-butyl ether (MTBE) to Chlorella ellipsoidea and Aphanizomenon flos-aquae was tested and assessed for a 15-d incubation with concentrations of MTBE from high (2.00 x 10(4) mg/L) to low (2 mg/L). The results showed that the toxicity was low when the concentration of MTBE was in the range 1.00 x 10(4) - 2.00 x 10(4) mg/L (the greatest inhibition of growth-rate was 70%-71%, occurred during the day 1-5). Low concentrations (2-500 mg/L) stimulated algal growth up to the greatest effect of 85%-200% when the concentration of MTBE was 50-100 mg/L during day 3-5. The toxicity of MTBE (72-120 h EC50) was 6.65 x 10(3) - 9.58 x 10(3) mg/L for C. ellipsoidea and that is 1.14 x 10(4) - 2.00 x 10(4) mg/L for A. floc-aquae. We found that the toxicity and ecological risk of MTBE for the algal community structure were low and the toxicity was influenced by the duration time of the test.

Level of contamination and impact of pesticides in cupped oyster, Crassostrea gigas, reared in a shellfish production area in Normandy (France)

Over the last decade, oysters in the Bay of Veys (Northwest France) have sporadically experienced significant summer mortality events which appear to be due to a combination of extrinsic and intrinsic factors. In the present work, the involvement of pesticides (as additional stressors) was investigated using both artificial exposure and field studies (at two sites). Six herbicides were detected in seawater following tests for a total of 15 herbicides. The most estuarine site was the most contaminated, showing relatively high values compared with those recorded in a neighboring river. No pesticides were detected in the flesh of oysters in the field but exposure experiments led to an accumulation of two substituted ureas (diuron and isoproturon, from 0.5 micro g/L and 1 micro gL(- 1) respectively). Some physiological effects were observed in terms of reproduction (partial spawning) and histopathology (atrophy of the digestive tubule epithelium) but results related to other tissue alterations and to neutral red retention (NRR) assays were not conclusive and require further investigation.

A model compound study: the ecotoxicological evaluation of five organic contaminants employing a battery of marine bioassays

This paper describes the ecotoxicological evaluation of five organic contaminants frequently detected in marine sediments (tributyltin, triphenyltin, benzo[a]pyrene, fluoranthene, and PCB 153) using three marine species (Vibrio fischeri, Tetraselmis suecica, and Tisbe battagliai). The sensitivity of each species varied for all compounds. The triorganotins were consistently the most toxic to all species. The applicability of each test system to assess the acute toxicity of environmental contaminants and their use in Toxicity Identification Evaluation (TIE) is discussed. Suitability of the Microtox and T. battagliai tests for employment in TIE studies were further assessed through spiking experiments with tributyltin. Results demonstrated that the most effective treatment to remove organotin toxicity from the sample was the C18 resin. The results of this study have important implications for risk assessment in estuarine and coastal waters in Ireland, where, at present the monitoring of sediment and water quality is predominantly reliant on chemical analysis alone.

Predictability of copper, irgarol, and diuron combined effects on sea urchin Paracentrotus lividus

The aim of this work was to investigate the mixture toxicity of Irgarol (2-methylthio-4-t-butylamino-6-cyclopropylamino-s-triazine), Diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea), and copper upon the sea urchin Paracentrotus lividus and to compare the observed data with the predictions derived from approaches of Concentration Addition (CA) and Independent Action (IA). Copper spermiotoxicity was more sensitive (EC50 = 0.018 mg/L) than embryotoxicity (EC50 = 0.046 mg/L). The offspring malformations were mainly P1 type (skeletal alterations) in both cases, probably because copper competes to fix Ca2+. Irgarol and Diuron toxicity has been previously investigated. EC50 mixture embryotoxicity showed an EC50 of 1.79 mg/L, whereas spermiotoxicity mixture effects were lower than 11%. Both CA and IA modeling approaches failed to predict accurately mixture toxicity. For embryotoxicity, the IA model overestimated the mixture toxicity at effect levels of <80%. CA does not represent the worst-case approach showing values lower than IA (embryotoxicity) or similar (spermiotoxicity).

A bioluminescent signal system: detection of chemical toxicants in water

Prototype technologies of a bioluminescent signal system (BSS) based on the luminous bacterium Photobacterium phosphoreum and three enzymatic bioluminescence systems have been proposed for detecting and signalling the presence of toxicants in water systems. A number of pesticides, mostly known as poisonous substances, similar in their structures and physicochemical properties, have been taken as model compounds of chemical agents. The effect of toxicants (organophosphates, derivatives of dithiocarbamide acid, and pyrethroid preparations) on the bioluminescence of the four systems has been analysed. EC(50) and EC(80) have been determined and compared to the maximum permissible concentration for each of the analysed substances. The triple-enzyme systems with ADH and trypsin have been shown to be more sensitive to organophosphorous compounds (0.13-11 mg/L), while the triple-enzyme system with trypsin is highly sensitive to lipotropic poison, a derivative of dithiocarbamine acid (0.03 mg/L). Sensitivities of the triple-enzyme systems to pyrethroid preparations are similar to those of luminous bacteria (0.9-5 mg/L). The results can be used to construct an alarm-test bioluminescence system for detecting chemical toxicants, based on intact bacteria or enzyme systems.