Growth Endpoints Research Articles

The toxicity of a mixture of two antiseptics, triclosan and triclocarban, on reproduction and growth of the nematode Caenorhabditis elegans.

Many widely used healthcare products contain antiseptics, whose persistence in aquatic environments, soils, and sediments leads to the contamination of ecosystems and adversely affects wildlife. Recently, the impact not only of high but also low doses of contaminants and mixtures of several chemicals has become a focus of concern. In this study, toxicity tests of the antiseptics triclosan (TCS) and triclocarban (TCC) were performed in an aquatic test medium using the nematode Caenorhabditis elegans. Nominal concentrations of TCS and TCC were tested in separate single-substance toxicity tests (96-h-exposure), focussing on growth and reproduction endpoints. Median effective concentrations (EC50s) from the single-substance tests were subsequently used to set up five different ratios of TCS:TCC mixtures leading to the same toxicity. Six dilutions of each mixture ratio were tested for effon reproduction of C. elegans. In the single-substance tests, TCC was about 30 times more toxic than TCS when considering effects on growth and concerning reproduction, TCC was about 50 times more toxic than TCS. For both substances, the toxic effect on reproduction was more pronounced than the one on growth. Low doses of TCS (1-10 µmol L-1) stimulated reproduction by up to 301% compared to the control, which might be due to endocrine disruption or other stress-related compensation responses (hormesis). Neither antiseptic stimulated growth. In the mixtures, increasing amounts of TCC inhibited the stimulatory effects of TCS on reproduction. In addition, the interactions of TCS and TCC were antagonistic, such that mixtures displayed lower toxicity than would have been expected when TCS and TCC mixtures adhered to the principle of concentration addition.

Toxicity Evaluation of Individual and Mixtures of Nanoparticles Based on Algal Chlorophyll Content and Cell Count.

The toxic effects of individual and binary mixtures of five metal oxide nanoparticles (NPs) were evaluated based on changes in two endpoints of algal growth: the cell count and chlorophyll content. Various effects were observed according to the concentration tested and type of NPs, and there were no significant differences in findings for the two endpoints. In general, ZnO NPs caused the greatest inhibition of algal growth, and Fe2O3 NPs the least. The EC50 for ZnO was 2.0 mg/L for the cell count and 2.6 mg/L for the chlorophyll content, and it was 76 and 90 mg/L, respectively, for Fe2O3. The EC50 values were in the order ZnO > NiO > CuO > TiO2 > Fe2O3. Subsequently, the effects of 30 binary mixture combinations on the chlorophyll content were evaluated. Comparisons were made between the observed and the expected toxicities calculated based on the individual NP toxicities. Overall, additive action (67%) was mainly observed, followed by antagonistic (16.5%) and synergistic (16.5%) actions. These results suggest that environmental exposure to NP mixtures may cause toxicity levels similar to the sum of those of the constituent NPs.

Comparative toxicity of azo dyes to two infaunal organisms (Hexagenia spp. and Tubifex tubifex) in spiked-sediment exposures.

Azo dyes are synthetic compounds used as industrial colorants, and some are predicted to be inherently toxic, bioaccumulative, and/or persistent based upon their chemical composition. This study addresses data gaps in current research which include the need to evaluate the toxicity of hydrophobic azo dyes to benthic invertebrates. The toxicity of a solvent dye, Sudan Red G (SRG), and two disperse dyes, Disperse Yellow 7 (DY7) and Disperse Orange 13 (DO13), to Hexagenia spp. and Tubifex tubifex was assessed in spiked-sediment exposures. The dye compounds appeared to degrade readily in the equilibrium and exposure periods, suggesting a limited persistence of the parent compounds in the environment under test conditions. Although azo dye degradation products could not be reliably quantified, one was detected in DY7 sediment samples that elicited toxic effects to Hexagenia and Tubifex, providing evidence that DY7 degrades. Hexagenia survival and growth endpoints responded with similar sensitivity to the dyes, but DY7 was the most toxic, with a 21-day IC25 (concentration associated with 25% inhibition) for growth of 9.6μg/g. Comparatively, Tubifex reproduction was the most sensitive endpoint for all dyes with 28-day IC25s for young production ranging from 1.3 to 11.8μg/g. At sublethal concentrations, toxic effects to Tubifex differed between dyes: the solvent dye exerted an effect primarily on gametogenesis (cocoon production), while disperse dyes, most notably DY7, caused effects on embryogenesis (development of worm inside the cocoon). This study indicates that there could be potential hazard to oligochaetes based on the observed effect concentrations, but given the lack of environmental measurements, the risk of these compounds is unknown. Further research is required to determine if degradation products were formed in all dye samples and whether toxicity was caused by the parent molecules, which have limited persistence under test conditions, or by their degradation products. To avoid underestimating toxicity, this study stresses the need to use an infaunal deposit feeder such as the oligochaete Tubifex in sediment toxicity assessments where highly hydrophobic compounds are present.

Life-cycle studies with 2 marine species and bisphenol A: The mysid shrimp (Americamysis bahia) and sheepshead minnow (Cyprinodon variegatus).

Bisphenol A (BPA) is a high production volume compound primarily used to produce epoxy resins and polycarbonate plastic. Exposure to low concentrations of BPA occurs in freshwater and marine systems, primarily from wastewater treatment plant discharges. The dataset for chronic toxicity of BPA to freshwater organisms includes studies on fish, amphibians, invertebrates, algae, and aquatic plants. To broaden the dataset, a 1.5-generation test with sheepshead minnow (Cyprinodon variegatus) and a full life-cycle test with mysid shrimp (Americamysis bahia) were conducted. Testing focused on apical endpoints of survival, growth and development, and reproduction. The respective no-observed-effect concentration (NOEC) and lowest-observed-effect concentration (LOEC) values of 170 and 370 µg/L for mysid and 66 and 130 μg/L for sheepshead were based on reduced fecundity. The hazardous concentrations for 5% of the species (HC5) values of 18 μg/L were calculated from species sensitivity distributions (SSDs) with freshwater-only data and combined freshwater and marine data. Inclusion of marine data resulted in no apparent difference in SSD shape, R2 values for the distributions, or HC5 values. Upper-bound 95th percentile concentrations of BPA measured in marine waters of North America and Europe (0.024 and 0.15 μg/L, respectively) are below the HC5 value of 18 μg/L. These results suggest that marine and freshwater species are of generally similar sensitivity and that chronic studies using a diverse set of species can be combined to assess the aquatic toxicity of BPA. Environ Toxicol Chem 2018;37:398-410. © 2017 The Authors. Environmental Toxicology and Chemistry Published by Wiley Periodicals, Inc. on behalf of SETAC.

Assessing measurable adverse changes to benthic invertebrate communities based on site-specific sediment toxicity testing and community data at the Anniston, Alabama PCB site

ABSTRACTLaboratory toxicity tests were conducted for polychlorinated biphenyl (PCB)-containing sediment from Choccolocco Creek at the Anniston PCB Site. The objective of this investigation was to develop a site-specific PCB concentration–response relationship for invertebrate test organisms. Test results from reference locations were used to develop background-adjusted 10% (EC10*) and 20% (EC20*) effect concentrations for a range of survival, growth, and reproduction endpoints. The EC20* values ranged from 4.43 to 114 milligrams of PCBs per kilogram (mg/kg) of sediment on a dry weight basis for reproductive endpoints, 28 to 67.7 mg/kg sediment for growth, and 123 to 165 mg/kg sediment for survival. The aggregate EC20* response range for endpoints that demonstrated good test performance with reasonable ranges in control variability (<20%) and reference sample responses was 14.3 to 165 mg/kg. The PCB concentrations in sediments for a majority of the Site rarely exceed even the lowest of these thresholds. Given the protective process used to develop these thresholds, there is a high level of confidence that benthic communities are not impacted. This finding is supported by direct measurements of the benthic communities that have been living and reproducing on the Site.

Masculinization and reproductive effects in western mosquitofish (Gambusia affinis) after long-term exposure to androstenedione

Androstenedione (AED) is a naturally occurring steroid hormone. It is metabolized to potent androgens, which may induce androgenic effects in fish. However, little is known whether and how the androgens interfere with the fish gonadal development and reproduction. This study aimed at demonstrating the effects of long-term AED exposure on reproduction and development in mosquitofish (Gambusia affinis). The growth, development and several morphological endpoints, including the segment number and length of anal fin, histological changes of gonads and liver, were evaluated in mosquitofish during development from fertilized embryo to adulthood (180 days) after exposure of AED at environmentally relevant concentrations. We found that the growth (length, body weight and condition factor) of fish was negatively correlated with AED concentration in females, but not in males. The significant elongation of the ray and increment of segment numbers in the anal fin, were detected in all mosquitofish after exposure. Moreover, AED exposure (0.4gµ/L) caused damages in gonads and reduced the number of pregnant females. These findings indicate that AED has adverse effects on the growth and development of the western mosquitofish after long-term exposure (180d). Long-term exposure (180d) to AED, including environmentally relevant concentration (0.4µg/L and 4µg/L), induced masculinization in female mosquitofish under the experimental conditions.

The effects of Copper and Zinc on survival, growth and reproduction of the cladoceran Daphnia longispina: introducing new data in an “old” issue

Metal contamination is still a major environmental issue due to their continuous deposition and persistence. In this work we intended to assess the impact that Copper (Cu) and Zinc (Zn) exert in life-history parameters of Daphnia longispina, a common cladoceran in freshwater environments. Thus, we studied the effects of Cu (20-300 µg/L) and Zn (500-4000 µg/L) on the survival, growth, reproduction, feeding rate and population growth rate of D. longispina. Though survival was only reduced for the highest concentration of each metal, other endpoints were strongly affected by lower concentrations. Growth was affected by both metals, especially in the period 0-7 d, being significant for Cu ≥ 40 µg/L and Zn ≥ 500 µg/L. Indeed, growth endpoints at day 7 (body length and growth rate) were equally or more sensitive than the corresponding endpoints at day 21. The size at first reproduction decreased (significant for Cu ≥ 40 µg/L and Zn ≥ 500 µg/L). Reproduction decreased, which was partially explained by the reduced growth, but additional effects were supported by a direct effect of metals on reproduction (based on the relationship body length-brood size). Reduced growth and reproduction are likely a food mediated effect due to feeding inhibition caused by the metals. Globally, the studied endpoints were affected by Cu and Zn differently, supporting a chemical-specificity of the effects, with Zn causing more pronounced effects than Cu. This work presents an innovative approach to the effects of Cu and Zn to D. longispina, giving a general and comprehensive overview of those effects.

Acute toxicity tests using earthworms to estimate ecological quality of compost and digestate

Ecological quality of compost and digestate, used as fertilizers for agricultural use, was assessed through an acute ecotoxicological bioassay testing the earthworm Eisenia fetida (Annelida). The test evaluates the earthworm’s attitude to dig within 15 min into a soil medium constituted by a mixture of a standardized soil and different concentrations of compost/digestate. According to different classes of behavior responses, the sample is classified as good or bad quality (ON/OFF). The validity of this test was confirmed comparing the observations with the results from a standard chronic test developed by OECD (Organisation for Economic Co-operation and Development). Considering samples from different plants and at different stages of degradations, the replicates, the number of tested concentrations and the measured endpoints (ability to dig, mortality, growth, reproduction), a total of 996 observations were analyzed. The chronic test on earthworms uses the same media as in the acute one and measures the endpoints of mortality and growth within 28 days and reproduction within further 28 days. Thus, the test proposed here can be considered a not expensive and quick laboratory test and its implementation in quality assurance (QA) and quality of product (QC) schemes would enhance the protection of soil fauna. This last purpose is very important considering that, concerning the biological indicators of the quality of compost and digestate, the most important studies focused on the use of plants and microorganisms and scarce attention has been paid to soil invertebrates.

Derivation of predicted no-effect concentration and ecological risk for atrazine better based on reproductive fitness

Atrazine (ATZ) is an herbicide most commonly used in China and other regions of the world. It is reported toxic to aquatic organisms, and frequently occurs at relatively high concentrations. Currently, ATZ has been proved to affect reproduction of aquatic species at much lower levels. So it is controversial to perform ecological risk assessment using predicted no-effect concentrations (PENCs) derived from traditional endpoints, which fail to provide adequate protection to aquatic organisms. In this study, PNECs of ATZ were derived based on six endpoints of survival, growth, behavior, biochemistry, genetics and reproduction. The PNEC derived from reproductive lesion was 0.044μg ATZ L−1, which was obviously lower than that derived from other endpoints. In addition, a tiered ecological risk assessment was conducted in the Taizi River based on six PNECs derived from six categories of toxicity endpoints. Results of these two methods of ecological risk assessment were consistent with each other, and the risk level of ATZ to aquatic organisms reached highest as taking reproductive fitness into account. The joint probability indicated that severe ecological risk rooting in reproduction might exist 93.9% and 99.9% of surface water in the Taizi River, while 5% threshold (HC5) and 1% threshold (HC1) were set up to protect aquatic organisms, respectively. We hope the present work could provide valuable information to manage and control ATZ pollution.

Evaluating the effects of triclosan on 3 field crops grown in 4 formulations of biosolids.

A growing body of evidence suggests that amending soil with biosolids can be an integral component of sustainable agriculture. Despite strong evidence supporting its beneficial use in agriculture, there are concerns that chemicals, such as pharmaceuticals and personal care products, could present a risk to terrestrial ecosystems and human health. Triclosan is one of the most commonly detected compounds in biosolids. To date, laboratory studies indicate that triclosan likely poses a de minimis risk to field crops; however, these studies were either conducted under unrealistic exposure conditions or only assessed 1 or 2 formulations of biosolids. The purpose of the present study was to characterize the effects of triclosan on field crops in soils amended with 4 different formulations of biosolids (liquid, dewatered, compost, and alkaline-hydrolyzed), containing both background and spiked triclosan concentrations, following best management practices used in the province of Ontario. Three crop species (corn, soybean, and spring wheat) were evaluated using several plant growth endpoints (e.g., root wet mass, shoot length, shoot wet/dry mass) in 70-d to 90-d potted soil tests. The results indicated no adverse impact of triclosan on any crop-biosolids combination. Conversely, amending soil with biosolids either enhanced or had no negative effect, on the growth of plants. Results of the present study suggest little risk of triclosan to crops in agricultural fields amended with biosolids. Environ Toxicol Chem 2017;36:1896-1908. © 2016 SETAC.

Sodium chloride as a reference substance for the three growth endpoints used in the Lemna minor L. (1753) test

Lemna sp. growth inhibition test standardized protocols suggest the use of compounds such as 3,5-dichlorophenol as reference substances for checking the test organism’s sensitivity routinely. However, this and other recommended chemicals present risks to human health and to the environment. Sodium chloride (NaCl) appears as a less toxic alternative reference substance which has been successfully used in routine ecotoxicological tests. However, the evaluation of this compound in multiple growth endpoints used in the L. minor test, which is required for recommending it as a reference substance for this test organism, has not yet been reported. In the present study, NaCl was tested with L. minor for the growth endpoints frond number, total frond area and fresh weight. Results showed acceptable sensitivity and reproducibility (coefficient of variance &lt; 15.0%) for all three of the measured endpoints. Statistically significant differences were observed between the EC50 values calculated based on the three endpoints (p &lt; 0.05). Total frond area was the most sensitive one, with average EC50 value of 2742.80 ± 245.7 mg L-1. It was anticipated that NaCl can be a suitable alternative reference substance and that total frond area should be the endpoint of choice for sensitivity toxicity tests using NaCl.

Comparing the acute sensitivity of growth and photosynthetic endpoints in three Lemna species exposed to four herbicides

An ecological impact assessment of four herbicides (atrazine, diuron, paraquat and simazine) was assessed using the aquatic floating vascular plants, Lemna gibba, Lemna minor and Lemna paucicostata as test organisms. The sensitivity of several ecologically relevant parameters (increase in frond area, root length after regrowth, maximum and effective quantum yield of PSII and maximum electron transport rate (ETRmax), were compared after a 72 h exposure to herbicides. The present test methods require relatively small sample volume (3 mL), shorter exposure times (72 h), simple and quick analytical procedures as compared with standard Lemna assays. Sensitivity ranking of endpoints, based on EC50 values, differed depending on the herbicide. The most toxic herbicides were diuron and paraquat and the most sensitive endpoints were root length (6.0–12.3 μg L−1) and ETRmax (4.7–10.3 μg L−1) for paraquat and effective quantum yield (6.8–10.4 μg L−1) for diuron. Growth and chlorophyll a fluorescence parameters in all three Lemna species were sensitive enough to detect toxic levels of diuron and paraquat in water samples in excess of allowable concentrations set by international standards. CV values of all EC50s obtained from the Lemna tests were in the range of 2.8–24.33%, indicating a high level of repeatability comparable to the desirable level of <30% for adoption of toxicity test methods as international standards. Our new Lemna methods may provide useful information for the assessment of toxicity risk of residual herbicides in aquatic ecosystems.

Application of root growth endpoint in toxicity tests with lettuce (Lactuca sativa)

Ecotoxicological tests are an important tool to assess the toxicity of chemical substances and even the deleterious effects of adverse environmental conditions to different species. Ecotoxicological studies with land plants and animals are relatively recent compared to those with aquatic species, with few studies reported focusing on terrestrial species. The aim of the present study was to evaluate the sensitivity of root growth (Total Part; Radicle, Hypocotyl) in lettuce (Lactuca sativa) to sodium chloride (NaCl), by means of exposing the seeds to concentrations of 0, 1.0, 2.0, 4.0, 8.0 and 16.0 g L-1 for five days in Petri dishes. The average effective concentration (EC50;120h) on germination was 5.73 ± 0.56 g L-1 (CI= 4.61 to 6.86 g L-1). The effects on root growth were detected starting at a concentration of 1.0 g L-1 of NaCl and the radicle (Rad) was the most sensitive and reliable structure. Root growth was a more sensitive endpoint than germination, since the effects were detected at concentrations some 10 times lower. Besides this, the use of the radicle as an endpoint, proposed in the present study, should be intensified in ecotoxicological studies, since it provides satisfactory results at low cost and in a relatively short time frame.

Potential risk of acute toxicity induced by AgI cloud seeding on soil and freshwater biota

Silver iodide is one of the most common nucleating materials used in cloud seeding. Previous cloud seeding studies have concluded that AgI is not practically bioavailable in the environment but instead remains in soils and sediments such that the free Ag amounts are likely too low to induce a toxicological effect. However, none of these studies has considered the continued use of this practice on the same geographical areas and thus the potential cumulative effect of environmental AgI. The aim of this study is to assess the risk of acute toxicity caused by AgI exposure under laboratory conditions at the concentration expected in the environment after repeated treatments on selected soil and aquatic biota. To achieve the aims, the viability of soil bacteria Bacillus cereus and Pseudomonas stutzeri and the survival of the nematode Caenorhabditis elegans exposed to different silver iodide concentrations have been evaluated. Freshwater green algae Dictyosphaerium chlorelloides and cyanobacteria Microcystis aeruginosa were exposed to silver iodide in culture medium, and their cell viability and photosynthetic activity were evaluated. Additionally, BOD5 exertion and the Microtox® toxicity test were included in the battery of toxicological assays. Both tests exhibited a moderate AgI adverse effect at the highest concentration (12.5µM) tested. However, AgI concentrations below 2.5µM increased BOD5. Although no impact on the growth and survival endpoints in the soil worm C. elegans was recorded after AgI exposures, a moderate decrease in cell viability was found for both of the assessed soil bacterial strains at the studied concentrations. Comparison between the studied species showed that the cyanobacteria were more sensitive than green algae. Exposure to AgI at 0.43μM, the reference value used in monitoring environmental impact, induced a significant decrease in photosynthetic activity that is primarily associated with the respiration (80% inhibition) and, to a lesser extent, the net photosynthesis (40% inhibition) in both strains of phytoplankton and a moderate decrease in soil bacteria viability. These results suggest that AgI from cloud seeding may moderately affect biota living in both terrestrial and aquatic ecosystems if cloud seeding is repeatedly applied in a specific area and large amounts of seeding materials accumulate in the environment.

Implications of Cu and Ni toxicity in two members of the Hyalella azteca cryptic species complex: Mortality, growth, and bioaccumulation parameters.

Hyalella azteca, an amphipod crustacean, is frequently used in freshwater toxicity tests. Since the mid-1980s, numerous organizations have collected and established cultures of H. azteca originating from localities across North America. However, H. azteca is actually a large cryptic species complex whose members satisfy both the biological and the phylogenetic species concepts. Genetic analysis at the mitochondrial COI gene has revealed that only 2 clades are cultured in 17 North American laboratories; however, there are 85 genetically divergent lineages within this complex in the wild. In the present study, 2 members (clades 1 and 8) of the H. azteca species complex were identified using the mitochondrial COI gene. These 2 clades were exposed to Cu or Ni for 14 d. A saturation-based mortality model and the general growth model were used to determine mortality (lethal concentration, 25% and 50% [LC25 and LC50], lethal body concentration, 25% and 50% [LBC25 and LBC50]) and growth (inhibitory concentration, 25% [IC25, IBC25]) endpoints, respectively. A modified saturation-based model was used to estimate metal bioaccumulation parameters. Clade 8 was significantly more tolerant than clade 1, with differences in LC50s. However, the effects of the metals on growth were not significantly different between clades, even though clade 1 was significantly larger than then clade 8. Differences in Cu or Ni bioaccumulation were not observed between clades 1 and 8. The differences in Cu and Ni LC50s may have implications for risk assessments, and it is recommended that toxicity experiments should only be performed with properly identified members of the H. azteca complex to maintain consistency among laboratories. Environ Toxicol Chem 2016;35:2817-2826. © 2016 SETAC.

Sickle Cells Abolish Melanoma Tumorigenesis in Hemoglobin SS Knockin Mice and Augment the Tumoricidal Effect of Oncolytic Virus In Vivo.

Insights from the study of cancer resistance in animals have led to the discovery of novel anticancer pathways and opened new venues for cancer prevention and treatment. Sickle cells (SSRBCs) from subjects with homozygous sickle cell anemia (SCA) have been shown to target hypoxic tumor niches, induce diffuse vaso-occlusion, and potentiate a tumoricidal response in a heme- and oxidant-dependent manner. These findings spawned the hypothesis that SSRBCs and the vasculopathic microenvironment of subjects with SCA might be inimical to tumor outgrowth and thereby constitute a natural antitumor defense. We therefore implanted the B16F10 melanoma into humanized hemoglobin SS knockin mice which exhibit the hematologic and vasculopathic sequelae of human SCA. Over the 31-day observation period, hemoglobin SS mice showed no significant melanoma outgrowth. By contrast, 68–100% of melanomas implanted in background and hemoglobin AA knockin control mice reached the tumor growth end point (p < 0.0001). SS knockin mice also exhibited established markers of underlying vasculopathy, e.g., chronic hemolysis (anemia, reticulocytosis) and vascular inflammation (leukocytosis) that differed significantly from all control groups. Genetic differences or normal AA gene knockin do not explain the impaired tumor outgrowth in SS knockin mice. These data point instead to the chronic pro-oxidative vasculopathic network in these mice as the predominant cause. In related studies, we demonstrate the ability of the sickle cell component of this system to function as a therapeutic vehicle in potentiating the oncolytic/vasculopathic effect of RNA reovirus. Sickle cells were shown to efficiently adsorb and transfer the virus to melanoma cells where it induced apoptosis even in the presence of anti-reovirus neutralizing antibodies. In vivo, SSRBCs along with their viral cargo rapidly targeted the tumor and initiated a tumoricidal response exceeding that of free virus and similarly loaded normal RBCs without toxicity. Collectively, these data unveil two hitherto unrecognized findings: hemoglobin SS knockin mice appear to present a natural barrier to melanoma tumorigenesis while SSRBCs demonstrate therapeutic function as a vehicle for enhancing the oncolytic effect of free reovirus against established melanoma.

Chronic effects of non-weathered and weathered crude oil and dispersant associated with the Deepwater Horizon incident on development of larvae of the eastern oyster, Crassostrea virginica.

The present study examined the effects of chronic exposure of eastern oyster (Crassostrea virginica) larvae to the water-accommodated fractions of fresh and weathered oils collected from the Deepwater Horizon incident, with and without additions of the dispersant Corexit 9500A, as well as to solutions of Corexit alone. Both shell growth of larvae exposed to test materials for a period of 10 d and larval settlement after 28 d of exposure were the most sensitive endpoints, with the 10-d growth endpoint being less variable among replicates. Growth and settlement endpoints were more sensitive than larval survival and normal development after 10 d and 28 d. Acute-to-chronic ratios calculated in the present study suggest that acute toxicities of oils and dispersant for oysters are not predictive of chronic effect levels for growth and settlement; therefore, chronic bioassays are necessary to assess these sublethal effects, in addition to standard 48-h acute toxicity tests. Comparison of 10% effective concentration (EC10) values for chronic 10-d growth and 28-d settlement endpoints with concentrations of total polycyclic aromatic hydrocarbons and dipropylene glycol n-butyl ether (a marker for Corexit) in seawater samples, collected during and after the Deepwater Horizon incident, indicated it was unlikely that elevated concentrations of water-soluble fractions of oil and dispersant in the nearshore environment had significant adverse effects on the growth and settlement of eastern oyster larvae. Environ Toxicol Chem 2016;35:2029-2040. © 2016 SETAC.

Three Functional Biomarkers for Monitoring the Nanoscale Zero-Valent Iron (nZVI)-Induced Molecular Signature on Soil Organisms

Currently, there are increasing efforts to utilize nanoremediation as an environmental technology for cleaning up polluted environments using nanoscale zero-valent iron (nZVI); however, concerns exist regarding the long-term environmental impact of this strategy. In this study, an innovative methodology for evaluating nZVI impact on soil bacteria is utilized, based on transcriptional analysis of three novel biomakers: tnaA, sodB and trx genes. At the same time, classical toxicological bioassays with the nematode Caenorhabditis elegans were performed. Microcosms treated with 1, 5 and 10 % w/w of nZVI were set up using a commercial standard soil and incubated for 21 days. The tnaA gene, involved in indole production, was significantly upregulated at all assessed nZVI concentrations, suggesting that bacterial cells used this molecule to inform the rest of the community about the changes produced upon nZVI soil treatment. The higher the exposure time, the lower nZVI concentration needed to detect these changes. Consequently, soil bacteria activate a cellular adaptive response to cope with the nZVI-induced oxidative stress, increasing the expression of genes encoding key reactive oxygen species (ROS)-scavenging enzymes; in fact, an upregulation of the sodB and katB genes was recorded upon nZVI exposure. On the contrary, C. elegans survival and growth endpoints were not affected at any nZVI concentration whereas the exposure time significantly increased nematode growth in the soil. Therefore, despite the lack of toxicity revealed by the classical conducted tests, the transcriptional analyses demonstrated the usefulness of combining the set of proposed biomarkers for early detection and monitoring the impact of nZVI on soil bacteria after environmentally important periods of exposure.

Survival and Growth of Freshwater Pulmonate and Nonpulmonate Snails in 28-Day Exposures to Copper, Ammonia, and Pentachlorophenol.

We performed toxicity tests with two species of pulmonate snails (Lymnaea stagnalis and Physa gyrina) and four taxa of nonpulmonate snails in the family Hydrobiidae (Pyrgulopsis robusta, Taylorconcha serpenticola, Fluminicola sp., and Fontigens aldrichi). Snails were maintained in static-renewal or recirculating culture systems with adults removed periodically to isolate cohorts of offspring for toxicity testing. This method successfully produced offspring for bothspecies of pulmonate snails and for two hydrobiid species, P. robusta and Fluminicola sp. Toxicity tests were performed for 28days with copper, ammonia, and pentachlorophenol in hard reconstituted water with endpoints of survival and growth. Tests were started with 1-week-old L. stagnalis, 2-week-old P. gyrina, 5- to 13-week-old P. robusta and Fluminicola sp., and older juveniles and adults of several hydrobiid species. For all three chemicals, chronic toxicity values for pulmonate snails were consistently greater than those for hydrobiid snails, and hydrobiids were among the most sensitive taxa in species sensitivity distributions for all three chemicals. These results suggest that the toxicant sensitivity of nonpulmonate snails in the family Hydrobiidae would not be adequately represented by results of toxicity testing with pulmonate snails.

Multi-Toxic Endpoints of the Foodborne Mycotoxins in Nematode Caenorhabditis elegans.

Aflatoxins B1 (AFB1), deoxynivalenol (DON), fumonisin B1 (FB1), T-2 toxin (T-2), and zearalenone (ZEA) are the major foodborne mycotoxins of public health concerns. In the present study, the multiple toxic endpoints of these naturally-occurring mycotoxins were evaluated in Caenorhabditis elegans model for their lethality, toxic effects on growth and reproduction, as well as influence on lifespan. We found that the lethality endpoint was more sensitive for T-2 toxicity with the EC50 at 1.38 mg/L, the growth endpoint was relatively sensitive for AFB1 toxic effects, and the reproduction endpoint was more sensitive for toxicities of AFB1, FB1, and ZEA. Moreover, the lifespan endpoint was sensitive to toxic effects of all five tested mycotoxins. Data obtained from this study may serve as an important contribution to knowledge on assessment of mycotoxin toxic effects, especially for assessing developmental and reproductive toxic effects, using the C. elegans model.