bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of feeding in 30-day bioaccumulation assays usingHyalella aztecain fluoranthene-dosed sediment
Authors: Harkey Gail A , Driscoll Susan Kane , Landrum Peter F 
Published: March 2010

AbstractCurrent protocols for conducting freshwater sediment bioaccumulation tests recommend that food not be added to exposures, whereas toxicity tests require food addition. To determine effects of adding food on exposure, 30-d sediment exposures were conducted with Hyalella azteca to sediment dosed with four fluoranthene concentrations (trace level to 897 nmol/g dry weight). Accumulation was significantly greater in fed versus nonfed animals at all dose levels after 96 h of exposure and continued to be greater after 30 d in the low dose levels. At sediment concentrations above 478 nmol/g dry weight, survival of unfed animals dropped to 34% after 30 d. After 30 d of exposure, growth and reproduction were observed in fed animals exposed to sediment concentrations 20 to 90 times the expected median lethal concentration (LC50) values for fluoranthene in sediment, according to 10-d studies reported in the literature using sediment with comparable organic carbon concentrations. Samples of sediment in exposure beakers taken from the sediment–water interface (flocculant layer) and 1 to 2 cm below the interface had large differences in fluoranthene and organic carbon concentrations. The concentration of fluoranthene was 2 to 10 times greater in the flocculant layer, the area inhabited by H. azteca, compared to the deeper sediment. These data raise questions concerning the interpretation of standard toxicity and bioaccumulation tests when food is routinely added.
Sediment contaminants and biological effects in southern California: Use of a multivariate statistical approach to assess biological impact
Authors: Maxon Cynda L , Barnett Arthur M , Diener Douglas R 
Published: March 2010

Abstract
This study attempts to predict biological toxicity and benthic community impact in sediments collected from two southern California sites. Contaminant concentrations and grain size were evaluated as predictors using a two-step multivariate approach. The first step used principal component analysis (PCA) to describe contamination type and magnitude present at each site. Four dominant PC vectors, explaining 88% of the total variance, each corresponded to a unique physical and/or chemical signature. The four PC vectors, in decreasing order of importance, were: (1) high molecular weight polynuclear aromatic hydrocarbons (PAH), most likely from combusted or weathered petroleum; (2) low molecular weight alkylated PAH, primarily from weathered fuel product; (3) low molecular weight nonalkylated PAH, indicating a fresh petroleum-related origin; and (4) fine-grained sediments and metals. The second step used stepwise regression analysis to predict individual biological effects (dependent) variables using the four PC vectors as independent variables. Results showed that sediment grain size alone was the best predictor of amphipod mortality. Contaminant vectors showed discrete depositional areas independent of grain size. Neither contaminant concentrations nor PCA vectors were good predictors of biological effects, most likely due to the low concentrations in sediments.
Estimating low toxic effects
Authors: Moore Dwayne R J , Caux Pierre-Yves 
Published: March 2010

AbstractThe use of no-observed-effect levels (NOLs) and lowest-observed-effect levels (LOELs) assummary statistics for low toxic effects has been criticized recently. In this paper, we explore the regression-based approach for estimating low toxic effects. Key questions with this approach include: (1) is the approach practical with typical toxicity data sets, (2) can low toxic effects be estimated with confidence, (3) what models are appropriate for typical data sets and endpoints, and (4) how do point estimates of low toxic effects (e.g., EC10) compare with their corresponding LOELs and NOELs? Analyses of 198 toxicity data sets (all but 13 unpublished) revealed that: (1) even with a range of models to choose from (three models in the logistic family, probit model, Weibull model), &gt;80% of the data sets did not produce a single adequate model fit; (2) estimates of low toxic effects were often model dependent when an extrapolation beyond the toxicity data was required; (3) confidence intervals can be quite large at 5% effect and lower; (4) of the five models, the three-parameter logistic equation with a steep slope parameter had the best model fit in the majority of the data sets; and (5) 76.9% of the NOELs and 100% of the LOELs were higher than their corresponding 10% effect point estimates from the best-fit model equations, suggesting that NOELs and LOELs are poor indicators of low toxic effects. We believe that the regression-based approach is a better tool than hypothesis testing for estimating low toxic effects. The approach, however, does not produce adequate model fits unless there is an obvious concentration–response relationship and several treatments with partial effects.
Comparison of contaminant accumulation in three species of marine invertebrates with different feeding habits
Authors: Kaag Nicholas H B M , Foekema Edwin M , Scholten Martin C Th , van Straalen Nico M 
Published: March 2010

AbstractIn order to assess the importance of the mode of feeding for the bioaccumulation of contaminants from sediments, three marine benthic invertebrates, with different feeding habits, were exposed to contaminated sediments in outdoor mesocosms. Residue analyses were carried out for several polychlorinated biphenyls and polycyclic aromatic hydrocarbons after exposure periods of 60 to 140 days. It was shown that sediment ingestion is a major uptake route for the sediment-feeding lugworm, Arenicola marina, and for the facultative deposit-feeding baltic tellin, Macoma balthica. Residues in the filter-feeding mussel, Mytilus edulis, appeared to be independent of contaminant concentrations in the sediment. The difference between deposit and filter-feeding bivalves was confirmed in experiments involving the baltic tellin, with differences in the food availability in the overlying water. A simple linear regression model was used to describe contaminant concentrations in sediment-feeding invertebrates as a function of concentrations in sediment. A correction for the accumulation from water was made by subtracting the concentrations in filter feeders. It was concluded that chemical equilibrium partitioning alone is not sufficient for the assessment of the risks of contaminated sediments to sediment-feeding invertebrates, but that feeding habits should also be considered.
Assessment of toxicological interactions of benzene and its primary degradation products (catechol and phenol) using a lux-modified bacterial bioassay
Authors: Boyd Elaine M , Meharg Andrew A , Wright Julian , Killham Ken 
Published: March 2010

Abstract
A bacterial bioassay has been developed to assess the relative toxicities of xenobiotics commonly found in contaminated soils, river waters, and ground waters. The assay utilized decline in luminescence of lux-marked Pseudomonas fluorescens on exposure to xenobiotics. Pseudomonas fluorescens is a common bacterium in the terrestrial environment, providing environmental relevance to soil, river, and ground water systems. Three principal environmental contaminants associated with benzene degradation were exposed to the luminescence-marked bacterial biosensor to assess their toxicity individually and in combination. Median effective concentration (EC50) values for decline in luminescence were determined for benzene, catechol, and phenol and were found to be 39.9, 0.77, and 458.6 mg/L, respectively. Catechol, a fungal and bacterial metabolite of benzene, was found to be significantly more toxic to the biosensor than was the parent compound benzene, showing that products of xenobiotic biodegradation may be more toxic than the parent compounds. Combinations of parent compounds and metabolites were found to be significantly more toxic to the bioassay than were the individual compounds themselves. Development of this bioassay has provided a rapid screening system suitable for assessing the toxicity of xenobiotics commonly found in contaminated soil, river, and ground-water environments. The assay can be utilized over a wide pH range and is therefore more applicable to such environmental systems than bioluminescence-based bioassays that utilize marine organisms and can only be applied over a limited pH and salinity range.
Genotoxicity testing using the Mutatox™ assay: Evaluation of benzo[a]pyrene as a positive control
Authors: Klamer Hans J C , Villerius Leen A , Roelsma Jan , de Maagd P Gert-Jan , Opperhuizen Antoon 
Published: March 2010

AbstractIn a study on bioassay-directed chemical factionation of sediment extracts, problems were encountered using benzo(a)pyrene (BaP) as a positive control in the Mutatox™ bacterial genotoxicity assay. Genotoxic responses of tests with this compound, prescribed by the Mutatox supplier, could only be measured using supersaturated concentrations that exceeded its aqueous solubility more than 250 times. Additional to three obvious requirements for a positive control of this test system (it should demonstrate that the bacteria are alive and grow after reconstitution, that the bacteria are mutated, and that the bacteria emit light), a positive control should meet two criteria: the metabolic routes of genotoxic response induction for positive control and test compound(s) should be identical, and test concentrations (of both positive control and test compound) should be at environmentally relevant concentrations, i.e., below the aqueous solubilities. As BaP does not meet this last criterion, it does not fully qualify as a positive control in testing genotoxicity of solutes with the Mutatox assay. Testing of other unsubstituted polycyclic aromatic hydrocarbon (PAHS) did not yield another PAH as choice for positive control. Furthermore, the results of our study imply that calculating the bioavailability of BaP from the aqueous solubility alone is not sufficient, as this tends to underestimate the amount of BaP available to either the S9 enzyme system or the bacteria, whereas the interference between toxic and genotoxic effects hampered the interpretation of test results, as variations in toxicity may be interpreted as variations in genotoxicity. Quantitative S9-mediated genotoxicity assessments using the Mutatox test appeared difficult to make, as the two parameters that are proposed by the supplier (CMR, concentration of maximum genotoxic response, and LOEC, lowest observable [genotoxic] effect concentration) showed significant dependency on the sensitivity of the S9 system toward the test compound (CMR) or the initial test compound concentration (LOEC).
Kinetic evaluation of the effects of bioavailability of organic ligands on biodegradation in the presence of common sesquioxide grain coatings
Authors: Brooks Scott C , Mills Aaron L , Herman Janet S , Hornberger George M 
Published: March 2010

Abstract
Radionuclides and metals can be mobilized by chelating agents typically present in low-level radioactive liquid wastes that are disposed of in shallow land trenches; persistence of the organic chelating agent in the subsurface environment is a critical control on solubilization and transport of the complexed nuclide. Low-molecular-weight organic compounds are susceptible to uptake by bacteria, yet the biodegradation rates of nuclide-ligand complexes in a mixture of solids (soil minerals) and liquids (ground water) are poorly known. We investigated the rate of citrate uptake in the presence of cobalt by a mixed bacterial community under experimental conditions designed to explore the impacts of citrate concentration, temperature, and chemistry of mineral surfaces. Dilute solutions with a typical sandy-aquifer groundwater composition and equimolar amounts of cobalt and citrate ranging from 4 to 320 μM were combined with four different sand treatments: uncoated quartz sand, Fe-coated quartz sand, Mn-coated quartz sand, and no sand. Mineralization (net 14CO2 produced) and assimilation (14C retained on a 0.2-μm filter) were quantified. Initial rates of citrate mineralization and of assimilation were independent of temperature in the presence of Fe- and Mn-coated sands but were lower at lower temperatures (15°C versus 25°C) for the no-sand and the uncoated sand, but the fraction of total carbon taken up (respiration plus assimilation) that the cells assimilated was greater at 15°C than at 25°C. In the presence of Fe-coated sand, the mixed culture assimilated a greater fraction of carbon at both temperatures. The van Slyke equation, based on a model of sequential irreversible reactions, was fit to the results of the heterotrophic uptake experiments. The estimated value of the van Slyke constant indicated that mass-transfer constraints limited the overall rate of citrate uptake, and that biokinetic limitations became more important at the lower temperature for the no-sand and uncoated sand treatments. The sorption of citrate to the sand surface did not limit the rate of uptake. Further, complexation with cobalt did not alter the rate of citrate degradation or the rate of bacterial growth. The results suggest that transmembrane citrate transport limited the rate of uptake. The benefit that the bacteria derived from being associated with the solid sand surface was not directly related to the extent of citrate sorption, but might have resulted from a local elevation in the concentration of nutrients (e.g., P or N) available to the adsorbed bacteria, which may have allowed a more efficient processing of carbon into biomass. Sesquioxide coatings enhance the sorptive properties of the mineral grains, and in these experiments, the bacteria derived benefit from being associated with the solid sand surface.
Chromium(VI) toxicity to luminescent bacteria
Authors: Villaescusa Isabel , Marti Salvi , Matas Carme , Martine Maria , Ribó Josep M 
Published: March 2010

Abstract
The toxicity of chromium(VI) to luminescent bacteria was determined using the Microtox® bioassay. The aim of this study was to assess the influence of pH on the toxicity of Cr(VI) samples because its speciation depends on this parameter. A Microtox test basic protocol, modified to assure the same pH in all the cuvettes, was used to determine the toxicity of the Cr(VI) compounds. In the range studied, 4.6 to 9.3, the observed EC50 values increased with the pH (31–1,184 mg/L Cr(VI)). These toxicity results were related to the percentage of the different Cr(VI) species. Hydrogenchromate anion was found to be the most toxic species. In general, only slight differences in toxicity were found when the Microtox test basic protocol was used. Nevertheless, when 20.4% (w/v) sucrose was used as an alternative medium to 2% (w/v) NaCl, the results obtained could not be compared because the sensitivity of the bacteria in this medium was found to be different. The influence of an exposure-time effect was also evaluated. In 2% (w/v) NaCl medium, the toxicity increased with time, which indicates a slow response of the bacteria to the toxin.
Aquatic toxicity of eighteen phthalate esters
Authors: Staples Charles A , Adams William J , Parkerton Thomas F , Gorsuch Joseph W , Biddinger Gregory R , Reinert Kevin H 
Published: March 2010

Abstract
The extensive database of acute and chronic aquatic toxicity data for 18 phthalate esters was reviewed and summarized for freshwater and saltwater aquatic microorganisms, algae, invertebrates, and fish. Phthalate esters have been tested with six species of microorganisms, including bacteria and protozoans. Fifteen algal species have been tested, including green and bluegreen algae in both freshwater and saltwater. Nineteen freshwater and saltwater invertebrate species inhabiting surface waters and sediments and 21 freshwater and saltwater fish inhabiting cold and warm water bodies have been tested. The results of most studies indicate that acute and chronic toxicity to microorganisms, algae, aquatic invertebrates, and fish are limited to the lower molecular weight phthalate esters (i.e., dimethyl-, diethyl-, diallyl-, dipropyl-, dibutyl-, diisobutyl-, and butylbenzylphthalate). In contrast, higher molecular weight phthalate esters are not acutely or chronically toxic to aquatic organisms. Although conflicting data on chronic effects for high molecular weight phthalate esters have been reported for daphnids, these inconsistencies are attributed to physical effects imposed on daphnids when exposed to test concentrations in excess of true water solubilities. Altogether, nearly 400 test results covering more than 60 species of microorganisms, algae, invertebrates, and fish are reported for both freshwater and saltwater aquatic species. While most investigators used several common species and standard protocols to assay conventional endpoints, many nontraditional species and toxicological endpoints were also used. This has created a toxicological database of both sufficient depth to compare many similar tests and sufficient breadth to encompass virtually all important types of aquatic habitats and classes of aquatic species.
Glucocorticoid-xenobiotic interactions: Dexamethasone-mediated potentiation of cytochrome P4501A induction by β-naphthoflavone in a fish hepatoma cell line (PLHC-1)
Authors: Celander Malin , Bremer Jessica , Hahn Mark E , Stegeman John J 
Published: March 2010

AbstractThe induction of CYP1A by the polycyclic aromatic hydrocarbon (PAH)-type inducer β-naphthoflavone (BNF) in the Poeciliopsis-lucida hepatocellular carcinoma cell line (PLHC-1), and the effects of the glucocorticoid receptor (GR) agonist dexamethasone (DEX) on this response were examined. Dose-response studies revealed that BNF is three orders of magnitude less potent than the planar halogenated aromatic hydrocarbon 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as an inducer of the CYP1A activity ethoxyresorufin-O-deethylase (EROD), and that the apparent efficacy for the induction by BNF is 50% of that obtained with TCDD. Addition of 10 μM DEX resulted in potentiation of CYP1A induction at all doses of BNF tested. The degree of that potentiation of induction of CYP1A protein levels and EROD activity differed substantially between doses of BNF and at different times of exposure. For example, the maximal degree of potentiation of EROD induction by DEX was 12-fold in PLHC-1 cells treated with 0.1 μM BNF, 19-fold in cells treated with 1 μM BNF, and 8-fold in cells treated with 10 μM BNF. These maximal degrees of potentiation of EROD induction were obtained after 30 h with 0.1 μM BNF, 48 h with 1 μM BNF, and 72 h with 10 μM BNF. These results demonstrate interactions between GR and aryl hydrocarbon receptor pathways that could influence the response of fish to xenobiotic exposure.
MFO induction in fish by spent cooking liquors from kraft pulp mills
Authors: Hodson Peter V , Maj M K , Efler S , Burnison B K , van Heiningen A R P , Girard R , Carey J H 
Published: March 2010

AbstractWithin bleached kraft mills, the main sources of compounds inducing the mixed function oxygenase (MFO) activities of fish are waste cooking liquor, black liquor, and effluents from the first stages of the bleaching process. We measured the potency for MFO induction in rainbow trout (Oncorhynchus mykiss) of black liquors from pulp mills using kraft pulping and either softwood or hardwood furnish. Concentrations causing induction ranged from 0.0032 to 0.2%(v/v), and below critical thresholds, concentration-response relationships were linear. Above threshold concentrations, activity declined, and lethality occurred at concentrations greater than 0.1% (v/v) black liquor during 4-d exposures. Hardwood pulping generated black liquor that was less potent than that from softwood, but much of the difference was due to a higher water content; hardwood black liquor was more dilute as indicated by normalizing results to dissolved organic carbon. Compounds inducing MFO activity may be natural wood extractives associated with wood resins, or compounds created by the digestion of lignin. A high potency of black liquor from alcohol pulping supports the hypothesis of a natural compound because alcohol extraction does not chemically alter lignin to the same extent as kraft pulping; inducing compounds can also be extracted from wood chips with dichloromethane. The high potency of black liquor compared to bleaching or extraction-stage effluents suggests that control of black liquor losses may be very important in limiting exposure of fish to inducing compounds.
Ecotoxicology of arsenic in the marine environment
Authors: Neff Jerry M 
Published: March 2010

Abstract
Arsenic has a complex marine biogeochemistry that has important implications for its toxicity to marine organisms and their consumers, including humans. The average concentration of total arsenic in the ocean is about 1.7 μg/L, about two orders of magnitude higher than the U.S Environmental Protection Agency's human health criterion (fish consumption) value of 0.0175 μg/L. The dominant form of arsenic in oxygenated marine and brackish waters is arsenate (As V). The more toxic and potentially carcinogenic arsenite (As III) rarely accounts for more than 20% of total arsenic in seawater. Uncontaminated marine sediments contain from 5 to about 40 μg/g dry weight total arsenic. Arsenate dominates in oxidized sediments and is associated primarily with iron oxyhydroxides. In reducing marine sediments, arsenate is reduced to arsenite and is associated primarily with sulfide minerals. Marine algae accumulate arsenate from seawater, reduce it to arsenite, and then oxidize the arsenite to a large number of organoarsenic compounds. The algae release arsenite, methylarsonic acid, and dimethylarsinic acid to seawater. Dissolved arsenite and arsenate are more toxic to marine phytoplankton than to marine invertebrates and fish. This may be due to the fact that marine animals have a limited ability to bioconcentrate inorganic arsenic from seawater but can bioaccumulate organoarsenic compounds from their food. Tissues of marine invertebrates and fish contain high concentrations of arsenic, usually in the range of about 1 to 100 μg/g dry weight, most of it in the form of organoarsenic compounds, particularly arsenobetaine. Organoarsenic compounds are bioaccumulated by human consumers of seafood products, but the arsenic is excreted rapidly, mostly as organoarsenic compounds. Arsenobetaine, the most abundant organoarsenic compound in seafoods, is not toxic or carcinogenic to mammals. Little of the organoarsenic accumulated by humans from seafood is converted to toxic inorganic arsenite. Therefore, marine arsenic represents a low risk to human consumers of fishery products.