bluuebunny/crossref_metadata_2025 huggingface dataset:
Percent methylmercury and organic mercury in tissues of marine mammals and fish using different experimental and calculation methods
Authors: Wagemann Rudolf , Trebacz Ewa , Hunt Robert , Boila Gail
Published: March 2010

Muscle and liver tissues of marine mammals and fish were extracted with methylene chloride–hexane (DCM-hexane) or toluene and the extracts were analyzed for organic mercury by cold vapor atomic absorption spectroscopy (CVAAS) and for methylmercury by gas liquid chromatography with an electron capture detector (GC-ECD). Total mercury in tissues was determined by CVAAS. Methylmercury and organic mercury concentrations in muscle agreed with each other and with total mercury for both marine mammals and fish, indicating that on average 100% of the total mercury in this tissue was in the form of methylmercury. Either total mercury or organic mercury determined by CVAAS was found to be a valid measure of the average methylmercury concentration in muscles of marine mammals and fish. In liver, the CVAAS method produced higher mercury values (15% organic mercury) than the GC-ECD method (6% methylmercury), methylmercury being only 38% of organic mercury. From this, the presence of organic mercury compound(s) other than methylmercury was inferred. The CVAAS method produced a biased estimate of methylmercury in liver; an accurate measure of methylmercury in this tissue was obtained by GC-ECD, either with DCM-hexane or with toluene extraction. The DCM-hexane extract could be directly analyzed by CVAAS for organic mercury while toluene required an additional back-extraction step for such a determination. In calculating the average percentage of methylmercury and organic mercury in a sample, three different calculation methods were used. Only one of them, linear, robust regression analysis produced acceptable results when the variables (MeHg, organic Hg, total Hg) were significantly correlated. The other two methods overestimated the mean percentage under these conditions.
Short-term tissue distribution, depuration and possible gene expression effects of [3H]TCDD exposure in soft-shell clams (Mya arenaria)
Authors: Rhodes Linda D , Gardner George R , Van Beneden Rebecca J
Published: March 2010

A short-term, waterborne exposure and depuration study of Mya arenaria to [3H]tetrachlorodibenzo-p-dioxin([3H]TCDD) was performed. Gill, digestive gland, foot, and gonad were sampled up to 2 weeks after a 24-h exposure to a low dose (10 parts per trillion [pptr]) or high dose (2,000 pptr) of [3H]TCDD in the water. In the gill, peak concentrations occurred at the beginning of depuration (406 and 8,658 pg/g wet weight, low- and high-dose groups, respectively), whereas peak concentrations in the digestive gland and foot were found 12 to 24 h after exposure (digestive gland, 539 and 9,369 pg/g wet weight; foot, 146 and 2,718 pg/g wet weight; low- and high-dose groups, respectively). In contrast, tissue concentrations in the gonad increased through the post-exposure period; at 2 weeks after exposure, tissue concentrations were highest in the gonad (243 and 3,012 pg/g wet weight, low-and high-dose groups, respectively). Examination of gill and gonad by differential display polymerase chain reaction identified potential alterations in expression of genes that may be associated with increased cell cycling or translation initiation. This study shows that M. arenaria can accumulate TCDD in the gonad from an acute exposure, and it identifies several M. arenaria genes whose expression may be altered by TCDD exposure.
Exposure to β-sitosterol alters the endocrine status of goldfish differently than 17β-estradiol
Authors: MacLatchy Deborah , Peters Lisa , Nickle John , Van Der Kraak Glen
Published: March 2010

Wild fish exposed to bleached kraft-mill effluent (BKM) have a variety of reproductive dysfunctions. BKM contains β-sitosterol, a presumed phytoestrogen. In this study, goldfish were exposed for 12 d to concentrations of β-sitosterol typical of BKME (75, 300, 600, and 1,200 μg/L) and to 17β-estradiol (E2) (75 and 300 μg/L) for comparative purposes. In general, plasma reproductive steroid levels in males and females were decreased by β-sitosterol treatment. E2 exposure significantly increased plasma steroid levels. Basal in vitro production of testosterone (T) and pregnenolone by testes of β-sitosterol-treated fish were either unchanged or decreased, while human chorionic gonadotropin (hCG)-stimulated T and pregnenolone production were decreased. 25-OH Cholesterol treatment stimulated only pregnenolone production. In E2-treated fish, basal, hCG- and 25-OH cholesterol-treated testes had either unchanged or increased T and pregnenolone production. Steroids of β-sitosterol fish increased in response to Ovaprim (salmon GnRH and the dopamine receptor antagonist domperidone) to a lesser degree than in control fish. Overall, gonadotropin II (GtH-II) levels were not changed by β-sitosterol treatment. In E2-treated fish, plasma GtH-II levels were decreased; plasma GtH-II following Ovaprim injection was unchanged. Gonadal cholesterol levels were decreased in the 1,200-μg/L β-sitosterol-treated fish but were unchanged in E2-treated fish. These results suggest that decreases in plasma steroids by β-sitosterol are possibly due to alterations in cholesterol availability to P450scc (enzyme that converts cholesterol to pregnenolone) or P450scc activity. β-Sitosterol also appears to affect gonadal steroidogenesis between pregnenolone and T. These findings strengthen the suggestion that β-sitosterol could be a contributing factor to the reproductive dysfunctions observed in BKME-exposed fish.
Metabolic androgenization of female Daphnia magna by the xenoestrogen 4-nonylphenol
Authors: Baldwin William S , Graham Stephen E , Shea Damian , LeBlanc Gerald A
Published: March 2010

Vrtebrates and invertebrates metabolize testosterone to a variety of less-polar derivatives that elicit varying degrees of androgenicity as well as polar elimination products. We have developed a model, using the cladoceran Daphnia magna, with which the ability of xenobiotics to alter steroid hormone metabolism can be assessed and possible physiologic consequences evaluated during a 3-week assay. This model was used to assess the effects of the xenoestrogen 4-nonylphenol on steroid-metabolic processes. Exposure of daphnids to 100 μg/L 4-nonylphenol for 48 h caused a significant increase in the accumulation of radioactivity derived from [14C]testosterone provided to the exposure media. More definitive analyses demonstrated that both 25 and 100 μg/L 4-nonylphenol disrupted components of the testosterone metabolic pathway that would lead to a decrease in the metabolic elimination of testosterone and an increase in the accumulation of androgenic derivatives. Exposure of daphnids to 100 μg/L 4-nonylphenol significantly decreased fecundity of the organisms while having no effect on survival of the parental organisms. Comparison of metabolic and reproductive effects of 4-nonylphenol revealed that 71 μg/L, the reproductive chronic value, would reduce the metabolic elimination of testosterone by approximately 50%. This relationship is consistent with that which we have reported for other toxicants and identifies a mechanism, in addition to estrogenicity, that may contribute to the reproductive toxicity of this compound.
Exposure of atlantic salmon parr (Salmo salar) to a combination of resin acids and a water soluble fraction of diesel fuel oil: A model to investigate the chemical causes of Pigmented Salmon Syndrome
Authors: Croce Bronwen , Stagg Ronald M
Published: March 2010

Pigmented Salmon Syndrome is a pollutant-induced hemolytic anemia and hyperbilirubinemia. As part of an investigation of this condition, S2 Atlantic salmon parr (Salmo salar) were exposed to a diesel fuel oil, water soluble fraction (WSF) in combination with a mixture of three resin acids (isopimaric, dehydroabietic, and abietic acids) in a continuous-flow freshwater system. The total nominal concentrations of resin acids in the exposure tanks were 10, 50, and 100 μg/L; the diesel WSF was generated in situ and provided a mean hydrocarbon concentration of 2.0 ±0.1 mg/L (n = 12) during the 9-d exposure period. Exposure to the diesel WSF alone depressed liver bilirubin UDP-glucuronosyl transferase (UDPGT) activity and induced phenol UDPGT activity. Exposure to the diesel WSF in the absence or presence of resin acids induced liver cytochrome P4501A and increased the concentrations in the plasma of the enzymes lactate dehydrogenase, alkaline phosphatase, and glutamic oxaloacetic transaminase. The combined exposure to diesel WSF with either 50 or 100 μg/L total resin acid caused significant elevations in the concentrations of bilirubin in the plasma and many of these fish had yellow pigmentation on the ventral surface and around the gill arches. The results demonstrate that exposure to combinations of two groups of contaminants can result in the manifestation of toxic effects not apparent from exposure to either of these chemicals in isolation.
Tadpole swimming performance and activity affected by acute exposure to sublethal levels of carbaryl
Authors: Bridges Christine M
Published: March 2010

General activity and swimming performance (i.e., sprint speed and distance) of plains leopard frog tadpoles (Rana blairi) were examined after acute exposure to three sublethal concentrations of carbaryl (3.5, 5.0, and 7.2 mg/L). Both swimming performance and spontaneous swimming activity are important for carrying out life history functions (e.g., growth and development) and for escaping from predators. Measured tadpole activity diminished by nearly 90% at 3.5 mg/L carbaryl and completely ceased at 7.2 mg/L. Sprint speed and sprint distance also decreased significantly following exposure. Carbaryl affected both swimming performance and activity after just 24 h, suggesting that 24 h may be an adequate length of exposure to determine behavioral effects on tadpoles. Slight recovery of activity levels was noted at 24 and 48 h post-exposure; no recovery of swimming performance was observed. Reduction in activity and swimming performance may result in increased predation rates and, because activity is closely associated with feeding, may result in slowed growth leading to a failure to emerge before pond drying or an indirect reduction in adult fitness. Acute exposure to sublethal toxicants such as carbaryl may not only affect immediate survival of tadpoles but also impact critical life history functions and generate changes at the local population level.
Decreased toxicity of Al to Juvenile Atlantic salmon (Salmo salar) in acidic soft water containing natural organic matter: A test of the free-ion model
Authors: Roy Robert L , Campbell Peter G C
Published: March 2010

Toxicological experiments were designed to test the predictions of the free-ion model (FIM) in a soft, acidic water containing Al and a natural fulvic acid (FA). Juvenile Atlantic salmon (Salmo salar) were exposed to Al in either inorganic or organic acidic soft waters, at pH 5.0, and 50% lethal concentrations (LC50) values were determined for both exposure solutions. Contrary to the predictions of the FIM, the LC50s, expressed as inorganic Al (Ali), were significantly higher (p < 0.05) in the organic solution (6.1–8.0 μM Ali) than in the inorganic medium (2.9–4.0 μM Ali). Preexposure of the fish to a 10-mg/L FA solution at pH 5.0, without Al, did not protect the animals from a subsequent Al challenge in solutions without FA. A regression model related mortality with Ali and total organic carbon (TOC) and was highly significant (proportion mortality [arcsine] = −0.215 + [0.81]log[Ali] — [0.44]TOC; p < 0.0001, R2 = 0.71). We conclude that natural FA may play an independent protective role in solutions containing Al, in addition to that of decreasing Al toxicity by complexation of the metal and reducing the free Al3+ concentration.
Acute toxicity and structure-activity relationships of nine alcohol ethoxylate surfactants to fathead minnow and Daphnia magna
Authors: Wong Diana C L , Dorn Philip B , Chai Eric Y
Published: March 2010

Auatic toxicity of nine commercial-grade alcohol ethoxylate surfactants was studied in acute exposures to fathead minnow (Pimephalespromelas) and Daphnia magna. All studies were conducted in accordance with USEPA TSCA Good Laboratory Practice Standards. Mean measured surfactant concentrations in the exposure solutions showed good agreement with nominal concentrations for both fathead minnow (R2 = 0.98, p = 0.05) and daphnid (R2 = 0.99, p = 0.05) tests. Surfactant recoveries ranged from 59 to 97% and 67 to 106% in the fathead minnow and daphnid solutions, respectively. Response of both species to the surfactants was generally similar. Surfactant toxicity tended to increase with increasing alkyl chain lengths. The effect of low average ethylene oxide (EO) groups on increased surfactant toxicity was more evident in the daphnid exposures. Quantitative structure-activity relationship (QSAR) models were developed from the data, which relate surfactant structure to toxicity. The models predict increasing toxicity with decreasing EO number and increasing alkyl chain length. The models also indicate that average alkyl chain length has a greater effect on toxicity than average EO groups. Further, the models indicate that both species did not differ markedly in their response to alkyl chain length effects, while the number of EO groups had a stronger effect on daphnids than fathead minnow. Model-predicted toxicity agreed well with toxicity estimated from USEPA alkyl ethoxylates SARs and with toxicity values reported in the literature for several surfactants previously studied.
Risk assessment on the basis of simplified life-history scenarios
Authors: Calow Peter , Sibly Richard M , Forbes Valery
Published: March 2010

Ecological risk assessment ought to make predictions about the likely effects of chemical contaminants on populations and ecosystems. However, current procedures either make these links on the basis of oversimplified approaches that obscure the relationship between what is measured in ecotoxicological tests and what we are trying to protect or are too demanding in terms of both data and understanding to be used practically and routinely. Here we develop an approach that uses simplified life-history models to make explicit and ecologically relevant links between test results and their implications for population dynamics and explore the possibility of extending this to an appreciation of ecosystem effects. These models also make a number of simplifying assumptions but in being explicit they are open to challenge and elaboration, and we argue that, in general, the assumptions are usually precautionary. The development of these models in itself gives some nonintuitive insights into the theory of ecotoxicological responses, and we illustrate the practical application of the theory using a number of hypothetical case studies.
Statistical models to predict the toxicity of major ions to Ceriodaphnia dubia, Daphnia magna and Pimephales promelas (fathead minnows)
Authors: Mount David R , Gulley David D , Hockett J Russell , Garrison Tyler D , Evans James M
Published: March 2010

Toxicity of fresh waters with high total dissolved solids has been shown to be dependent on the specific ionic composition of the water. To provide a predictive tool to assess toxicity attributable to major ions, we tested the toxicity of over 2,900 ion solutions using the daphnids, Ceriodaphnia dubia and Daphnia magna, and fathead minnows (Pimephales promelas). Multiple logistic regression was used to relate ion composition to survival for each of the three test species. In general, relative ion toxicity was K+ > HCO3− ≈ Mg2+ > Cl− > SO42−; Na+ and Ca2+ were not significant variables in the regressions, suggesting that the toxicity of Na+ and Ca2+ salts was primarily attributable to the corresponding anion. For C. dubia and D. magna, toxicity of Cl−, SO42−, and K+ was reduced in solutions enriched with more than one cation. Final regression models showed a good quality of fit to the data (R2 = 0.767–0.861). Preliminary applications of these models to field-collected samples indicated a high degree of accuracy for the C. dubia model, while the D. magna and fathead minnow models tended to overpredict ion toxicity.
Sampling of air streams and incorporation of samples in the Microtox™ toxicity testing system
Authors: Kleinheinz Gregory T , St. John Wayne P
Published: March 2010

A sudy was conducted to develop a rapid and reliable method for the collection and incorporation of biofiltration air samples containing volatile organic compounds (VOCs) into the Microtox™ toxicity testing system. To date, no method exists for this type of assay. A constant stream of VOCs was generated by air stripping compounds from a complex mixture of petroleum hydrocarbons (PHCs). Samples were collected on coconut charcoal ORBO (Supelco, Inc.) tubes and the VOCs extracted with methylene chloride. The compounds extracted were then solvent exchanged into dimethyl sulfoxide (DMSO) under gaseous nitrogen. The resulting DMSO extract was directly incorporated into the Microtox toxicity testing system. In order to determine the efficiency of the solvent exchange, the VOCs in the DMSO extract were then extracted into hexane and subsequently analyzed using gas chromatography (GC) with a flame ionization detector (FID). It was determined that all but the most volatile VOCs could be effectively transferred from the ORBO tubes to DMSO for Microtox testing. Potential trace amounts of residual methylene chloride in the DMSO extracts showed no adverse effects in the Microtox system when compared to control samples.
Effects of water hardness on the toxicity of manganese to developing brown trout (Salmo trutta)
Authors: Stubblefield William A , Brinkman Steven F , Davies Patrick H , Garrison Tyler D , Hockett James R , McIntyre Matthew W
Published: March 2010

Manganese is a common constituent of point and nonpoint discharges from mining and smelting activities. Available data indicate that Mn is acutely toxic at relatively high aqueous concentrations, when compared with trace metals, and its toxicity is affected by water hardness. Little information is available regarding the chronic toxicity of manganese. Early-life-stage (ELS) tests were conducted to determine the toxicity of manganese to brown trout (Salmo trutta) and to evaluate the extent to which water hardness (ranging from 30 to 450 mg/L as CaCO3) affects the chronic toxicity of Mn. Water hardness significantly affected Mn chronic toxicity, with toxicity decreasing with increasing hardness. Decreased survival was the predominant effect noted in the 30-mg/L hardness experiment, while significant effects on growth (as measured by changes in body weight) were observed in both the 150- and 450-mg/L hardness experiments. Twenty-five percent inhibition concentration (IC25) values, based on the combined endpoints (i.e., survival and body weight), were 4.67, 5.59, and 8.68 mg Mn/L (based on measured Mn concentrations) at hardness levels of approximately 30, 150, and 450 mg/L as CaCO3, respectively.
The use of cholinesterase and carboxylesterase activities fromMytilus galloprovincialisin pollution monitoring
Authors: Escartín Estefania , Porte Cinta
Published: March 2010

Acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and carboxylesterase (CbE) activities have been measured in gills and digestive gland of the mussel Mytilus galloprovincialis. AChE activity was predominantly localized in gills, whereas the highest BChE and CbE specific activities were detected in digestive glands. Commonly used pesticides were examined in vitro for their ability to inhibit mussel esterases; the results obtained pointed out the highest sensitivity of mussel CbE to low concentrations of pesticides, but also the higher sensitivity of gill cholinesterases over digestive gland forms. Seasonal variation in the activity of gill esterases was determined monthly in mussels collected from the Ebro Delta, an area where pesticides and biocides are frequently used. As a general trend, elevated cholinesterase activities were detected in winter, possibly indicating little or no exposure to organophosphorous compounds, whereas the lowest cholinesterase activities were reported over the summer period. These changes were related to agricultural activities in the area and are supported by the detection of organophosphorous pesticides in the tissue of M. galloprovincialis.
Comparative developmental dermal toxicity and mutagenicity of carbazole and benzo[a]carbazole
Authors: Dutson Sheryl M , Booth Gary M , Schaalje G Bruce , Castle Raymond N , Seegmiller Robert E
Published: March 2010

The objectives of this study were (1) to determine the developmental toxicity of carbazole and benzo[a]carbazole following daily dermal administration to female Sprague-Dawley rats on days 0 through 20 of gestation and (2) to determine the mutagenicity of these two compounds using a modified version of the Ames assay. These chemicals are of concern because they are found in a variety of environmental matrices including crude oil mixtures. No signs of maternal or developmental toxicity were considered to be related to dermal administration of carbazole at doses of 2.5, 25.0, and 250.0 mg/kg. Signs of maternal toxicity considered to be related to administration of benzo[a]carbazole included significantly decreased body-weight gain and decreased absolute-food consumption at a dose of 250.0 mg/kg. Signs of developmental toxicity considered to be related to administration of benzo[a]carbazole included significantly decreased number of total (live and dead combined) and live pups on lactation day 0 as well as significantly decreased average pup weight on lactation days 0 and 4 at a dose of 250.0 mg/kg. Because developmental toxicity following benzo[a]carbazole treatment was observed only at a dose at which maternal toxicity was observed, it is likely that the effects on the offspring are secondary to the treatment effects on the dam. Evidence of toxic effects with benzo[a]carbazole in the absence of effects with carbazole suggests that the substituted benzene ring enhances the biological activity of this compound. Carbazole was nonmutagenic with or without S-9 activation, whereas benzo[a]carbazole showed a clear dose–response with S-9 activation. Without S-9 activation, benzo[a]carbazole was nonmutagenic. Apparently benzo[a]carbazole must be enzymatically activated in order to be mutagenic.
Assessing sediment quality in heterogeneous environments: A case study of a small urban harbor in Lake Champlain, Vermont, USA
Authors: Watzin Mary C , McIntosh Alan W , Brown Erik A , Lacey Rebekah , Lester Deborah C , Newbrough Kathleen L , Williams Ann R
Published: March 2010

Relatively few case studies have been conducted demonstrating the utility of multiple endpoint approaches to sediment quality assessment in areas with moderate contaminant levels and heterogeneous conditions. Because variability is commonplace in natural systems, assessment approaches must be designed explicitly for these conditions. In an assessment of highly heterogeneous freshwater sediments in Lake Champlain, Vermont, USA, we measured multiple endpoints, including physical and chemical characteristics of the sediment, acute and chronic toxicity in three tests (Ceriodaphnia dubia, Chironomus tentans, and Pimephales promelas), and benthic community composition, at 19 sites throughout Inner Burlington Harbor. Multiple regression techniques were used to investigate whether significant relationships existed between biological endpoints and the physical and chemical characteristics of the sediments. Although all three laboratory exposures indicated toxicity at some sites, little correspondence was found among the tests. No changes in the benthic community could be attributed to trace contaminants. Multiple regression was useful in showing associations between contaminants, grain size, toxicity, and benthic community composition. Although not demonstrating causal linkages, these statistical analyses suggested which factors might be important in driving measured responses. In heterogeneous sites, an individualized assessment approach based on a preliminary analysis of variability might provide the most useful information.
Phototoxicity of individual polycyclic aromatic hydrocarbons and petroleum to marine invertebrate larvae and juveniles
Authors: Pelletier Marguerite C , Burgess Robert M , Ho Kay T , Kuhn Anne , McKinney Richard A , Ryba Stephan A
Published: March 2010

Phototoxicity resulting from photoactivated polycyclic aromatic hydrocarbons (PAHs) has been reported in the literature for a variety of freshwater organisms. The magnitude of increase in PAH toxicity often exceeds a factor of 100. In the marine environment phototoxicity to marine organisms has not been reported for individual or complex mixtures of PAHs. In this study, larvae and juveniles of the bivalve, Mulinia lateralis, and juveniles of the mysid shrimp, Mysidopsis bahia, were exposed to individual known phototoxic PAHs (anthracene, fluoranthene, pyrene), as well as the water-accommodated fractions of several petroleum products (Fuel Oil #2, Arabian Light Crude, Prudhoe Bay Crude, Fuel Oil #6) containing PAHs. Phototoxicity of individual PAHs was 12 to >50,000 times that of conventional toxicity. Three of the petroleum products demonstrated phototoxicity while the lightest product, Fuel Oil #2, was not phototoxic at the concentrations tested. The phototoxicity of petroleum products appears to be dependent on the composition and concentrations of phototoxic PAHs present: lighter oils have fewer multiple aromatic ring, phototoxic compounds while heavier oils have higher levels of these types of molecules. This study shows that phototoxicity can occur in marine waters to marine species. Further, the occurrence of oil in marine waters presents the additional risk of phototoxicity not routinely assessed for during oil spills.
Ion-exclusion chromatographic determination of carboxylic acids used to support the microbially mediated reductive dechlorination of tetrachloroethene
Authors: Xu Ning , Vandegrift Steve , Fine Dennis D , Sewell Guy W
Published: March 2010

An analytical method was developed for the determination of lactic acid, formic acid, acetic acid, propionic acid, and butyric acid in environmental microcosm samples using ion-exclusion chromatography. The chromatographic behavior of various eluents was studied to determine the optimum analytical conditions for eluent concentration and flow rate. Matrix effects caused by inorganic anions including carbonate were investigated. Methods for carbonate removal were also examined. Sub mg/L detection limits and small analytical variations (less than 1%) were obtained with all five acids. Calibration curves with regression coefficients (r2) of 0.998 to 1.000 were obtained for acid concentrations ranging from 2.00 to 200.00 mg/L. The total run time for five carboxylic acids was less than 20 min with a relatively small sample volume requirement (∼0.5 ml). The recoveries of the acids from microcosm samples were between 80 to 102%.
Use of ceriofast™ for monitoring the toxicity of industrial effluents: Comparison with the 48-H acute Ceriodaphnia toxicity test and Microtox®
Authors: Jung Keumhee , Bitton Gabriel
Published: March 2010

A comparison of an acute1-h Ceriodaphnia dubia toxicity test (CerioFAST™) with Microtox® and the standard acute 48-h C. dubia acute toxicity test was undertaken to determine the toxicity of a variety of industrial effluents. CerioFAST is based on suppression of feeding activity of C. dubia in the presence of toxicants and consists of a 1-h-exposure period to a given toxicant followed by a 20-min-feeding period using fluorescent yeast cells. Twenty-eight industrial effluent samples, collected from northern and central Florida, were tested and compared using the CerioFAST and the standard 48-h C. dubia acute toxicity test. The results of the CerioFAST assay were well correlated with the standard 48-h C. dubia test (r2 = 0.98). Therefore, CerioFAST is useful as a rapid-screening test or range-finding test for assessing the toxicity of environmental samples.
Different susceptibilities to white phosphorus poisoning among five species of ducks
Authors: Steele Benjamin B , Reitsma Leonard R , Racine Charles H , Burson Sherman L , Stuart Robin , Theberge Rebecca
Published: March 2010

Three species of ducks, mallard (Anas platyrhynchos), northern pintail (Anas acuta), and green-winged teal (Anas crecca), that frequent an estuarine salt marsh in Alaska during migration die in large numbers from ingesting particles of white phosphorus. Two other common species, northern shoveler (Anas clypeata) and American wigeon (Anas americana), are rarely found dead. Selectivity indices show that this difference in mortality is not due to different numbers of each species being present. We investigated three hypotheses for the difference in susceptibility to this poison. First, we found that wigeons had more total grit in their gizzards than the susceptible species and shovelers had a high proportion of particles >1 mm compared to other species. Thus, ingestion of particles of white phosphorus as grit cannot explain the differences in susceptibility. Second, feeding behavior could not completely account for the lack of susceptibility in shovelers. Shovelers often forage with their neck or more in the water and often have their bills in the sediments. Wigeon, however, frequently forage with just their bill in the water and rarely penetrate the sediments. This feeding behavior, coupled with a diet consisting mainly of plants, may limit exposure of wigeon. Third, shovelers have wide upper bills, with lamellae consisting of long thin filaments extending from the upper bill inward toward the lower bill. These lamellae may allow white phosphorus particles to be flushed out during feeding. Thus, if physiological tolerance to white phosphorus is similar among these species, the difference in susceptibility appears to be due to differences in feeding behavior and bill morphology.
Ecological risk assessment of a wetland exposed to boron
Authors: Powell Rebecca L , Kimerle Richard A , Coyle Gerald T , Best G Ronnie
Published: March 2010

A wetland located in the southeastern portion of the United States was the site of an investigation to determine the potential ecological risk of elevated boron concentrations to the flora and fauna living in the wetland. The conceptual model identified the vegetation as the primary receptor of concern, and thus the vegetation is the focus of this article. Samples of surface water, sediments, and selected vegetation were collected from the study wetland and several nearby reference sites and were analyzed for boron. Concentrations of boron in all three media exceeded reference site concentrations. Boron concentrations were highest near the suspected source but decreased almost to reference-site concentrations near the outer perimeter of the wetland. Some plants appeared stressed with yellowing and necrotic leaves; however, a correlation between tissue boron concentrations and the plant's visual appearance was not apparent for all species studied. Modeling of the fate of boron indicated that the wetland has likely been at a steady state for many years and that boron concentrations were not expected to increase. It was concluded that no observable adverse ecological impacts to the vegetation could be attributed to boron, nor is it likely that the boron poses an unacceptable risk to the surrounding areas.
Predicting plant uptake of organic chemicals from soil or air using octanol/water and octanol/air partition ratios and a molecular connectivity index
Authors: Dowdy Deanna L , McKone Thomas E
Published: March 2010

A bioconcentration ratio (BCR) represents the ratio of the concentration of a chemical found in an exposed biological system, such as a plant or fish, to the concentration in the exposure medium (water, soil, or air). A comparison is made of the precision and accuracy of the molecular connectivity index (MCI) and the octanol/water partition coefficient (Kow) as predictors of BCRs from the soil matrix into above- or below-ground vegetation tissues. Calculated octanol/air partition coefficient (Koa) values are compared with calculated Kow and MCI values as predictors of measured air-to-plant BCRs. Based on a statistical evaluation of explained variance, residual error, and cross-validation, this evaluation reveals that the MCI provides higher precision, greater ease of use, and a more cost-effective method for predicting the potential bioconcentration of a chemical from soil into above-ground vegetation. Statistical analyses of the various methods reveal that both the Kow and MCI approaches have a similar level of precision for predicting BCRs from soil solution into roots and, among MCI, Koa and Kow; Koa is somewhat more precise and valid than MCI and Kow for estimating uptake, but all have limited accuracy as bioconcentration predictors. These latter results are derived mainly from the paucity of both reliable Koa values and measured air-to-plant BCRs and indicate a need for more experimental measurements from which more accurate models may be developed.
Effects of pH, chloride and Calcium(II) on adsorption of monomethylmercury by soils
Authors: Yin Yujun , Allen Herbert E , Huang C.-P , Sanders Paul F
Published: March 2010

Adsorption of monomethylmercury (MMHg) by soil from 2 × 10−7 and 1 × 10−6 M solutions was investigated to understand soil-water partitioning of MMHg. The effects of three factors—pH, Cl−, and Ca2+—on adsorption were examined. Adsorption as a function of pH followed a concave downward profile with the maximum adsorption occurring at pH between 5 and 6. Less adsorption at low pH values mainly resulted from the proton competition for surface sites and Cl− complexation for MMHg. Decreases in adsorption at high pH values are attributed to the complexation of MMHg with soluble organic ligands whose concentrations increase with pH. Addition of 1.0 × 10−3 M CL decreased adsorption at low pH where CH3HgCl was dominant over CH3HgOH, and exhibited no effect on adsorption at high pH when CH3HgOH became predominant. The presence of a low concentration of Ca2+ (1.0 × 10−4 M) had no effect on MMHg adsorption; however, a high concentration of Ca2+ (3.3 × 10−3 M) increased adsorption at pH < 6 but had no effect at pH > 6. This is ascribed to the combined effects of pH and Ca2+ on the solubility of organic ligands.
Influence of sludge amendment on transport and sorption ideality ofs-triazines in soil columns
Authors: Graber Ellen R , Sluszny Chanan , Gerstl Zev
Published: March 2010

The aim of this work was to examine the effect of organic soil amendments (municipal sewage sludge and composted municipal sewage sludge) on transport ideality, sorption equilibrium, and s-triazine (atrazine, simazine, ametryn, and terbuthylazine) retardation compared with nonamended soil. Organic-matter amendment resulted in increased nonequilibrium sorption effects, including early breakthrough, increased breakthrough, and elution front-tailing. Organic amendments likewise caused greater solute retardation compared with transport in nonamended soil columns. As the organic matter content increased, retardation increased and the desorption rate constant decreased. The fraction of fast sorption sites also decreased, resulting in greater sorption non-equilibrium. In a given column, the fraction of fast sorption sites was essentially equal for the different s-triazine compounds. The desorption rate constant decreased as the organic carbon partition coefficient (Koc) increased in the order atrazine > simazine ≥ ametryn > terbuthylazine. Soil amendment with sludge and compost resulted in some nonideal physical transport, which was negligible compared with sorption nonideality effects. The linear sorption isotherm nonequilibrium (LNE) model adequately simulated the measured breakthrough curves. The breakthrough curve for ametryn in an amended, nonrinsed column was identical to that in an amended, rinsed column, indicating that sludge-/soil-derived dissolved organic carbon did not affect ametryn sorption and transport in this system.
Comparative toxicity of four insecticides, including imidacloprid and tebufenozide, to four aquatic arthropods
Authors: Song Mee Young , Stark John D , Brown John J
Published: March 2010

The tolerance of four aquatic organisms to four chemicals (aldicarb, dimethoate, imidacloprid, and tebufenozide) was determined using 48-h acute toxicity tests at 27°C. Species included two saline (Artemia sp. and Aedes taeniorhynchus (Wiedemann)) and two freshwater (Daphnia magna Straus and Aedes aegypti (L.)) organisms. Temperature was also evaluated as a toxicity modifying factor for the freshwater species. Two selective insecticides (imidacloprid and tebufenozide) were compared with two broad-spectrum insecticides, aldicarb and dimethoate. In general, A. taeniorhynchus was the most susceptible, and Artemia sp. was the most tolerant to insecticides used under our experimental conditions. Both aldicarb and dimethoate caused neurotoxicity in all organisms tested. Mortality associated with molting suggested that tebufenozide affected the molting process of all organisms, causing the formation of an incompletely sclerotized head capsule and the failure of ecdysis in the mosquito species. These responses resulted in lethal larval molts. Imidacloprid, on the other hand, caused delayed symptoms of general nerve poisoning compared with the two acetylcholine esterase inhibitors. Our results suggest that both tebufenozide and imidacloprid would be selective insecticides that can be used with reasonable environmental safety toward nontarget aquatic crustaceans. There was a greater correlation of susceptibility to test chemicals within taxonomically close organisms than between organisms that share habitats.
Multispecies toxicity assessment of compost produced in bioremediation of an explosives-contaminated sediment
Authors: Gunderson Carla A , Kostuk Joanne M , Gibbs Mitchell H , Napolitano Guillermo E , Wicker Linda F , Richmond Jacqueline E , Stewart Arthur J
Published: March 2010

A multispecies terrestrial test system was used to assess the environmental effectiveness of composting for bioremediation of explosives-contaminated soils. The assessment involved comparing biological responses, from the individual to the community level, in remediated and reference composts. A 6-month greenhouse study incorporated two soil invertebrate species, three plant species and an associated symbiont, and the naturally occurring complement of soil microorganisms. Measured parameters included growth and reproduction of earthworms and isopods; soil mite diversity; soil lipid class composition as an indicator of soil microbial community structure; plant growth, photosynthesis, and reproduction; and root nodulation and symbiotic N2 fixation. Additional short-term toxicity tests of seed germination and earthworm survival were performed to supplement the mesocosm data. Compost prepared from the explosives-contaminated soil inhibited several aspects of plant growth and physiology, but few adverse effects on soil invertebrates were detected. An initial lag in earthworm and isopod reproduction occurred in the reference compost, reflecting some inherent compost differences not associated with contamination, and highlighting the importance and the difficulty of finding appropriate reference soils for assessing hazardous waste sites or remediation technologies. Nonetheless, the results from this study suggested some nonlethal effects from the contaminated-soil compost, primarily to plants. The mesocosm methodology used in this study can bridge the gap between traditional short-term toxicity testing and longer term field assessments, and provide information on ecological effects by explicitly including measurements of multiple species across several levels of ecological organization.
Exposure of captive feral pigeons to fonofos-treated seed in a semifield experiment
Authors: Pascual Juan A , Hart Andrew D M
Published: March 2010

This study aimed to investigate factors affecting risks to birds from toxic seed treatments under typical field use. Feral pigeons (Columba livia) were exposed for 2 d to fonofos-treated wheat seeds by holding them in pens in plots sown at two depths following standard husbandry in winter sowings in English fenland. In the shallow plots, seeds were readily available to pigeons on the soil surface (8.20 seeds/0.25 m2) while in the deep plots little seed was left uncovered (0.20 seeds/0.25 m2). Serum butyrylcholinesterase analysis revealed negligible exposure to fonofos of birds from deep plots but significant exposure of those in shallow plots. Data on body weight and the availability of exposed seed showed that pigeons in the shallow plots stopped eating treated seeds without depleting those exposed on the soil even though the seed consumed was less than 26% of birds' daily food requirements. Neither mortality nor signs of poisoning were observed. Though seeds were treated at the approved rate (1,080 mg a.i./kg seed), fonofos concentration in seeds from the hopper (586.5 mg/kg) and from plots during testing (260.2 and 201.7 mg/kg for days +1 and +2 after sowing, respectively) was substantially lower. In this experiment, the avoidance of fonofos-treated seeds together with the low concentration of fonofos in seeds prevented pigeons from ingesting a lethal dose. In the wild, however, pigeons are poisoned occasionally by fonofos, and it has yet to be determined under what conditions this occurs.
Esterase activity and allele frequency in field populations of Simulium equinum (L.) (Diptera: Simuliidae) exposed to organophosphate pollution
Authors: Parker Penelope Judy-Ann Nicole , Callaghan Amanda
Published: March 2010

Esterase activity and allele frequencies in field populations of blackfly larvae, Simulium equinum, were used in a preliminary study to identify any long-term genetic effects of low-level organophosphate insecticide exposure in rivers and streams. Esterase mean activity in S. equinum collected downstream from a cress farm where malathion 60 was periodically applied was significantly higher than in a population taken from a clean site. Polyacrylamide gel electrophoresis analysis of esterase electromorphs revealed that elevated esterase activity was correlated with fast-running dark-staining alleles, whose frequency and activity was significantly higher in blackflies from the polluted site. The genetic differences at the cress site may suggest a long-term exposure to malathion selecting individuals with more active detoxification enzymes. A third S. equinum population was collected downstream from a trout farm and areas of substantial agricultural usage. Esterase activity and high activity allele frequencies were also significantly higher in this population. These preliminary results allow us to conclude that esterases in S. equinum have potential as long-term biomarkers of organophosphate pollution.
Soil-to-indoor air exposure models for volatile organic compounds: The effect of soil moisture
Authors: Sanders Paul F , Talimcioglu Nazmi M
Published: March 2010

Two finite-source models that calculate volatilization of contaminants from soil to indoor air were used to study the effect of soil moisture on indoor air concentrations and inhaled doses, using a representative model volatile organic chemical. A hypothetical scenario was used that assumed that subsurface contaminant diffuses through a layer of clean soil and is then swept into the building interior via advection. Both models simulated depletion of source contaminant via volatilization and degradation. One was an analytical model adapted from the behavior assessment model of Jury et al., which could be used to calculate time-dependent volatilization rates (and indoor air concentrations) as a function of constant soil moisture contents and steady-state moisture advection. The second model, the Integrated Moisture Plus Contaminant Transport (IMPACT) model, had the additional capability of simulating daily and seasonal variations in soil moisture behavior from actual daily temperature and rainfall data. Predicted indoor air concentrations and inhaled doses for the model contaminant varied by up to seven orders of magnitude, depending on the soil moisture conditions and whether or not contaminant degradation was considered. Over extended time periods, inhaled doses predicted under conditions of daily and seasonal variations in soil moisture were in general agreement with those predicted using average soil moistures or average moisture fluxes, suggesting that simplified treatment of soil moisture behavior may be adequate if accurate soil moisture data are available.
The role of ligand flexibility in predicting biological activity: Structure–activity relationships for aryl hydrocarbon, estrogen, and androgen receptor binding affinity
Authors: Bradbury Steven P , Mekenyan Ovanes G , Ankley Gerald T
Published: March 2010

Recent studies indicate that the potency and agonist or antagonist activity of steroid hormone ligands are dependent, in part, on ligand–receptor binding affinity as well as the conformation of the ligand–receptor complex. The binding of ligands to hormone receptors is thought to involve interactions by which shapes of both the receptor and ligand are modified in the formation of the ligand–receptor complex. As a consequence, it is essential to explore the significance of ligand flexibility in the development of screening-level structure–activity relationships. In this review, examples are provided of techniques used to generate and screen ligand conformers in the development of quantitative structure–activity relationships and active analogue search algorithms. The biological endpoint modeled was binding affinity of natural ligands and xenobiotics to the aryl hydrocarbon, estrogen, and androgen receptors. These approaches may be useful in future studies to evaluate relationships between ligand structure, receptor binding affinity, and, ultimately, transactivational events associated with receptor interactions with DNA response elements and associated proteins. An improved understanding of ligand–receptor interactions in the context of well-defined effector systems will enhance the development of credible predictive models that can be used to screen large sets of chemicals for potential agonist or antagonistic activity.
Critical appraisal of the evidence for tributyltin-mediated endocrine disruption in mollusks
Authors: Matthiessen Peter , Gibbs Peter E
Published: March 2010

This article reviews the field and laboratory evidence for endocrine disruption in gastropod mollusks caused by tributyltin (TBT). Abundant and undisputed field data link TBT with an irreversible sexual abnormality of female neogastropod snails known as “imposex.” This phenomenon is a masculinization process involving the development of male sex organs, notably a penis and a vas deferens; in certain species the imposition of a vas deferens disrupts oviducal structure and function, preventing normal breeding activity and causing population disappearance. In some species, oogenesis is supplanted by spermatogenesis. A related condition referred to as “intersex” has been reported in littorinid mesogastropods, and these too become unable to lay eggs. Field evidence clearly associates these syndromes with the use of TBT as an antifoulant, chiefly on boat hulls, and dose-related effects can be replicated in laboratory exposures to environmentally relevant concentrations of TBT compounds. It has now been established that imposex and intersex are forms of endocrine disruption caused by elevated testosterone titers that masculinize TBT-exposed females. The precise mechanism by which increased levels of testosterone are produced has not been fully described, but the weight of evidence suggests that TBT acts as a competitive inhibitor of cytochrome P450-mediated aromatase. Some recent data suggest that TBT may also inhibit the formation of sulfur conjugates of testosterone and its active metabolites, thus interfering with its excretion. In summary, TBT-induced masculinization in gastropods, imposex and intersex, is the clearest example of endocrine disruption described in invertebrates to date that is unequivocally linked to a specific environmental pollutant.