bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of octamethylcyclotetrasiloxane (OMCTS) on freshwater and marine organisms
Authors: Sousa Joseph V. , McNamara Pauline C. , Putt Arthur E. , Machado Mark W. , Surprenant Donald C. , Hamelink Jerry L. , Kent David J. , Silberhorn Eric M. , Hobson James F. 
Published: March 2010

Abstract
The toxicity of octamethylcyclotetrasiloxane (OMCTS) to representative freshwater and marine fish and invertebrates was investigated. Testing procedures followed Toxic Substance Control Act (TSCA) guidelines with chemical-specific adaptations as presented in the OMCTS Testing Consent Order (Docket OPTS-42071A). The physicochemical properties and behavior of OMCTS (i.e., high volatility, low water solubility) precluded the use of conventional experimental practices and exposure systems. Procedures and systems developed during these investigations provided a mechanism that produced exposure levels equal to the maximum achievable (i.e., “functional”) solubility of OMCTS in natural dilution waters. The toxicant delivery systems and exposure chambers were designed to minimize volatilization by elimination of the air/water interface. The flow-through systems maintained consistent exposure concentrations and adhered to U.S. Environmental Protection Agency (EPA) Guideline test performance criteria. The “functional” water solubility of OMCTS in freshwater and seawater ranged from 14 to 30 μg/L and from 6.0 to 9.0 μg/L, respectively. Functional water solubility appeared to vary slightly with test conditions and dilution water characteristics. Continuous exposures of 2 to 93 d were conducted during these investigations with daphnids (Daphnia magna), rainbow trout (Oncorhynchus mykiss), mysids (Mysidopsis bahia), and sheepshead minnow (Cyprinodon variegatus). The rainbow trout was determined to be the most sensitive species to OMCTS (14-d LC50 = 10 μg/L). At levels equal to the functional water solubility, OMCTS was not acutely toxic to D. magna, mysids, or sheepshead minnow. The survival of D. magna was reduced by 16%, relative to the control organisms, after 21-d exposures to 15 μg/L OMCTS; exposure to 7.9 μg/L OMCTS or less had no effect on daphnid survival or reproduction. No toxicity was observed at the highest concentration tested in a 93-d exposure of rainbow trout early life stages. The no-observed-effect concentration for this study was 4.4 μg/L, the same as determined in a 14-d extended acute study.
Bioconcentration by fish of a highly volatile silicone compound in a totally enclosed aquatic exposure system
Authors: Fackler Paul H. , Dionne Emily , Hartley Deborah A. , Hamelink Jerry L. 
Published: March 2010

Abstract
Two aqueous exposures of fathead minnows (Pimephales promelas) were conducted to determine the bioconcentration factor (BCF) for [14C]octamethylcyclotetrasiloxane (OMCTS). The high volatility, high sorptive capacity, and low water solubility of OMCTS required that the testing be conducted in a novel, totally enclosed, flow-through exposure system that prevented the volatilization of the test substance. In a preliminary study, fish were continuously exposed to OMCTS at a concentration of approximately 0.5 μg/L for 6 d. In the definitive study, fish were exposed for 28 d at approximately 0.3 μg/L. In each case, OMCTS exposures were followed by a 14-d depuration period. Water concentrations and fish residues were measured periodically in both studies. Data from the 6-d study resulted in a maximum measured BCF of 7,000. Model calculations based on data from the 6-d exposure phase predicted a steady-state BCF of 10,000 after 19 d of exposure. The definitive study resulted in a steady-state measured BCF of 12,400 after 28 d of exposure. Model calculations based on the measured data from the 28-d exposure phase provided an estimated BCF of 13,400. The OMCTS bioconcentration factors could be accurately estimated from the data produced during a 6-d continuous exposure. The use of innovative test systems was key to the development of useful bioconcentration data.
Octamethylcyclotetrasiloxane (OMCTS), a case study: Summary and aquatic risk assessment
Authors: Hobson James F. , Silberhorn Eric M. 
Published: March 2010

Abstract
This paper presents an aquatic ecological risk assessment, including an aquatic effects assessment, an exposure assessment, and a characterization of risk to aquatic organisms. In a number of acute and chronic studies with several aquatic species, octamethylcyclotetrasiloxane (OMCTS) toxicity was observed, but only after extended, continuous exposures of 7 to 14 d; survival was the only biological end point affected. The symptoms of toxicity observed were highly consistent with narcosis as the mechanism of action. For all aquatic toxicity testing, the lowest NOEC was 4.4 μg/L for rainbow trout in both 14-d and 90-d tests. The physicochemical characteristics of OMCTS (low solubility, high Kow, and very high Henry's law constant) indicate that the water concentrations should be low and transient, consistent with results of environmental-fate studies that demonstrate that OMCTS moves rapidly out of water. The primary route of release of OMCTS to the environment is associated with use in personal-care products, which would potentially result in release to air and water via public sewer systems. Environmental-fate models predict low concentrations of OMCTS in air and water. Monitoring studies indicate mean measured concentrations of OMCTS in sewage treatment plant effluents of 0.06 to 0.41 μg/L. Assuming 50% bioavailability of OMCTS and a dilution factor of three, calculated mean concentrations of dissolved OMCTS in surface waters range from 0.01 to 0.068 μg/L. Comparison of the lowest no-observed-effect concentration (NOEC) from all toxicity testing with this predicted range of surface water concentrations indicates a conservative margin of safety to 64 to 444 for aquatic organisms. Rapid volatilization and additional dilution in most aquatic environments will increase this margin of safety even further. Based on all available evidence, the risk of OMCTS to aquatic ecosystems is characterized as very low.
A preliminary evaluation of the relationship between bioconcentration and hydrophobicity for surfactants
Authors: Tolls Johannes , Sijm Dick T.H.M. 
Published: March 2010

Abstract
A statistical analysis was done of the relationship between hydrophobicity and bioconcentration parameters (uptake and elimination rate constants and bioconcentration factor) predicted by the diffusive mass-transfer (DMT) concept of bioconcentration developed previously. We employed polychlorinated biphenyls and benzenes (PCB/zs) as model compounds and the octanol/water partition coefficient as hydrophobicity parameter. We conclude that the model is consistent with the data. Subsequently, we applied the DMT concept to a set of preliminary bioconcentration data for surfactants using the critical micelle concentration (CMC) as hydrophobicity parameter. The obtained relationships qualitatively agree with the DMT concept, indicating that hydrophobicity is of great influence on surfactant bioconcentration. Finally, we investigated the hydrophobicity-bioconcentration relationships of surfactants and PCB/zs using aqueous solubility as common hydrophobicity parameter and found the relationships between the bioconcentration parameters and hydrophobicity to agree with the DMT concept. These findings are based on total radiolabel data. Therefore, they need to be confirmed using compound-specific surfactant bioconcentration data.
Acute toxicity of heavy metals for benthic epiphytic foraminifera Pararotalia spinigera (le calvez) and influence of seaweed-derived doc
Authors: Bresler Vladimir , Yanko Valentina 
Published: March 2010

Abstract
The acute toxicity of cadmium, copper, and mercury to the benthic epiphytic foraminiferan Pararotalia spinigera (Le Calvez) was investigated using seven different vital cytophysiological and cytochemical methods. The ability to enzymatically hydrolyze the fluorogenic substrates fluorescein diacetate or fluorescein dibutyrate was the most sensitive method of LC50 value determination. The LC50 (24-h) values for cadmium, copper, and mercury determined by this assay with fluorescein diacetate was 0.56, 1.4, and 0.07 μM, respectively. The content of seaweed-derived dissolved organic carbon (DOC), measured by absorbance at 436 nm, produced a dramatic increase of LC50 values for the heavy metals in a dose-dependent manner. “Intact” epiphytic foraminifera attached to seaweeds are less sensitive to acute toxicity of cadmium, copper, and mercury than are “detached” foraminifera.
Immunopathology of 8-week-old ring-necked pheasants (Phasianus colchicus) exposed to malathion
Authors: Day Brad L. , Walser Mary M. , Sharma Jagdev M. , Andersen David E. 
Published: March 2010

Abstract
In addition to their acute neurotoxic effects, some organophosphorus compounds have been shown to have immunotoxic properties. Alterations in the immune system may lead to chronic morbidity and/or mortality that is not readily apparent at the time of initial exposure. Because it often inhabits land that is intensely farmed, the ring-necked pheasant (Phasianus colchicus) may be a suitable biomonitor of agroecosystems, especially those used in the production of corn. We examined immunopathologic effects of a widely used organophosphate insecticide, malathion, on 8-week-old, cage-reared ring-necked pheasants 3 d after a single oral dose. No differences were seen in hematologic parameters, body weight, or weight of the bursa of Fabricius. Birds given a high dose of malathion (230 mg/kg) displayed significant decreases in absolute and relative thymic and splenic weights (p ± 0.05). Significant changes were also seen in thymic and splenic histomorphometry (p ± 0.05). The high-dose group and, in some cases, the low-dose group (92 mg/kg) displayed significant histologic lesions. These findings indicate that a single dose of malathion, at the LD50 level (230 mg/kg) and occasionally at 40% of the LD50 level (92 mg/kg), is capable of inducing quantitative and qualitative changes in the lymphoid organs of the ring-necked pheasant that may affect immune function.
Survival of copper-exposed juvenile fathead minnows (Pimephales promelas) differs among allozyme genotypes
Authors: Schlueter Mark A. , Guttman Sheldon I. , Oris James T. , Bailer A. John 
Published: March 2010

Abstract
The effects of seven variable enzyme loci and multiple-locus heterozygosity on time to death (TTD) during an acute 96-h copper exposure were examined by two failure-time regression models. Allozymes for five enzyme loci (GPI-1*, GPI-2*, IDHP-1*, MDH-2*, and PGM*) were significantly related to TTD. Heterozygosity was not significantly related to TTD. Fish weight was found to have a negative relationship with TTD, larger fish having shorter TTD. This unusual relationship may have resulted from differential survivorship of individuals with sensitive and resistant alleles at the MDH-2* and the IDHP-1* loci. For the IDHP-1* locus the allele *a was associated with increased copper survivorship; however, it was also associated with small size. Conversely, the allele *a at the MDH-2* locus, which was present in higher frequency in larger fish, was associated with decreased survivorship. These results indicate that genetic selection for one characteristic may have a negative impact on other characteristics. Survivors of the copper exposure were genetically selected for copper resistance, resulting in the significant reduction in frequencies of several sensitive genotypes in the population. We conclude that monitoring population genetic structure and frequency changes of sensitive genotypes is a useful biomarker.
Fathead minnow (Pimephales promelas rafinesque) reproduction in outdoor microcosms: An assessment of the ecological effects of fish density
Authors: Shaw Jennifer L. , Maund Stephen J. , Marshall Stacey J. , Hill Ian R. 
Published: March 2010

Abstract
This study was part of a research program designed to evaluate fathead minnow (Pimephales promelas) reproduction in 17-m3 outdoor microcosms as a test system to investigate ecosystem-level impacts of toxicants. Sex ratios of fathead minnow (FHM) adults at stocking were manipulated to regulate the biomass and numbers of young-of-the-year (YOY) following reproduction. This study reports the effect of fish densities obtained from six different sex ratios on microcosm ecology that were compared to a fishless control during a 4.5-month period. Fish sampled during the study were representative of the actual population. Taxa collected from FHM stomachs were very diverse (16 groups) representing various communities and trophic levels. Bacillariophyta, filamentous algae, and macrophytes were the dominant food source; however, Crustacea, rotifers, chironomids, and other macroinvertebrates were also important. Effects on community structure were investigated using multivariate discriminant analysis. There were no fish density effects on zooplankton or benthic macroinvertebrate community structures. Microcosms with high FHM densities had fewer emerging chironomids, and phytoplankton levels were elevated. Phytoplankton taxa, which discriminated phytoplankton community structure differences between fish biomass groups, were also positively correlated with total phosphorus.
Further investigations of the etiology of subcutaneous neoplasms in native gizzard shad (Dorosoma cepedianum)
Authors: Jacobs Ann Durham , Ostrander Gary K. 
Published: March 2010

Abstract
Aspects of the etiology of subcutaneous spindle-cell neoplasms in feral gizzard shad (Dorosoma cepedianum) collected from Lake of the Arbuckles, Oklahoma, were investigated. Field collections of adult and juvenile gizzard shad were conducted to determine the prevalence and seasonality of neoplasms and site specificity of neoplasm-bearing fish. Overall neoplasm prevalence for adult gizzard shad was 22.1%; no juveniles exhibited neoplasms. Neoplasm occurrence did not appear seasonal. Neoplasm-bearing gizzard shad were found at all three sampling sites within Lake of the Arbuckles with similar neoplasm prevalence rates (Guy Sandy Creek 22.1%, Rock Creek, 17.9%, and Buckhorn Creek 22.4%). No gizzard shad (juvenile or adult) collected from Lake Carl Blackwell, Oklahoma, the reference site, exhibited neoplasms. Water, sediment, and shad liver tissue from Lake of the Arbuckles and the reference site were analyzed for total recoverable metals (cadmium, chromium, copper, nickel, and lead, by graphite furnace atomic absorption). Chromium, copper, and nickel were found in the water samples at concentrations of &gt;1 to 8.6 μg/L. Low concentrations (&gt;1 to 13.6 μg/g wet weight) of all the metals were found in the sediment and liver tissue from both sites. Heavy metal contamination does not appear linked to neoplasm occurrence. To determine if a nonbacterial infectious agent was responsible for tumor formation, cell-free neoplasm homogenates were injected into healthy rainbow trout. Neoplasms were not transmitted into rainbow trout. The etiology of these neoplasms remains unknown.
Biodegradation of no. 2 diesel fuel in the vadose zone: A soil column study
Authors: Widrig David L. , Manning John F. 
Published: March 2010

Abstract
Packed soil columns were used to simulate and investigate in situ biological remediation of soil contaminated with diesel fuel. We investigated and evaluated several operating strategies, including continuous flooding of the column soil with nutrient solution, and periodic operating cycles consisting of flooding followed by draining and aeration. The objectives were (a) to determine the extent of diesel fuel degradation in soil columns under four operating conditions (biologically inhibited control; continuous saturation with nitrogen and phosphorus amendments; periodic operation, consisting of flooding with nitrogen and phosphorus, followed by draining and forced aeration; and periodic operation, consisting of flooding with nitrogen, phosphorus, and calcium and magnesium amendments, followed by draining and forced aeration); (b) to evaluate CO2 production and oxygen consumption as indicators of biodegradation; (c) to monitor hydraulic conductivity under different operating strategies; and (d) to examine the system requirements for nitrogen and phosphorus. Our results showed that periodic operation promoted higher rates of biodegradation of diesel fuel in soil and minimized the use of water containing nutrient amendments, and consequently the possible need to collect and treat such water. We believe that monitoring CO2 and O2 levels in situ may provide a means of optimizing the timing of flooding and aeration events to increase degradation rates. Results of this laboratory study will aid in improving the design and operation of field-scale bioremediation systems.
Laboratory methods for volatile organic compounds evolved in mineralization studies
Authors: Hickey William J. , Arnold Scott M. , Moran Bridget N. 
Published: March 2010

Abstract
A system to study mineralization of volatile organic compounds (VOCs) was developed using commercially available solid-phase VOC traps and impingers to collect CO2 as well as VOCs breaking out from the solid-phase trap. The efficiencies of VOC traps containing activated charcoal (AC) or graphitized carbon black (GCB) for absorbing [14C]trichloroethylene ([14C]TCE) and 14CO2 were evaluated, and approaches for minimizing VOC losses from reaction vessels were established. Mass balances showed AC and GCB absorbed similar amounts of [14C]TCE. However, GCB had no detectable 14CO2 retention, whereas AC absorbed about 7% of the 14CO2. Because 14CO2 absorption could influence the interpretation of mineralization experiments, GCB was concluded to be the better VOC-trapping matrix.
Environmental fate of methylcyclopentadienyl manganese tricarbonyl
Authors: Garrison Arthur W. , Lee Wolfe N. , Swank Robert R. , Cipollone Mark G. 
Published: March 2010

Abstract
Methylcyclopentadienyl manganese tricarbonyl (MMT) has been proposed as an octane booster for unleaded gasoline; such use could result in ecological and human exposure through surface water and groundwater ecosystems. To evaluate the environmental risks from MMT, its environmental fate constants and transformation pathways must be known. Constants for physical parameters that would likely influence MMT fate were collected from the literature or calculated; the compound's octanol/water partition coefficient and water solubility were determined in the laboratory. Experiments were designed to screen MMT for transformation pathways that are significant over environmentally short time frames. The MMT was found to be fairly stable in the dark in aquifer materials and sediments at various Eh levels; half-lives ranged from 0.2 to 1.5 years in aquifer materials at 25°C. (These matrices were not optimized for biodegradation.) On the other hand, MMT photolyzes rapidly in distilled water; its half-life in midday sunlight in water is approximately 1 min and the disappearance quantum yield is 0.13. Photodegradation products were identified as cyclopentadiene, methyl cyclopentadiene, carbon monoxide, and a manganese carbonyl that readily oxidized to trimanganese tetroxide.
Metal and arsenic impacts to soils, vegetation communities and wildlife habitat in southwest Montana uplands contaminated by smelter emissions: I. Field evaluation
Authors: Galbraith Hector , Lejeune Katherine , Lipton Joshua 
Published: March 2010

Abstract
Concentrations of arsenic and metals in soils surrounding a smelter in southwest Montana were correlated with vegetative community structure and composition and wildlife habitat quality. Soils in the uplands surrounding the smelter were highly enriched with arsenic and metals. Concentrations of these analytes decreased with distance from the smelter and with soil depth, suggesting that the smelter is the source of the enrichment. In enriched areas, marked modifications to the native vegetation community structure and composition were observed. These included replacement of evergreen forest with bare unvegetated ground; species impoverishment and increased dominance by weed species in grasslands; and reductions in the vertical complexity of the habitat. Significant negative correlations existed between soil arsenic and metals concentrations and the extent of vegetative cover and the vertical diversity of plant communities. Loss of vegetative cover in the affected areas has been accompanied by reductions in their capacity to support indigenous wildlife populations.
Metal and arsenic impacts to soils, vegetation communities and wildlife habitat in southwest montana uplands contaminated by smelter emissions: II. Laboratory phytotoxicity studies
Authors: Kapustka Lawrence A. , Lipton Joshua , Galbraith Hector , Cacela Dave , Lejeune Katherine 
Published: March 2010

Abstract
Vegetation communities on metal- and arsenic-contaminated uplands surrounding a smelter in southwest Montana have been eliminated or highly modified. Laboratory toxicity tests were performed using site soils from the impacted areas to determine whether the soils limit the ability of plants to establish and grow. The germination and growth of alfalfa, lettuce, and wheat in impacted area soils was compared to germination and growth of the three species in reference soils. The degree of phytotoxicity was quantified using a species-endpoint toxicity score calculated on the magnitude of difference between germination and growth of plants in impacted and reference soils. The impacted soils exhibited substantial toxicity to plants: 5% of the sites were severely phytotoxic, 55% were highly phytotoxic, 10% were moderately phytotoxic, 20% were mildly phytotoxic, and 10% were nontoxic. Root growth was consistently the most affected endpoint (18 of 20 impacted soils) and reduction in root length and mass was observed. Correlation and partial correlation analysis was used to evaluate the causes of phytotoxicity. Concentrations of As, Cu, and Zn and, to a lesser extent, Pb and Cd were found to be positively correlated with phytotoxicity.
Comparative acute toxicity of a synthetic mine effluent to Ceriodaphnia dubia, larval fathead minnow and the freshwater mussel Anodonta imbecilis
Authors: Masnado Robert G. , Geis Steven W. , Sonzogni William C. 
Published: March 2010

Abstract
To determine if water quality-based effluent limitations recommended for a proposed discharger would provide adequate protection of aquatic life, site-specific acute toxicity tests were performed. The proposed discharger studied was a mine to be located in northern Wisconsin. The mine's discharge would flow into the Flambeau River, a relatively pristine river that harbors endangered freshwater mussels. The toxicity effects of synthetic effluents, representing a mixture of five different metals under contrasting conditions of hardness, were tested on several different organisms. Results indicated that Ceriodaphnia dubia exhibited a much greater sensitivity to various mixtures of cadmium, hexavalent chromium, copper, nickel, and zinc than did either larval fathead minnows (Pimephales promelas) or the freshwater mussel Anodonta imbectlis. Mixtures of metals at the permitted discharge levels of individual metals were also found to be consistently toxic to C. dubia. Because C. dubia was found to be much more sensitive than A. imbecilis, an effluent safe for C. dubia should also be safe for A. imbecilis and the physiologically similar endangered mussels found in the river. Based on such testing, aquatic life toxicity-testing conditions and criteria suggested for the National Pollution Discharge Elimination System (NPDES) permit should be protective of C. dubia and, hence, other aquatic life such as endangered mussels. Overall, effluent limitations for proposed dischargers need to be based on the combined effect of complex effluents. Aquatic toxicity testing using synthetic effluents that approximate the expected discharge characteristics provides a viable approach to determining the limits for proposed dischargers of multiple pollutants.