bluuebunny/crossref_metadata_2025_split huggingface dataset:
An overview of the use of quantitative structure-activity relationships for ranking and prioritizing large chemical inventories for environmental risk assessments
Authors: Russom Christine L. , Breton Roger L. , Walker John D. , Bradbury Steven P. 
Published: November 2004

Abstract
Ecological risk assessments for chemical stressors are used to establish linkages between likely exposure concentrations and adverse effects to ecological receptors. At times, it is useful to conduct screening risk assessments to assist in prioritizing or ranking chemicals on the basis of potential hazard and exposure assessment parameters. Ranking of large chemical inventories can provide evidence for focusing research and/or cleanup efforts on specific chemicals of concern. Because of financial and time constraints, data gaps exist, and the risk assessor is left with decisions on which models to use to estimate the parameter of concern. In this review, several methods are presented for using quantitative structure-activity relationships (QSARs) in conducting hazard screening or screening-level risk assessments. The ranking methods described include those related to current regulatory issues associated with chemical inventories from Canada, Europe, and the United States and an example of a screening-level risk assessment conducted on chemicals associated with a watershed in the midwest region of the United States.
Quantitative structure-activity relationships for oxidation reactions of organic chemicals in water
Authors: Canonica Silvio , Tratnyek Paul G. 
Published: November 2004

Abstract
Even in the absence of microbiological mediation, oxidation is one of the most important chemical processes contributing to the degradation of organic contaminants in the aquatic environment. The oxidants that are responsible for these reactions include hydroxyl radical, carbonate radical, organic oxyl and peroxyl radicals, peroxides, excited triplet states of organic chromophores, singlet molecular oxygen, ozone, chlorine dioxide, permanganate, and chromate. Some of these oxidants contribute to natural attenuation of organic contaminants, but many are of greater interest because of their role in engineered remediation technologies. Kinetic studies of these processes have lead to numerous quantitative structure-activity relationships (QSARs). Many of these QSARs are simple empirical correlations to common convenient descriptor variables like Hammett constants (σ), half-wave oxidation potentials (E1/2), energies of the highest occupied molecular orbital (EHOMO) or rate constants for other oxidation reactions. However, several environmentally relevant, aqueous-phase oxidation reactions have been described with QSARs based on theoretical models for electron transfer that were developed by Marcus-Hush and Rehm-Weller. This review summarizes many of the reported QSARs for aquatic oxidations of organic compounds with emphasis on the interrelation between traditional empirical models and the potential for future development of QSARs based on theoretical models.
Quantitative structure-activity relationships for predicting soil-sediment sorption coefficients for organic chemicals
Authors: Doucette William J. 
Published: November 2004

Abstract
Sorption coefficients are used to describe the equilibrium distribution of a chemical between a soil or sediment and the aqueous phase that it is in contact with. Although sorption coefficients for a particular organic chemical vary greatly from soil to soil, the observation has been made that sorption generally increases as the organic carbon content of the soil and the hydrophobicity of the chemical increases. This general observation resulted in the acceptance of organic carbon normalized sorption coefficients (Koc) as unique properties or constants of organic chemicals. In turn, Koc values have been estimated by quantitative structure-activity relationships (QSARs) developed by correlation with a variety of physical or chemical properties and structural descriptors related to the hydrophobicity of the chemical such as octanol-water partition coefficients, aqueous solubilities, molecular connectivity indices, molecular weight, molecular surface area, and reverse-phase high-performance liquid chromatography retention times. The selection and application of the most appropriate QSAR for predicting Koc depend on several factors, including the availability of required input, the appropriateness of model to chemical of interest, and the methodology for calculating the necessary topological or structural information. A review of the existing QSARs for predicting Koc and the limitations of using the Koc approach to estimate sorption coefficients will be presented.
Quantitative structure-property relationships for prediction of boiling point, vapor pressure, and melting point
Authors: Dearden John C. 
Published: November 2004

Abstract
Boiling point, vapor pressure, and melting point are important physicochemical properties in the modeling of the distribution and fate of chemicals in the environment. However, such data often are not available, and therefore must be estimated. Over the years, many attempts have been made to calculate boiling points, vapor pressures, and melting points by using quantitative structure-property relationships, and this review examines and discusses the work published in this area, and concentrates particularly on recent studies. A number of software programs are commercially available for the calculation of boiling point, vapor pressure, and melting point, and these have been tested for their predictive ability with a test set of 100 organic chemicals.
Modifications to the fathead minnow (Pimephales promelas) chronic test method to remove mortality due to pathogenic organisms
Authors: Geis Steven W. , Fleming Kari , Mager Amy , Reynolds Lou 
Published: November 2004

Abstract
Whole effluent toxicity testing is used to evaluate the discharge of materials that may be harmful to indigenous aquatic life. Unlike most environmental analyses, receiving water (the water body into which the effluent is discharged) often is used as dilution water in whole effluent toxicity tests to simulate the aquatic environment into which the effluent is introduced. In approximately 26% of whole effluent toxicity tests conducted by Wisconsin (USA) certified labs between 1988 and 1998, a pathogenic effect caused failure of the receiving water controls during the fathead minnow chronic test (i.e., &gt;20% mortality). We performed microbiological work to isolate pathogenic organisms from receiving waters, the fish, and their food. We found pathogenic organisms such as Flexibacter columnaris, Aeromonas hydrophila, and Flavobacter spp. to be ubiquitous and were not able to remove them from the test (e.g., through decontamination of the fish food and carefully following sterility procedures). To eliminate the pathogenic effect, we evaluated manipulations of the sample and the test method including filtering receiving water, irradiating receiving water, using older fish (48 h), using clean test beakers each day of the test, and using smaller test beakers (30 ml) with two fish per beaker. In samples demonstrating the pathogenic effect, most of these manipulations significantly reduced mortality. The use of smaller tests cups was significantly better at reducing the effect than all of the other sample and method manipulations. These results indicate that a simple method modification to the fathead minnow chronic test will improve test reliability when diluting effluents with receiving waters.
Quantitative structure–biodegradation relationships for Ortho-substituted biphenyl compounds oxidized by Methylosinus trichosporium OB3b
Authors: Lindner Angela S. , Whitfield Callie , Chen Ning , Semrau Jeremy D. , Adriaens Peter 
Published: November 2004

Abstract
Methanotrophs, bacteria that thrive in the presence of stable methane and oxygen concentrations, can cometabolically oxidize ortho-substituted biphenyls to yield a variety of hydroxylated products. Despite awareness of the susceptibility of ortho-substituted biphenyls and other aromatic compounds to methanotrophic oxidation, the molecular properties relevant for predicting rates of methanotrophic oxidation are unknown. To this end, we have developed quantitative structure-biodegradation relationships using oxygen uptake activity by the type 2 methanotroph, Methylosinus trichosporium OB3b, expressing the soluble form of methane monooxygenase and in the presence of nine ortho-substituted biphenyls. Multivariate analysis yielded the strongest correlations using the initial slope of the oxygen uptake rate versus substrate concentration curve as the dependent variable. Quantum mechanical descriptors, including the sum of carbon charges on the substituted ring, the charge on the substituted carbon, and the width of compound calculated using computationally derived bond lengths and dihedral angles, correlated more strongly with oxygen uptake activity than did empirically derived electronic descriptors. The resulting models suggest a significant influence of substituent electronic nature and size and the involvement of the substituted carbon site in the oxidation of these compounds by M. trichosporium OB3b.
Similarities in bioaccumulation patterns of polychlorinated dibenzo-p-dioxins and furans and polychlorinated diphenyl ethers in laboratory-exposed oligochaetes and semipermeable membrane devices and in field-collected chironomids
Authors: Lyytikäinen Merja , Rantalainen Anna-Lea , Mikkelson Pirjo , Hämäläinen Heikki , Paasivirta Jaakko , Kukkonen Jussi V. K. 
Published: November 2004

Abstract
Sediment and chironomid samples were collected from a river in the vicinity of and downstream from a closed chlorophenol production plant, and they were analyzed for polychlorinated dibenzo-p-dioxins and furans (PCDD/F) and polychlorinated diphenyl ethers (PCDE). Bioaccumulation of these compounds from the sediments by the oligochaeta, Lumbriculus variegatus, and semipermeable membrane devices (SPMDs) was studied in a 28-d bioaccumulation test. The sum concentrations of PCDD/Fs and PCDEs in sediments varied spatially, peaking at the site below the production plant, but the congener composition remained fairly constant throughout the river. The sum concentrations of chironomids, oligochaetes, and SPMDs all varied independently of sediment concentrations. Both invertebrates accumulated more PCDEs, whereas PCDD/Fs dominated in sediments and SPMDs. Despite the variable sum concentrations, similarities were observed in concentrations and compositions of individual congeners. A significant correlation was found between sediments and oligochaetes, and between oligochaetes and chironomids, for both PCDD/Fs and PCDEs. These results suggest that bioaccumulation of PCDD/Fs and PCDEs in invertebrates is nonselective. Furthermore, the laboratory bioaccumulation tests seem to yield relevant results. The SPMDs were found to give good predictions of the PCDD/F concentrations of sediments and oligochaetes. For PCDEs, the estimates were slightly poorer, but still useful for preliminary concentration assessments.
Occurrence of polychlorinated biphenyls and polybrominated diphenyl ethers in green mussels (Perna viridis) from Singapore, Southeast Asia
Authors: Bayen Stephane , Thomas Gareth Owen , Lee Hian Kee , Obbard Jeffrey Philip 
Published: November 2004

Abstract
The green mussel, Perna viridis, was used in this study to measure levels of polychlorinated biphenyls (PCBs) and, for the first time, polybrominated diphenyl ethers (PBDE) in the marine environment. Samples were collected from eight different locations in the coastal waters of Singapore between April and May 2002. Forty-one PCB and 21 PBDE congeners were quantified by gas chromatography–mass spectrometry and were all positively detected in the mussel tissues. Total concentrations in green mussel tissues ranged from 6.1 to 82 ng/g and 2.0 to 38 ng/g on a dry-weight basis for PCBs and PBDEs, respectively. Such levels reflect the ubiquity of these persistent organic pollutants in a tropical marine environment. Principal component analysis was applied to the PCB data and revealed similarities in the congener composition of mussel tissues to that of the commercial PCB mixture, Aroclor 1254. The PBDE levels, to date, were approximately one order of magnitude greater than the upper concentrations reported for blue mussel (Mytilus edulis) tissues in Europe. At some sampling sites, the congener composition of PBDEs in P. viridis tissues indicated recent exposure to a commercial pentabrominated flame retardant.
Time-dependent toxicokinetics of [14c]lindane in the terrestrial isopod Porcellionides pruinosus
Authors: Santos Sónia A. P. , Sousa José P. , Frost Matthias , Soares Amadeu M. V. M. 
Published: November 2004

Abstract
Preliminary acute soil toxicity tests are a starting point for risk assessment. These tests are performed at one exposure time and are used to estimate the lethal concentration for 50% of the population (LC50). However, it is known that LC50 varies over time, following an exponential decay model. Here, we present the variation of LC50 over time in the isopod Porcellionides pruinosus exposed to [14C]lindane when considering the concentrations measured in bulk soil and in extracted water. Using a wide range of concentrations, the percent mortality was recorded over various time intervals. Higher concentrations strongly influenced isopod survival. The LC50∞ value for P. pruinosus was 3.57 μg/g for bulk soil concentration, suggesting a great sensitivity of this species to lindane. Simultaneously, the values estimated for the lethal body concentration (LBC) were 2.36 μg/g animal for bulk soil concentrations and 2.79 μg/g animal when extracted water concentrations are considered. An alternative to the LC50 determination is the estimation of LBC, which is proposed as a better way to describe the acute toxicity of chemicals. Kinetic-based toxicity models were fitted to the data and revealed uptake rate constants of 1.1 g soil/g animal/week and 84.3 ml extracted water/g animal/week for bulk soil and extracted water concentrations, respectively. Elimination rate constants of 1.7 per week were found for both pathways of exposure.
Bacterial detection of the toxicity of dioxins, polychlorinated biphenyls, and polybrominated diphenyl ethers
Authors: Min Jiho , Chang Yoon-Seok , Gu Man Bock 
Published: November 2004

Abstract
Polychlorinated dibenzo- p-dioxins (PCDDs), biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) were found to induce several specific stresses within bacterial cells. Four different recombinant Escherichia coli with specific stress promoters (i.e., the recA responsive to DNA damage, fabA responsive to membrane damage, katG responsive to oxidative damage, and grpE responsive to protein damage) that were fused to the lux operon from Vibrio fischeri showed very unique specificities in terms of their stress responses in the presence of PCDD and PCBs. In addition, a recombinant bacterium with the lac promoter fused to the lux operon from Xenorhabdus luminescens also showed dose-dependent responses via a loss of bioluminescence because of the addition of the PCDDs and PCBs. Brominated diphenyl ethers (BDE)-47, −99, and −153 congeners, however, were not found to induce any stress within the bacterial cells, indicating that these chemicals do not stimulate any cellular stresses related to those tested. These three congeners, however, did result in different levels of general cellular toxicity, which was found to be dependent on the position of the bromine. Finally, the cellular toxicity within the bacteria was found to increase when exposed to mixtures of dioxins, PCBs, and PBDEs, possibly from synergistic effects.
Mineralization of desorption-resistant 1,4-dichlorobenzene in wetland soils
Authors: Lee Sangjin , Pardue John H. , Moe William M. , Valsaraj Kalliat T. 
Published: November 2004

Abstract
Laboratory studies were conducted to investigate the biologically mediated, aerobic mineralization of both freshly added and artificially aged, desorption-resistant 1,4-dichlorobenzene (1,4-DCB). The adsorption and desorption of 1,4-DCB isotherms were established in three wetland soils using decant–refill batch techniques. Significant nonlinearity and hysteresis were observed in the isotherms with a hysteresis index ranging from 0.11 (relatively low hysteresis) in a marsh soil to 2.26 (relatively high hysteresis) in a bottomland hardwood soil from the Petro Processor (PPI) Superfund site. Mineralization of freshly added 1,4-DCB was observed in all three soils without lag after the addition of a 1,4-DCB degrading culture. Mineralization curves were plotted above theoretical lines predicted from a first-order model assuming instantaneous desorption, indicating that the microbial population had access to sorbed 1,4-DCB. In separate experiments, mineralization of artificially aged, desorption-resistant 1,4-DCB was also observed. Mineralization curves in these studies also indicated that the microbial population could directly access sorbed 1,4-DCB. The extent and rate of mineralization of desorption-resistant 1,4-DCB decreased significantly, including rate constants decreasing from approximately 0.01 d−1 in the freshly added treatments to approximately 0.002 d−1 in the desorption-resistant treatments. Although sorption/desorption partitioning helped explain mineralization patterns in the treatments with freshly added 1,4-DCB, no differences were observed in mineralization curves in the desorption-resistant treatments between soils with widely varying sorption/desorption properties.
Comparison of synthetic surfactants and biosurfactants in enhancing biodegradation of polycyclic aromatic hydrocarbons
Authors: Makkar Randhir S. , Rockne Karl J. 
Published: November 2004

Abstract
Polycyclic aromatic hydrocarbon (PAH) contamination of the environment represents a serious threat to the health of humans and ecosystems. Given the human health effects of PAHs, effective and cost-competitive remediation technologies are required. Bioremediation has shown promise as a potentially effective and low-cost treatment option, but concerns about the slow process rate and bioavailability limitations have hampered more widespread use of this technology. An option to enhance the bioavailability of PAHs is to add surfactants directly to soil in situ or ex situ in bioreactors. Surfactants increase the apparent solubility and desorption rate of the PAH to the aqueous phase. However, the results with some synthetic surfactants have shown that surfactant addition can actually inhibit PAH biodegradation via toxic interactions, stimulation of surfactant degraders, or sequestration of PAHs into surfactant micelles. Biosurfactants have been shown to have many of the positive effects of synthetic surfactants but without the drawbacks. They are biodegradable and nontoxic, and many biosurfactants do not produce true micelles, thus facilitating direct transfer of the surfactant-associated PAH to bacteria. The results with biosurfactants to date are promising, but further research to elucidate surfactant–PAH interactions in aqueous environments is needed to lead to predictive, mechanistic models of biosurfactant-enhanced PAH bioavailability and thus better bioremediation design.
Influence of natural organic matter source on copper toxicity to larval fathead minnows (Pimephales promelas): Implications for the biotic ligand model
Authors: Ryan Adam C. , Van Genderen Eric J. , Tomasso Joseph R. , Klaine Stephen J. 
Published: November 2004

Abstract
The influence of dissolved natural organic matter (NOM) source on copper toxicity was investigated with larval fathead minnows (Pimephales promelas) in reconstituted moderately hard water. Ninety-six–hour static renewal toxicity tests were conducted to investigate an assumption of the biotic ligand model (BLM) that NOM source does not need to be considered to adequately predict copper toxicity. The nine different NOM isolates used in these toxicity tests were chemically well-characterized substances that were obtained by reverse osmosis as part of an NOM typing project based in southern Norway. Three median lethal concentration (LC50) values were estimated for toxicity tests conducted with each NOM, at nominal dissolved organic carbon (DOC) concentrations of 2, 5, and 10 mg/L. Tests also were conducted in dilution waters in which no NOM was added. Regression analyses were conducted to compare NOM-specific (specific NOM source) LC50s versus DOC concentration relationships to each other, as well as to the overall LC50 versus DOC concentration relationship. Statistical differences were found regarding the effects of NOM source on copper toxicity. Similar analyses were conducted with humic acid (HA) concentrations and spectral absorbance, and differences in the effect of NOM source on copper toxicity were similarly concluded. These results do not support the assumption that copper toxicity can be adequately predicted by utilizing DOC concentration, regardless of NOM source. Evaluation of relationships between LC50 values and other NOM characteristics revealed that despite significant differences due to NOM source on copper toxicity, DOC and HA concentrations were the most effective parameters in explaining variability in LC50 values. When BLM-predicted LC50 values were compared to observed LC50 values, predicted values showed reasonable agreement with observed values, but some deviations occurred due to NOM source and DOC concentration.
Expression and inducibility of aryl hydrocarbon receptor pathway genes in wild-caught killifish (Fundulus heteroclitus) with different contaminant-exposure histories
Authors: Meyer Joel N. , Wassenberg Deena M. , Karchner Sibel I. , Hahn Mark E. , DiGiulio Richard T. 
Published: November 2004

Abstract
Wildcaught killifish from a contaminated site on the Elizabeth River (VA, USA) are refractory to induction of cytochrome P4501A (CYP1A, measured as catalytic activity and immunodetectable CYP1A protein) after exposure to typical aryl hydrocarbon receptor (AHR) agonists, as has been reported for fish from other sites highly contaminated with these compounds. In an attempt to understand the molecular basis for the lack of inducibility of CYP1A protein expression and activity in Elizabeth River killifish, we analyzed the expression of CYP1A and four other members of the AHR signal transduction pathway: AHR1, AHR2, AHR repressor (AHRR), and AHR nuclear translocator (ARNT). Gene expression was measured by cycleoptimized reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of messenger ribonucleic acid (mRNA) extracted from livers of killifish from the Elizabeth River and King's Creek (VA, USA) (reference site), 36 h after injection with β-naphthoflavone (BNF, an AHR agonist) or corn oil (carrier control). Hepatic CYP1A mRNA was inducible in King's Creek killifish. However, in Elizabeth River killifish, no induction of CYP1A mRNA was observed, confirming and extending previous results showing no induction of CYP1A protein or catalytic activity in this population. Similarly, AHRR and AHR2 mRNA levels were induced by BNF in King's Creek but not Elizabeth River killifish. No population or treatment-related differences were observed in expression of AHR1 or ARNT mRNAs. The results reveal in Elizabeth River killifish a consistent lack of inducibility of genes that are normally inducible by AHR agonists (CYP1A, AHRR AHR2). However, the expression of AHR1, AHR2, and AHRR in vehicle-treated fish did not differ between Elizabeth River and King's Creek killifish, suggesting that altered constitutive expression of AHRs or AHRR does not underlie the refractory CYP1A phenotype in Elizabeth River killifish.