Abstract  A series of samples of magnetic fluids stabilized with low-molecular weight polypropylene glycol (PPG) of different molecular masses were synthesized. The use of PPG allowed the maximum extension of the carrier fluid range to include ethyl- and butyl-acetate, ethanol, butanol, acetone, carbon tetrachloride, toluene, kerosene and PPG itself. Magnetic and rheological properties of the samples were investigated. Based on the results of investigation it has been concluded that magnetic nanoparticles are covered by a monolayer of surfactant molecules. At low temperatures the propanol-based sample preserves fluidity upto -115 degrees C. Measurement of critical temperatures of other base fluids showed that alcohols are the best carrier medium. Coagulation stability of the ethanol-based ferrocolloid with respect to water and kerosene was explored. It has been found that kerosene, whose fraction by weight exceeds 22.5%, does not mix with the colloid. This effect can be used to produce magneto-controllable extractors of ethyl alcohol. Under the action of water the colloid coagulates, which allows one to substitute the carrier fluid and to separate the colloid into fractions. (C) 2010 Elsevier B.V. All rights reserved.

Abstract  Samples of mother's milk were collected from Bayonne, NJ; Jersey City, NJ; Pittsburgh, PA; Baton Rouge, LA; and Charleston, WV, and analyzed for volatile (purgeables) and semivolatile (extractable) organics using glass capillary gas chromatography/mass spectrometry/computer. In the volatile fraction, 26 halogenated hydrocarbons, 17 aldehydes, 20 ketones, 11 alcohols, 2 acids, 3 ethers, 1 epoxide, 14 furans, 26 other oxygenated compounds, 4 sulfur-containing compounds, 7 nitrogen-containing compounds, 13 alkanes, 12 alkenes, 7 alkynes, 11 cyclic hydrocarbons, and 15 aromatics were found, including major peaks for hexanal, limonene, dichlorobenzene, and some esters. The levels of dichlorobenzene appeared to be significantly higher in the samples from Jersey City and Bayonne than in samples from other sites. Jersey City samples also appeared to have significantly higher levels of tetrachloroethylene. Charleston and Jersey City samples appeared to have significantly higher levels of chloroform; however, chloroform was observed in the blanks at about 20% of that in the samples. Due to the small sample size and lack of control over the solicitation of sample donors, the data cannot be used to extrapolate to the general population. Fewer semivolatile compounds of interest were found. Polychlorinated naphthalenes, polybrominated biphenyls, chlorinated phenols, and other compounds were specifically sought and not detected (limit of detection about 20-100 ng/mL milk). Polychlorinated biphenyls (PCBs) and DDE were found.

Abstract  The present study focused on monitoring the concentration of 14 halogenated volatile organic compounds in surface waters, including sea, estuarine, river water and industrial effluents in order to determine the most ubiquitous compounds and their concentration levels, which were used to establish their geographical and temporal distribution. EPA Method 502, based on purge and trap techniques, was used. In this method volatile organic pollutants are extracted (purged) from the water sample by bubbling inert gas through the aqueous sample. Purged sample components are trapped in a cartridge containing the polymeric sorbent Tenax and, thereafter, the cartridge is heated and backflushed with helium to desorb the trapped sample components directly into a gas chromatograph with electron capture detector (GC-ECD). The linearity range of the method varied from 0.1 to 4 microg L(-1) with a limit of detection at the low microg L(-1) level. The present study consisted of a monthly monitoring of 46 points throughout Portugal, during 14 months. Chloroform was found in 50% of the samples analyzed, its presence being correlated to both agricultural and industrial activities. Other compounds detected were tetrachloroethylene, trichloroethylene, carbon tetrachloride and 1,2,4 trichlorobenzene, which were present in 10-20% of the samples at concentrations up to 18 microg L(-1). 1,1,2,2-Tetrachloroethane and its degradation product 1,1,2-trichloroethane were found in 5% of the samples, the levels of the latter being higher than those of the parent compound in most samples. Sporadic high concentrations of some volatile halogenated organic compounds were attributed to local uses as solvents.

Abstract  This research determined the removal and fate of 11 selected RCRA compounds in a pilot‐scale activated sludge system with a 4‐day SRT and 7.5‐hour HRT. Screened and degritted raw wastewater from a Cincinnati, OH, wastewater treatment plant was used for this study at the U.S. EPA's Test and Evaluation (T&E) Facility. A continuous feed of spike toxic cocktail of 0.25 mg/L each of acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, carbon tetrachloride, 1,1,1‐trichloroethane, 1,1,2‐trichloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, and ethylbenzene was used to produce an acclimated biomass. The test was run for 7 weeks. Volatilization losses in primary sedimentation exceeded 10% for carbon tetrachloride, 1,1,1‐trichloroethane, 1,1,2‐trichloroethane, and tetrachloroethylene. Sorption of the 11 compounds to primary and secondary sludge ranged from 0.6 to 5.1%. Nine of the 11 test compounds were removed >94% with estimated biodegradation ranging from 0 to 93.4%.

Abstract  Some of the most frequent drinking water contaminants are halogenated hydrocarbons formed, in part, by the chlorination of water. This study involves the gas-chromatographic analysis of water samples from the water supply of different cities in Galicia (Spain): La Coruna, Ferrol, Lugo, Orense, Pontevedra and Vigo. The compounds investigated were: bromochloromethane, bromodichloromethane, chlorobenzene, chloroform, dibromochloromethane, 1,2-dichloroethane, dichloromethane, tetrachloroethylene, carbon tetrachloride and trichloroethylene. A total of 400 samples were analyzed. The results obtained showed that the range of concentrations is between 160.9-1.3-mu-g.l-1 for bromochloromethane, 79.5-2.0-mu-g.l-1 for chloroform, 53-1.5-mu-g.l-1 for dichloromethane, 58.7-1.5-mu-g.l-1 for tetrachloroethylene, 39.5-1.5-mu-g.l-1 for carbon tetrachloride, 44.6-2-mu-g.l-1 for bromodichloromethane, 22-2-mu-g.l-1 for 1,2 dichloroethane and 11.6-1.0-mu-g.l-1 for trichloroethylene. Dibromochloromethane and chlorobenzene were not detected.

Abstract  Results of C-6-C-12 hydrocarbon measurements at three sites in the southern part of The Netherlands, a polluted region in Western Europe, are presented. The measurements were carried out over the period March 1991-February 1997. The concentrations at the sites, with 100-150 km distance between them, are quite similar and they are predominantly determined by large-scale transport. The concentrations in this part of the country are substantially higher than those observed at a coastal site in the north of The Netherlands, but much lower compared to the concentrations in cities and near streets. A distinct difference between the trends of aromatics and aliphatics was observed. The concentrations of the aromatic components display trends that are systematically 4-5% yr(-1) lower than the trends of the aliphatics, which is possibly related to the increased use of catalysts in cars and, partly, to an enhanced atmospheric chemical activity. For the chlorinated species the trends are highly significant. The trend of 1,1,1-trichloroethane is in the order of 8-12% yr(-1) downward while for tetrachloromethane an annual downward trend of 4-6% is found. These downward trends suggest that measures have been taken to fulfil the requirements of the Montreal Protocol to ban the production of these species in a few years time from now. (C) 1999 Elsevier Science Ltd. All rights reserved.

Abstract  Reductive dechlorination of 2,4,6-trichlorophenol (2,4,6-TCP) was conducted with Zn and Zn bimetals, Pd/Zn, Ni/Zn, Cu/Zn, Pt/Zn. Zn showed relatively low reaction rate toward 2,4,6-TCP, while Pd/Zn had dramatically increased reactivity and other bimetals had higher reaction rates than that of plain zinc. Phenol and less chlorinated phenols were found as dechlorination products. Pd/Zn produced cyclohexanone which is a product of aromatic ring reduced. Surface area normalized kinetic constants and second metal contents normalized kinetic constants were calculated and compared. Two mechanisms, mainly catalytic activation and enhanced corrosion, were proposed for the reactivity enhancement.

Abstract  BIOSIS COPYRIGHT: BIOL ABS. The transformability of trihalomethanes, carbon tetrachloride, 1,1,1-trichloroethane, 1,2-dibromomethane, tetrachloroethylene, dibromochloropropane, and chlorinated benzenes was evaluated by a biofilm utilizing a mixture of primary electron acceptors (oxygen, nitrate, and sulfate). These compounds at concentrations commonly found in groundwater were continuously administered for 4 years to a biofilm column reactor that resembled polluted groundwater environments. Acetate was the primary substrate to support microbial growth. Sequential biofilm zones of aerobic respiration, denitrification, and sulfate reduction developed within the column. Transformation of the halogenated aliphatic compounds coincided with the onset of sulfate reduction in the column. The temporary absence of nitrate and sulfate in the column feed decreased the steady-state removals for several of the halogenated aliphatic compounds. These results suggest that sulfate was an important primary electron

Abstract  Development of practical techniques to predict the mobility of halogenated hydrocarbons in aquifers is an important step toward protecting the quality of groundwater resources. This study involved the use of laboratory-column and field-column experiments to estimate retardation coefficients of five halogenated hydrocarbons (bromoform, carbon tetrachloride, tetrachloroethylene, 1,2-dichlorobenzene and hexachloroethane) in the Borden aquifer. These compounds were selected because they were used in the highly-monitored, natural-gradient field-tracer experiment conducted in the unconfined sand aquifer at Canadian Forces Base Borden in southern Ontario, Canada. The field-column experiments were conducted in the vicinity of the natural-gradient tracer experiment, and the laboratory experiments were conducted using aquifer material collected from the field site. The retardation coefficients were found to increase as the average pore-water velocity in the columns decreased, suggesting the presence of non-equilibrium conditions in the reactive transport process. Analysis of the data with a two-site reactive-solute transport model, that allows for time-dependent interaction between solutes and a fraction of reaction sites, provided significant improvement over analysis with a reactive-solute transport model that assumes local equilibrium. For experiments conducted at similar velocities, the mobilities were in close agreement for both the laboratory-and field-column experiments. Retardation factors calculated from batch experiments also agreed closely with the column results and were consistent with those obtained from previous studies at the Borden site. While the retardation factors calculated from the present small-scale methods were in close agreement with those observed during the first month of the large-scale natural-gradient experiment, large deviations were observed for longer travel times.

Abstract  In this review, we present the various microbial enzymatic systems involved in chlorocarbon biodegradation and evaluate their potential use as biocatalysts for the destruction of chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons. Based on our present knowledge of the microbial metabolism of halogenated organic compounds, both anaerobic and aerobic processes could theoretically be used for the destruction of CFCs. The anaerobic processes result in the reductive dehalogenation of halogenated compounds. We describe the biological systems that were found to be involved in the reductive dehalogenation of halogenated hydrocarbons, present a number of hypotheses that have been proposed to explain this phenomenon, and discuss the potential use of these systems for the destruction of CFCs. The aerobic processes are based on the capacity of several large-spectrum activity mono- and dioxygenases that catalyze the initial oxidative step of aliphatic as well as aromatic compounds. In this case, the halogenated alkenes are converted to alkene epoxides that are quite unstable and break down to products that are readily metabolizable by other microorganisms. We discuss the potential use of this type of reaction for the destruction of CFCs and present approaches using genetically engineered microorganisms to more efficiently degrade these compounds.

Abstract  The mechanisms responsible for ethanol-mediated teratogenesis have not been resolved. However, possible etiologies include the local formation of the teratogen acetaldehyde or oxygen radicals by fetal ethanol-oxidizing enzymes. As alcohol dehydrogenases are expressed at very low concentrations in human embryonic tissues, the ethanol-inducible P450 enzyme, CYP2E1, could be the sole catalyst of fetal ethanol oxidation. With this in mind, we examined the expression of this P450 in liver samples from fetuses ranging in gestational age from 16 to 24 weeks. Immunoblot analysis of fetal liver microsomes revealed the presence of a protein immunoreactive with CYP2E1 antibodies that exhibited a slightly lower molecular weight than that found in adult liver samples. Embryonic CYP2E1 expression was further confirmed by the reverse transcriptase reaction with RNA from a 19-week gestational fetal liver used as template. Catalytic capabilities of human fetal microsomes were assessed by measurement of the rate of ethanol oxidation to acetaldehyde, which were 12-27% of those exhibited by adult liver microsomes. Immunoinhibition studies with CYP2E1 antibodies revealed that the corresponding antigen was the major catalyst of this reaction in both fetal and adult tissues. We then assessed whether embryonic CYP2E1 was, like the adult enzyme, inducible by xenobiotics. Treatment of primary fetal hepatocyte cultures with either ethanol or clofibrate demonstrated a 2-fold increase in CYP2E1 levels compared with untreated cells. Collectively, our results indicate that CYP2E1 is present in human fetal liver, that the enzyme is functionally similar to CYP2E1 from adults, and that fetal hepatocyte CYP2E1 is inducible in culture by xenobiotics, including ethanol. Because fetal CYP2E1 mediates ethanol metabolism, the enzyme may play a pivotal role in the local production of acetaldehyde and free radicals, both of which have potential deleterious effects on the developing fetus.

Abstract  Corrosion of iron pipes leads to the release of ferrous iron, Fe(II), and the formation of iron oxides, such as goethite and magnetite, on the pipe surface. Fe(II), a potent reductant when associated with iron oxide surfaces, can mediate the reduction of halogenated organic compounds. Batch experiments were performed to investigate the kinetics and pathways of the degradation of selected chlorinated disinfection byproducts (DBPs) by Fe(II) in the presence of synthetic goethite and magnetite. Trichloronitromethane was degraded via reduction, while trichloroacetonitrile, 1,1,1-trichloropropanone, and trichloroacetaldyde hydrate were transformed via both hydrolysis and reduction. Chloroform and trichloroacetic acid were unreactive. Observed pseudo-first-order reductive dehalogenation rates were influenced by DBP chemical structure and identity of the reductant. Fe(II) bound to iron minerals had greater reactivity than either aqueous Fe-(II) or structural Fe(II) present in magnetite. For DBPs of structure Cl sub(3)C-R, reductive dehalogenation rate constants normalized by the surface density of Fe(II) on both goethite and magnetite correlated with the electronegativity of the -R group and with one electron reduction potential. In addition to chemical transformation, sorption onto the iron oxide minerals was also an important loss process for 1,1,1-trichloropropanone.

Abstract  The document presents a compilation of measured values for physiological parameters used in pharmacokinetic modeling. The physiological parameters include body weight, tissue volumes, cardiac output distribution, and respiration parameters. Reference values for use in risk assessment are given for each of the physiological parameters based on analyses of valid measurements obtained from the literature and other reliable sources. The proposed reference values are for generic mice and rats without regard to sex or strain. Reference values for humans are without regard to age or sex. Differences between the sexes in mice, rats, and humans are accounted for by scaling the reference parameters within species on the basis of body weight. Reference physiological parameters are for a 0.025 kg mouse, 0.25 kg rat, and a 70 kg man.

Abstract  Previous studies have demonstrated that alpha-tocopheryl hemisuccinate (TS) protects hepatocyte suspensions from chemical-induced toxicity. It has been suggested that TS cytoprotection is related to unique properties of the TS molecule or is dependent on the cellular release and activity of unesterified alpha-tocopherol (T). To test the unique cytoprotective nature of TS in vivo, the protective ability of T and tocopherol esters against carbon tetrachloride (CCl4)-induced hepatotoxicity in rats was examined. Hepatoprotection [determined by serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels and histopathology] was not observed after T (or tocopheryl acetate and tocopheryl nicotinate) administration, even though this treatment resulted in a fivefold elevation in hepatic T content. Only pretreatment with TS (100 mg/kg, intraperitoneally) resulted in partial hepatoprotection against CCl4 (2.9 g/kg, orally) toxicity. These findings suggest that hepatoprotection results not from the cellular accumulation of T but rather from the intact TS molecule. To test this hypothesis, the hepatoprotective capacity of cholesteryl hemisuccinate (CS), unesterified cholesterol, and cholesteryl acetate (CA) was examined against CCl4 toxicity. As observed with the tocopherol derivatives, pretreatment with unesterified cholesterol or CA demonstrated no protective ability. However, when rats were pretreated with CS (100 mg/kg), the hepatotoxic effects of CCl4 (elevated serum AST and ALT levels and centrilobular necrosis) were completely prevented. The prevention of CCl4-induced hepatotoxicity by CS and TS do not appear to result from an alteration in hepatic drug metabolism. These data dearly demonstrate that CS and TS are unique and powerful cytoprotective agents against CCl4 hepatotoxicity in vivo. Furthermore, the protection observed is not the result of cellular T accumulation, but rather appears to depend on the hepatocellular accumulation of the intact TS molecule.

Abstract  The public depends on competent risk assessment from the federal government and the scientific community to grapple with the threat of pollution. When risk reports turn out to be overblown--or when risks are overlooked--public skepticism abounds. This comprehensive and readable book explores how the U.S. Environmental Protection Agency (EPA) can improve its risk assessment practices, with a focus on implementation of the 1990 Clean Air Act Amendments. With a wealth of detailed information, pertinent examples, and revealing analysis, the volume explores the "default option" and other basic concepts. It offers two views of EPA operations: The first examines how EPA currently assesses exposure to hazardous air pollutants, evaluates the toxicity of a substance, and characterizes the risk to the public. The second, more holistic, view explores how EPA can improve in several critical areas of risk assessment by focusing on cross-cutting themes and incorporating more scientific judgment. This comprehensive volume will be important to the EPA and other agencies, risk managers, environmental advocates, scientists, faculty, students, and concerned individuals.

Abstract  The effects of trichloroethylene (79016) and 1,1,1-trichloroethane (71556) on plasma lipoproteins of rats were studied and related to the changes in liver and plasma transaminase activities. The effects were compared with effects of carbon-tetrachloride (56235). Male Fischer-344-rats were used in the study. The solvents were dissolved in 1 milliliter of olive-oil/kilogram of body weight and injected intraperitoneally at 19 hours before sacrifice. On the administration of carbon-tetrachloride at 30 to 1000mg/kg, very low density lipoproteins (VLDL) and high density lipoproteins (HDL) were dose dependently reduced, but the reduction in low density lipoproteins (LDL) was not dose dependent. Injection of trichloroethylene at 30 to 30mg/kg decreased the lipid contents of VLDL and LDL fractions. Trichloroethylene at 1000mg/kg increased VLDL and LDL. The HDL was decreased with increasing doses of trichloroethylene at 30 to 1000mg/kg. VLDL and LDL were increased by treatment with 100 or 300mg/kg 1,1,1-trichloroethane. HDL levels rose at 100 but fell at 1000mg/kg. Liver to body weight ratios were raised with increasing doses of the three compounds. Plasma GOT and GPT activities rose at much higher doses of solvents than dose levels which produce the changes in lipoproteins and the increases in liver weights.

Abstract  A physiologically based pharmacokinetic model which describes the behavior of inhaled styrene in rats accurately predicts the behavior of in baled styrene in humans. The model consists of a series of mass-balance differential equations which quantify the time course of styrene concentration within four tissue groups representing (1) highly perfused organs, (2) moderately perfused tissues such as muscle. (3) slowly perfused fat tissue, and (4) organs with high capacity to metabolize styrene (principally liver). The pulmonary compartment of the model incorporates uptake of styrene controlled by ventilation and perfusion rates and the blood:air partition coefficient The metabolizing tissue group incorporates saturable Michaelis-Menten metabolism controlled by the biochemical constants Vmax and Km. With a single set of physiological and biochemical constants, the model adequately simulates styrene concentrations in blood and fat of rats exposed to 80, 200, 600, or 1200 ppm styrene (data from previously published studies). The simulated behavior of styrene is particularly sensitive to changes in the constants describing the fat tissue group, and to the maximum metabolic rate described by Vmax, The constants used to simulate the fate of stvrene in rats were scaled up to represent humans. Simulated styrene concentrations in blood and exhaled air of humans are in good agreement with previously published data. Model simulations show that styrene metabolism is saturated at inhaled concentrations above approximately 200 ppm in mice, rats, and humans. At inhaled concentrations below 200 ppm, the ratio of styrene concentration in blood to inhaled air is controlled by perfusion limited metabolism. At inhaled concentrations above 200 ppm. This ratio is controlled by the blood:air partition coefficient and is not linearly related to the ratio attained at lower (nonsaturating) exposure concentrations. These results show that physiologically based pharmacokinetic models provide a rational basis with which (1) to explain the relationship between blood concentration and air concentration of an inhaled chemical, and (2) to extrapolate this relationship from experimental animals to humans.

Abstract  Simultaneous sampling of chlorinated hydrocarbons (CHs) and monocyclic aromatic hydrocarbons (MAHs), potentially harmful to humans and/or responsible for the formation of ozone and secondary particles, in dew water and in the ambient air was carried out from August 2004 to July 2005 in Hino City, situated in the western part of Greater Tokyo, Japan. CHs were less contained in dew water than MAHs. Toluene (volume-weighted mean concentration, VWM: 4.77 nM) and m,p-Xylenes (VWM: 5.07 nM) except dichloromethane, which was abnormally high (VWM: 1.14 μM), were abundant among eleven VOCs determined in dew water. Chloroform, carbon tetrachloride, 1,2-dichloroethane, and benzene were not detected in dew water during the study period. Dew water contained higher amounts of VOCs than would have been expected from the ambient gas-phase concentrations and the temperature-corrected Henry's law constants. Following the determination method of humic substances in river water proposed by Hiraide et al. [Hiraide, M., Shima, T., Kawaguchi, H., 1994. Separation and determination of dissolved and particulate humic substances in river water. Mikrochim. Acta 113, 269–276], the VWM of soluble humic and fulvic acid fractions in dew water was found to be 1.00 mg/L and 0.87 mg/L (n = 20), respectively, while the VWM of particulate humic and fulvic acid fractions was found to be 0.61 mg/L and 0.42 mg/L (n = 20), respectively. Surface tension decreased with an increase in dissolved fulvic acid fraction in dew water, indicating that humic-like substances with relatively lower molecular weight, which is soluble in acid solution, could be an effective surface-active species within dew water. The enrichment factors, which were defined as the ratio of the observed VOCs concentration to the estimated, were over 102 for MAHs except for benzene and increased as the increment of total humic-like substances (HULIS) concentration (the sum of humic and fulvic acid fractions in both dissolved and particulate form) normalized by total inorganic ion concentration in dew water. Our results indicate that total HULIS in dew water could enhance the dissolution of atmospheric VOCs into dew droplets.

Abstract  The neurobehavioral effects of 10 known toxicants were examined as part of a multidisciplinary screening battery. The toxicants included carbaryl (CAR), triadimefon (TDM), heptachlor (HEP), chlordane (CDN), diethylhexyl phthalate (DEHP), carbon tetrachloride (CCl4), phenol, trichloroethylene (TCE), tetrachloroethylene (PER or perchlorethylene), and dichloromethane (DCM or methylene chloride). A functional observational battery and motor activity measurements were conducted before exposure, at specified times after an acute exposure, and during and after 14-d exposure. Severity scoring analysis was used to generate profiles of effect. The pesticides, CAR, TDM, HEP, and CDN, displayed the most acute neurotoxicity and were active at lower proportions of their respective acute LD50 values than were the solvents or the industrial chemicals. Although CAR and TDM showed little or no neurobehavioral effects with repeated dosing, cumulative neurotoxicity and lethality were evident with HEP and CDN. Phenol produced acute convulsive effects, and the most prominent finding with repeated exposure was lethality. DEHP displayed no neurobehavioral toxicity. The organic solvents, TCE, PER, CCl4, and DCM, produced various degrees of general nervous system depression following acute administration of high dose levels. Repeated dosing produced little or no effect with TCE or PER, marked physiological changes with CCl4, and cumulative toxicity and lethality with DCM. Some results of these studies were unexpected and should provide impetus for further research. Overall, these findings illustrate the utility of these screening methods.

Abstract  There are many well documented similarities in the anatomy and physiology of mammalian species. There are also numerous examples in which the equilibrium distribution of foreign chemicals in the body appears to follow principles of thermodynamic partitioning with relatively minor interspecies variations to be expected. Information on metabolic pathways and their kinetic characteristics can be obtained from a variety of in vitro systems. It may be possible to use such information in pharmacokinetic models that incorporate existing knowledge and judgment to predict pharmacokinetics in intact animals including man.

Abstract  The effect of acetone (67641) on trichloroethylene (79016) and carbon-tetrachloride (56235) hepatotoxicity was studied in rats. Male Sprague-Dawley-rats were administered 0, 0.25, 0.75, or 1.5 milliliters per kilogram (ml/kg) acetone orally. Eighteen hours later they were injected intraperitoneally with 0 or 0.25ml/kg trichloroethylene or 0.1 or 0.6ml/kg carbon-tetrachloride alone or in combination. The rats were killed 24 hours later, the livers were removed, and assayed for hepatotoxicity by determining plasma alanine-aminotransferase (ALT) activity, total bilirubin, and by histological examination. Acetone alone or combined with trichloroethylene had no effect on ALT activity or total bilirubin. ALT activity was higher in rats treated with trichloroethylene plus either dose of carbon-tetrachloride than with carbon-tetrachloride alone. Bilirubin concentration was increased only by trichloroethylene plus 0.6ml/kg carbon-tetrachloride. Acetone enhanced carbon-tetrachloride liver injury to a greater extent than trichloroethylene. Acetone markedly potentiated liver injury induced by trichloroethylene plus carbon-tetrachloride in a dose/dependent manner. Histological analyses showed no statistical differences in the percentages of normal, degenerated, or necrotic hepatocytes between carbon-tetrachloride or trichloroethylene treated rats and controls. Trichloroethylene plus carbon-tetrachloride significantly reduced the percentage of normal hepatocytes and increased the percentage of degenerated or necrotic hepatocytes. Acetone pretreated rats given the carbon-tetrachloride plus trichloroethylene mixtures showed a significant dose related decrease in the percentage of normal hepatocytes and a dose related increase in the percentage of necrotic hepatocytes. The authors conclude that trichloroethylene can potentiate carbon-tetrachloride induced liver injury. Acetone exerts a potentiating effect on the hepatotoxic response of the carbon-tetrachloride plus trichloroethylene mixtures.

Abstract  We review the experimental evidence for various shapes of dose-response relationships for carcinogens and summarize those experiments that give the most information on relatively low doses. A brief review of some models is given to illustrate the shapes of dose-response curve expected from them. Our major interest is in the use of dose-response relationships to estimate risks to humans at low doses, and so we pay special attention to experimentally observed and theoretically expected nonlinearities. There are few experimental examples of nonlinear dose-response relations in humans, but this may simply be due to the limitations in the data. The several examples in rodents, even though for high dose data, suggest that nonlinearity is common. In some cases such nonlinearities may be rationalized on the basis of the pharmacokinetics of the test compound or its metabolites.

Abstract  The influences of amphiphiles, including humic acid (HA) and various types of surfactants, on dechlorination of carbon tetrachloride (CTC) and chloroform (CF) by the nano-scale Fe particles were investigated. Since the amphiphiles would modify the surface tension between the liquid-liquid and solid-liquid interface, in the presence of amphiphile matrix solution the Fe corrosion rate and the parent compound dechlorination rate would be different from those in the ultrapure water. Among the four amphiphile solutions, Fe corrosion rate was the highest in the anionic surfactant sodium dodecyl sulfate (SDS) solution, presumably due to the existence of chemisorption between the hydrophilic head of SDS and Fe particles. The dechlorination rates of CTC and CF could be described with the pseudo-first order kinetic model. The influences of amphiphiles on the dechlorination reaction rate were related to the species of parent compound and concentration of the matrix solution. The influences of HA on the dechlorination of CTC and CF were the most significant compared to other matrix solutions. At relatively low HA concentration (<0.1 g L(-1)), the HA molecules (serving as electron transfer mediator) would significantly accelerate the dechlorination rate of CF. The two-parameter regression with energy of the lowest unoccupied molecular orbital (E(LUMO)) and HA concentration as the descriptors was developed to predict the specific reduction rate constants of chlorinated methanes in HA solution. The analysis of variance (ANOVA) indicated the existence of significant relationship between the dechlorination rate constants and the two descriptors.