Concentrations Of Tetrachloroethylene Research Articles

Interaction between methanogenic and sulfate-reducing microorganisms during dechlorination of a high concentration of tetrachloroethylene.

A methanogenic and sulfate-reducing consortium, which was enriched on medium containing tetrachloroethylene (PCE), had the ability to dechlorinate high concentrations of PCE. Dehalogenation was due to the direct activity of methanogens. However, interactions between methanogenic and sulfate-reducing bacteria involved modification of the dechlorination process according to culture conditions. In the absence of sulfate, the relative percentage of electrons used in PCE dehalogenation increased after an addition of lactate in batch conditions. The sulfate reducers would produce further reductant from lactate catabolism. This reductant might be used by methanogenic bacteria in PCE dechlorination. A mutualistic interaction was observed in the absence of sulfate. However in the presence of sulfate, methanogenesis and dechlorination decreased because of interspecific competition, probably between the H(2)-oxydizing methanogenic and sulfate-reducing bacteria in batch conditions. In the semicontinuous fixed-bed reactor, the presence of sulfate did not affect dechlorination and methanogenesis. The sulfate-reducing bacteria may not be competitors of H(2)-consuming methanogens in the reactor because of the existence of microbial biofilm. The presence of the fixed film may be an advantage for bioremediation and industrial treatment of effluent charged in sulfate and PCE. This is the first report on the microbial ecology of a methanogenic and sulfate-reducing PCE-enrichment consortium.

Tetrachloroethylene Intoxication in an Autoerotic Fatality

This case report describes an accidental death due to the inhalation of tetrachloroethylene during an autoerotic episode. Tetrachloroethylene was administered from a can of Fix-A-Flat tire repair. Analysis of tetrachloroethylene was performed using headspace gas chromatography and electron capture detection. The blood tetrachloroethylene concentration of 62 mg/L was consistent with acute tetrachloroethylene intoxication.

Trichloroethylene, tetrachloroethylene, nitrates, and other chemicals in well water in the Fresno-Clovis Metropolitan Area.

In this study, the author examined the spatial and temporal distribution of tetrachloroethylene, trichloroethylene, nitrate, and several other organic and inorganic chemicals in large community wells in the Fresno-Clovis Metropolitan Area and estimated the lifetime cancer risk associated with exposure to tetrachloroethylene and trichloroethylene. By 1992-1993, investigators found the industrial solvent tetrachloroethylene in 34 wells and found trichloroethylene in 16 wells. All wells had detectable levels of nitrate. In addition, investigators found radon, arsenic, cadmium, iron, manganese, trihalomethanes, and several other volatile organic chemicals in the wells, but only radon and arsenic posed a significant health risk. In 1995, 16 wells were closed because chemicals were found in them. Twenty-six of 248 (10.5%) active wells and 24 of 43 (55.8%) closed wells contained multiple contaminants, excluding nitrate. Between 1988 and 1993, concentrations of trichloroethylene, tetrachloroethylene, and nitrates increased in selected wells. Daily, monthly, and bimonthly variations in the concentrations of tetrachloroethylene, trichloroethylene, and nitrate were often considerable. Granulated activated carbon filtration reduced trichloroethylene levels in well water by 91%-95%, and the author examined its usefulness as a remedial measure. Estimated lifetime cancer risks for tetrachloroethylene and trichloroethylene were 1 excess cancer death per 9.5 million people and 1 excess death per 250 million, respectively. The author also included recommendations for the conduct of further epidemiological and environmental studies.

Characterization of an anaerobic soil enrichment capable of dechlorinating high concentrations of tetrachloroethylene

An anaerobic soil enrichment culture could dechlorinate high concentrations of tetrachloroethylene (PCE; 150 mg/liter nominal concentration; approximately 58 mg/liter in aqueous concentration) nearly stoichiometrically to cis-1,2-dichloroethylene (cis-DCE) via trichloroethylene (TCE) at high rates; a maximum dechlorination rate was 0.4 μmol of PCE transformed/mg volatile suspended solids per hr, using citrate as an electron and carbon source and yeast extract as a nutritional requirement. This dechlorinating activity was comparable with those of the previously-reported, efficient bacterial cultures. Some substrates such as pyruvate, succinate, formate, acetate, and acetate with H2 could replace citrate but propionate could not, and yeast extract could be replaced by a vitamin mixture. However the PCE dechlorination rate decreased more than threefold by the addition of the vitamin mixture, suggesting that the vitamin mixture could not be a complete supplement for the nutritional requirement. Optimal pH and temperature of the enrichment for PCE dechlorination were 7 and 30 °C, respectively. Dechlorination of PCE was completely inhibited by the addition of NO3− and NO2− as potential alternative electron acceptors. S2O3−2 and SO3−2 delayed PCE dechlorination but SO4−2 had no significant effect on PCE reduction. 2-bromoethanesulfonic acid (BES, an inhibitor of methanogenesis) also showed no influence on PCE dechlorination, suggesting methanogens were not concerned with PCE removal in this enrichment. Further, microbial investigations on the enrichment showed that it contains four types of bacteria; cocci, large rods, curved rods, and small rods. The small rods seemed to nutritionally support the PCE dechlorinating bacteria, presumably the curved rods.

Characterization of an anaerobic soil enrichment capable of dechlorinating high concentrations of tetrachloroethylene

An anaerobic soil enrichment culture could dechlorinate high concentrations of tetrachloroethylene (PCE ; 150 mg/liter nominal concentration; approximately 58 mg/liter in aqueous concentration) nearly stoichiometrically to cis-1,2-dichloroethylene (cis-DCE) via trichloroethylene (TCE) at high rates; a maximum dechlorination rate was 0.4 /μmol of PCE transformed/mg volatile suspended solids per hr, using citrate as an electron and carbon source and yeast extract as a nutritional requirement. This dechlorinating activity was comparable with those of the previously-reported, efficient bacterial cultures. Some substrates such as pyruvate, succinate, formate, acetate, and acetate with H2 could replace citrate but propionate could not, and yeast extract could be replaced by a vitamin mixture. However the PCE dechlorination rate decreased more than threefold by the addition of the vitamin mixture, suggesting that the vitamin mixture could not be a complete supplement for the nutritional requirement. Optimal pH and temperature of the enrichment for PCE dechlorination were 7 and 30 °C, respectively. Dechlorination of PCE was completely inhibited by the addition of N03− and N02− as potential alternative electron acceptors. S203−2 and SO3−2 delayed PCE dechlorination but SO4−2 had no significant effect on PCE reduction. 2-bromoethanesulfonic acid (BES, an inhibitor of methanogenesis) also showed no influence on PCE dechlorination, suggesting methanogens were not concerned with PCE removal in this enrichment. Further, microbial investigations on the enrichment showed that it contains four types of bacteria; cocci, large rods, curved rods, and small rods. The small rods seemed to nutritionally support the PCE dechlorinating bacteria, presumably the curved rods.

Determination of bioconcentration potential of tetrachloroethylene in marine algae by 13C

The use of stable isotope of organic-carbon, organic- 13C, as a tracer for the determination of the concentration of tetrachloroethylene (PCE), C A, in Heterosigma akashiwo and Skeletonema costatum was examined. C A determined by the 13C and GC methods showed good agreement with each other. This suggests that it is reasonable and reliable to determine the bioconcentration potentail of PCE in marine algae. Fitting values of bioconcentration potentail parameters, including uptake rate constant k 1, elimination rate constant k 2 and bioconcentration factor on the basis of dry weight BCF D, were done not only to the time course for PCE uptake by the algae with the bioconcentration model, but also to experimental data for “percent inhibition(%)∼exposure concentration of PCE∼time” with the combined bioconcentration and probability model. The values obtained from the bioconcentration model were consistent with those from the combined bioconcentration and probability model. With the parameters (such as k 1, k 2, growth rate constant k G, critical concentration of HOCs in the organism resulting in growth inhibition C A ∗ and spread factor S) the variability in toxicity (such as EC 10, EC 50, EC 70) can be estimated from the combined bioconcentration and probability model, which fits well with the experimental observations.

Assessment of urban population exposure to trichloroethylene and tetrachloroethylene by means of biological monitoring.

Exposure of the general population to trichloroethylene and tetrachloroethylene under normal environmental conditions, achieved with biological monitoring, was assessed, and the possible influence of these compounds via drinking water on the body burden was revealed. A total of 79 subjects with no known solvent exposure was selected, by stratified sampling, from the residents of the city of Zagreb. Trichloroethylene and tetrachloroethylene were determined in blood, and trichloroethanol and trichloroacetic acid were determined in plasma and urine. Drinking water samples were also analyzed for trichloroethylene and tetrachloroethylene. Concentrations of trichloroethylene and tetrachloroethylene in blood, trichloroacetic acid in plasma, trichloroacetic acid in urine, trichloroethylene in drinking water, and tetrachloroethylene in drinking water were as follows: < 0.015 to 0.090 micrograms/l, < 0.010 to 0.239 micrograms/l, 8.6 to 148.1 micrograms/l, 1.67 to 102.3 micrograms/24 h, < 0.05 to 22.93 micrograms/l, and 0.21 to 7.80 micrograms/l, respectively. The variation in all results presented is probably a reflection of different environmental contamination with trichloroethylene and tetrachloroethylene in the different city areas. Correlation analyses revealed significant relationships between trichloroethylene and tetrachloroethylene in blood (r = .402, p = .0004); trichloroacetic acid in urine and in plasma (r = .522, p = .0000); and trichloroethylene and tetrachloroethylene in drinking water (r = .800, p = .0000). A division of all parameters into a subgroup (n = 58), taking drinking water concentrations of trichloroethylene above 3 micrograms/l as a basis, demonstrated the same significant relationships as mentioned above.(ABSTRACT TRUNCATED AT 250 WORDS)

Lactational Transfer of Tetrachloroethylene in Rats

Tetrachloroethylene (PCE) is a commonly used organic solvent and a suspected human carcinogen, reportedly transferred to human breast milk following inhalation exposure. Transfer of PCE to milk may represent a threat to the nursing infant. A physiologically based pharmacokinetic (PBPK) model was developed to quantitatively assess the transfer of inhaled PCE into breast milk and the consequent exposure of the nursing infant. The model was validated in lactating rats. Lactating Sprague-Dawley female rats were exposed via inhalation to PCE at concentrations ranging from 20-1000 ppm, and then returned to their nursing, 10- to 11-day-old pups. Tetrachloroethylene concentrations in the air, blood, milk, and tissue were determined by gas chromatography and compared to model predictions. The model described the distribution of inhaled PCE in maternal blood and milk, as well as the nursed pup's gastrointestinal tract, blood, and tissue. Several computer simulations of PCE distribution kinetics in exhaled air, blood, and milk of exposed human subjects were run and compared with limited human data available from the literature. It is concluded that the PBPK model successfully described the concentration of PCE in both lactating rats and humans. Although predictions vs. observations were good, the model slightly underpredicted the peak whole pup PCE concentration and underpredicted systemic clearance of PCE from the pup.

Evaluating the Adequacy of Maximum Contaminant Levels as Health-Protective Cleanup Goals: An Analysis Based on Monte Carlo Techniques

At many sites in the United States, health-based remediation goals for contaminated groundwater have been set at levels far below USEPA′s drinking water standards (i.e., maximum contaminant levels or MCLs). This is due to the fact that, while the USEPA must often consider technical and economic factors (e.g.. cost of compliance, risk/benefit analysis) when setting MCLs for public water systems, cleanup goals for contaminated groundwater are often based solely on conservative "point" estimates of exposure. One of the more recent refinements in the risk assessment process is the use of ranges of exposure estimates or "probability density functions" (PDFs), rather than fixed point estimates, to estimate exposure and chemical uptake. This approach provides a more thorough description of the range of potential risks, rather than a single "worst-case" value, and allows one to understand the conservatism inherent in assessments based on regulatory default parameters. This paper uses a number of PDFs and the Monte Carlo technique to assess whether the USEPA′s MCLs for drinking water are sufficiently low to protect persons exposed to these levels. A case study involving daily exposure to tapwater containing MCL concentrations of tetrachloroethylene, chloroform, bromoform, and vinyl chloride is presented. Several direct and indirect exposure pathways are evaluated, including inhalation and dermal contact while showering, direct ingestion, and inhalation of emissions from household fixtures and appliances. PDFs for each exposure factor are based on the most recent and applicable data available. Our analysis indicates that the estimated increased cancer risks at the 50th and 95th percentile of exposure are within the range of increased cancer risks typically considered acceptable at Superfund sites ( 10 −4-10 −6), These results suggest that, at least for some chemicals, groundwater need not be cleanedup to concentrations less than drinking water standards (i.e., MCLs) to protect human health.

Hematological toxicity of tetrachloroethylene in mice.

Female C57/BL/6 x DBA/2 hybrid mice were exposed to two concentrations (270 and 135 ppm) of tetrachloroethylene (PER) in inhalation chambers for 6 h/day, 5 days per week, up to 11.5 weeks (270 ppm) and 7.5 weeks (135 ppm), respectively, followed by a 3-week exposure-free period. In the peripheral blood a reduction of lymphocytes/monocytes and of neutrophils was observed with an almost complete regeneration in the exposure-free period. A reticulocytosis during and also after the exposure indicated a compensatory reaction in the erythroid cell system. Bone marrow pluripotent stem cells (CFU-S) were not affected up to 7.5 weeks. Erythroid committed cells (BFU-E and CFU-E) did react, with a reduction of CFU-E numbers at 7.5 and 11.5 weeks. A slight reduction of CFU-C numbers at 7.5 weeks indicated, in accordance with the peripheral blood data, a disturbance of the granulocytic cell series as well.

土壌ガスモニタリングを用いた揮発性有機塩素化合物による地下水汚染調査

Soil gas was collected and analyzed for tetrachloroethylene to examine the possibility of soil gas monitoring as a tool for identifying pollutant source and delineating plume boundary of pollution in specified groundwater. Field surveys in a shallow groundwater region show that tetrachloroethylene concentration in soil gas detected around pollutant source seems to be affected by gaseous diffusion from highly contaminated soil. With distance away from pollutant source, it is becoming in a possitive relationship to the tetrachloroethylene concentration in shallow groundwater. In particular, soil gas monitoring is recognized to be an effective technique for identifying pollutant source, as tetrachloroethylene concentration contours displayed around pollutant source are extending like concentric circles.

Adsorption of chlorinated organic compounds on activated carbon from water

The adsorption capacities and rates of seven principal chlorinated organic compounds for six commercial GACs were investigated. All the adsorption isotherms were expressed by the Freundlich equation, and the isotherms for the chloroethylenes such as trans - 1,2-dichloroethylene, trichloroethylene and tetrachloroethylene could be shown by the modified Freundlich equation Q′ = k′ ( C/ C s ) l/ n for each GAC. The magnitude of adsorption of the chlorinated organic compounds was in the order of: tetrachloroethylene > trichloroethylene > trans - 1,2-dichloroethylene > 1,1-dichloroethane > carbontetrachloride > 1.1,1-trichloroethane > chloroform. The value of k for a certain GAC could be predicted from the quantity of pores smaller than 2 nm in diameter. The adsorbed amounts were decreased by 10–20% when humic substances coexisted. The working periods of a fixed bed adsorber before regeneration were predicted by calculating breakthrough curves for various influent concentrations of trichloroethylene and tetrachloroethylene at the space velocities of 5 or 10 h −1, and it was certified that the adsorption method by GAC was feasible for removing these compounds from water.

Mapping Zones of Contaminated Ground‐Water Discharge Using Creek‐Bottom‐Sediment Vapor Samplers, Aberdeen Proving Ground, Maryland

AbstractForty passive vapor samplers were placed in creek‐bottom sediment in an area where ground water contaminated with volatile organic compounds is discharging to surface water. The vapor samplers were composed of activated carbon fused to a ferromagnetic wire in a test tube. The samplers were analyzed in a laboratory using an extranuclear quadrupole mass spectrometer. Data from the samplers reveal distributions of chloroform, tetrachloroethylene, trichloroethylene, and benzene in the bottom sediment that closely correspond to the distribution of those compounds in the adjacent ground water. Moreover, concentrations of tetrachloroethylene in bottom sediment estimated from the samplers are similar to those measured in observation wells near the shoreline. Thus, the passive vapor samplers may be used to locate and map areas where contaminated ground water is being discharged to surface water and to determine the approximate concentrations of specific contaminants in the discharging ground water.

Uptake by foods of tetrachloroethylene, trichloroethylene, toluene, and benzene from air

Transition rates from air into food as well as equilibrium concentrations in air and critical foods were determined for tetrachloroethylene, trichloroethylene, benzene and toluene. From these data, maximum concentrations of the four substances in air were estimated that keep contamination of critical foods at an acceptable level. A simple and rapid method allowed us to determine the risk of food contamination from the air, e.g. in shops and kitchens, by the analysis of the air. Estimations showed that concentrations in the air of shops should not exceed 1 mg/m3 if tetrachloroethylene concentrations in foods are limited to 100 micrograms/kg (slightly higher concentrations can be accepted for the other three compounds); in kitchens of restaurants and households, even 0.3 mg/m3 cause the target concentration to be exceeded rather frequently If the limit in foods is 50 micrograms/kg, recommended maximum concentrations in air are 0.5 and 0.15 mg/m3. The data also shows that the recommended limits for concentrations in air conflict with the accepted emission limits: If emission at the accepted limit occurs near shops or households, contamination of foods far exceed that considered as tolerable.

Residual tetrachloroethylene in dry-cleaned clothes

A large amount of residual tetrachloroethylene (TCE), up to 13.6 mg/g, was found in dry-cleaned clothes. The amounts varied among dry-cleaning establishments as well as with the type of fiber. The causes of these variations are discussed. Air TCE concentrations in the closed environment of dry-cleaning outlets were elevated: the highest reading was 4.8 mg/m3. The expired air of outlet employees also showed an increased level of TCE (average, 36.9 micrograms/m3). Increased air contamination from TCE released from dry-cleaned clothes was also observed in the home of a consumer. To reduce environmental contamination from TCE released from any of these sources, the amount of residual TCE in dry-cleaned clothes should be minimized.

Statistical approach towards point sources of groundwater pollution with tetrachloroethylene: a field study.

Tetrachloroethylene contamination of well water occurred in a primarily residential area. To search for point source(s) of tetrachloroethylene contamination, 91 water samples were collected on three separate occasions from 41 shallow wells scattered in the areas. Three methods of groundwater level analysis (limited to 30 wells), cluster analysis of water quality indicators and contour drawing of tetrachloroethylene concentrations were applied. The former two analyses showed that the pollution took place in aquifers of two terraces out of the three in the polluted area. The contour mapping demonstrated the presence of three spots of suspected pollution sources as the estimated points of highest tetrachloroethylene concentrations. The available information suggested the existence of a facility with possible use of tetrachloroethylene in the past.

Chlorinated organic compounds in urban air in Japan

Air pollution by the principal chlorinated organic compounds chloroform, carbon tetrachloride, 1,1,1-trichloroethane, trichloroethylene and tetrachloroethylene was investigated over a period of ∼ 1 year at 15 sites in an urban area. Each compound was detected in the range from ∼ 0.1 to several ppb; the concentrations of these compounds, with the exception of carbon tetrachloride, were higher than their global pollution levels. The concentrations of 1,1,1-trichloroethane and trichloroethylene especially were very high in the industrial regions, and the concentration of tetrachloroethylene was very high in the industrial and commercial regions. Concentrations were low in spring and summer and high in fall, winter and the rainy season. The correlation between the reciprocal of wind speed and concentrations was found to be subject to seasonal variations. Intake of chlorinated organic compounds by man from the air was estimated from the data to be larger than the allowable intakes determined by WHO and EPA for drinking water.

Urinary excretion of tetrachloroethylene (perchloroethylene) in experimental and occupational exposure.

Fifteen human volunteers were exposed to tetrachloroethylene (perchloroethylene, tetrachloroethene) vapor at 3.6-316 mg/m3 for 2-4 hr at rest (10 cases) and during light physical exercise (5 cases). Subsequently, 55 workers who were occupationally exposed to tetrachloroethylene in eight commercial dry cleaning facilities were studied (median value, 66 mg/m3; geometric standard deviation, 3.15 mg/m3). In both the experimentally exposed subjects and occupationally exposed workers the urinary concentration of tetrachloroethylene showed a linear relationship to the corresponding environmental time-weighted average concentration. The findings indicate that the urinary concentration of tetrachloroethylene can be used as an appropriate biological exposure indicator. In occupationally exposed subjects performing moderate work, the urinary tetrachloroethylene concentration corresponding to the time-weighted average of the threshold limit value proved to be 120 mcg/L and its 95% lower confidence limit (biological threshold) 100 mcg/L. The effects of workload on the tetrachloroethylene urinary elimination are also accounted for.

A cryogenic trap/porous polymer sampling technique for the quantitative determination of ambient volatile organic compound concentrations

A technique is described for concentrating atmospheric volatile organic compounds (VOCs) to permit their quantitative determination. The technique relies on cryogenic trapping followed by volatilization of the sample components and subsequent transfer to a Tenax tube cartridge assembly. This technique was evaluated using standard samples and by sampling and analysis for selected hydrocarbons (chloroethane, chlorobenzene, tetrachloroethylene, benzene and toluene) in Philadelphia, PA, and San Jose, CA. The results are compared with those obtained using a cryogenic concentration technique with on-site chromatographic analysis. On the average, these two techniques agreed to ± 40%, for benzene, toluene and tetrachloroethylene concentrations ranging from ~ 1–30 ppb (for similar sampling times). The technique for this data set is shown to have a detection limit of ~ 10–20 ppt (using GC/MS analysis), an estimated accuracy and precision of ± 20% and 15%, respectively, and is shown to circumvent many of the disadvantages associated with using cryogenic or porous polymer concentration techniques alone. The technique should be applicable to determinations of VOCs having a wide range of volatilities.

Sound Speeds and Isentropic Compressibility's of Tetrachloroethylene With N-Alcohols Comparison With Theories

Abstract Sound velocities for binary mixtures of tetrachloroethylene with 1-propanol, 1-butanol. 1-pentanol, 1-hexanol, 1-heptanol, and 1-octanol were determined at 303.15 K. The results were analysed in terms of the free length theory (FLT) due to Jacobson and Collision factor theory (CFT) due to Schaaffs. The analyses showed that both theories predict satisfactorily sound velocities of the mixtures. Further, isentropic compressibility's, ks . of the mixtures were computed by combining sound velocities and density data derived from excess volumes. The deviation in isentropic compressibility, As, is negative over the whole range of composition for all the mixtures formed by tetrachloroethylene with alcohols. An inversion in the sign of Ks is observed certain ranges of concentration of tetrachloroethylene with 1-octanol. The deviation in isentropic compressibility was found to decrease with increase in chain length of the alcohol.