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There is a need to study the spatiotemporal distribution of chlorinated solvent releases in groundwater to understand the risk/threat they pose to human health, water quality, and the environment, which then can be used to prioritize clean-up and evaluate regulatory closure with appropriate risk management controls. This paper provides a statistical analysis of spatiotemporal distribution of perchloroethylene (PCE) (and its degradation products including trichloroethene [TCE]) from eighty-three cases across California for which data were available onthe State Water Resources Control Board's GeoTracker database and the Department of Toxic Substance Control Board's Envirostor database. These cases consisted of seventy-one dry cleaning sites and twelve other similar small solvent release sites. Statistical analyses of available groundwater data were performed to estimate: maximum concentrations at the source area, groundwater plume length, plume stability; and correlations between plume length, concentrations, and plume age. At 90% of the sites, the PCE and TCE plume lengths were less than 1,569 feet (478 meters) and 1,782 feet (543 meters), respectively. The average plume lengths for PCE and TCE were 670 feet (204 meters) and 701 feet (213 meters), respectively. At 90% of the sites that have reached stable conditions, PCE and TCE concentrations at the source areas were less than 2,670 and 660 micrograms per liter (µg/L) respectively. This study for the first time provides key characteristics of small chlorinated-solvent plume behaviors in California that can be used to prioritize management of small chlorinated-solvent release sites and to develop strategies towards achieving closure at these sites. [ABSTRACT FROM AUTHOR]

Abstract Background Advanced understanding of tumor biology has recently revealed the complexity of cancer genetics, intra/inter-tumor heterogeneity, and diverse mechanisms of resistance to cancer treatment. In turn, there has been a growing interest in cancer prevention and minimizing exposure to potential environmental carcinogens that surround us. In the 1980s, several chemical carcinogens, including perchloroethylene (PCE), trichloroethylene (TCE), and benzene, were detected in water systems supplying Camp Lejeune, a US Marine Corps Base Camp located in North Carolina. Case presentation This article presents three cases of cancer patients who have lived at Camp Lejeune, and, decades later, came to our clinic located 1000 miles from the original exposure site. The first patient is a young Caucasian man who was diagnosed with T cell acute lymphoblastic leukemia at the age of 37, and the second patient is a Caucasian man who had multiple types of cancer in the prostate, lung, and colon as well as chronic lymphocytic leukemia in his 60s and 70s. The third patient is another Caucasian man who had recurrent skin cancers of different histology, namely basal cell carcinomas, squamous cell carcinomas, and melanoma, from his 50s to 70s. Conclusions The US Congress passed the Honoring America’s Veterans and Caring for Camp Lejeune Families Act in 2012, which covers appropriate medical care for the people affected by the contamination. We hope that this article raises awareness about the history of Camp Lejeune’s water contamination among cancer care providers, so the affected patients can receive appropriate medical coverage and cancer screening across the country.

Background: Advanced understanding of tumor biology has recently revealed the complexity of cancer genetics, intra/inter-tumor heterogeneity, and diverse mechanisms of resistance to cancer treatment. In turn, there has been a growing interest in cancer prevention and minimizing exposure to potential environmental carcinogens that surround us. In the 1980s, several chemical carcinogens, including perchloroethylene (PCE), trichloroethylene (TCE), and benzene, were detected in water systems supplying Camp Lejeune, a US Marine Corps Base Camp located in North Carolina.Case Presentation: This article presents three cases of cancer patients who have lived at Camp Lejeune, and, decades later, came to our clinic located 1000 miles from the original exposure site. The first patient is a young Caucasian man who was diagnosed with T cell acute lymphoblastic leukemia at the age of 37, and the second patient is a Caucasian man who had multiple types of cancer in the prostate, lung, and colon as well as chronic lymphocytic leukemia in his 60s and 70s. The third patient is another Caucasian man who had recurrent skin cancers of different histology, namely basal cell carcinomas, squamous cell carcinomas, and melanoma, from his 50s to 70s.Conclusions: The US Congress passed the Honoring America's Veterans and Caring for Camp Lejeune Families Act in 2012, which covers appropriate medical care for the people affected by the contamination. We hope that this article raises awareness about the history of Camp Lejeune's water contamination among cancer care providers, so the affected patients can receive appropriate medical coverage and cancer screening across the country. [ABSTRACT FROM AUTHOR]

Bacteria often employ different respiratory chains that comprise membrane proteins equipped with various cofactors. Monitoring the protein inventory that is present in the cells under a given cultivation condition is often difficult and time‐consuming. One example of a metabolically versatile bacterium is the microaerophilic organohalide‐respiring Sulfurospirillum multivorans. Here, we used surface enhanced Raman spectroscopy (SERS) to quickly identify the cofactors involved in the respiration of S. multivorans. We cultured the organism with either tetrachloroethene (perchloroethylene, PCE), fumarate, nitrate, or oxygen as electron acceptors. Because the corresponding terminal reductases of the four different respiratory chains harbor different cofactors, specific fingerprint signals in SERS were expected. Silver nanostructures fabricated by means of electron beam lithography were coated with the membrane fractions extracted from the four S. multivorans cultivations, and SERS spectra were recorded. In the case of S. multivorans cultivated with PCE, the recorded SERS spectra were dominated by Raman peaks specific for Vitamin B12. This is attributed to the high abundance of the PCE reductive dehalogenase (PceA), the key enzyme in PCE respiration. After cultivation with oxygen, fumarate, or nitrate, no Raman spectral features of B12 were found. [ABSTRACT FROM AUTHOR]

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Microcosm experiments with CE-contaminated groundwater from a former industrial site were set-up to evaluate the relationships between biological CE dissipation, dehalogenase genes abundance and bacterial genera diversity. Impact of high concentrations of PCE on organohalide respiration was also evaluated. Complete or partial dechlorination of PCE, TCE, cis-DCE and VC was observed independently of the addition of a reducing agent (Na2S) or an electron donor (acetate). The addition of either 10 or 100 μM PCE had no effect on organohalide respiration. qPCR analysis of reductive dehalogenases genes (pceA, tceA, vcrA, and bvcA) indicated that the version of pceA gene found in the genus Dehalococcoides [hereafter named pceA(Dhc)] and vcrA gene increased in abundance by one order of magnitude during the first 10 days of incubation. The version of the pceA gene found, among others, in the genus Dehalobacter, Sulfurospirillum, Desulfuromonas, and Geobacter [hereafter named pceA(Dhb)] and bvcA gene showed very low abundance. The tceA gene was not detected throughout the experiment. The proportion of pceA(Dhc) or vcrA genes relative to the universal 16S ribosomal RNA (16S rRNA) gene increased by up to 6-fold upon completion of cis-DCE dissipation. Sequencing of 16S rRNA amplicons indicated that the abundance of Operational Taxonomic Units (OTUs) affiliated to dehalogenating genera Dehalococcoides, Sulfurospirillum, and Geobacter represented more than 20% sequence abundance in the microcosms. Among organohalide respiration associated genera, only abundance of Dehalococcoides spp. increased up to fourfold upon complete dissipation of PCE and cis-DCE, suggesting a major implication of Dehalococcoides in CEs organohalide respiration. The relative abundance of pceA and vcrA genes correlated with the occurrence of Dehalococcoides and with dissipation extent of PCE, cis-DCE and CV. A new type of dehalogenating Dehalococcoides sp. phylotype affiliated to the Pinellas group, and suggested to contain both pceA(Dhc) and vcrA genes, may be involved in organohalide respiration of CEs in groundwater of the study site. Overall, the results demonstrate in situ dechlorination potential of CE in the plume, and suggest that taxonomic and functional biomarkers in laboratory microcosms of contaminated groundwater following pollutant exposure can help predict bioremediation potential at contaminated industrial sites.

Objective: To establish a method for determination of Perchloroethylene (PCE) in blood by headspace gas chromatography-mass spectrometry (HS/GC-MS) . Methods: From Dctober to December 2021, A total of 3 mL blood samples were taken into a 10 mL headspace bottle, after heated at 60 ℃ for 30 mins, PCE in the top air was separated by VF-WAXms capillary column and detected by GC-MS. The retention time and external standard method were used for qualitative and quantitative analysis of PCE in samples, respectively. Results: There was good linear relationship in the range of 5.09-200.17 μg/L. The linear correlation coefficient was 0.9993.The detection limit was 0.21 μg/L and the lower limit of quantitation was 0.70 μg/L. The recovery rates of samples with different concentrations were 95.3%-103.8%. The intra-batch relative standard deviations ( RSD ) were 3.2%-4.6%, and inter-batch RSD was 4.0%-6.1%. The samples can be stored at 4 ℃ for three days and at -20 ℃ for seven days. Conclusion: This method is proved to be simple, practical and highly sensitive, which is suitable for the determination of PCE in blood.

Background and objectives: Perchloroethylene (PCE) is categorized as contaminant of concern because of its adverse health effects and persistence in drinking water resources. Permeable reactive barrier with zero valent iron (ZVI-PRB) is a passive zone in which chlorinated ethenes are degraded in situ through the chemical reduction mechanism. The objective of the present investigation was optimization and modelling of ZVI-PRB technology for the elimination of PCE from the aqueous environment using response surface methodology. Materials and methods: In order to simulate ZVI-PRB, a column filled with silica sand and ZVI was used. effects of three variables including pH, column height or barrier thickness and flow on reductive dechlorination efficiency were assessed. Design of experiment, modelling, and data analysis were carried out using response surface method. Results: The dechlorination efficiency was about 93% under optimum conditions (pH=5, 26 cm column height and 2 mL/min flow rate). The ascending trend of pH along the column revealed that the reductive condition was dominant within the column. The R2 value of 0.98 also indicated good fitness of the experimental results and model predictions. Conclusion: Based on the results, ZVI-PRB technology has high efficiency in dechlorination of PCE. Likewise, regarding to no need of energy consumption, abundance of iron, no production of harmful by-products and cost-effectiveness, ZVI-PRB is propounded as a stable, green, and environmental friendly technology in groundwater remediation.

Microcosm experiments with CE-contaminated groundwater from a former industrial site were set-up to evaluate the relationships between biological CE dissipation, dehalogenase genes abundance and bacterial genera diversity. Impact of high concentrations of PCE on organohalide respiration was also evaluated. Complete or partial dechlorination of PCE, TCE, cis -DCE and VC was observed independently of the addition of a reducing agent (Na2S) or an electron donor (acetate). The addition of either 10 or 100 μM PCE had no effect on organohalide respiration. qPCR analysis of reductive dehalogenases genes (pceA, tceA, vcrA , and bvcA) indicated that the version of pceA gene found in the genus Dehalococcoides [hereafter named pceA (Dhc)] and vcrA gene increased in abundance by one order of magnitude during the first 10 days of incubation. The version of the pceA gene found, among others, in the genus Dehalobacter, Sulfurospirillum, Desulfuromonas , and Geobacter [hereafter named pceA (Dhb)] and bvcA gene showed very low abundance. The tceA gene was not detected throughout the experiment. The proportion of pceA (Dhc) or vcrA genes relative to the universal 16S ribosomal RNA (16S rRNA) gene increased by up to 6-fold upon completion of cis- DCE dissipation. Sequencing of 16S rRNA amplicons indicated that the abundance of Operational Taxonomic Units (OTUs) affiliated to dehalogenating genera Dehalococcoides, Sulfurospirillum , and Geobacter represented more than 20% sequence abundance in the microcosms. Among organohalide respiration associated genera, only abundance of Dehalococcoides spp. increased up to fourfold upon complete dissipation of PCE and cis -DCE, suggesting a major implication of Dehalococcoides in CEs organohalide respiration. The relative abundance of pceA and vcrA genes correlated with the occurrence of Dehalococcoides and with dissipation extent of PCE, cis -DCE and CV. A new type of dehalogenating Dehalococcoides sp. phylotype affiliated to the Pinellas group, and suggested to contain both pceA (Dhc) and vcrA genes, may be involved in organohalide respiration of CEs in groundwater of the study site. Overall, the results demonstrate in situ dechlorination potential of CE in the plume, and suggest that taxonomic and functional biomarkers in laboratory microcosms of contaminated groundwater following pollutant exposure can help predict bioremediation potential at contaminated industrial sites. [ABSTRACT FROM AUTHOR]

The objectives of this work were first to evaluate the effect of coupling a zero-valent side filter to anaerobic fluidized bed bioreactors (HFBB) versus bioreactors without the zero-valent filter, also called methanogenic fluidized bed bioreactors (MFBB); and second to study the diversity of the microbial community in both types of bioreactors. At the end of operation (in the last 75 d), the HFBB reached a 95% removal of the incoming tetrachloroethylene, whereas the MFBBs without filter achieved a removal of 88%. Genera such as Dehalobacter spp., Desulfurospirillum spp., Desulfitobacterium spp., and Dehalococcoides spp., and Methanosarcina were found at the end of the treatment. Coupling zero-valent filters to bioreactors (HFBB) fed with high tetrachloroethylene concentration improved reactor performance [high tetrachloroethylene removal and reduction of concentrations of vinyl chloride (VC) and dichlorethylene (DCE)]. This performance was consistent with significant higher concentrations of dehalogenating bacteria found in the HFBB. [ABSTRACT FROM AUTHOR]

The performance of chelated Fe(II)-based catalyzed sodium percarbonate (SPC) stimulating the degradation of perchloroethylene (PCE) in aqueous solution was investigated using six different chelating agents (CA), namely, citric acid monohydrate (CIT), oxalic acid (OA), l -ascorbic acid (ASC), ethylenediaminetetraacetic acid (EDTA), trisodium citrate 2-hydrate (CIT-Na 3 ), and EDTA-Na 2 , at CA/Fe(II)/SPC/PCE molar ratios of 2/4/4/1, 4/4/4/1 and 8/4/4/1. The results indicated that the addition of CIT and OA significantly enhanced the PCE degradation. In addition, investigations using free radical probe compounds and radical scavengers revealed that PCE was primarily degraded by HO radical oxidation in Fe(II)/SPC, CIT/Fe(II)/SPC, and OA/Fe(II)/SPC systems and O 2 − also participated in the degradation of PCE in CIT/Fe(II)/SPC and OA/Fe(II)/SPC systems. The intensity of HO detected by electron paramagnetic resonance (EPR) in CIT/Fe(II)/SPC and OA/Fe(II)/SPC systems indicated that the addition of CIT or OA indeed enhanced the continuous production of HO and enabled the intensity of HO to be more stable. The results demonstrated that CIT and OA significantly improved the PCE degradation efficiency by increasing the concentration of Fe(II) and maintaining the concentration of HO radicals in solution. In conclusion, chelated Fe(II)-based catalyzed SPC oxidation process shows enormous practical prospects for the remediation of PCE-contaminated groundwater because of the effectiveness without pre-adjusting the solution pH and complete mineralization in Fe(II)/SPC, CIT/Fe(II)/SPC and OA/Fe(II)/SPC systems. [ABSTRACT FROM AUTHOR]

The performance of Fe 2+ -catalyzed sodium percarbonate (SPC) stimulating the oxidation of perchloroethylene (PCE) in groundwater remediation was investigated. The experimental results showed that PCE could be completely oxidized in 5 min at 20 °C with a Fe 2+ /SPC/PCE molar ratio of 8/8/1, indicating the effectiveness of Fe 2+ -catalyzed SPC oxidation for PCE degradation. Fe 2+ -catalyzed SPC oxidation was suitable for the nearly neutral pH condition, which was superior to the conventional Fenton oxidation in acidic condition. In addition, the investigations by using hydroxyl radical scavengers and free radical probe compounds elucidated that PCE was degraded mainly by hydroxyl radical (HO ) oxidation in Fe 2+ /SPC system. In conclusion, Fe 2+ -catalyzed SPC oxidation is a highly promising technique for PCE-contaminated groundwater remediation, but more complex constituents in groundwater should be carefully considered for its practical application. [ABSTRACT FROM AUTHOR]

Abstract: In order to characterize the effect of vegetation on performance of constructed wetlands (CWs) treating low and high chlorinated hydrocarbon, two pilot-scale horizontal subsurface flow (HSSF) CWs (planted with Phragmites australis and unplanted) treating sulphate rich groundwater contaminated with MCB (monochlorobenzene, as a low chlorinated hydrocarbon), (about 10mgL−1), and PCE (perchloroethylene, as a high chlorinated hydrocarbon), (about 2mgL−1), were examined. With mean MCB inflow load of 299mgm−2 d−1, the removal rate was 58 and 208mgm−2 d−1 in the unplanted and planted wetland, respectively, after 4m from the inlet. PCE was almost completely removed in both wetlands with mean inflow load of 49mgm−2 d−1. However, toxic metabolites cis-1,2-DCE (dichloroethene) and VC (vinyl chloride) accumulated in the unplanted wetland; up to 70% and 25% of PCE was dechlorinated to cis-1,2-DCE and VC after 4m from the inlet, respectively. Because of high sulphate concentration (around 850mgL−1) in the groundwater, the plant derived organic carbon caused sulphide formation (up to 15mgL−1) in the planted wetland, which impaired the MCB removal but not statistically significant. The results showed significant enhancement of vegetation on the removal of the low chlorinated hydrocarbon MCB, which is probably due to the fact that aerobic MCB degraders are benefited from the oxygen released by plant roots. Vegetation also stimulated completely dechlorination of PCE due to plant derived organic carbon, which is potentially to provide electron donor for dechlorination process. The plant derived organic carbon also stimulated dissimilatory sulphate reduction, which subsequently have negative effect on MCB removal. [Copyright &y& Elsevier]

Objectives Few studies have examined whether exposure to chlorinated solvents is associated with multiple myeloma. We evaluated associations between multiple myeloma and occupational exposure to six chlorinated solvents: 1,1,1-trichloroethane, trichloroethylene (TCE), methylene chloride (DCM), perchloroethylene, carbon tetrachloride and chloroform. Methods In-person interviews obtained occupational histories and information on jobs with likely solvent exposure. We assigned exposure metrics of probability, frequency, intensity and confidence using job-exposure matrices modified by job-specific questionnaire information. We used logistic regression to estimate ORs and 95% CIs for associations between multiple myeloma and ever exposure to each, and any, chlorinated solvent and analysed whether associations varied by duration and cumulative exposure. We also considered all occupations that were given the lowest confidence scores as unexposed and repeated all analyses. Results Risk of multiple myeloma was elevated for subjects ever exposed to 1,1,1-trichloroethane (OR (95% CI): 1.8 (1.1 to 2.9)). Ever exposure to TCE or DCM also entailed elevated, but not statistically significant, risks of multiple myeloma; these became statistically significant when occupations with low confidence scores were considered unexposed (TCE: 1.7 (1.0 to 2.7); DCM: 2.0 (1.2 to 3.2)). Increasing cumulative exposure to perchloroethylene was also associated with increasing multiple myeloma risk. We observed non-significantly increased multiple myeloma risks with exposure to chloroform; however, few subjects were exposed. Conclusions Evidence from this relatively large case-control study suggests that exposures to certain chlorinated solvents may be associated with increased incidence of multiple myeloma; however, the study is limited by relatively low participation (52%) among controls. [ABSTRACT FROM PUBLISHER]

Abstract: A two-stage process integrating ultraviolet oxidation and biotrickling filtration (UV–BTF) was developed for treatment of industrial air streams contaminated with trichloroethylene (TCE) and perchloroethylene (PCE). Laboratory-scale studies demonstrated that the UV–BTF system consistently achieved contaminant removal efficiencies of 99–100% under optimal conditions. The UV–BTF process employs an advanced oxidation process (AOP) such as UV photooxidation as pretreatment for alleviating biological toxicity attributed to high and/or fluctuating contaminant concentrations, and for transforming the contaminants to more easily biodegradable products. The UV–BTF process showed significantly better performance than the BTF process without UV photooxidation pretreatment. Free-radical reaction mechanisms, pathways, and product formations were proposed for the UV photolysis of TCE and PCE. The photooxidation was mediated by chlorine atom reactions, and the principal products for TCE were phosgene, dichloroacetyl chloride (DCAC), low levels of trichloroacetyl chloride (TCAC), carbon monoxide, and hydrochloric acid; while those for PCE were phosgene, TCAC, low levels of DCAC, carbon dioxide, and hydrochloric acid. These products were identified and quantified by a combination of techniques, namely, gas chromatography–mass spectrometry (GC–MS) and Fourier transform infrared (FTIR) spectroscopy. These photooxidation products were completely removed in the BTF stage of the UV–BTF process, as indicated by subsequent GC–MS analyses. The destruction of photolysis products in the BTF stage occurred by a combination of hydrolysis, adsorption and microbial degradation. [Copyright &y& Elsevier]

There is evidence of hepatotoxic effects caused by Perchloroethylene (PCE), presumably due to reactive metabolic intermediates; lipid peroxidation is under study as a potential mechanism of toxicity. We aimed to verify if PCE levels comparable to those reached in the blood of exposed subjects can cause cell damage and lipid peroxidation. The association of PCE with lipid peroxidation inducing drugs (cyclosporine A, valproic acid and amiodarone) was also tested on rat isolated hepatocytes. AST and LDH release, MTT test and lipid peroxidation assay showed that PCE determines dose-dependent effects on rat isolated hepatocytes. The toxic potential resulting from our data would be valproic acid

A surficial clay acquitard extends through the urban area where Mexico City is located. It has been assumed to function as a protective layer to the underlying aquifer that provides 42 m3/s out of 63 m3/s of water used by 18 million inhabitants. To provide such protection, the acquitard must be impermeable to water flow and, ideally, have a significant capacity to sorb contaminants. The latter aspect was addressed, studying the vertical variability of sorption of perchloroethylene (PCE), a widely used organic compound considered to pose health risks in groundwater. Batch sorption tests were used and the clay-rich strata in the depth interval from 8 to 75 m were studied. The results suggest that sorption depends mainly on the fraction of organic carbon (foc) present in the clayey materials. The sorption data were fit to the linear and Freundlich models; many strata could be fit well by either model, while some strata were distinctly non-linear. The linear isotherms showed a mean value of 32.8 ml/g, and the Freundlich isotherm 96.6 ml/g, confirming that the clay-rich media have significant sorption capacity for PCE. From the environmental perspective the clay-rich materials are serving as protection to the groundwater system. [ABSTRACT FROM AUTHOR]

Ultrasound has been evaluated as an alternative to replacing perchloroethylene with nontoxic alternative solvents and aqueous systems. Over 130 solvents were screened based on their ability to dissolve fats, waxes, and grease. Those with adverse properties were eliminated, leaving 11 solvents. Five fiber types were tested for cleaning effectiveness, redeposition, and shrinkage using ultrasound. Three hard-to-remove soils were selected for evaluation. Soiled samples were cleaned in both an Atlas Launder-Ometer and an ultrasonic cleaning system and cleaning performance was evaluated using the AATCC Gray Scale for Staining. It was observed that soil removal is very solvent-soil specific. Cleaning trials showed that three solvents performed similar to perchloroethylene. Results showed that if a solvent is capable of removing a particular soil using the Launder-Ometer, then ultrasound is also capable of removing hydrophobic soils using aqueous-based recipes of about 6% solvent and 90% water, indicating that ultrasonic wetcleaning could be a possible way of cleaning textiles that are normally drycleaned. [ABSTRACT FROM AUTHOR]

Objectives: To investigate the association between spontaneous abortion and work within dry cleaning units in the United Kingdom where the solvent perchloroethylene is used.Methods: A retrospective occupational study of reproductive outcome in 7305 women aged 16 and 45 years, who were currently or previously employed in dry cleaning or laundry units in the United Kingdom. Data on workplace exposures and reproductive outcome were obtained by postal survey. A sample of reported spontaneous abortions was validated from medical records. Machine operator versus non-operator was used as a surrogate for exposure to perchloroethylene in dry cleaning units as no data on individual doses were available for women in this study.Results: The response rate was higher for current workers of dry cleaning units (78%), than for past workers of dry cleaning units (46%). Similarly, the response for current laundry workers (65%) was higher than that for past laundry workers (40%). Overall, the reproductive characteristics of the respondents were similar to expectation. Examination of exposure at the time of pregnancy, however, showed that the rate of spontaneous abortion varied according to the type of work the women did during the pregnancy or in the three months before conception: being lowest for pregnancies not exposed to either dry cleaning or laundry work (10.9%), higher for those exposed to laundry work (13.4%), and higher still for those exposed to dry cleaning work (14.8%). Within the group of pregnancies exposed to dry cleaning, the proportion was higher if the woman reported that she worked as an operator at the time of the pregnancy (17.1%) rather than as a non-operator (11.6%). Adjusted odds ratios for the period 1980-95 showed that the risk was over 50% higher in operators than non-operators (p = 0.04). The physical demands of the two jobs are likely to be similar. A higher risk was found when work as a dry cleaning operator was compared with no work in either dry cleaning or laundry units during pregnancy. Exposure to dry cleaning as a non-operator was not associated with any excess risk.Conclusions: Women who worked in dry cleaning shops at the time of their pregnancy or in the three months before who described themselves as operators were about half as likely again to report that their pregnancy ended in a spontaneous abortion than women who described themselves as non-operators. [ABSTRACT FROM AUTHOR]

Attempts to remediate ground water contaminated with tetrachloroethylene at a Superfund site in Minnesota included the installation of a vacuum vaporizer well. Prior to the remedial system installation, thecontaminant source half-life was approximately 0.3 years. Aquifer aeration by the vacuum vaporizer well unintentionally disrupted the ambient natural attenuation rate. Although the overall plume size did not increase, concentrations of the anaerobic breakdown products of tetrachloroethylene -- trichloroethylene,cis-dichloroethylene, and vinylchloride -- all increased in downgradient monitoring wells after startup of the vacuum vaporizer well. At a well 360 feet downgradient ofthe source, trichloro- ethylene increased from concentrations below 10 mug/L to over 35 mug/L, whilecis-dichloroethylene concentrations increased from 70 mug/L to 370 mug/L. Vinyl chloride, which was below detection limits at this location prior to operation of the vacuum vaporizor well, increased in concentration to 83 mug/L. Concentrations of these contaminants returned to pre-sparging levels after deactivation of the system, indicating that existing anaerobic natural attenuation processes play an important role in the remediation of ground water at this site. Investigations should routinely assess the role of natural attenuation in remediation before implementing engineered remedies that may disrupt existing beneficial attenuation processes. [ABSTRACT FROM AUTHOR]

The role served by the presence of methanogenic activity within a tetrachloroethene (PCE)-dechlorinating culture was investigated througha series of supplementation experiments. An acclimated lactate-enrichment culture (LEC 1) capable of rapidly converting PCE to ethene wassupplemented with a 20% dilution (v/v) of one of three actively acetoclastic enrichment cultures or with filtered supernatant from each of these cultures. When this set of experiments was conducted during aperiod of inhibited acetoclastic activity in LEC 1, whole-culture amendments significantly decreased chlorinated ethene removal times (8 to 78%), while increasing methane production rates (92 to 275%). Supplementation with supernatant improved dechlorination rates relative to undiluted LEC 1 without significantly impacting methanogenesis, indicating that the benefit was provided directly to dechlorinating organisms via the secretion of extracellular components from the added culture. Because no benefit was observed when the experiment was repeated during a period of increased methanogenic activity in LEC 1, it was apparent that the catalytic or nutritional needs of specific dechlorinating organisms were satisfied when a non-dechlorinating population was more active. The results presented here suggest that survival of different members of a microbial community may be necessary to ensure effective remediation of the common pollutant PCE with a minimum of external amendments. [ABSTRACT FROM AUTHOR]

Chlorinated degreasing solvents are multicomponent liquids containing not only the chlorinated hydrocarbons with which their name is associated (e.g., trichloroethylene or [TCE], perchloroethylene or [PCE],1,1,1-trichloroethane [TCA]) but also a number of organic additives included as corrosion inhibitors and antioxidants. The additives, such as 1,4-dioxane, are likely to be of significant public-health importance as ground water contaminants due to their toxicity, solubility,and mobility. Following their use in vapor degreasing systems by industry, chlorinated degreasing solvents will also contain about 25% solubilized oil and grease. A number of physical-chemical properties become especially important in the light of the multicomponent nature of these solvents. First, the higher aqueous solubility and lower sorption of the additives makes it is reasonable to expect that faster moving plumes of these solvent additives will precede plumes of the chlorinated hydrocarbons. Second; due to high losses of chlorinated hydrocarbons by volatilization from vapor degreasers during years in the middle of the century, it is probable that background concentrations of these hydrocarbons are present in ground water flow systems due totheir downwind washout. Finally, the solubilized oil and grease may cause profound changes to the wettability of aquifer materials contacted by the solvents during their subsurface migration. It is argued, therefore, that the wettability of aquifer materials contaminated by chlorinated degreasing solvents needs to be experimentally determinedbefore remediation of DNAPL at each site, rather than being simply assumed as water wet. [ABSTRACT FROM AUTHOR]

A soil from a former chemical redistribution company, contaminated with mainly chlorinated aliphatics, was studied for bioremediation purposes. Groundwater analyses revealed that the original pollutants, i.e. tetrachloroethene (PCE) and trichloroethene (TCE), were present atlevels ranging from 2.3 to 122 mg/L. Dichloroethcne (DCE), vinylchloride (VC), ethene and ethane were also detected at significant concentrations although they had never been introduced to the soil. Relatively high concentrations of cis-DCE as compared to trans-DCE and 1,1-DCE indicated that a slow in situ biodegradation had taken place by reductive dechlorination. Laboratory experiments with flow-through soilcolumns were performed to determine the optimal conditions for the enhancement of reductive dechlorination by the indigenous dechlorinating population. The addition of single electron donors to artificial groundwater resulted in the dechlorination of PCE to TCE and cis-DCE, whereas complete dechlorination to ethene was solely achieved with compost extract added to native groundwater. (c) 1998 IAWQ Published byElsevier Science Ltd. [ABSTRACT FROM AUTHOR]

A full-scale evaluation of an advanced oxidation process (AOP) involving the use of ozone (O3) and hydrogen peroxide (H2O2) at a 126-L/s (2,000-gpm) flow rate was completed in a plug-flow hydraulic regime by the Los Angeles (alif.) Department of Water and Power. This facility is the first full-scale AOP for trichloroethylene (TCE) and tetrachloroethylene (PCE) treatment in the United States, if not the world. The purpose of this study was to challenge the performance of the plant with typical groundwater pollutants, propose a kinetic model forthe process, and confirm past laboratory and pilot studies. Groundwater containing up to 447 micron/L TCE and 163 micron/L PCE was treated to below the maximum contaminant (MCL) level of 5 micron/L. The optimum H2O2/O3 dose ratio was 0.5-0.6. Removal efficiency of TCE andPCE declined as groundwater alkalinity increased. Investigation of by-product formation showed formation of assimilable organic carbon and bromate following the treatment process. A kinetic model calibrated using the experimental data predicted the concentration of TCE andPCE in the finished water reasonable well. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) commonly detected in urban waters across the United States include gasoline-related compounds (e.g. toluene, xylene) and chlorinated compounds (e.g. chloroform, tetrachloroethane [PCE], trichloroethene [TCE]). Statistical analysis of observational data and results of modeling the partitioning of VOCs between air and water suggest that urban land surfaces are the primary nonpoint source of most VOCs. Urban air is a secondary nonpoint source, butcould be an important source of the gasoline oxygenate methyl-tert butyl ether (MTBE). Surface waters in urban areas would most effectively be protected by controlling land-surface sources. [ABSTRACT FROM AUTHOR]

In laboratory experiments performed to evaluate the efficiency of surfactant flushing for remediation of non-aqueous phase liquid (NAPL) in the unsaturated zone, less than 0.001% of the original mass of tetrachloroethylene (PCE) remained in the column after 15 pore volumes of a 1% sorbitan monooleate solution or after 7 pore volumes of a 1% Ethomid O/17 solution were passed through the columns. Mass removed asdissolved phase in the effluent accounted for more than 90% of PCE removed, the remainder was lost by volatilization. To determine the influence of parameters that may affect the remediation process, columntests were repeated with different values of parameters, including grain size, application rate, surfactant type, surfactant concentration, and solution viscosity. The results from the column experiments were simulated with the two-dimensional finite element computer code for multiphase flow and transport, MOTRANS. Results of the simulation were similar to those from the experiments. Both experimental and modeling results that surfactant flushing has a great potential to removemass from NAPL in the unsaturated zone. [ABSTRACT FROM AUTHOR]

The Site Characterization and Analysis Cone Penetrometer System (SCAPS), equipped with real-time petroleum, oils and lubricants (POL) hydrocarbon detection capabilities was used to delineate subsurface contaminant releases at a former fire fighter training facility. Records indicated that both petroleum hydrocarbons and chlorinated solvents were released at the site. The investigators advanced the SCAPS petroleum hydrocarbon sensor to depths beneath the water table of the principal water bearing zone. The water table was located 8 to 10 ft (2.44to 3.05 m) below ground surface (bgs) across the site. Fuel compounds were detected at depths ranging from7.5 to 13.3 ft (4.05 m) bgs andfrom 37.5 to 51.0 ft (11.48 to 15.54 m) bgs. Petroleum compounds present in the deeper soils suggest that chlorinated solvents (which aremore dense than water) transported them to these unexpected depths as they migrated via gravity and advection. Analyses of soil samples taken from the subaqueous depths In question confirmed that vinyl chloride was co-mingled with petroleum hydrocarbons. This discovery suggests that the SCAPS fuel hydrocarbon detection system may be capable of indirectly delineating vadose zone and subaqueous chlorinated solvents and other dense non-aqueous phase liquid (DNAPL) plumes at contaminant release sites. [ABSTRACT FROM AUTHOR]

In 1989 the Occupational Safety and Health Administration (OSHA) lowered the permissible exposure limit (PEL) for perchloroethylene (tetrachloroethylene) to 25 parts per million (ppm) as averaged over an 8-hour time period. This rule was later struck down by the courts and the PEL reverted to the original limits of 100 ppm as an 8-hour time-weighted average (TWA), 200 ppm ceiling concentration, and a peak value of 300 ppm for 5 minutes during any 3-hour period. The threshold limit value (TLV) from the American Conference of Governmental Industrial Hygienists (ACGIH) lists a perchloroethylene TLV of 25 ppm with a short-term exposure limit (STEL) of 100 ppm. There are an estimated 30,000 dry cleaning establishments in the United States with a total estimated employment of over 240,000 workers. The majority of these work sites use perchloroethylene as the dry cleaning solvent of choice.Exposure to perchloroethylene is the primary health hazard for workers in the dry cleaning industry today. Signs and symptoms of worker exposure to perchloroethylene include depression of the central nervous system, dizziness, headache, nausea, and irritation of the mucous membranes. Perchloroethylene is a known animal carcinogen and has beenassociated with an elevated risk of cancer of the urinary tract, esophagus, and pancreas. A recent evaluation of the industry by the National Institute for Occupational Safety and Health found that the machine operator had an average exposure between 13 and 19 ppm. Real-timemonitoring of the machine operator found that the average exposure to perchloroethylene was higher while loading than while unloading themachine (846 versus 271 ppm). This same evaluation found that the highest instantaneous exposures occurred during cleaning of the lint trap (200 ppm). The evaluation further re- ported that the ventilation at the facility was overall sufficient to keep the exposures below 22ppm. The following case study reports on worker exposure to perchloroethy [ABSTRACT FROM AUTHOR]

The production of micronuclei in rat bone marrow cells by the synthetic pyrethroid insecticide meothrin was investigated. Three differentdoses of meothrin were orally administered to rats for 14 consecutive days. All tested doses of meothrin increased the frequency of micronucleated polychromatic erythrocytes but the increase was statistically significant only at the two highest doses. Meothrin also affected the rate of bone marrow cell proliferation, as determined by changes in the ratio of polychromatic erythrocytes to normochromatic erythrocytes. [ABSTRACT FROM AUTHOR]

The degradability of chlorinated aliphatic compounds (tetra-chloromethane (TeCM); 1,1,1-trichloroethane (l,l,l-TCA); 1,1,2-trichloroethane (1,1,2-TCA); tetrachloroethene/perchloroethylene (PCE); and trichloroethene/trichloroethylene (TCE)) was studied under methanogenic conditions in batch reactors with leachate from eight landfills in Denmark. All landfill leachates showed fast abiotic degradation of TeCM and1,1,1-TCA, while 1,1,2-TCA seemed unaffected during the methanogenicincubation. PCE and TCE were degraded biologically by reductive dehalogenation, but only in three of the eight leachates. The conversion rates of the chlorinated ethenes (PCE, TCE, dichloroethene (DCE)) andmonochloroethene/vinyl chloride (VC) varied significantly between the three landfill leachates transforming chlorinated ethenes. In one leachate, complete conversion of all ethenes, including conversion ofVC, was observed within 40 days, while another leachate during the same period showed only about 50% conversion of PCE. This indicates that transformation of these common solvents in the landfill environment may vary substantially between landfills. [ABSTRACT FROM AUTHOR]