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This study examined soil, sediment and groundwater microbial communities for a set of key functional genes important for contaminant biodegradation. This involved PICRUSt2 (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) predictions based on 16S rRNA gene amplicon datasets from three separate studies with different inocula and incubation conditions, as follows: aerobic soils, oxygen-limited microcosms containing sediments and groundwater, as well as methanogenic microcosms with different inocula. PICRUSt2 predicts functional profiles of microbial communities based on marker gene (16S rRNA gene) data. The relative abundances of genera previously associated with the biodegradation of chlorinated solvents/metabolites and/or 1,4-dioxane were also determined. Predicted values for each functional gene varied between the three datasets. In all, values were high for propane monooxygenase and low for soluble methane monooxygenase. Common phylotypes associated with propane monooxygenase in two of the three datasets included Mycobacterium, Rhodococcus and Pseudonocardia. Toluene monooxygenase predicted values were greater in the oxygen-limited microcosms compared to the other two datasets. The methanogenic microcosms exhibited the highest predicted values for particulate methane/ammonia monooxygenase. The most common genera detected, previously reported as chlorinated solvents/metabolites and/or 1,4-dioxane degraders, included Pseudomonas, Sphingomonas, Rhodococcus and Rhodanobacter. Eighteen of the queried genera were not detected. As expected, more potential anaerobic degrading genera were found in the oxygen-limited and methanogenic microcosms compared to the aerobic soils. The results provide key insights as to which genes and genera may be important for biodegradation over a range of inocula and redox conditions. • Predicted values were high for propane monooxygenase and low for soluble methane monooxygenase. • Mycobacterium, Rhodococcus and Pseudonocardia were commonly associated with propane monooxygenase. • Genes and genera important for biodegradation were predicted over a range of inocula and redox conditions. • Electron accepting conditions impacted the dominant genes and their phylotypes. [ABSTRACT FROM AUTHOR]

This study aims to precisely determine the effective diffusion coefficients of chlorohydrocarbons in low permeable units under in-situ field conditions. To this end, two controlled release field experiments using TCE and PCE as dense non-aqueous phase liquids (DNAPLs) were conducted in two natural clayey deposits. Several months to years after the controlled DNAPL release, highly resolved concentration profiles were determined for the chlorohydrocarbons that had diffused into the clayey deposits. Effective diffusion coefficients for TCE and PCE were then determined by calibrating a 3D numerical and 1D analytical model, respectively, to the measured high-resolution concentration profiles. The simulations revealed that the effective diffusion coefficients vary by as much as a factor of four within the same low permeability unit being consistent with observed small-scale heterogeneities. The determined chlorohydrocarbon effective diffusion coefficients were further used to determine the equivalent thickness of DNAPL that would completely dissolve in an idealized, parallel-plate fracture by diffusion transport into clayey deposits for the time periods of the controlled release field experiments. The equivalent TCE and PCE DNAPL film thicknesses ranged between 36 and 581 μm, respectively, comparable and exceeding fracture apertures measured in naturally fractured clay rich deposits. Hence, films of DNAPL initially contained within fractures in clay-rich deposits can completely dissolve away within a few months to a few years due to diffusion. This stored contaminant mass poses a risk to adjacent aquifers if it is re-released due to diffusion out of the matrix after source depletion or remediation. [Display omitted] • Performance of controlled release field experiments in natural clays. • Determination of high resolution chlorohydrocarbon profiles. • Precise determination of effective diffusion coefficients of chlorohydrocarbons. • Estimation of disappearance of DNAPL film thickness in fractures. [ABSTRACT FROM AUTHOR]

Through a survey with European companies and expert interviews we study how REACH authorisation affects the phase-out of hazardous chemicals focusing on trichloroethylene, a well-studied solvent used in metal parts cleaning. We find that most of the firms have substituted trichloroethylene by perchloroethylene, which has similar chemical characteristics. This allows them to continue to use the same machines and routines at low costs. Although perchloroethylene is only classified as a suspected rather than a proven carcinogenic substance in Europe, the "improvement" as the result of much regulatory effort must be considered fairly limited, particularly in the light of less hazardous alternatives being used on the market for a long time. Our survey shows that the REACH authorisation process has some effect. Many firms cited as their main reason for substitution that they wanted to avoid the renewed application process. Still, the fact that many firms report using old machines reinforces the impression that some firms are not feeling enough pressure to modify routines and engage in a more fundamental substitution process. The results illustrate the limited effectiveness of a substance by substance approach in chemical risk management. When companies can substitute chemicals of concern to substances with similar chemical characteristics, the health and environmental objectives of chemical regulation are not achieved. An important policy conclusion is that additional incentives need to be introduced in order to realize the ambition of a non-toxic environment in the European Chemicals Strategy for Sustainability. Increased use of measures targeting broader groups of structurally similar hazardous chemicals, in combination with fees that incentivize substitution, are promising avenues for a more sustainable European chemicals strategy. • REACH authorisation has lead to phase out of TCE in European metal parts cleaning. • Perchloroethylene is the main substitute for TCE in European metal parts cleaning. • Low costs for substituting TCE with perchloroethylene in existing machines. • Limited effectiveness of single substance approach to chemical risk management. [ABSTRACT FROM AUTHOR]

Phytoscreening has been demonstrated at a variety of sites over the past 15 years as a low-impact, sustainable tool in delineation of shallow groundwater contaminated with chlorinated solvents. Collection of tree cores is rapid and straightforward, but low concentrations in tree tissues requires sensitive analytics. Solid-phase microextraction (SPME) is amenable to the complex matrix while allowing for solvent-less extraction. Accurate quantification requires the absence of competitive sorption, examined here both in laboratory experiments and through comprehensive examination of field data. Analysis of approximately 2,000 trees at numerous field sites also allowed testing of the tree genus and diameter effects on measured tree contaminant concentrations. Collectively, while these variables were found to significantly affect site-adjusted perchloroethylene (PCE) concentrations, the explanatory power of these effects was small (adjusted R2= 0.031). 90th quantile chemical concentrations in trees were significantly reduced by increasing Henry's constant and increasing hydrophobicity. Analysis of replicate tree core data showed no correlation between replicate relative standard deviation (RSD) and wood type or tree diameter, with an overall median RSD of 30%. Collectively, these findings indicate SPME is an appropriate technique for sampling and analyzing chlorinated solvents in wood and that phytoscreening is robust against changes in tree type and diameter. [ABSTRACT FROM AUTHOR]

The results of batch tests of anaerobic dechlorination on groundwater samples collected downgradient from an industrial site in Northern Italy are presented and discussed. The experiments were carried out using sucrose as electron donor at equimolar concentration and at selected excess with respect to the total reducible species. The purpose of the study was to investigate the effectiveness of sucrose to achieve a complete chlorinated solvents degradations at the specific site, and comparing its effectiveness with milk whey. The results of batch tests experiments indicate that the overall process pathway involves the initial denitrification, followed by simultaneous sulfate reduction and methane production. The process was faster when using milk whey rather than sucrose as electron donor. However, in the presence of the larger excess of milk whey, a fast decrease of pH causes a partial inhibition of methanogens activity, thus retarding the beginning of methane production. In the reactors fed with milk whey, methanogenesis started after 17-20 days of incubation. The results of kinetic tests performed on digesters fed with a large excess of sucrose showed that PCE and TCE degradation to ethylene was completed within 40 days, with a TCE degradation rate of about 11 μmol.l-1.d-1. [ABSTRACT FROM AUTHOR]

Anaerobic, fixed film, bioreactors bioaugmented with a dechlorinating microbial consortium were evaluated as a potential technology for cost effective, sustainable, and reliable treatment of mixed chlorinated ethanes and ethenes in groundwater from a large groundwater recovery system. Bench- and pilot-scale testing at about 3 and 13,500 L, respectively, demonstrated that total chlorinated solvent removal to less than the permitted discharge limit of 100 μg/L. Various planned and unexpected upsets, interruptions, and changes demonstrated the robustness and reliability of the bioreactor system, which handled the operational variations with no observable change in performance. Key operating parameters included an adequately long hydraulic retention time for the surface area, a constant supply of electron donor, pH control with a buffer to minimize pH variance, an oxidation reduction potential of approximately −200 millivolts or lower, and a well-adapted biomass capable of degrading the full suite of chlorinated solvents in the groundwater. Results indicated that the current discharge criteria can be met using a bioreactor technology that is less complex and has less downtime than the sorption based technology currently being used to treat the groundwater. [ABSTRACT FROM AUTHOR]

Chlorinated solvents and trihalomethanes were the most frequently detected volatile organic compound (VOC) groups in groundwater in two metropolitan cities and three industrial complexes in Korea. Groundwater contamination with carbon tetrachloride and chloroform was noticeable in the industrial complexes, while MTBE was frequently detected only in metropolitan cities. In particular, groundwater was severely contaminated with chlorinated solvents and their dechlorination intermediates, including cis-1,2-DCE from TCE and 1,1-DCE from 1,1,1-TCA. Their co-occurrences were analyzed based on detection frequencies, rates of exceeding the water quality criteria, and a correlation matrix. Meanwhile, frequently co-occurring VOCs and VOC concentrations exceeding the water quality criteria were detected in only a few samples, which demonstrates the effects of land use due to the application of various types of VOCs. Thus, the effects of local land use were investigated by categorizing groundwater samples based on land use at the sampling locations; the effects of regional land use were assessed using factor analysis with administrative district statistics. The assessment results showed that public garages at the sampling locations were correlated with groundwater contamination. The detection of MTBE was correlated with vehicle use, while the detection of both toluene and chloroform was correlated with manufacturing and sewage collection and disposal systems; PCE was correlated with hazardous wastes. The contribution of this work is that the co-occurrence of some VOCs and persistent dechlorination intermediates was analyzed using a correlation matrix. Local and regional land uses were separately defined; their impacts on groundwater quality were assessed. Furthermore, a factor analysis included anthropogenic variables and VOC detection rates to better define latent variables. [ABSTRACT FROM AUTHOR]

Direct injection of reactive nanoscale zerovalent iron particles (NZVI) is considered to be a promising approach for remediation of aquifers contaminated by chlorinated organic pollutants. In this study we show that the extent of sulfidation of NZVI enhances the rate of dechlorination of trichloroethylene (TCE) compared to that by unamended NZVI, and the enhancement depends on the Fe/S molar ratio. Experiments where TCE was reacted with NZVI sulfidated to different extents (Fe/S molar ratios 0.62–66) showed that the surface-area normalized first-order TCE degradation rate constant increased up to 40 folds compared to non-sulfidated NZVI. Fe/S ratios in the range of 12–25 provided the highest TCE dechlorination rates, and rates decreased at both higher and lower Fe/S. In contrast, sulfidated NZVI exposed to water in the absence of TCE showed significantly lower hydrogen evolution rate (2.75 μmol L −1 h −1 ) compared to that by an unamended NZVI (6.92 μmol L −1 h −1 ), indicating that sulfidation of NZVI suppressed corrosion reactions with water. Sulfide (HS − ) ions reacted rapidly with NZVI and X-ray photoelectron spectroscopy analyses showed formation of a surface layer of FeS and FeS 2 . We propose that more electrons are preferentially conducted from sulfidated NZVI than from unamended NZVI to TCE, likely because of greater binding of TCE on the reactive sites of the iron sulfide outer layer. Resuspending sulfidated NZVI in sulfide-free or sulfide containing solutions altered the TCE degradation rate constants because of changes in the FeS layer thickness. Sulfidated NZVI maintained its high reactivity in the presence of multiple mono and divalent ions and with polyelectrolyte coatings. Thus, sulfide ions in groundwater can significantly alter NZVI reactivity. [ABSTRACT FROM AUTHOR]

Ethylene dichloride tar (EDC-tar) is a dense non-aqueous phase liquid (DNAPL) waste originated from the process of vinyl chloride production, with major constituents including chlorinated aliphatic and aromatic hydrocarbons. This study investigated the feasibility of Surfactant Enhanced Aquifer Remediation (SEAR) for treating EDC-tar contaminated aquifers. Initial experiments explored the potential to enhance the apparent solubility of EDC-tar using single or mixed surfactants. The results showed that an aqueous solution mixed anionic and non-ionic surfactants (i.e., SDS/Tween 80) exhibited higher EDC-tar apparent solubility and lower surface tension than other surfactant systems tested. Additionally, alkaline pH aids in increasing the EDC-tar apparent solubility. In column flushing experiments, it was seen that the alkaline mixed SDS/Tween 80 solution showed better removal of pure EDC-tar from silica sand porous media. Furthermore, separation of EDC-tar in the surfactant solution was conducted employing a salting-out effect. Significant separation of DNAPL was observed when 13 wt.% or more NaCl was added to the solution. Overall, this study evaluates the feasibility of using SEAR for remediating EDC-tar contaminated subsurface soil and groundwater. [ABSTRACT FROM AUTHOR]

This paper investigated the reductive dechlorination (RD) of cis-dichloroethylene (cis-DCE) (average influent 14.2 ± 0.7 μM) by a bioelectrochemical system (BES), in the presence of real contaminated groundwater containing high levels of nitrate and sulfate. The BES enhanced both the RD and competing reactions, such as nitrate and sulfate reductions, which occurred with neither an external organic carbon source nor any inoculum other than the indigenous microbial consortia in the real groundwater. In preliminary batch tests, RD and full nitrate removal occurred after a short lag phase, whereas sulfate reduction occurred slowly and alongside the RD. Under continuous flow conditions (hydraulic retention time, HRT, 1.4 d), the competition of different electron acceptors was strongly affected by the cathodic potential in the range −550 to −750 mV vs. standard hydrogen electrode (SHE). Nitrate reduction was driven to completion at all tested cathodic potentials, whereas sulfate reduction and the RD rate increased as the cathodic potential became more negative. At −750 mV vs. SHE, strong methanogenesis was also observed and became the most important sink of electrons. The overall coulombic efficiency decreased while the potential became more negative. The RD contribution was always less than 1%. Hence, greater energy consumption was required to obtain higher RD rate and better conversion. Anodic oxidation was only observed at −750 mV vs. SHE where almost 39% of residual vinyl chloride (VC) was oxidized and the sulfate was formed back from sulfide (further contributing to electric waste). [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) enter indoor environments through internal and external sources. Indoor air concentrations of VOCs vary greatly but are generally higher than outdoors. Plants have been promoted as indoor air purifiers for decades, but reports of their effectiveness differ. However, while air-purifying applications may be questionable, the waxy cuticle coating on leaves may provide a simple, cost-effective approach to sampling indoor air for VOCs. To investigate the potential use of plants as indoor air VOC samplers, a static headspace approach was used to examine the relationship between leaf and air concentrations, leaf lipid contents and octanol-air partition coefficients (Koa) for six VOCs and four plant species. The relationship between leaf and air concentrations was further examined in an actual residence after the introduction of several chlorinated VOC emission sources. Leaf-air concentration factors (LACFs), calculated from linear regressions of the laboratory headspace data, were found to increase as the solvent extractable leaf lipid content and Koa value of the VOC increased. In the studies conducted in the residence, leaf concentrations paralleled the changing air concentrations, indicating a relatively rapid air to leaf VOC exchange. Overall, the data from the laboratory and residential studies illustrate the potential for plant leaves to be used as cost effective, real-time indoor air VOC samplers. [ABSTRACT FROM AUTHOR]

The possible approaches for in situ aerobic cometabolism of aquifers and vadose zones contaminated by chlorinated solvents are critically evaluated. Bioaugmentation of resting-cells previously grown in a fermenter and in-well addition of oxygen and growth substrate appear to be the most promising approaches for aquifer bioremediation. Other solutions involving the sparging of air lead to satisfactory pollutant removals, but must be integrated by the extraction and subsequent treatment of vapors to avoid the dispersion of volatile chlorinated solvents in the atmosphere. Cometabolic bioventing is the only possible approach for the aerobic cometabolic bioremediation of the vadose zone. The examined studies indicate that in situ aerobic cometabolism leads to the biodegradation of a wide range of chlorinated solvents within remediation times that vary between 1 and 17 months. Numerous studies include a simulation of the experimental field data. The modeling of the process attained a high reliability, and represents a crucial tool for the elaboration of field data obtained in pilot tests and for the design of the full-scale systems. Further research is needed to attain higher concentrations of chlorinated solvent degrading microbes and more reliable cost estimates. Lastly, a procedure for the design of full-scale in situ aerobic cometabolic bioremediation processes is proposed. [ABSTRACT FROM AUTHOR]

Background Some studies have noted an association between maternal occupational exposures to chlorinated solvents and birth defects in offspring, but data are lacking on the potential impact of industrial air emissions of these solvents on birth defects. Methods With data from the Texas Birth Defects Registry for births occurring in 1996-2008, we examined the relation between maternal residential proximity to industrial air releases of chlorinated solvents and birth defects in offspring of 60,613 case-mothers and 244,927 control-mothers. Maternal residential exposures to solvent emissions were estimated with metrics that took into account residential distances to industrial sources and annual amounts of chemicals released. Logistic regression was used to generate odds ratios and 95% confidence intervals for the associations between residential proximity to emissions of 14 chlorinated solvents and selected birth defects, including neural tube, oral cleft, limb deficiency, and congenital heart defects. All risk estimates were adjusted for year of delivery and maternal age, education, race/ethnicity, and public health region of residence. Results Relative to exposure risk values of 0, neural tube defects were associated with maternal residential exposures (exposure risk values >0) to several types of chlorinated solvents, most notably carbon tetrachloride (adjusted odds ratio [aOR] 1.42, 95% confidence interval [CI] 1.09, 1.86); chloroform (aOR 1.40, 95% CI 1.04, 1.87); ethyl chloride (aOR 1.39, 95% CI 1.08, 1.79); 1,1,2-trichloroethane (aOR 1.56, 95% CI 1.11, 2.18); and 1,2,3-trichloropropane (aOR 1.49, 95% CI 1.08, 2.06). Significant associations were also noted between a few chlorinated solvents and oral cleft, limb deficiency, and congenital heart defects. We observed stronger associations between some emissions and neural tube, oral cleft, and heart defects in offspring of mothers 35 years or older, such as spina bifida with carbon tetrachloride (aOR 2.49, 95% CI 1.09, 5.72), cleft palate with 1,2-dichloroethane (aOR 1.93, 95% 1.05, 3.54), cleft lip with or without cleft palate with ethyl chloride (aOR 1.81, 95% CI 1.06, 3.07), and obstructive heart defects with trichloroethylene (aOR 1.43, 95% CI 1.08, 1.88). Conclusions These findings suggest that maternal residential proximity to industrial emissions of chlorinated solvents might be associated with selected birth defects in offspring, especially among older mothers. [ABSTRACT FROM AUTHOR]

Chlorinated solvents including tetrachloroethene (perchloroethene and trichloroethene), are widely used industrial solvents. Improper use and disposal of these chemicals has led to a widespread contamination. Anaerobic treatment technologies that utilize Dehalococcoides spp. can be an effective tool to remediate these contaminated sites. Therefore, the aim of this study was to develop, optimize and validate peptide nucleic acid (PNA) probes for the detection of Dehalococcoides spp. in both pure and mixed cultures. PNA probes were designed by adapting previously published DNA probes targeting the region of the point mutations described for discriminating between the Dehalococcoides spp. strain CBDB1 and strain 195 lineages. Different fixation, hybridization and washing procedures were tested. The results indicated that the PNA probes hybridized specifically and with a high sensitivity to their corresponding lineages, and that the PNA probes developed during this work can be used in a duplex assay to distinguish between strain CBDB1 and strain 195 lineages, even in complex mixed cultures. This work demonstrates the effectiveness of using PNA fluorescence in situ hybridization to distinguish between two metabolically and genetically distinct Dehalococcoides strains, and they can have strong implications in the monitoring and differentiation of Dehalococcoides populations in laboratory cultures and at contaminated sites. © 2014 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Objectives: Lifetime occupational history (OH) questionnaires often use open-ended questions to capture detailed information about study participants’ jobs. Exposure assessors use this information, along with responses to job- and industry-specific questionnaires, to assign exposure estimates on a job-by-job basis. An alternative approach is to use information from the OH responses and the job- and industry-specific questionnaires to develop programmable decision rules for assigning exposures. As a first step in this process, we developed a systematic approach to extract the free-text OH responses and convert them into standardized variables that represented exposure scenarios. Methods: Our study population comprised 2408 subjects, reporting 11991 jobs, from a case–control study of renal cell carcinoma. Each subject completed a lifetime OH questionnaire that included verbatim responses, for each job, to open-ended questions including job title, main tasks and activities (task), tools and equipment used (tools), and chemicals and materials handled (chemicals). Based on a review of the literature, we identified exposure scenarios (occupations, industries, tasks/tools/chemicals) expected to involve possible exposure to chlorinated solvents, trichloroethylene (TCE) in particular, lead, and cadmium. We then used a SAS macro to review the information reported by study participants to identify jobs associated with each exposure scenario; this was done using previously coded standardized occupation and industry classification codes, and a priori lists of associated key words and phrases related to possibly exposed tasks, tools, and chemicals. Exposure variables representing the occupation, industry, and task/tool/chemicals exposure scenarios were added to the work history records of the study respondents. Our identification of possibly TCE-exposed scenarios in the OH responses was compared to an expert’s independently assigned probability ratings to evaluate whether we missed identifying possibly exposed jobs. Results: Our process added exposure variables for 52 occupation groups, 43 industry groups, and 46 task/tool/chemical scenarios to the data set of OH responses. Across all four agents, we identified possibly exposed task/tool/chemical exposure scenarios in 44–51% of the jobs in possibly exposed occupations. Possibly exposed task/tool/chemical exposure scenarios were found in a nontrivial 9–14% of the jobs not in possibly exposed occupations, suggesting that our process identified important information that would not be captured using occupation alone. Our extraction process was sensitive: for jobs where our extraction of OH responses identified no exposure scenarios and for which the sole source of information was the OH responses, only 0.1% were assessed as possibly exposed to TCE by the expert. Conclusions: Our systematic extraction of OH information found useful information in the task/chemicals/tools responses that was relatively easy to extract and that was not available from the occupational or industry information. The extracted variables can be used as inputs in the development of decision rules, especially for jobs where no additional information, such as job- and industry-specific questionnaires, is available. [ABSTRACT FROM AUTHOR]

Highlights: [•] Kinetic and equilibrium characteristics of five passive samplers were determined. [•] The PDMS sampler was capable of measuring plant PCE and TCE concentrations. [•] Passive sampling devices in trees are a helpful phytoscreening tool. [Copyright &y& Elsevier]

Accumulation of volatile organic compounds ( VOCs) that migrate inside buildings from underlying contaminated soils and groundwater poses human health risks. VOCs intrusion into buildings driven only by diffusion was reproduced by a laboratory-scale experiment. Effective diffusion coefficients and fluxes of a group of selected chlorinated solvents and BTEX through two types of isolation material - that is, concrete (anhydrite screed) and geo-membrane - were estimated. The laboratory experiment indicated that the diffusive transfer of pollutants through sediments into indoor air of buildings cannot be prevented by building sealing material, but it could be attenuated to a certain degree by concrete and up to non-detectable levels by the geo-membrane. Effective diffusion coefficients through concrete and geo-membrane ranged from 3.17 × 10−2 to 5.90 × 10−5 cm2/s and from 5.47 × 10−6 to 5.50 × 10−8 cm2/s, respectively. [ABSTRACT FROM AUTHOR]

A procedure for the design of an aerobic cometabolic process for the on-site degradation of chlorinated solvents in a packed bed reactor was developed using groundwater from an aquifer contaminated by trichloroethylene (TCE) and 1,1,2,2-tetrachloroethane (TeCA). The work led to the selection of butane among five tested growth substrates, and to the development and characterization from the site's indigenous biomass of a suspended-cell consortium capable to degrade TCE (first order constant: 96 L g day at 30 °C and 4.3 L g day at 15 °C) with a 90 % mineralization of the organic chlorine. The consortium immobilization had strong effects on the butane and TCE degradation rates. The microbial community structure was slightly changed by a temperature shift from 30 to 15 °C, but remarkably affected by biomass adhesion. Given the higher TCE normalized degradation rate (0.59 day at 15 °C) and attached biomass concentration (0.13 g L at 15 °C) attained, the porous ceramic carrier Biomax was selected as the best option for the packed bed reactor process. The low TeCA degradation rate exhibited by the developed consortium suggested the inclusion of a chemical pre-treatment based on the TeCA to TCE conversion via β-elimination, a very fast reaction at alkaline pH. To the best of the authors' knowledge, this represents the first attempt to develop a procedure for the development of a packed bed reactor process for the aerobic cometabolism of chlorinated solvents. [ABSTRACT FROM AUTHOR]

A retrospective exposure assessment was performed for use in a health outcomes study of a facility manufacturing circuit boards, business machines, and other equipment during the years 1969–2002. A matrix was developed identifying chemical use by department-year based on company-provided information. Use of six chemical agents (fiberglass, lead, methylene chloride, methyl chloroform, perchloroethylene, and trichloroethylene) and six chemical classes (acid-base, aromatic hydrocarbons, chlorinated hydrocarbons, other hydrocarbons, chlorofluorocarbons, and metals), and general (including unspecified) chemicals was identified. The matrix also contained an assignment for each department-year categorizing the potential for use of chemicals as negligible, intermittent/incidental, or routine. These department-based exposure matrix data were combined with work history data to provide duration of potential chemical use for workers. Negligible, intermittent/incidental or routine extent-of-chemical-use categories comprised 42.6%, 39.4%, and 17.9%, respectively, of total person-years of employment. Cumulative exposure scores were also developed, representing a relative measure of the cumulative extent of potential exposure to the six chemical agents, six chemical classes, and general (including unspecified) chemicals. Additionally, the study period was divided into manufacturing eras showing trends in chemical use, and showing that process use of trichloroethylene and methylene chloride ended in the mid-1980s and the mid-1990s, respectively. This approach may be useful in other assessments addressing a variety of chemicals, and with data constraints common to retrospective chemical exposure studies. [ABSTRACT FROM AUTHOR]

Abstract: The use of compound specific multi-isotope approach (C and Cl) in the characterization of a chlorinated ethenes contaminated fractured aquifer allows the identification of several sources and contaminant plumes, as well as the occurrence of biodegradation and mixing processes. The study site is located in Spain with contamination resulting in groundwater concentrations of up to 50mg/L of trichloroethene (TCE), the most abundant chlorinated ethene, and 7mg/L of tetrachloroethene (PCE). The potential sources of contamination including abandoned barrels, an underground tank, and a disposal lagoon, showed a wide range in δ13C values from −15.6 to −40.5‰ for TCE and from −18.5 to −32.4‰ for PCE, allowing the use of isotope fingerprinting for tracing of the origin and migration of these contaminants in the aquifer. In contrast, there is no difference between the δ37Cl values for TCE in the contaminant sources, ranging from +0.53 to +0.66‰. Variations of δ37Cl and δ13C in the different contaminant plumes were used to investigate the role of biodegradation in groundwater. Moreover, the isotopic data were incorporated into a reactive transport model for determination of whether the isotope pattern observed downstream from the tank's source could be explained by the simultaneous effect of mixing and biodegradation. The results demonstrate that a multi-isotope approach is a valuable tool for characterization of complex sites such as fractured bedrock aquifer contaminated by multiple sources, providing important information which can be used by consultants and site managers to prioritize and design more successful remediation strategies. [Copyright &y& Elsevier]