Perchloroethylene Concentrations Research Articles

A Physiologically Based Pharmacokinetic Assessment of Tetrachloroethylene in Groundwater for a Bathing and Showering Determination

A two-step methodology is described to make a health-based determination for the bathing and showering use of the water from a private well contaminated with volatile organic chemicals. The chemical perchloroethylene (PERC) is utilized to illustrate the approach. First, a chemical-specific exposure model is used to predict the concentration of PERC in the shower air, shower water, and in the air above the bathtub. Second, a physiologically based pharmacokinetic (PBPK) model is used to predict the concentration of PERC delivered to the target tissue, the brain, since the focus is on neurological endpoints. The simulation exercise includes concurrent dermal and inhalation routes of exposure. A reference target tissue level (RTTL) in the brain is estimated using the PBPK model. A hazard index based on this benchmark guideline is used to make a regulatory determination for bathing and showering use of the contaminated water.

Biological exposure indices of organic solvents for Korean workers.

Biological exposure indices (BEIs) of toluene, perchloroethylene (PCE) and methyl ethyl ketone (MEK) for Korean workers were studied respectively. Exposure in workplace to organic solvents were measured by personal sampling. Blood toluene, blood PCE, urinary trichloroacetic acid and urinary MEK were determined by headspace GC. Urinary hippuric acid was determined by HPLC and corrected for creatinine. BEIs for Korean workers were calculated with the levels of the determinants corresponding to permissible exposure limits in Korea which were the same with TLV of ACGIH. Blood toluene level of 2.2 mg/l and urinary hippuric acid level of 1.7 g/g creatinine corresponded to exposure of 100 ppm toluene. Blood PCE concentration of 1.6 mg/l and urinary trichloroacetic acid concentration of 2.9 mg/l corresponded to exposure to 50 ppm PCE. Urinary MEK concentration of 1.4 mg/l corresponded to exposure to 200 ppm of MEK. In conclusion, BEIs for Korean workers determined in this study were different to ACGIH's BEI as urinary determinants were lower and blood determinants were higher than ACGIH's BEI.

Prediction of the movement of perchlor0ethylene in soil columns

Many toxic volatile organic compounds (VOCs) are being released to the soil through improper waste disposal practices, industrial impoundments, landfills and accidental spills during transport and handling. Once released, the VOCs migrate toward the groundwater and cause contamination. One of the most frequently found VOCs in groundwater supplies is perchloroethylene (PCE). In this study an attempt was made to investigate the transport of PCE in two types of soil. PCE spills were created on soil columns in the laboratory and column breakthrough theory was used to analyze the data. Empirical equations were used to calibrate a contaminant transport model. The programs for this simple model have been prepared for use with IBM microcomputers and are capable to predicting the breakthrough time and concentration of PCE at various depths in the profile.

Reductive dechlorination of high concentrations of tetrachloroethene to ethene by an anaerobic enrichment culture in the absence of methanogenesis

Tetrachloroethene, also known as perchloroethylene (PCE), is a common groundwater contaminant throughout the United States. The incomplete reductive dechlorination of PCE--resulting in accumulations of trichloroethene, dichloroethene isomers, and/or vinyl chloride--has been observed by many investigators in a wide variety of methanogenic environments. Previous mixed-culture studies have demonstrated that complete dechlorination to ethene is possible, although the final dechlorination step from vinyl chloride to ethene is rate limiting, with significant levels of vinyl chloride typically persisting. In this study, anaerobic methanol-PCE enrichment cultures which proved capable of dechlorinating high concentrations PCE to ethene were developed. Added concentrations of PCE as high as 550 microM (91-mg/liter nominal concentration; approximately 55-mg/liter actual aqueous concentration) were routinely dechlorinated to 80% ethene and 20% vinyl chloride within 2 days at 35 degrees C. The methanol level used was approximately twice that needed for complete dechlorination of PCE to ethene. The observed transformations occurred in the absence of methanogenesis, which was apparently inhibited by the high concentrations of PCE. When incubation was allowed to proceed for as long as 4 days, virtually complete conversion of PCE to ethene resulted, with less than 1% persisting as vinyl chloride. An electron balance demonstrated that methanol consumption was completely accounted for by dechlorination (31%) and acetate production (69%). The high volumetric rates of PCE dechlorination (up to 275 mumol/liter/day) and the relatively large fraction (ca. one-third) of the supplied electron donor used for dechlorination suggest that reductive dechlorination could be exploited for bioremediation of PCE-contaminated sites.

Emissions of perchloroethylene from dry cleaned fabrics

A study was conducted to evaluate the emissions of perchloroethylene (tetrachloroethylene) from dry cleaned fabrics to determine: (a) how the introduction of fresh dry cleaning into a home affects the indoor concentration of perchloroethylene, and (b) the effectiveness of ‘airing out’ dry cleaned clothes in reducing perchloroethylene emissions. Small chamber tests were conducted to determine perchloroethylene emission characteristics for three fabrics at several air exchange rates. Test house studies were conducted to determine the indoor concentration of perchloroethylene due to the placement of dry cleaned clothing in the house. Based on the study results, and assuming that test conditions were representative of normal dry cleaning and consumer practices, the following conclusions were reached. (1) Emissions from freshly dry cleaned clothing cause elevated levels of perchloroethylene in residences. (2) For the three fabrics tested, ‘airing out’ of dry cleaned clothing by consumers for short time periods (4–8 h) will not be effective in reducing perchloroethylene emissions. (3) Adsorptive surfaces (i.e. sinks) in residences may have a major impact on consumer exposure to perchloroethylene. It is emphasized that these conclusions are based on the results of the study reported. Significant variations in dry cleaning practices and/or in the mix of fabrics and clothing being cleaned could provide different results and conclusions.

PCE Volatilized from Stagnant Water and Soil

Batch equilibrium studies are conducted under controlled laboratory conditions to determine the volatilization rate for perchloroethylene (PCE) from water and soil. The PCE is observed to volatilize rapidly from water. The rate of volatilization and the rate constant of PCE from water are found to increase with an increase in area to volume ratio but are independent of aqueous PCE concentration. Rate constants determined in this study indicate that aqueous PCE volatilizes faster from soil than from water. However, volatilization from soil depends not only on area to volume ratio but also on the presence of organic carbon and concentration of aqueous PCE applied to the soil. The greater the organic carbon of soil media content, the slower is the rate of volatilization. The rate of volatilization of pure PCE from soil is comparatively low and is greatly retarded by organic carbon content of the soil. A flux experiment is also carried out with pure PCE. The results indicate a low flux rate of submerged PCE i...

Mixed reactant photocatalysis: Intermediates and mutual rate inhibition

Near UV-illuminated slurries of titanium dioxide were used to study the photocatalyzed degradation kinetics of benzene and perchloroethylene (PCE) as water contaminants. In all runs, the concentration(s) of reactant(s) (initially 15–500 μM) as well as the evolution of CO 2 final product were monitored. The single component initial rate data were well described by Langmuir-Hinshelwood rate forms, and integration of these rate equations provided simulations of the entire time course of each reaction. Perchloroethylene degraded completely without any evidence of kinetically significant chemical intermediates; however, adequate simulation of the benzene time course data required the incorporation in the model of at least two reaction intermediates. Subsequent GC MS analysis of a benzene reaction slurry revealed several intermediate species, with positive identification of phenol and quinone. Using the kinetic rate parameters obtained from the single component initial rate data and including competitive intermediate terms, the Langmuir-Hinshelwood rate form was able to simulate the results of several binary reactant experiments. The data showed that the effect of PCE concentration on benzene reaction rate was negligible, while benzene and its intermediates significantly inhibited PCE degradation. Simulations with this simple model for diminution of both reactants as well as CO 2 product evolution were quite good for low initial reactant concentrations, but overestimated the competitive inhibitory effect of high (≈ 300 μM) initial PCE concentrations.

Radiation-induced decomposition of small amounts of perchloroethylene in water

In air-saturated reagent grade water and at concentrations between 5 and 10 ppm, perchloroethylene is decomposed by γ radiation with a constant G-value of 4.4. At lower concentrations, and in drinking waters, the G-value decreases with decreasing perchloroethylene concentration and with increasing concentration of inorganic (especially HCO 3 − and NO 3 −) and organic solutes present. Below 1 ppm perchloroethylene, the decomposition in most cases follows first-order kinetics. Nearly 100% of the organic chlorine degraded is converted to chloride ions. A tentative reaction scheme is given.

和服しみ抜き作業者にみられたパークロル・エチレン中毒と思われる２症例

1) Recently, dry cleaning with perchloroethylene has become available in Japan, and this dry cleaning has become to be used even for cleaning Japanese clothes made of silk. Two patients visited us one after another, who were engaged in cleaning Japanese clothes and thought to be poisoned by perchloroethylene. Their health states and working conditions were examined from the viewpoint of occupational hygiene.2) The patients complained similarly of memory disturbance, easy fatigability and decrease of tolerance to alcohol after contact with perchloroethylene. The medical examination at the Nagoya University hospital revealed a slight disturbance of liver function, a slight narrowness of left visual field, and diffuse distribution of α rhythm, sporadic θ activities and mixed fast wave in EEG in the first patient. And, evident disturbance of liver function, decrease of retinal potential and diffuse distribution of a rhythm and mixed fast wave in EEG were revealed also in the second patient. Liver function and function of the central nervous system were commonly disturbed in the two patients, although the degree of the disturbance was different between them.3) A large amount of perchloroethylene was used in the work room of the first patient, and his work room was narrow. Therefore, high concentrations of perchloroethylene were detected at the time of survey. The concentration of perchloroethylene was 30-70 ppm under his nose at washing Japanese clothes by hand brush, and 100-400 ppm near Japanese clothes wetted with perchloroethylene and hanged on.the wash-line poles.As regards to the second patient, the work room was fairly improved after his health disturbance. But high concentrations of perchloroethylene were detected at the out of the fun for ventilation and at the exhaust opening, and this fact proposes another kind of environmental pollution problem.4) Japanese clothes wetted with perchloroethylene were hung on wash-line poles to become dry naturally in the room so that the clothes did not become wrinkled and remain soft after cleaning. Consequently, perchloroethylene is consumed about 60 % by weight of Japanese clothes and on top of that, most of perchloroethylene is vaporized in the work room, whereas in the ordinary dry cleaning perchloroethylene is consumed at about 5% by clothes weight, most of which is exhausted from the cleaner to the outdoor. Accordingly, the concentration of perchloroethylene in the work room may become very high and the worker may have a danger to be poisoned with perchloroethylene. As there are many workers engaged in this kind of work in Japan, it is necessary to make countermeasures for them from the viewpoint of occupational hygiene.

Weather towers near completion at Brookhaven Laboratory

This study pilot-tested carboxymethyl cellulose (CMC) stabilized zero-valent iron (ZVI) nanoparticles (with a trace amount of Pd catalyst) for in situ destruction of chlorinated ethenes such as perchloroethylene (PCE) and trichloroethylene (TCE) and polychlorinated biphenyls (PCBs) that had been in groundwater for decades. The test site was located in a well-characterized secondary source zone of PCBs and chlorinated ethenes. Four test wells were installed along the groundwater flow direction (spaced 5 ft apart), including one injection well (IW), one up-gradient monitoring well (MW-3) and two down-gradient monitoring wells (MW-1 and MW-2). Stabilized nanoparticle suspension was prepared on-site and injected into the 50-ft deep, unconfined aquifer. Approximately 150 gallons of 0.2 g/L Fe–Pd (CMC = 0.1 wt%, Pd/Fe = 0.1 wt%) was gravity-fed through IW-1 over a 4-h period (Injection #1). One month later, another 150 gallons of 1.0 g/L Fe–Pd (CMC = 0.6 wt%, Pd/Fe = 0.1 wt%) was injected into IW-1 at an injection pressure <5 psi (Injection #2). When benchmarked against the tracer, approximately 37.4% and 70.0% of the injected Fe was detected in MW-1 during injection #1 and #2, respectively, confirming the soil mobility of the nanoparticles through the aquifer, and higher mobility of the particles was observed when the injection was performed under higher pressure. Rapid degradation of PCE and TCE was observed in both MW-1 and MW-2 following each injection, with the maximum degradation being observed during the first week of the injections. The chlorinated ethenes concentrations gradually returned to their pre-injection levels after ∼2 weeks, indicating exhaustion of the ZVI's reducing power. However, the injection of CMC-stabilized nanoparticle and the abiotic reductive dechlorination process appeared to have boosted a long-term in situ biological dechlorination thereafter, which was evidenced by the fact that PCE and TCE concentrations showed further reduction after two weeks. After 596 days from the first injection, the total chlorinated ethenes concentration decreased by about 40% and 61% in MW-1 and MW-2, respectively. No significant long-term reduction of PCB 1242 was observed in MW-1, but a reduction of 87% was evident in MW-2. During the 596 days of testing, the total concentrations of cis-DCE (dichloroethylene) and VC (vinyl chloride) decreased by 20% and 38% in MW-1 and MW-2, respectively. However, the combined fraction of cis-DCE and VC in the total chlorinated ethenes (PCE, TCE, cis-DCE and VC) increased from 73% to 98% and from 62% to 98%, respectively, which supports the notion that biological dechlorination of PCE and TCE was active. It is proposed that CMC-stabilized ZVI-Pd nanoparticles facilitated the early stage rapid abiotic degradation. Over the long run, the existing biological degradation process was boosted with CMC as the carbon source and hydrogen from the abiotic/biotic processes as the electron donor, resulting in the sustained enhanced destruction of the chlorinated organic chlorinated ethenes in the subsurface.