Trichloroethylene

Dichloroacetic acid (DCA) is a compound found in chlorinated drinking water. In addition, the compound is a metabolite of several halogenated solvents, including trichloroethylene (TCE) and perchloroethylene (PCE). Exposure to DCA is of concern because high doses of the compound have been shown to cause cancer in laboratory animals. Dosages of TCE administered to animals in cancer studies are designed to elicit maximal DCA formation in vivo, whereas levels of DCA to which individuals are exposed in drinking water are very low. Analysis of DCA in biological samples has been quite challenging. Derivatizing reagents commonly used to convert DCA into a more volatile form for analysis by gas chromatography (GC) have been found to convert trichloroacetic acid (TCA), a major metabolite of TCE and PCE, into DCA. High-performance liquid chromatography (HPLC) analysis does not require derivatization of DCA and can thus avoid this problem. However, the most popular stationary phases in HPLC columns do not retain small, polar compounds such as DCA well. The liquid chromatography/tandem mass spectrometry (LC/MS/MS) method described in this paper uses hydrophilic interaction liquid chromatography (HILIC), a type of chromatography that is able to retain these small, polar compounds. Method validation was performed using the United States Food and Drug Administration (USFDA) and International Conference on Harmonziation (ICH) Guidance for Industry: Bioanalytical Method Validation as a guide. Levels of DCA found in rats dosed with 2 g/kg TCE were 17.2 ng/mL (liver), 262.4 ng/mL (kidney), 175.1 ng/mL (lung), and 39.5 ng/mL (blood). Copyright © 2005 John Wiley & Sons, Ltd.

Electrode polarity reversal is evaluated for electrochemical transformation of trichloroethylene (TCE) in aqueous solution using flow-through reactors with mixed metal oxide electrodes and Pd catalyst. The study tests the hypothesis that optimizing electrode polarity reversal will generate H2O2 in Pd presence in the system. The effect of polarity reversal frequency, duration of the polarity reversal intervals, current intensity and TCE concentration on TCE removal rate and removal mechanism were evaluated. TCE removal efficiencies under 6 cycles h(-1) were similar in the presence of Pd catalyst (50.3%) and without Pd catalyst (49.8%), indicating that Pd has limited impact on TCE degradation under these conditions. The overall removal efficacies after 60 min treatment under polarity reversal frequencies of 6, 10, 15, 30 and 90 cycles h(-1) were 50.3%, 56.3%, 69.3%, 34.7% and 23.4%, respectively. Increasing the frequency of polarity reversal increases TCE removal as long as sufficient...

Trichloroethylene (TCE) has been a long-time concern for workers, unions, occupational experts and residents of Ontario and other jurisdictions where the compound has been used. TCE can be absorbed by the body through inhalation, ingestion and dermal absorption. Inhalation of TCE can cause headaches, dizziness and damage to facial nerves.  Contact with the skin can result in rashes.

Ingestion or inhalation can result in liver and kidney damage in animals, as well as developmental effects on mouse foetuses.
Human epidemiological studies and animal studies suggest that TCE may cause cancer.  The International Agency for Research on Cancer classifies TCE as “probably carcinogenic to humans” based on “limited evidence” from human studies and “sufficient evidence” from animal studies.  Vinyl chloride, another breakdown product of TCE, is far more toxic than TCE. It is a colorless gas that burns easily and is unstable at high temperatures.

Residents of Ontario have repeatedly raised concerns about lax TCE standards and MOE enforcement.  For example, the Environmental Commissioner of Ontario received applications regarding this contaminant as far back as 1995, when four applications requesting that the Ontario Drinking Water Objectives (1994) for TCE be tightened were filed under the Ontario Environmental Bill of Rights.  In 2000, the ECO received another application from the residents of Beckwith Township, whose wells were contaminated by TCE.  In 2006, MOE finally decided to strengthen the TCE drinking water standards from 0.05 mg/L to 0.005 mg/L set under O. Reg. 169/03 of the Safe Drinking Water Act, 2002.

In October 2011, soil vapour samples were collected from several locations in the vicinity of the former OMCC facility and down-gradient in the City of Peterborough.  Elevated TCE concentrations were reported.  Concentrations were high enough that when modeled, the predicted indoor air concentrations suggested a potential risk. At this time MOE initiated the development of an indoor air sampling program, in consultation with the local health unit, City of Peterborough and Ministry of Labour.  A second round of soil vapour sampling was undertaken in December 2011, and although the results were lower, continued to suggest a potential risk to indoor air.  In February 2012 notices were delivered to the occupants and homeowners in the targeted area requesting their participation in the program.  Interviews were conducted with homeowners/occupants beginning in March and continuing throughout the program.  Sampling began the last week of March 2012 and continued into the first week of May.  Homeowners/occupants were notified verbally (by telephone) of their indoor air results upon receipt by the local MOE office.  Written confirmation of results were mailed May 17, 2012. 
 
In June 2012 MOE's Standards Development Branch (SDB) began further analysis and interpretation. As a quick summary 26 homes were sampled, 3 homes reported indoor TCE concentrations exceeding the Ministry’s 0.5 µg/m3 target level, with the highest concentration being 2.58 µg/m3.  All three locations had visible pathways for vapour intrusion in the form of dirt floors or cut-outs in the basement’s concrete floor.  
 
Soil vapour sampling had previously been done, since 2001 by the Environmental Remediation Receiver (Dillon); however, in 2011 the MOE had requested modifications to their sampling program, including the installation of additional monitoring locations in the area north of Lansdowne Street.
 
This presentation reviews the legal background to the TCE plume in Peterborough, Ontario and provides an overview for residents.  It originally was prepared at the request of the MOE and the Peterborough City and County Health Unit (PCCHU).

A mesocosm system was designed to study evaporation kinetics and transport of TCE in flowing surface water. The airtight unit, with a total internal volume of 52.01 × 10−2 m3, was fabricated with glass and Teflon material, and was provided with 8.53 m long channel to simulate water flow in an open channel. The peristaltic pumps, connected to the inlet and the outlet of the mesocosm, provided a constant water flow through the channels. The experimental studies were conducted at two different velocities, 9.42 × 10−3 and 4.71 × 10–3 m/s, respectively. For both the velocities, a tracer (NaBr) test confirmed uniform water flow in the channels. The total length and the length between the sampling ports were found sufficient to record gradual decrease in TCE concentrations along the direction of the flow in the channels. The volatilization coefficient for TCE was found to be 0.49 and 1.07 h−1 for the experiments conducted at lower and higher water velocities, respectively. The TCE evaporation half life (t 1/2) and the corresponding evaporation half distance (d 1/2) were 1.41 h and 23.98 m for lower velocity, and 0.65 h and 21.96 m for higher velocity, respectively.

Dehalospirillum multivorans is a strictly anaerobic bacterium that is able to dechlorinate tetrachloroethene (perchloroethylene; PCE) via trichloroethene (TCE) to cis-1,2-dichloroethene (DCE) as part of its energy metabolism. The present communication describes some features of the dechlorination reaction in growing cultures, cell suspensions, and cell extracts of D. multivorans. Cell suspensions catalyzed the reductive dechlorination of PCE with pyruvate as electron donor at specific rates of up to 150 nmol (chloride released) min-1 (mg cell protein)-1 (300 microM PCE initially, pH 7.5, 25 degrees C). The rate of dechlorination depended on the PCE concentration; concentrations higher than 300 microM inhibited dehalogenation. The temperature optimum was between 25 and 30 degrees C; the pH optimum at about 7.5. Dehalogenation was sensitive to potential alternative electron acceptors such as fumarate or sulfur; nitrate or sulfate had no significant effect on PCE reduction. Propyl iodide (50 microM) almost completely inhibited the dehalogenation of PCE in cell suspensions. Cell extracts mediated the dehalogenation of PCE and of TCE with reduced methyl viologen as the electron donor at specific rates of up to 0.5 mumol (chloride released) min-1 (mg protein).-1 An abiotic reductive dehalogenation could be excluded since cell extracts heated for 10 min at 95 degrees C were inactive. The PCE dehalogenase was recovered in the soluble cell fraction after ultracentrifugation. The enzyme was not inactivated by oxygen.