Who/sde/wsh/05. 08/22 English only Trichloroethene in Drinking-water

GENERAL DESCRIPTION 1.1 Identity

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1.2 Physicochemical properties 1
Reference
1.3 Organoleptic properties
1.5 Environmental fate
2. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE
2.2 Water

1. GENERAL DESCRIPTION

1.1 Identity

CAS No.:	79-01-6
Molecular formula:	C₂HCl₃

Trichloroethene is also known as trichloroethylene and TCE.

1.2 Physicochemical properties^¹

Property	Value	Reference
Boiling point	86.7 °C	Windholz et al., 1976
Vapour pressure	8.0–9.9 kPa at 20–25 °C	McNeill, 1979; ATSDR, 1989
Water solubility	1.1–1.4 g/litre	ATSDR, 1997
Log octanol–water partition coefficient	2.29–2.42	Hansch & Leo, 1985; US EPA, 1985b
Henry’s law constant	1.1 kPa·m³/mol at 25 °C	Hine & Mookerjee, 1975

1.3 Organoleptic properties

TCE has a sweet odour. Its odour thresholds are 546–1092 mg/m³ in air and 0.31 mg/litre in water (Amoore & Hautala, 1983; Ruth, 1986).

1.4 Major uses and sources in drinking-water

TCE is used primarily in metal degreasing operations. It is also used as a solvent for greases, oils, fats and tars, in paint removers, coatings and vinyl resins, and by the textile processing industry to scour cotton, wool and other fabrics. TCE may be used as a chemical intermediate in the production of polyvinyl chloride, pharmaceuticals, flame retardant chemicals and insecticides. It may also be present in household and consumer products, such as typewriter correction fluids (ATSDR, 1997).

Most of the TCE used for degreasing is believed to be emitted to the atmosphere (US EPA, 1985a). TCE may also be introduced into surface water and groundwater in industrial effluents (IPCS, 1985). Poor handling as well as improper disposal of TCE in landfills have been the main causes of groundwater contamination. The biodegradation of another volatile organic pollutant, tetrachloroethene (or perchloroethylene, PCE), in groundwater may also lead to the formation of TCE (Major et al., 1991).

1.5 Environmental fate

In the atmosphere, TCE is highly reactive and does not persist for any significant length of time (ATSDR, 1993). In surface water, volatilization is the principal route of degradation, while photodegradation and hydrolysis play minor roles. In groundwater, TCE is degraded slowly by microorganisms. Bioconcentration of trichloroethene in aquatic species is low (ATSDR, 1993).

2. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE

2.1 Air

TCE has been detected in outdoor and indoor air in Canada. Levels of TCE in air were determined in Toronto and Montreal for 1 year (1984–1985) and in Sarnia and Vancouver for 1 month (autumn 1983). Mean levels for the four cities were 1.9, 0.7, 1.2 and 1.0 µg/m³, respectively, with maxima of 8.6, 1.7, 3.6 and 3.4 µg/m³, respectively (Environment Canada, 1986). In another survey, mean concentrations of TCE in ambient air at 11 urban sites and 1 rural site in Canada (1988–1990) ranged from 0.07 to 0.45 µg/m³ (Vancouver and Calgary, respectively), with an overall mean value of 0.28 µg/m³ and a maximum single value of 19.98 µg/m³ reported in Montreal (Dann, 1993).

Recent US data are similar to the levels measured in Canada. In 1998, ambient air measurement data from 115 monitors located in 14 states indicated that TCE levels ranged from 0.01 to 3.9 µg/m³, with a mean of 0.88 µg/m³. Mean TCE air concentrations (1985–1998) for rural, suburban, urban, commercial and industrial land uses were 0.42, 1.26, 1.61, 1.84 and 1.54 µg/m³, respectively (US EPA, 1999a).
The mean air concentration in approximately 750 homes from 10 Canadian provinces surveyed in 1991 was 1.4 µg/m³, with a maximum value of 165 µg/m³ (Otson et al., 1992). In two homes tested, it was reported that showering with well water containing extremely high levels of TCE (40 mg/litre) increased levels of TCE in bathroom air from <0.5 to 67–81 mg/m³ in less than 30 min (Andelman, 1985).

2.2 Water

TCE has been detected frequently in natural water and drinking-water in Canada and other countries. Due to its high volatility, TCE concentrations are normally low in surface water (1 µg/litre). However, in groundwater systems where volatilization and biodegradation are limited, concentrations may be higher if contamination has occurred in the vicinity and leaching has taken place.

Because analytical methods have improved over the years since TCE was first assayed, concentrations that were once considered “non-detectable” are now quantifiable. This confounds the use of historical TCE data, as the values for “non-detectable” have changed over time.
TCE was detected in raw and treated water at 10 potable water supply facilities in Ontario in 1983 at levels ranging from 0.1 to 0.8 µg/litre (Mann Testing Laboratories Ltd, 1983). In 1979, TCE was found in over half of potable water samples taken at 30 treatment facilities across Canada; mean concentrations were 1 µg/litre or less, and the maximum level was 9 µg/litre (Otson et al., 1982).
Monitoring data from eight Canadian provinces for the period 1985–1990 indicated that 95% of 7902 samples from drinking-water supplies (raw, treated or distributed water) had TCE concentrations below 1 µg/litre. The maximum concentration was 23.9 µg/litre (groundwater sample). Most (75%) of the samples in which TCE was detected were from groundwater sources (Department of National Health and Welfare, 1993). More recent data from New Brunswick (1994–2001), Alberta (1998–2001), the Yukon (2002), Ontario (1996–2001) and Quebec (1985–2002) for raw (surface water and groundwater), treated and distributed water indicated that more than 99% of samples contained TCE at concentrations less than or equal to 1.0 µg/litre. The maximum concentration was 81 µg/litre. Of those samples with detectable TCE concentrations, most were from groundwater (Alberta Department of Environmental Protection, New Brunswick Department of Health and Wellness, Ontario Ministry of Environment and Energy, Yukon Department of Health and Social Services and Quebec Ministry of the Environment, personal communications, 2002).
A 2000 survey of 68 First Nations community water supplies (groundwater and surface water) in Manitoba found that TCE concentrations were non-detectable (<0.5 µg/litre) (Yuen & Zimmer, 2001).
Groundwater is the sole source of water for an estimated 25–30% of the Canadian population (Statistics Canada, 1994). In 1995, a national review of TCE occurrence data was carried out to determine the extent of groundwater contamination by TCE and the number of people potentially exposed to contaminated drinking-water. The majority of sites were from Ontario and New Brunswick. The review was based on urban groundwater supplies. Of the 481 municipal/communal and 215 private/domestic groundwater supplies (raw water), 8.3% and 3.3%, respectively, contained TCE, at average maximum concentrations of 25 µg/litre and 1680 µg/litre, respectively. This review involved a compilation of data from a variety of sources over different periods of time. Consequently, interpretation of the data is made more difficult by the range of detection limits. A majority of all sites (93%) had non-detectable levels (<0.01–10 µg/litre), 3.6% had a maximum concentration of <1 µg/litre, 1.4% had a maximum of 1–10 µg/litre, 0.43% had a maximum of 10–100 µg/litre and 1.3%^² had a maximum of >100 µg/litre (Raven and Beck Environmental Ltd, 1995).
It was estimated that approximately 1.67 million of the 7.1 million Canadians who relied on groundwater for household use in 1995 were covered by this study. Of the 1.67 million surveyed, the water supplies of 49% had non-detectable levels of TCE (<0.01–10 µg/litre), 48.1% had a maximum of 1–10 µg/litre, 2.1% had a maximum of 10–100 µg/litre and 0.8% had a maximum of >100 µg/litre. Despite the problems associated with the wide range of detection limits reported in this study, the results of the survey suggested that more than 95% of Canadians who rely on groundwater are exposed to less than 10 µg/litre in their drinking-water. In fact, this probably represents a worst-case scenario, since the sampled data were for raw water and may not be representative of water received at households (Raven and Beck Environmental Ltd, 1995).
In the USA, TCE has been the volatile organic contaminant that is most frequently found in groundwater and the one present in the highest concentrations (ATSDR, 1997). TCE was detected (detection limit 0.2 µg/litre) in 91 of 945 (9.6%) samples of finished water using groundwater sources nationwide. The median level in positive samples was 1 µg/litre, and the maximum was 130 µg/litre. In samples taken from tap water in homes near the Love Canal waste site, TCE levels ranged from 10 to 250 ng/litre. In New Jersey, TCE was detected in 388 of 669 (58%) samples taken between 1977 and 1979, with a maximum concentration of 635 µg/litre (ATSDR, 1997). TCE levels ranging from 900 to 27 300 µg/litre were found in contaminated wells in a survey of four states (Pennsylvania, New York, Massachusetts and New Jersey) (ATSDR, 1997). TCE was detected in 28% of 9295 surface water samples taken nationwide between 1980 and 1982 in the USA. A similar percentage was found in two surveys (n = 6322) of the Ohio River system (1978–1979 and 1980–1981), with TCE levels ranging from 0.1 to 1 µg/litre. TCE was detected (maximum level of 32.6 µg/litre) in 261 of 462 (56%) surface water samples collected in New Jersey between 1977 and 1979. In 1981, mean TCE levels of 0.008–0.13 µg/litre were detected in the Niagara River and Lake Ontario (ATSDR, 1997).