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Trichloroethene

DESIGNATIONS

CAS No.: 79-01-6
Registry name: Trichloroethene
Chemical name: Ethene, trichloro
Synonyms, Trade names: Tri, ethene trichloride, trichloroethene, Chlorylen, Algylen, Benzinol, Circosolv, Lanadin, Perm-a-chlor, Triasol, Trichloran, Triclene, Trimar, Vitran and many others
Chemical name (German): Trichlorethen
Chemical name (French): Trichloroéthène, éthène trichloré
Appearance: colourless, volatile liquid with sweet odour reminiscent of chloroform, the gas is much denser than air.

BASIC CHEMICAL AND PHYSICAL DATA

Empirical formula: C2HCl3
Rel. molecular mass: 131.4 g
Density: 1.46 g/cm3 at 20°C
Relative gas density: 4.54
Boiling point: 86.7°C
Melting point: -73 to -87°C
Vapour pressure: 77 hPa at 20°C
Ignition temperature: 410°C
Explosion limits: 7.9 - 41 Vol%
Odour threshold: 50 ppm in air
Solvolysis/solubility: in water: 1.1 g/l at 20°C; readily soluble in organic solvents
Conversion factors: 1 ppm = 5.46 mg/m3
1 mg/m3 = 0.18 ppm

ORIGIN AND USE

Usage:
Trichloroethene is used for a wide range of applications. 75-80% of the worldwide trichloroethene production is used for degreasing in the metal and glass industry (DVGW, 1985). Because of its good solvent properties, it was formerly used in dry-cleaning facilities and for the extraction of natural substances (e.g. for decaffeinated coffee and for fruit juice extracts). It is also used as an intermediate product in the manufacture of chloroacetic acid and as a solvent for greases, oils, waxes, resins, rubber, paints, lacquers, cellulose ester and cellulose ether.

Origin/derivation:
Trichloroethene is an artificial compound; it is produced synthetically from 1,2-dichloroethane. Stabilisers are added to the marketed product.

Production figures:

Worldwide 1978-80 600,000 t (RIPPEN, 1989)
EC 1984 200,000 t (ULLMANN, 1986)
USA 1984 110,000 t (ULLMANN, 1986)
Federal Republic of Germany 1984 30,400 t (RIPPEN, 1989)
Japan 1984 80,000 t (ULLMANN, 1986)

with a common annual decline of 5 - 7 % worldwide

Toxicity

Humans: LD100 150 g, dermal acc. RIPPEN, 1989
TCL0 44 mg/l, inhalation (83 min) acc. RIPPEN, 1989
Mammals:
Rat: LC50 7,200 mg/kg, oral (14 d) acc. RIPPEN, 1989
LC50 28-29 mg/kg, dermal acc. RIPPEN, 1989
NEL 400 mg/kg, oral (28 d) acc. RIPPEN, 1989
Mouse: LD50 2,400 mg/kg, oral acc. RIPPEN, 1989
LC50 45 mg/l, inhalation (4 h) acc. RIPPEN, 1989
Rabbit: LD 7,330 mg/kg acc. DVGW, 1985
Cat: LD 5,860 mg/kg acc. DVGW, 1985
Dog: LD50 5,900 mg/kg acc. DVGW, 1985
Aquatic organisms:
  LC50 120-150 mg/l (48 h) acc. RIPPEN, 1989
American minnow: LC50 41-67 mg/l (96 h) acc. RIPPEN, 1989
EC50 22 mg/l (96 h) acc. RIPPEN, 1989
Blue perch: LC50 41-45 mg/l (96 h) acc. RIPPEN, 1989
Water flea: EC50 21 mg/l (48 h) acc. RIPPEN, 1989
Plants:
Green algae: EC50 530 mg/l (24 h) acc. RIPPEN, 1989

Characteristic effects:

Humans/mammals: Trichlorethene irritates the eyes and skin as well as having a narcotic effect; loss of consciousness occurs on inhaling an amount of more than 3 mg/kg weight. Loss of weight and nervous phenomena such as headaches, disturbance of consciousness, agitation and frenzy are the consequences of chronic absorption which damages the central nervous system (with female employees from more than 200 vppm; RIPPEN, 1989).

Trichloroethene likewise affects the heart, liver and kidneys. For a long time the substance was considered carcinogenic, but the current opinion is that the pure substance is not. The enhanced tumour rates in animal experiments were the result of stabilisers added to trichloroethene such as epichlorohydrin or epoxybutane. Experiments performed in the USA with pure trichloroethene have, however, revealed an increase in the number of tumours in two types of animal (UBA, 1986).

A direct degradation product has likewise proven to be injurious to humans: trichloroacetyldehydride forms in the body and has a mutagenic effect.

Plants: Trichloroethene inhibits cell reproduction and stunts growth. Slight yellowing of leaves is sometimes encountered.

ENVIRONMENTAL BEHAVIOUR

Water:
Trichloroethene is denser than water and sinks gradually to the bottom even in groundwater. Groundwater contamination may last for many decades. It is listed in water hazard class 3 (extremely hazardous) in Germany.

Air:
Because of its volatility, large quantities of the substance produced (an estimated 50,000 t in 1979; DVGW, 1985) evaporate and are uniformly distributed in the atmosphere (ubiquitous). Exchange takes place between air and water. According to RIPPEN (1989), the substance makes a minor contribution to the formation of smog. It is washed out by precipitation and thus ingresses into surface water or groundwater.

Soil:
The substance accumulates in sediment; in sewage sludge, sometimes even to an extent which damages anaerobes.

Half-life:
The estimated dwell time in the atmosphere is roughly 1 week. If not evaporated, trichloroethene is persistent for 2-18 months in water-unsaturated soils. The half-life in seawater (pH 8 / 10°C) is 39 weeks and 2.5 - 6 years in freshwater (RIPPEN, 1989). The half-life in darkness is 11 months. Trichloroethene is stable under normal conditions (pH 7 / 25°C) (RIPPEN, 1989).

Degradation, decomposition products:
Trichloroethene is converted when exposed to light and heat in the atmosphere to phosgene, formyl chloride, acetyl chloride and finally to CO2 and HCl. In water, it forms CHCl2COCl. Hexachlorobenzene is formed at high temperatures; reaction with alkaline materials (e.g. mortar) to form dichloroacetylene. Anaerobic transformation to dichloroethene isomers and vinyl chloride takes place in contaminated groundwater, in anaerobic soil and on dumps. There is no transformation in sandy soils. There is degradation by adapted microorganisms.

Food chain:
Approx. 2-4% of the human intake of trichloroethene results from drinking water, 3-26% from foodstuffs and 70-95% from the air (UBA, 1986). Metabolism and accumulation take place in the bodily tissue.

ENVIRONMENTAL STANDARDS

Medium/
acceptor		 Sector Country/organ. Status Value Cat. Remarks Source
Water:   CH

G

25 µg/l

   1) acc. RIPPEN, 1989
Drinkw A

L

30 µg/l

   2) acc. RIPPEN, 1989
Drinkw A  

100 µg/l

   3) acc. RIPPEN, 1989
Drinkw D

G

10 µg/l

 TVO 4) acc. DVGW, 1985
Drinkw DDR

G

1 µg/l

     acc. RIPPEN, 1989
Drinkw EC

G

1 µg/l

   5) acc. DVGW, 1985
Drinkw USA

G

75 µg/l

   6) acc. RIPPEN, 1989
Drinkw WHO

G

30 µg/l

     acc. DVGW, 1985
Surface USA

G

27 µg/l

     acc. UBA, 1986
Waste water D

R

5 g/m3

   At point of discharge acc. ROTH, 1989
Air: Emiss. D

L

0.1 g/m3

   mass flow > 2 kg/h acc. TA Luft, 1986
Workp D

L

270 mg/m3

 TRK Kat. 3 DFG, 1994
Workp DDR

L

750 mg/m3

 MAKK   acc. HORN, 1989
Workp DDR

L

250 mg/m3

 MAKD   acc. HORN, 1989
Workp SU

(L)

10 mg/m3

 PDK   acc. RIPPEN, 1989
Workp USA

(L)

270 mg/m3

 TWA   acc. RIPPEN, 1989
Workp USA

(L)

1,080 mg/m3

 STEL   ACGIH, 1986
  D

L

30 mg/m3

 MIKK   acc. BAUM, 1988
  D

L

90 mg/m3

 MIKD   acc. BAUM, 1988
  D

G

5 mg/m3

   1/2 h, VDI Guideline 2310 acc. LAU-BW, 1989
  DDR

L

4 mg/m3

 MIKK   acc. HORN, 1989
  DDR

L

1 mg/m3

 MIKD   acc. HORN, 1989
  WHO

G

1 mg/m3

   24 h acc. LAU-BW, 1989
  D

L

500 µg/dl

 BAT 8) DGE, 1989
  D

L

100 mg/l

 BAT 9) DFG, 1989
Foodstuffs:   D

L

0 mg/kg

 LHmV   acc. UMWELT, 1989
    D

L

0.2 mg/kg

 LHmV 10) acc. UMWELT, 1989

Notes:

1) Provisional tolerance value (sum total of all chlorinated solvents)
2) Sum total of 14 halogenated hydrocarbons
3) Sum total of 14 halogenated hydrocarbons in less than 6 months
4) Sum total of trichloroethane, trichloroethene, tetrachloroethene and dichloromethane
5) Sum total of organic chlorine compounds except pesticides
6) With chronic exposure
7) Criterion for water quality
8) Parameter, trichloroethanol in whole blood
9) Parameter, trichloroacetic acid in urine
10) Cumulative value for several solvents in one item of food

COMPARISON/REFERENCE VALUES

Medium/origin Country Value Source
Drinking water:
Bremen (1980) D 0.1 µg/l acc. DVGW, 1985
Mannheim (1980) D 0.3 - 7.1 µg/l acc. DVGW, 1985
Taunus (1980) D <9.5 µg/l acc. DVGW, 1985
Great Britain (1981) GB 0.24 µg/l acc. DVGW, 1985
Japan (1977) J 0.2-0.9 µg/l (5 cities) acc. DVGW, 1985
USA (1977) USA 0.1-0.5 µg/l (5 cities) acc. DVGW, 1985
Vienna 1984) A <3.5 µg/l acc. RIPPEN, 1989
Zurich (1977) CH 0.005-0.105 µg/l acc. DVGW, 1985
Gothenburg S 0.015 µg/l acc. DVGW, 1985
Surface water
Rhine (Basle, 1982) D 0.2-2.44 µg/l acc. DVGW, 1985
Rhine (Cologne, 1983) D 0.06-0.81 µg/l acc. DVGW, 1985
Main (1980) D 0.4-13 µg/l acc. DVGW, 1985
Lake Constance (1982) D 0.01- 0.08 µg/l acc. DVGW, 1985
Liverpool Bay GB 0.3 µg/l acc. RIPPEN, 1989
Niagara (1981) USA 8 µg/l (mean value) acc. RIPPEN, 1989
Lake Ontario (1981) CDN 13 µg/l (mean value) acc. RIPPEN, 1989
Gulf of Kavala GR 0.26-2.80 ng/l acc. RIPPEN, 1989
Switzerland (1981-83) CH <1.3 µg/l (mean value) acc. RIPPEN, 1989
Japan (1974) J 5 µg/l (mean value) acc. RIPPEN, 1989
Gulf of Mexico, coast MEX 10-50 ng/l acc. RIPPEN, 1989
South Pacific (1981)   0.1-0.7 ng/l acc. RIPPEN, 1989
Groundwater
North Bremen (1985) D <100 µg/l acc. DVGW, 1985
Holland NL <1,000 µg/l (mean value) acc. RIPPEN, 1989
Holland, contaminated NL 3,000 µg/l acc. RIPPEN, 1989
Great Britain GB <0.01 - 60 µg/l acc. RIPPEN, 1989
Minnesota USA 0.2 - 6.8 µg/l acc. RIPPEN, 1989
Ohio, contaminated USA <6,000 µg/l acc. RIPPEN, 1989
Switzerland (1981-83) CH <15 µg/l acc. RIPPEN, 1989
Sediment/soil:
Rhine (1978) D <300 µg/kg acc. DVGW, 1985
Rhine (Hitdorf) (1982) D <10 µg/kg acc. DVGW, 1985
Black Forest, west facing D 8 - 30 µg/m3 acc. RIPPEN, 1989
Close to dry cleaning establishments D 30 - 200 µg/m3 acc. RIPPEN, 1989
Sewage sludge (dry subst.) USA 0.048 - 44 mg/kg acc. RIPPEN, 1989
Air
Northern hemisphere   87 ng/m3 acc. RIPPEN, 1989
Southern hemisphere   8.2 ng/m3 acc. RIPPEN, 1989
Arctic (1980-82)   22 - 220 ng/m3 acc. RIPPEN, 1989
Frankfurt, city centre D 2-46 µg/m3 (max.: 1,100) acc. RIPPEN, 1989
Berlin (1977) D 1-61 µg/m3 acc. RIPPEN, 1989
Japan (1979) J 0.08-32 µg/m3 acc. RIPPEN, 1989
Sweden (city) S 10 µg/m3 acc. RIPPEN, 1989
Mammals:
Invertebrates   1-10 µg/kg acc. RIPPEN, 1989
Fish   0.5-100 µg/kg acc. RIPPEN, 1989
Waterfowl   1-100 µg/kg acc. RIPPEN, 1989
Mammals   1-10 µg/kg acc. RIPPEN, 1989
Humans (fat)   < 32 µg/kg acc. RIPPEN, 1989
Humans (total)   1 µg/kg acc. RIPPEN, 1989
Foodstuffs:
Beverages D <0.1-8 µg/kg acc. RIPPEN, 1989
Solid food D 0.1-64 µg/kg acc. RIPPEN, 1989

Assessment/comments

Because of the high toxicity in aquatic organisms, the US EPA recommends a general surface-water concentration of zero. As the risk of cancer due to the consumption of contaminated drinking water cannot be precluded, a quality value has been established for the sum of four similar chlorinated hydrocarbons. Despite an extremely broad span in various countries, this figure should not exceed 10 m g/l for drinking water.

As trichloroethene is a typical contaminant for sewage water from cities and communities, it must be handled carefully to minimise emissions.

In the Nineties, several countries restricted the use of trichloroethene by law, so that gradually a replacement is taking place.

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