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Tetrachloroethene

DESIGNATIONS

CAS No.: 127-18-4
Registry name: Tetrachloroethene
Chemical name: Tetrachloroethene
Synonyms, Trade names: Perchloroethene, PER, ethylene tetrachloride, 1,1,2,2-tetrachloroethene, Cecolin 2, Dekapir 2, Digrisol, Dow-Per, Drosol, Dynaper, Etilin, Peran, Perawin, Perclone, Sirius 2, Tetralex, Tetralina, Ankliostin, Didakene, Nema, Perc and many others
Chemical name (German): Tetrachlorethen, Perchlorethylen
Chemical name (French): Tetrachlorothne, perchlorthne
Appearance: colourless liquid with chloroform-like odour, vapour is much denser than air

BASIC CHEMICAL AND PHYSICAL DATA

Empirical formula: C2Cl4
Rel. molecular mass: 165.83 g
Density: 1.624 g/cm3 at 20C
Relative gas density: 5.73
Boiling point: 121.1C
Melting point: -23C
Vapour pressure: 18.9 hPa at 20C; 32 hPa at 30C; 84 hPa at 50C
Flash point: none
Odour threshold: 0.3-5 mg/l in water
4.7-70 ppmv in air
Solvolysis/solubility: in water: 129 mg/l
readily soluble in organic solvents
Conversion factors: 1 ppm = 6.89 mg/m3
1 mg/m3 = 0.145 ppm

ORIGIN AND USE

Usage:
Tetrachloroethene is a useful solvent. According to BGA (1988), 35% of the amount produced is used to degrease metal surfaces and 50% in dry cleaning establishments. LAI (1988) estimates that 60-65% are used for the treatment of metal surfaces and 20% in dry cleaning establishments. Stabilisers with widely differing chemical compositions are added to reduce the vapour pressure. Important products are e.g. contact adhesives, degreasing agents, wax removers, shoe polishes, garden pesticides, upholstery cleaners and carpet cleaners. In most products, tetrachloroethene has been replaced by other less toxic solvents.

Origin/derivation:
Tetrachloroethene is produced by oxyhydrochlorination, perchlorination and dehydrochlorination of hydrocarbons or chlorinated hydrocarbons.

Production figures:

Worldwide 1978-80 1,100,000 t (RIPPEN, 1989)
Worldwide 1985 650,000 t (ULLMANN, 1986)
EC 1980 < 500,000 t (BGA, 1988)
USA 1977 304,000 t (BGA, 1988)
USA 1985 220,000 t (ULLMANN, 1986)
D 1979 113,000 t (BMI, 1985)
D 1985 110,000 t (ULLMANN, 1986)
D 1986 75,000 t (LAI, 1988)
Japan 1973 57,000 t (RIPPEN, 1989)
France 1981 26,000 t (RIPPEN, 1989)
Mexico (Import) 1984 15,000 t (RIPPEN, 1989)
Sweden 1977 5,300 t (RIPPEN, 1989)

Toxicity

Humans: LD0 140 mg/m3 (1.3 or 7.5 h/d for 5 d/w) acc. WHO, 1984
Mammals:
Mouse: LD50 8,000-11,000 mg/m3, oral acc. VERSCHUEREN, 1983
Mouse: LC100 135,000 mg/m3 (2 h) acc. MALTONI et al., 1986
Mouse: LC50 332,200 mg/m3 (0,5 h) acc. MALTONI et al., 1986
Rat: NEL 475 mg/m3, inhalation (8 h/d for 5 d/w) acc. VERSCHUEREN, 1983
Rat: LD50 > 5,000 mg/kg, oral acc. VERSCHUEREN, 1983
Rat: LD50 13,000 mg/kg, oral (6 h) acc. WHO, 1984
Rat: LC100 20,000 ppm, inhalation (0,4 h) acc. MALTONI et al., 1986
Rat: LC100 2,500 ppm, inhalation (7 h) acc. MALTONI et al., 1986
Rabbit: LD 20,000 ppm, inhalation (2 h) acc. MALTONI et al., 1986
Guinea pig: LC100 37,000 ppm, inhalation (0,67 h) acc. MALTONI et al., 1986
Cat: LCL0 6,074 ppm, inhalation (2 h) acc. MALTONI et al., 1986
Aquatic organisms:
Water flea: LC50 18 mg/l (48 h) acc. WHO, 1984
Water flea: NEL 10 mg/l (48 h) acc. WHO, 1984
American minnow: LC50 23.5 ng/l (24 h) acc. VERSCHUEREN, 1983
Blue perch: LC50 46 mg/l (24 h) acc. WHO, 1984
Blue perch: LC50 13 mg/l (96 h) acc. WHO, 1984

Characteristic effects:

Humans/mammals: Tetrachloroethene is resorbed through the skin because of its fat-dissolving properties. Concentrations above 680 mg/m3 irritate the eyes and the respiratory tract, concentrations of 4,000-6,000 mg/m3 during 45 minutes cause numbness. The substance acts on the central nervous system and produces headaches, dizziness and nausea. Inhalation often results in delayed neurological damage.

Both, the WHO and the German Research Foundation (DFG) have classified tetrachloroethene as a substance suspected of carcinogenic potential. A few experiments with yeast cells have also revealed mutagenic effects. There is no proof of teratogenity or fetal toxicity yet.

ENVIRONMENTAL BEHAVIOUR

Water:
Tetrachloroethene sinks in water because of its poor water solubility and its high density. Thus, it may accumulate in groundwater and surface water. Tetrachloroethene is classed as very hazardous to water (in Germany: water hazard class 3). It is toxic to aquatic organisms and decomposes slowly to form trichloroacetic acid and hydrochloric acid. Degradation by microorganisms has been observed (from sequential dehydrochlorination up to mineralisation). Tetrachloroethene finds its way into the water cycle via industrial waste water.

Air:
Because of its high vapour pressure, about 80-90% of the substance ingresses into the atmosphere where it is ubiquitously distributed. Tetrachloroethene may be degraded by photolysis and is probably involved in the depletion of the ozone layer. Exchange takes place between air and water with the transition into the atmosphere being the most common path.

Soil:
The accumulation of tetrachloroethene in soil is dependent on the grain size and the water and humus content. Biological degradation takes place in soil. High concentrations are to be found in the immediate vicinity of emission sources.

Half-life:
The half-life for hydrolysis in aerated water is between 9 months and 6 years (UBA, 1986). In the troposphere, half-life amounts to approx. 12 weeks or, if photodegradation takes place, up to 8 weeks (UBA, 1986 and MALTONI et al., 1986). The persistence in water-unsaturated soils is 2-18 months (DVGW, 1985).

Degradation, decomposition products:
Degradation in soil takes place via methanogenic, anaerobic microorganisms (UBA, 1986). In the troposphere, the substance is decomposed by photo-oxidation to form carbon dioxide and hydrochloric acid. In water, trichloroacetic and hydrochloric acid are formed (BGA, 1985). Other decomposition products are phosgene (COCl2), di- and trichloroacetyl chloride. The liver degrades tetrachloroethene in the human body.

Food chain:
There is a moderate accumulation of tetrachloroethene in fatty tissues.

ENVIRONMENTAL STANDARDS

Medium/
acceptor
Sector Country/organ. Status

Value

Cat. Remarks Source
Water: Drinkw D

L

0.01 mg/l

    acc. TVO, 1990
Drinkw EC

G

0.001 g/m3

    acc. LAU-BW, 1989
Drinkw WHO

G

10 g/l

    acc. WHO, 1984
Surface USA  

20 g/l

    acc. WHO, 1987
Waste water CH

L

0.05 g/m3

  For drinking water acc. LAU-BW, 1989
Waste water D

L

5 g/m3

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

L

35 mg/m3

MIK Long-time value acc. BAUM, 1988
  D

L

110 mg/m3

MIK Short-time value 2) acc. BAUM, 1988
  D

L

100 mg/m3

  1) acc. KHN & BIRETT, 1988
  D

G

5 mg/m3

  3) acc. BGA, 1988
  DDR

L

0.5 mg/m3

  Short-time value acc. HORN, 1989
  DDR

L

0.06 mg/m3

  Long-time value acc. HORN, 1989
  WHO

G

5 mg/m3

  24 h guide value acc. LAU-BW, 1989
  WHO

G

8 mg/m3

  30 min acc. LAU-BW, 1989
Emiss. D

L

0.1 g/m3

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

(L)

260 mg/m3

  Long-time value acc. MALTONI et al., 1986
Workp AUS

(L)

670 mg/m3

  Long-time value acc. WHO, 1987
Workp B

(L)

670 mg/m3

  Long-time value acc. WHO, 1987
Workp BG

(L)

10 mg/m3

    acc. MALTONI et al., 1986
Workp BR

(L)

525 mg/m3

  48 h/w acc. WHO, 1987
Workp CH

(L)

345 mg/m3

  Long-time value, skin acc. WHO, 1987
Workp CS

(L)

250 mg/m3

  4) acc. WHO, 1984
Workp CS

(L)

1,250 mg/m3

  Short-time value acc. WHO, 1984
Workp D

L

345 mg/m3

  TRK (IIIB) DFG, 1989
Workp DDR

(L)

300 mg/m3

  Long-time value acc. HORN, 1989
Workp DDR

(L)

900 mg/m3

  Short-time value acc. HORN, 1989
Workp E

(L)

110 mg/m3

  Long-time value acc. MALTONI et al., 1986
Workp ET

(L)

267 mg/m3

  Long-time value acc. MALTONI et al., 1986
Workp F

(L)

405 mg/m3

  Long-time value acc. MALTONI et al., 1986
Workp F

(L)

1,080 mg/m3

  4) acc. MALTONI et al., 1986
Workp GB

(L)

678 mg/m3

  Long-time value acc. WHO, 1987
Workp GB

(L)

1,000 mg/m3

  10 min acc. WHO, 1987
Workp H

(L)

10 mg/m3

  Long-time value acc. WHO, 1987
Workp H

(L)

50 mg/m3

  30 min acc. WHO, 1987
Workp I

(L)

400 mg/m3

  Long-time value acc. MALTONI et al.,1986
Workp I

(L)

1,000 mg/m3

  Skin acc. MALTONI et al.,1986
Workp J

(L)

268 mg/m3

  Long-time value acc. MALTONI et al.,1986
Workp J

(L)

345 mg/m3

  4) acc. WHO, 1987
Workp NL

(L)

190 mg/m3

  Long-time value acc. MALTONI et al.,1986
Workp NL

(L)

240 mg/m3

  Long-time value, skin acc. WHO, 1987
Workp PL

(L)

60 mg/m3

  4) acc. WHO, 1987
Workp RO

(L)

400 mg/m3

  Long-time value acc. WHO, 1987
Workp RO

(L)

500 mg/m3

  4) acc. WHO, 1987
Workp S

(L)

140 mg/m3

  1 day acc. WHO, 1987
Workp S

(L)

350 mg/m3

  15 min acc. WHO, 1987
Workp SF

(L)

335 mg/m3

    acc. WHO, 1987
Workp SU

(L)

10 mg/m3

  4) acc. MALTONI et al.,1986
Workp USA

(L)

335 mg/m3

TWA   ACGIH, 1986
Workp USA

(L)

1,340 mg/m3

STEL 15 min ACGIH, 1986
Workp YU

(L)

10 mg/m3

  Long-time value acc. WHO, 1987
Workp YU

(L)

200 mg/m3

  Long-time value acc. MALTONI et al.,1986
Workp D

L

100 g/dl

BAT Blood DFG, 1989
Workp D

L

9.5 ml/m3

BAT Alveolar air DFG, 1989
Foodstuffs:   D

L

1 mg/kg

    acc. BGA, 1988
  D

L

0.1 mg/kg

    acc. UMWELT, 1989
  D

L

0.2 mg/kg

  5) acc. UMWELT, 1989
Cosmetics:   D

L

0 mg/kg

  Ban acc. DVGW, 1985
  EC

L

0 mg/kg

  Ban acc. WHO, 1984

Notes:

1) With mass flow of 2 kg/h and more
2) With in 4 hours with max. 30 min. overshoot
3) Indoor air
4) Maximum value
5) Cumulative value for several solvents in one foodstuff

Comparison/reference values

Medium/origin Country Value Source
Surface water
Rhine (Basle, 1982): D 0.18-1.73 g/l acc. DVGW, 1985
Rhine (Karlsruhe, 1982): D 0.2-1.39 g/l acc. DVGW, 1985
Rhine (Wiesbaden, 1983): D 0.14-4.1 g/l acc. DVGW, 1985
Rhine (Cologne, 1983): D 0.16-0.63 g/l acc. DVGW, 1985
Main (Frankfurt, 1979): D 0.35-2.8 g/l acc. DVGW, 1985
Ruhr (Witten, 1983): D 0.1-0.6 g/l acc. DVGW, 1985
Elbe (1982/83): D 0.2-9.3 g/l acc. UBA, 1986
Weser (1982/83): D 0.5-1 g/l acc. UBA, 1986
Danube (1983-1985): D 0.1-2.8 g/l acc. UBA, 1986
Drinking water:
Wiesbaden (1980) D < 1.8 g/l acc. DVGW, 1985
Taunus (1980) D < 10.5 g/l acc. DVGW, 1985
Medmenham (1981) GB < 0.01 g/l acc. DVGW, 1985
5 cities (1977) J 0.2-0.6 g/l acc. DVGW, 1985
22 cities (1977) USA < 2 g/l acc. DVGW, 1985
Gothenburg (1978) S < 0.008 g/l acc. DVGW, 1985
Sediment:
Rhine: (Hitdorf, 1982) D 4 g/kg acc. DVGW, 1985
Ruhr: (1972-1981) D 4-36 g/kg acc. DGVW, 1985

Assessment/comments

According to the Chemicals Law, tetrachloroethene is classed as non-toxic in Germany, but the risk of cancer has not yet been ruled out. Due to the various sources of contamination, chronic exposure of employees to concentrations which may cause adverse effects is frequent.

Assessment is made more difficult because of the variety of stabilisers which are added to technical tetrachloroethene. Some of the reactive hydrocarbons contained in the stabiliser mixtures such as epichlorohydrin and 1,4-dioxane are suspected of being carcinogenic. The contamination of groundwater and drinking water is of major concern as tetrachloroethene is only slowly degraded in groundwater.

Therefore, the usage of tetrachloroethene should be considerably restricted, production plants should be converted into closed systems and provided with solvent-recovery systems. Whenever it is necessary to work on open systems (e.g. servicing, repairs), these have to be cooled down previously, and respiratory protection must be worn.


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