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Chlorophenols

DESIGNATIONS

CAS No.:
Registry name:
Chlorophenols
Chemical name: Chlorophenols
Synonyms, Tradenames:
Chemical name (German):
Chlorphenole
Chemical name (French):
Chlorophnols
Appearance:
colourless solids (except o-chlorophenol) with offensive odour

Note: The group of the chlorophenols consists of 19 different compounds. As pentachlorophenol (PCP) is the most important compound in this group, the basic chemical and physical data refer to PCP.

CAS No.: 87-86-5
Registry name: Pentachlorophenol
Chemical name: Pentachlorophenol
Synonyms, Tradenames: PCP, 2,3,4,5,6-Pentachlorophenol, Dowicide G, Dowicide 7, Penta, Santophen 20, Pentacon, Penchlorol, Pentakil, Sontobrite, Weedone
Chemical name (German): Pentachlorphenol
Chemical name (French): Pentachlorophnol
Appearance: colourless solid with offensive odour

BASIC CHEMICAL AND PHYSICAL DATA

Empirical formula: C6Cl5OH
Rel. molecular mass: 266.35 g
Density: 1.978 g/cm3
Boiling point: 300C (decomposition)
Melting point: 190C
Vapour pressure: 23 x 10-3 Pa
Solvolysis/solubility: in water: 20 mg/l

soluble in alcohol, ether, acetone, benzene

Conversion factors: 1 ppm = 11.1 mg/m3

1 mg/m3 = 0.09 ppm

ORIGIN AND USE

Usage:
Because of their broad-spectrum antimicrobial properties, chlorophenols have been used as preservative agents for wood, paints, vegetable fibres and leather and as disinfectants. In addition, they are used as herbicides, fungicides and insecticides and as intermediates in the production of pharmaceuticals and dyes.

Origin/derivation:
Most of the commercially important chlorophenols are obtained by direct chlorination of phenol using chlorine gas. In the technical product, there are impurities of other chlorophenol isomers or chlorophenols with more or less chlorine. The heavy chlorophenols are mainly contaminated by polychlorophenoxyphenols, chlorodibenzoparadioxins and chlorodibenzofurans. Emissions are mainly due to the manufacture, storage, transportation and application of chlorophenols.

Production figures:

World (excluding former COMECON and China) 100,000 t/a
heavy chlorophenols (4-5 chlorine atoms) 35-40,000 t/a
light chlorophenols (1-3 chlorine atoms) 60,000 t/a

(figures taken from ULLMANN 1985)

Toxicity

Humans: LD 50-500 mg/kg, oral (estimated)  
Mammals:
Rat LD50 670 mg/kg, oral (2-chlorophenol) acc. ULLMANN 1986
Rat LD50 950 mg/kg, percutaneous (2-chlorophenol) acc. ULLMANN 1986
Rat LD50 570 mg/kg, oral (3-chlorophenol) acc. ULLMANN 1986
Rat LD50 1030 mg/kg, percutaneous (3-chlorophenol) acc. ULLMANN 1986
Rat LD50 261 mg/kg, oral (4-chlorophenol) acc. ULLMANN 1986
Rat LD50 1390 mg/kg, percutaneous (4-chlorophenol) acc. ULLMANN 1986
Rat LD50 580 mg/kg, oral (2,4-dichlorophenol) acc. ULLMANN 1986
Rat LD50 1730 mg/kg, percutaneous (2,4-dichlorophenol) acc. ULLMANN 1986
Rat LD50 820 mg/kg, oral (2,4,5-trichlorophenol) acc. ULLMANN 1986
Rat LD50 2260 mg/kg, percutaneous (2,4,5-trichlorophenol) acc. ULLMANN 1986
Rat LD50 1620 mg/kg, oral (2,4,5-trichlorophenol, sodium salt) acc. ULLMANN 1986
Rat LD50 820 mg/kg, oral (2,4,6-trichlorophenol) acc. ULLMANN 1986
Rat LD50 140 mg/kg, oral (2,3,4,6-tetrachlorophenol) acc. ULLMANN 1986
Rat LD50 210 mg/kg, percutaneous (2,3,4,6-tetrachlorophenol) acc. ULLMANN 1986
Rat LD50 50 mg/kg, oral (pentachlorophenol) acc. ULLMANN 1986
Rat LD50 100 mg/kg, percutaneous (pentachlorophenol) acc. ULLMANN 1986
Rat LD50 210 mg/kg, oral (pentachlorophenol,sodium salt) acc. ULLMANN 1986
Rat LD50 72 mg/kg, percutaneous (pentachlorophenol, sodium salt) acc. ULLMANN 1986
Aquatic organisms:
Golden orfe LC50 0.60 mg/l (96 h), pentachlorophenol acc. RIPPEN 1990
Rainbow trout LC50 0.12-0,26 mg/l (96 h), pentachlorophenol acc. RIPPEN 1990
Water flea LC50 0.33-0.41 mg/l (96 h), pentachlorophenol acc. RIPPEN 1990
Bacteria (div.) NOEC 12.3 mg/l (30 min), growth acc. RIPPEN 1990
Algae EC50 10-7000 g/l (96h), growth, pentachlorophenol acc. RIPPEN 1990

Characteristic effects:

Humans/mammals: Chlorophenols can be absorbed through the lungs, the gastro-intestinal tract and the skin. Some 80% is excreted via the kidneys without undergoing any transformation.

The toxicity of chlorophenols depends upon the degree of chlorination, the position of the chlorine atoms and the purity of the sample. Chlorophenols have an irritating effect on the eyes and on the respiratory tract. Toxic doses of chlorophenols cause convulsions, shortness of breath, coma and finally death. After repeated administration, toxic doses may result in damage to the inner organs (primarily liver) and the bone marrow.

Pentachlorophenol has a toxic effect on embryos in animal experiments (lethal at higher concentrations). Technical PCP may possibly be carcinogenic not least due to contamination. Mutagenic potential can not be excluded.

ENVIRONMENTAL BEHAVIOUR

Water:
In the aquatic environment, chlorophenols may be dissolved in free or complexed form or adsorbed on suspended matter. Removal is mainly by way of biodegradation which is rapid when adapted microorganisms are already present. However, PCP is biodegraded much more difficultly than other chlorophenols. Chlorophenols are also removed from water by photodecomposition and volatilisation. Finally, adsorption of chlorophenols on suspended matter plays a role in the amount of chlorophenols in water: light chlorophenols are hardly fixed whereas PCP is fixed very strongly.

Air:
PCP ingresses into the atmosphere on account of its volatility. Volatility increases considerably with increasing temperature, but is likewise dependent on possible additives and e.g. the nature of the treated wood. Burning wood treated with PCP liberates polychlorinated dibenzodioxins and -furans (PCDD/F).

Soil:
The persistence of chlorophenols in soil depends on their adsorption-desorption characteristics. Only the adsorption of PCP has been studied in depth. It is fixed very strongly on soil particles and not easily washed off by rain. Apart from adsorption and desorption, rapid seepage paths can play an important role in the transportation of PCP in soil. Once it reaches the groundwater, it is doubtful whether PCP is degraded. Since 1984 there has been a ban in Germany on the storage of waste products from the manufacture of PCP on open dumps to avoid the infiltration of PCP-contaminated seepage water.

Degradation, decomposition products, half-life:
Free PCP or PCP dissolved in water is photomineralised within a few days when exposed to sunlight (even more so with adsorption on solids). There is no such degradation if PCP has reached lower soil levels or the groundwater. The degradation in water is always dependent on the pH and the temperature. It is subject to pronounced fluctuations (example: half-life at pH 5.1 = 328 h, at pH 6 = 3,120 h (at 30C in both cases)). Although PCP may be degraded by microorganisms under certain conditions, the substance is to be classed as scarcely biodegradable. Quinone forms in the course of degradation and the process may involve complete mineralisation.

Food chain:
Bioaccumulation in aquatic ecosystems does not only appear to be extremely type-specific, but also dependent to a large extent on the biotope as well as the duration and the intensity of exposure. Excretion is likewise type/organ-specific with half-lives ranging between 7 hours and 7 days. There are contradictory findings as to whether PCP is absorbed directly from the water by fish and other aquatic organisms or whether the food chain is involved. Plants may accumulate PCP stored in the soil over the course of several vegetation periods.

ENVIRONMENTAL STANDARDS

Medium/acceptor Sector Country/organ.

Status

Value Cat. Remarks Source
Water: Drinkw D

L

0.1 g/l     acc. DVGW, 1988
Drinkw EC

L

0.1 g/l     acc. EC, 1980
Groundw D(HH)

G

0.3 g/l   Individual substance1) acc. LAU-BW, 1989
Groundw D(HH)

G

1.5 g/l   Individual substance2) acc. LAU-BW, 1989
Groundw D(HH)

G

0.5 g/l   Substance group1) acc. LAU-BW, 1989
Groundw D(HH)

G

2 g/l   Substance group2) acc. LAU-BW, 1989
Groundw NL

G

0.25 g/l   Monochlorophenol (sum)

Reference

acc. TERRA TECH 6/94
Groundw NL

L

100 g/l   Monochlorophenol (sum)

Intervention

acc. TERRA TECH 6/94
Groundw NL

G

0.08 g/l   Dichlorophenol (sum)

Reference

acc. TERRA TECH 6/94
Groundw NL

L

30 g/l   Dichlorophenol (sum)

Intervention

acc. TERRA TECH 6/94
Groundw NL

G

0.025 g/l   Trichlorophenol (sum)

Reference

acc. TERRA TECH 6/94
Groundw NL

L

10 g/l   Trichlorophenol (sum)

Intervention

acc. TERRA TECH 6/94
Groundw NL

G

0.01 g/l   Tetrachlorophenol (sum)

Reference

acc. TERRA TECH 6/94
Groundw NL

L

10 g/l   Tetrachlorophenol (sum)

Intervention

acc. TERRA TECH 6/94
Groundw NL

G

0.02 g/l   Pentachlorophenol (sum)

Reference

acc. TERRA TECH 6/94
Groundw NL

L

3 g/l   Pentachlorophenol (sum)

Intervention

acc. TERRA TECH 6/94
Surface D

G

1 g/l   Individual substance3) acc. LAU-BW5), 1989
Surface D

G

5 g/l   Individual substance3) acc. LAU-BW6), 1989
Surface D

G

2 g/l   Substance group4) acc. LAU-BW5), 1989
Surface D

G

10 g/l   Substance group4) acc. LAU-BW6), 1989
Soil:   NL

L

10 mg/kg AD   Substance group, Intervention acc. TERRA TECH 6/94
  NL

L

5 mg/kg AD   Pentachlorophenol,

Intervention

acc. TERRA TECH 6/94
Air: Workp D

L

0.5 mg/m3 MAK   acc. DFG, 1989
Workp SU

(L)

0.1 mg/m3     acc. DVGW, 1988
Workp USA

(L)

0.5 mg/m3 TWA   acc. DVGW, 1988

Notes:

1) The groundwater quality should be investigated in depth
2) Rehabilitation measures should be taken
3) For drinking water treatment using natural methods
4) For drinking water treatment using chemical and physical methods
5) Closer investigation necessary
6) Rehabilitation measures necessary
The use of all chlorophenols have been banned in Sweden since 1978.

Assessment/comments

Chlorophenols should be avoided where at all possible on account of the high toxicity level for aquatic organisms in some cases. The chlorination of drinking water to sterilise river water is problematic since this can lead to the formation of chlorophenols with penetrating odour and taste. Technical PCP contains impurities of other chlorinated phenols and aromatic substances as well as traces of polychlorinated dibenzo-p-dioxins and -furans (PCDD/F); it is thus one of the major sources of the ingress of these substances into the environment. Part of the toxicity of PCP can be attributed to such impurities.

Refer also to information sheets for 'phenols'.


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