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Toluene

DESIGNATIONS

CAS No.: 108-88-3
Registry name: Toluene
Chemical name: Toluene
Synonyms, Trade names: Toluene, methylbenzene, phenylmethane, methacide
Chemical name (German): Toluol, Methylbenzol, Toluen
Chemical name (French): Tolune, methylbenzne
Appearance: colourless liquid with benzene-like odour

BASIC CHEMICAL AND PHYSICAL DATA

Empirical formula: C7H8
Rel. molecular mass: 92.15 g
Density: 0.867 g/cm3 at 20C
Relative gas density: 3.18
Boiling point: 110.6C
Melting point: -95C
Vapour pressure: 28 hPa at 20C, 45 hPa at 30C, 109 hPa at 50C
Flash point: 6C
Ignition temperature: 535C
Explosion limits: 1.2-7 vol%
Odour threshold: 0.2 ppm
Solvolysis/solubility: in water: 0.53 g/l at 20-25C
in seawater: 0.38 g/l
unlimited in chloroform, acetone, ether
Conversion factors: 1 ppm = 3.83 mg/m3
1 mg/m3 = 0.261 ppm

ORIGIN AND USE

Usage:
Toluene is a parent substance in the manufacture of benzene derivatives, caprolactam, saccharine, pharmaceuticals, dyes, perfumes, TNT and detergents. It is used in fuels (anti-knock additive) and as a solvent for paints and coatings, rubber, resins, thinners in nitrocellulose lacquers and adhesives. It serves as a raw material in the manufacture of phenol (predominantly in Western Europe), benzene, cresol (chiefly Japan) and a wide range of other substances.

Origin/derivation:
Natural sources: in coal tar and mineral oils; produced in the combustion of natural resins (e.g. forest fires).

Production figures:
Estimates of worldwide production vary between 6.5 and more than 10 million t/a.

Federal Republic of Germany (1984) 358,000 t
Canada (1984) 430,000 t
France (1984) 39,000 t
Italy (1984) 312,000 t
Japan (1984) 784,000 t
Mexico (1984) 216,000 t
Taiwan (1984) 169,000 t
USA (1984) 2,390,000 t

Emission figures (estimated):
Various estimates vary between 6 and 8 million t/a. The proportional emissions were calculated as follows for a total of 6.2 million t:

Losses into sea 500,000 t/a
Losses into air from refineries 2,500,000 t/a
Evaporation of fuels 50,000 t/a
Exhaust fumes from motor vehicles 2,000,000 t/a
Solvent losses 1,000,000 t/a
Chemical industry losses 100,000 t/a

Toxicity

Humans: LD 50-500 mg/kg  
TCLo 0.77 mg/l, inhalation  
>2.9 mg/l, inhalation damage to central nervous system
50-100 ppm fatigue, headaches
200 ppm slight irritation of throat and eyes
100-300 ppm (8 h) slight signs of lack of coordination
300-800 ppm (8 h) distinct signs of lack of coordination
>4,000 ppm (1 h) loss of consciousness, fatal over a lengthy period
10,000-30,000 ppm loss of consciousness after several minutes,
  fatal over lengthy period
Mammals:
Rat LD50 5,000-7,000 mg/kg, oral  
Rat (new born) LD50 870 mg/kg, oral  
Rat NOEL >590 mg/kg and d, oral (193 d)  
Mouse LC50 20 mg/l (8 h)  
Aquatic organisms:
Freshwater fish LC50 13-240 mg/l (96 h)  
Golden orfe LC50 70 mg/l  
Salmon LC50 6.4-8.1 mg/l (96 h)  
Molluscs LC50 24-74 mg/l (24 h)  
Water flea (Daphnia magna) EC50 11.5-310 mg/l (48 h)  
Green algae EC50 134-210 mg/l (reduction of photosynthesis)  
Blue algae 10 mg/l (96 h, 75% reduction of photosynthesis)  
Plants:
Corn, soja 200-20,000 ppm in soil toxic  
Carrots, tomatoes, barley 3 ppm (0.5 h) in air toxic  

Note:
The data cited from various sources; all quoted in RIPPEN, 1989.

Characteristic effects:

Humans/mammals: Inhalation (100 ppm) causes headaches, dizziness, irritation of eyes and nose. Long-term exposure impairs the central nervous system, alters the blood count and causes other chronic effects. Chromosome damage was established in rats. The investigation of employees exposed to toluene revealed controversial results. Toluene itself is not known to be carcinogenic, but other components in a solvent mixture may be carcinogenic. Rats and mice revealed abnormal skeletons and reduced fetal weight with mice likewise being subject to increased embryonic mortality.

Synerg./antagon.:

- reduction of metabolism in rats with benzene, trichloroethylene or styrene;
- enhancement of toxic effect of acetylsalicylic acid (in particular deformities and anomalies in embryo);
- likelihood of increased chromosome damage in smokers exposed to toluene;
- attenuation of various toxic effects of benzene in mice;
- increase in skin cancer induced by 7,12-dimethyl-benz[b]anthracene.

ENVIRONMENTAL BEHAVIOUR

Water:
Toluene is hazardous to water. Because of its volatility, it is partly released into the atmosphere, but its solubility in water is sufficient to cause surface water and groundwater pollution problems.

Air:
The majority of the toluene which impacts the environment enters the atmosphere because of its high vapour pressure. Degradation is rather effective with the result that neither wet nor dry deposition causes large quantities to return to the Earth's surface.

Soil:
Adsorption takes place primarily on organic matter and clay particles. The adsorption capacity increases with decreasing pH value. If not spilled in large quantities, toluene which enters the soil passes into the atmosphere or is subject to chemical transformation and biodegradation.

Degradation, decomposition products, half-life:
The estimated mean half-life in air is about 60 h (reaction with .OH). The dwell time in summer in northern climates is approx. 4 days in contrast to several months in winter. In the tropics, the figure is between several days and several weeks irrespective of the time of year.

Laboratory experiments have shown that toluene escapes into the atmosphere with a half-life of 5 h from a uniformly mixed body of water with a depth of 1 m.

Some 20% of the dose absorbed by rats, rabbits and humans is exhaled. Approx. 80% is metabolised mainly into benzoic acid (via benzyl alcohol / benzaldehyde) with small quantities being converted into cresols.

Food chain:
Accumulation by way of the food chain is highly improbable since toluene is only slightly persistent and highly volatile.

ENVIRONMENTAL STANDARDS

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

(L)

20 g/l

    acc. RIPPEN, 1989
Drinkw SU

(L)

500 g/l

    acc. RIPPEN, 1989
Drinkw USA

G

14.3 g/l

    acc. RIPPEN, 1989
Surface USA

G

12.4 mg/l

    acc. RIPPEN, 1989
Surface USA

G

2.3 mg/l

  24 h average1) acc. RIPPEN, 1989
Surface USA

G

5.2 mg/l

  Peak value1) acc. RIPPEN, 1989
Seawater USA

G

0.1 mg/l

  24 h average2) acc. RIPPEN, 1989
Seawater USA

G

0.23 mg/l

  Peak value2) acc. RIPPEN, 1989
Groundw D(HH)

G

15 g/l

  Closer investigation acc. DVGW, 1988
Groundw D(HH)

G

30 g/l

  Rehabilitation investigation acc. DVGW, 1988
Groundw NL

G

15 mg/l

  Reference acc. RIPPEN, 1989
Groundw NL

L

50 mg/l

  Intervention acc. RIPPEN, 1989
Soil:   NL

G

0.05 mg/kg

  Reference acc. TERRA TECH, 6/94
  NL

L

130 mg/kg

  Intervention acc. TERRA TECH, 6/94
Air:   BG

(L)

0.6 mg/m3

  20 min/24 h acc. EPA, 1983
  DDR

(L)

2 mg/m3

  30 min acc. EPA, 1983
  DDR

(L)

0.6 mg/m3

  24 h acc. EPA, 1983
  Europe

G

8 mg/m3

  30 min WHO, 1987
  Europe

G

1 mg/m3

  24 h WHO, 1987
  SU

(L)

0.6 mg/m3

  20 min/24 h acc. WHO, 1985
  YU

(L)

0.6 mg/m3 3)

  20 min/24 h acc. EPA, 1983
  WHO

G

1 mg/m3 3)

  30 min acc. SLOOFF, 1988
  WHO

G

8 mg/m3

  24 h acc. SLOOFF, 1988
Emiss. D

L

0.1 g/m3

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

(L)

375 mg/m3

    acc. RIPPEN, 1989
Workp B

(L)

375 mg/m3

    acc. RIPPEN, 1989
Workp BG

(L)

50 mg/m3

    acc. RIPPEN, 1989
Workp CH

(L)

380 mg/m3

    acc. RIPPEN, 1989
Workp CS

(L)

800 mg/m3

  Short term acc. RIPPEN, 1989
Workp D

L

190 mg/m3

MAK   DFG, 1994
Workp DDR

(L)

200 mg/m3

    acc. RIPPEN, 1989
Workp H

(L)

50 mg/m3

    acc. RIPPEN, 1989
Workp I

(L)

300 mg/m3

    acc. RIPPEN, 1989
Workp IRL

(L)

375 mg/m3

    acc. RIPPEN, 1989
Workp J

(L)

375 mg/m3

    acc. RIPPEN, 1989
Workp NL

(L)

375 mg/m3

    acc. RIPPEN, 1989
Workp PL

(L)

100 mg/m3

    acc. RIPPEN, 1989
Workp RO

(L)

300 mg/m3

    acc. RIPPEN, 1989
Workp S

(L)

375 mg/m3

    acc. RIPPEN, 1989
Workp SF

(L)

750 mg/m3

    acc. RIPPEN, 1989
Workp USA

(L)

375 mg/m3

TWA   acc. RIPPEN, 1989
Workp USA

(L)

560 mg/m3

STEL   acc. RIPPEN, 1989
Workp YU

(L)

200 mg/m3

    acc. RIPPEN, 1989
Workp D

L

170 g/dl

BAT In blood acc. DVGW, 1988
Foodstuffs:   USA

G

30 mg/d

ADI   acc. RIPPEN, 1989

Notes:

1) Protection of freshwater organisms
2) Protection of saltwater organisms
3) Protected areas

Comparison/reference values

Medium/origin Country Value Source1)
Water:
Surface water GB 1.8-3.8 g/l  
Rhine (Basle-Duisburg, 1976) D 0.7-1.9 g/l  
Gulf of Mexico2)   3-10 ng/l  
Gulf of Mexico3)   4-60 ng/l  
Groundwater (contaminated) USA 0.01-0.1 g/l (n=8)  
Drinking water (5 cities) USA 1.5-8,300 g/l (n=6 of 13)  
    0.1-19 g/l  
Sediment/soil:
River Tees estuary GB    
Sewage sludge USA 1.2-6.4 g/kg NG (n=4)  
    1.4-705 mg/kg TG (n=12 of 13)  
Air:
Northern hemisphere4) (1980-83)      
Southern hemisphere4) (1980-83)   10-210 pptv (mean values)  
Desert Egypt <5-90 pptv (mean values)  
Background impact Brazil 0.22 ppbv (mean value)  
Background impact Kenya 0.04-0.19 ppbv (n=6)  
Urban air D 0.05-1.08 ppbv (n=13)  
Low pollution areas D 0.52-27 ppbv  
Dump gas D 1.3 ppbv  
Rainwater GB 0.2-620 mg/m3  
Rainwater USA 43 g/l  
    0.9-220 ng/l  

Notes:

1) All data quoted as per RIPPEN, 1989
2) Background value
3) Under anthropogenic influence
4) Clean air

Assessment/comments

Toluene vapours are dangerous especially in confined areas such as cellars or sewage systems when they reach the explosion limit. Accumulation in the food chain is unlikely. The toxicity in aquatic organisms is moderate. Symptoms of poisoning are inhibited growth and reduced reproduction rates. Spilled toluene may cause groundwater pollution.


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