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Naphthalene

DESIGNATIONS

CAS No.: 91-20-3
Registry name: Naphthalene
Chemical name: Naphthalene
Synonyms, Trade names:
Antimite, Tar camphor
Chemical name (German):
Naphthalin
Chemical name (French):
Naphthalne
Appearance:
white crystalline solid

BASIC CHEMICAL AND PHYSICAL DATA

Empirical formula: C10H8
Rel. molecular mass: 128.17 g
Density: 1.14 g/cm3
Relative gas density: 4.42
Boiling point: 218C
Melting point: 80C
Vapour pressure: 0.04 hPa
Flash point: 80C
Ignition temperature: 540C
Explosion limits: 0.9-5.9 % by vol.
Solvolysis/solubility: in water: very slightly soluble 30 mg/l
soluble in alcohol 77.4-98 g/l
benzene 1,130 g/l
quinoline 30.2 g/l
toluene 910 g/l
xylene 783 g/l
Conversion factors: 1 ppm = 5.33 mg/m3

1 mg/m3 = 0.19 ppm

ORIGIN AND USE

Usage:
Naphthalene is used as an intermediate in the manufacture of dyes, phthalic anhydride (production of PVC plasticisers), tanning agents, substances used for concrete, wetting agents for the textile industry and solvent components for pesticides (moth repellents).

Origin/derivation:
The raw material source in Germany is coal tar which contains some 10% naphthalene. As coke production is on the decline, increasing use is made of petroleum-based raw materials (gasoline pyrolysis, residual oils following pyrolysis); manufacture by means of distillation and fractioning. The naphthalene content of the technical product is at least 95% while the remainder is made up of impurities such as benzo(b)thiophene (thionaphthene) or, in petroleum-based naphthalenes, of methylindenes only.

Production figures:
World production of naphthalene in 1987

Western Europe 250,000 t
Eastern Europe 200,000 t
Japan 200,000 t
USA 125,000 t
World 1,000,000 t

(figures from ULLMANN, 1991)

Toxicity

Mammals:
Rat: LD50 1,110-9,430 mg/kg, oral acc. BUA, 1989
Rat: LD50 2,200 mg/kg, oral (male) acc. BUA, 1989
Rat: LD50 2,400 mg/kg, oral (female) acc. BUA, 1989
Rat: LD50 > 2,500 mg/kg, dermal (male,female) acc. BUA, 1989
Rat: LD50 > 500 mg/m3, inhalation (8 h) acc. BUA, 1989
Mouse: LD50 350-710 mg/kg, oral (female) acc. BUA, 1989
Mouse: LD50 533 mg/kg, oral (male) acc. BUA, 1989
Mouse: LD50 969-5,100 mg/kg, subcutaneous acc. BUA, 1989
Aquatic organisms:
American minnow: LC50 1.3-6.9 mg/l (96 h) acc. BUA, 1989
American minnow: LC50 5.95-6.77 mg/l (48 h) acc. BUA, 1989
Micropterus salmondes: LC50 0.31-9.7 mg/l (7 d) acc. BUA, 1989
Rainbow trout: LC50 0.1-0.14 mg/l (96 h) acc. BUA, 1989
Water flea: LC50 1.79-24.1 mg/l (48 h) acc. BUA, 1989

Characteristic effects:

Humans/mammals: Naphthalene is absorbed orally, dermally or by way of inhalation. The toxic effect is generally slight. Irritation of the mucous membranes and skin is extremely rare. The absorption of a large dose causes haemolytic anaemia, the formation of cataracts and sensitisation. Infants and foetuses are particularly at risk. There have also been cases of allergic reactions in humans.

The toxicity of chlorinated naphthalenes is considerably higher (refer to the "chloronaphthalene" information sheet).

ENVIRONMENTAL BEHAVIOUR

Water:
Naphthalene dissolves only very slightly in water and sinks as a solid. Because of its toxic effect on aquatic organisms even at low concentrations, naphthalene is considered as a substance hazardous to water (In Germany: Water Hazard Class 2).

Air:
Naphthalene is produced when organic material is incompletely combusted.

Half-life:
The half-life in the atmosphere is estimated at 7 to 24 hours (acc. BUA, 1989).

Degradation, decomposition products:
Naphthalene is degraded microbially or photochemically; mineralisation has however not been substantiated to date under anaerobic conditions. The primary metabolite in the organism is naphthalene-1,2-oxide which is converted to form other compounds. Naphthalene is oxidised in air to form alcohols (naphthols), aldehydes and carboxylic acids.

Food chain:
There is little bioaccumulation by way of food chains.

ENVIRONMENTAL STANDARDS

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

G

0.1 g/l   Reference acc. TERRA TECH 6/94
Groundw NL

L

70 g/l   Intervention acc. TERRA TECH 6/94
Soil:   NL

G

1 mg/kg   Reference,

Sum of 10 PAHs

acc. TERRA TECH 6/94
  NL

L

40 mg/kg   Intervention,

Sum of 10 PAHs

acc. TERRA TECH 6/94
Air:   D

L

2.5 mg/m3 MIK Long-time value acc. BAUM, 1988
  D

L

7.5 mg/m3 MIK Short-time value acc. BAUM, 1988
Emiss. D

L

0.1 g/m3   mass flow > 2 g/h acc. TA Luft, 1986
  DDR

(L)

3 mg/m3   Short-time value acc. HORN, 1989
  DDR

(L)

1 mg/m3   Long-time value acc. HORN, 1989
Workp D

L

50 mg/m3 MAK   DFG, 1989
Workp DDR

(L)

50 mg/m3   Short-time value acc. HORN, 1989
Workp DDR

(L)

20 mg/m3   Long-time value acc. HORN, 1989
Workp SU

(L)

20 mg/m3 PDK   acc. SORBE, 1989
Workp USA

(L)

50 mg/m3 TWA   ACGIH, 1986
Workp USA

(L)

75 mg/m3 STEL   ACGIH, 1986

Comparison/reference values

Medium/origin Country Value Source
Surface water:      
Rhine (1987) D < 0.01-0.03 g/l  
Lake Constance (summer, 1984) D 0.002-0.276 g/l acc. BUA, 1989
      acc. BUA, 1989
Air:
Urban air (1977-1984) D 0.3-0.6 g/m3  
Kiel D 0.009 g/m3 acc. BUA, 1989
Tbingen D 0.191-0.468 g/m3 acc. BUA, 1989
Cigarette smoke (unfiltered)   0.422 g/cigarette (main stream) acc. BUA, 1989
      acc. BUA, 1989

Assessment/comments

Naphthalene has only a slight toxic effect, but can cause allergic reactions in humans (single case reports). Because of the emissions from motor-vehicle exhausts, the exposure is higher in urban areas. This can result in enhanced hypersensitivity to other irritants. There is no information available on carcinogenic or mutagenic potential, but the substance is a proven hazard to foetuses.


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