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Polycyclic aromatic hydrocarbons

DESIGNATIONS

CAS No.:
Registry name: Polycyclic aromatic hydrocarbons
Chemical name: Polycyclic aromatic hydrocarbons
Synonyms, Trade names:
PAH
Chemical name (German):
Polyzyklische aromatische Kohlenwasserstoffe, PAK
Chemical name (French):
Hydrocarbures aromatiques polycycliques, HAP
Appearance:

Note: Collective name for aromatic compounds with condensed cyclic systems. As benzo[a]pyrene is the most investigated PAH and representative of the effects caused by compounds of this group, environmental impacts caused by PAHs are often expressed in terms of equivalents of benzo[a]pyrene.

CAS No.: 50-32-8
Chemical name: Benzo[a]pyrene
Synonyms, Trade names:
Benzo[def]chrysene; 1,2-Benzpyrene; 3,4-Benzpyrene; BaP; BAP
Chemical name (German):
Benzo[a]pyren
Chemical name (French):
Benzo[a]pyrne
Appearance:
yellowish crystals

BASIC CHEMICAL AND PHYSICAL DATA

Empirical formula: C20H12
Rel. molecular mass: 252.3
Density: 1.282 g/cm3 (chips); 1.351 g/cm3 (needles)
Melting point: 178C
Vapour pressure: 0.7 x 10-6 Pa at 20-25C
Solvolysis/solubility: in water: 4.5 x 10-6 g/l at 15-30C

ORIGIN AND USE

Origin/usage:

PAHs are natural components of organic raw materials and in particular crude oils; produced by pyrolysis of organic substances.

Some examples of benzo[a]pyrene content:

Coal tar 0.65%
Road tar 0.51-1%
Pitches 1.25% (max. value)
Impregnating oils 0.045-0.35%
Engine oil (fresh) 0.008-0.27 mg/kg
Engine oil (used) 5.2-35 mg/kg
Diesel oil 0.026 mg/l
Fuel 0.09-8.3 mg/kg
Crude oil (Kuwait) 2.8 mg/kg
Crude oil (Libya) 1.32 mg/l
Crude oil (Venezuela) 1.66 mg/l
Crude oil (Persian Gulf) 0.40 mg/l

Production figures:
Only a few compounds from this group such as anthracene ((r) dyes), carbazole ((r) dyes, insecticides) and pyrene ((r) dyes) are extracted commercially. There is no commercial use of benzo[a]pyrene, except as analytical standard.

Emissions:
Emissions of benzo[a]pyrene due to combustion of fossil fuels:

Coal-fired heating 100 m g/m3
Coking oven 13-35 m g/m3
Waste incineration 11 m g/m3
Diesel exhausts 5 m g/m3
Coal-fired power station 0.3 m g/m3
Gas-fired power station 0.1 m g/m3
Motor vehicle emissions 1-48 m g/l burned fuel

Emission contribution of different sources to the total emission (D 1981, estimated):

Brown-coal briquets 37%
Coke production 31%
Hard-coal briquets 14%
Car traffic 13%
Gas and gas flame coal 5%
Oil heating 0.1%
Anthracite 0.1%

Note:
Data from various sources; all quoted from RIPPEN, 1989.

Toxicity

Insects:
Cricket (Acheta domesticus) LC50 >15 mg/g, oral
Aquatic organisms:
Saltwater fish (Leuresthes tenius) EC0 0.024 mg/l (14 d, hatching rate, embryonic development, growth)
Rainbow trout EC0 <50 mg/kg food (18 months, formation of tumour)
Chaetopodae LC50 >1 mg/l (96 h)
Water flea (Daphnia pulex) LC50 0.005 mg/l (96 h)
Other organisms:
Earthworm LC50 >1mg/cm2 (48 h)
Plants:
Various cultivated plants 13 mg/l in nutrient medium (suspension cultures, no effect on growth)
Wheat germ plants 2.5 mg/l (initial solution, plants waste away)

Note: Data refer to benzo[a]pyrene. There are only few data available on toxic effects of single PAHs.
All data as per RIPPEN, 1989

Characteristic effects:

Humans/mammals: A number of PAHs turned out to be carcinogenic in animal experiments, some even have mutagenic effects. The carcinogenic effect of benzo[a]pyrene has been clearly substantiated.

ENVIRONMENTAL BEHAVIOUR

Water:
In brackish water and seawater 71 - 75 % adsorption after 3 h on particles, in particular phytoplankton and bacteria. Rapid reaction with chlorine and ozone. Photochemical transformation in water.

Degradation, decomposition products, half-life:
The data on the degradation of benzo[a]pyrene in surface water vary significantly thus not allowing any general statement. As to the microbial transformation of benzo[a]pyrene in sediment, durations of 8 weeks at higher concentrations and of more than two years at moderate to low concentrations may be found. In addition, half-lives of up to 10 years are quoted for the degradation of benzo[a]pyrene in sediment. The values for the degradation in soil likewise differ significantly between 2 days and 2 years depending on e.g. the type of soil, the microorganism species present in the soil and the degree of contamination. As a general rule, small concentrations are transformed more slowly than high concentrations [acc. RIPPEN, 1989 / KOCH, 1989].

Most important metabolites: 3-hydroxybenzo[a]pyrene and 9-hydroxybenzo[a]pyrene.

ENVIRONMENTAL STANDARDS

Medium/acceptor Sector Country/organ.

Status

Value Cat. Remarks Source
Water: Drinkw A

(L)

0.2 g/l

  BaP + 5 other substances acc. RIPPEN, 1989
Drinkw D

L

0.2 g/l

  BaP + 5 other substances acc. RIPPEN, 1989
Drinkw EC

G

0.2 g/l

  BaP + 5 other substances acc. RIPPEN, 1989
Drinkw SU

(L)

0.005 g/l

    acc. RIPPEN, 1989
Drinkw WHO

G

0.2 g/l

  BaP + 5 other substances acc. RIPPEN, 1989
Groundw D(HH)

G

0.2 g/l

  Closer investigation acc. LAU-BW, 1989
Groundw D(HH)

G

1 g/l

  Rehabilitation investigation acc. LAU-BW, 1989
Groundw NL

G

0.1 g/l

  Reference, Naphthalene acc. TERRA TECH 6/94
Groundw NL

L

70 g/l

  Intervention, Naphthalene acc. TERRA TECH 6/94
Groundw NL

G

0.02 g/l

  Reference, Anthracene + Phenanthrene acc. TERRA TECH 6/94
Groundw NL

L

5 g/l

  Intervention, Anthracene + Phenanthrene acc. TERRA TECH 6/94
Groundw NL

G

0.005 g/l

  Reference, Fluoranthene acc. TERRA TECH 6/94
Groundw NL

L

1 g/l

  Intervention, Fluoranthene acc. TERRA TECH 6/94
Groundw NL

G

0.002 g/l

  Reference, Benzo[a]anthracene acc. TERRA TECH 6/94
Groundw NL

L

0.5 g/l

  Intervention, Benzo[a]anthracene acc. TERRA TECH 6/94
Groundw NL

G

0.002 g/l

  Reference, Chrysene acc. TERRA TECH 6/94
Groundw NL

L

0.05 g/l

  Intervention, Chrysene acc. TERRA TECH 6/94
Groundw NL

G

0.001 g/l

  Reference, BaP acc. TERRA TECH 6/94
Groundw NL

L

0.05 g/l

  Intervention, BaP acc. TERRA TECH 6/94
Groundw NL

G

0.0002 g/l

  Reference, Benzo[ghi]perylene acc. TERRA TECH 6/94
Groundw NL

L

0.05 g/l

  Intervention, Benzo[ghi]perylene acc. TERRA TECH 6/94
Groundw NL

G

0.001 g/l

  Reference, Benzo[k]fluoranthene acc. TERRA TECH 6/94
Groundw NL

L

0.05 g/l

  Intervention, Benzo[k]fluoranthene acc. TERRA TECH 6/94
Groundw NL

G

0.0004 g/l

  Reference, Indeno[1,2,3-cd]pyrene acc. TERRA TECH 6/94
Groundw NL

L

0.05 g/l

  Intervention, Indeno[1,2,3-cd]pyrene acc. TERRA TECH 6/94
Soil:   NL

G

1 mg/kg DM

  Reference, PAHs acc. TERRA TECH 6/94
  NL

L

40 mg/kg DM

  Intervention, PAHs acc. TERRA TECH 6/94
Air: Emiss. D

L

0.1 mg/m3

  mass flow > 0.5 g/h acc. TA Luft, 1986

Note:
1) Baden-Wrttemberg Regional Environment Office

Comparison/reference values

Medium/origin Country Value
Water:
Rhine (Karlsruhe, Cologne, Leibheim) D <1-13 ng/l (aqueous phase)
Rhine (locations see above 1977-79) D <1-82 ng/l (suspensions)
Wupper (mouth, 1984) D 690 ng/l (max. value)
Lake Constance (Sipplingen, 1977-79) D <1-3 ng/l (aqueous phase)
Lake Constance (Sipplingen, 1977-79) D <1-4 ng/l (suspensions)
North Sea (various locations, 1980) D <0.02-0.56 ng/l (n=8)
Groundwater (non-contaminated) NL <5 ng/l (n=8)
Groundwater (contaminated) NL 1,000 ng/l
Groundwater (contaminated) USA 13 mg/l (max. value)
Drinking water (Helsinki, 1980) SF 0.05 ng/l
Drinking water N <0.05 ng/l
Drinking water (1984-1986) D <50-<120 ng/l (n=598)
Sediment:
Rhine (km 639, 1982/83) D 1.25 mg/kg
Wupper D 2 mg/kg (mean)
Lake Constance D/CH 1-1,620 mg/kg
North Sea (various locations)   0.15-460 mg/kg (impacted and non-impacted)
Adriatic   0.4-13 mg/kg (n=24)
Soil:
Forest soil (various locations) D 1.5-4 mg/kg DM
Various contaminated soils D 1-32 mg/kg
Soil covering (Solling) D 110-360 mg/kg
Soils away from industry   15-18 mg/kg (average)
Soils close to industry   200-500 mg/kg DM (average)
Air:
Urban air (Berlin, smog, 1980-82) D 8-92 ng/m3 (n=546)
Slightly polluted areas (1981) D 1.3-1.4 ng/m3 (n=208)
Non-polluted areas (1981) D <0.11-0.52 ng/m3 (n=3)
Urban precipitation (1979/80) D 1.8-3.6 ng/m3 (annual average)
Urban precipitation (1979/80) D 0.30-15 ng/m3 (monthly average)
Rainwater (Los Angeles, 1982) USA <2-115 ng/l
Fog (Northern Franconian Forest, 1983) D 260-880 ng/l (n=3)
Dust (Ruhr area, 1970-75) D 50-100 ng/l
Workplace (bitumen) CND 0.04-43 mg/m3 (roofing, road construction)
Indoor air (smoke-filled)   22 ng/m3
Aquatic animals:
Various molluscs Greenland 18-60 mg/kg
Various molluscs I 2-540 mg/kg
Sole (non-contaminated, contaminated) USA 30 and 570 mg/kg DS

Note:
All data refer to benzo[a]pyrene and are taken from RIPPEN, 1989. This work contains a large number of further investigation results including many relating to the benzo[a]pyrene content of plants and foodstuffs.

Assessment/comments

Although benzo[a]pyrene is a carcinogenic atmospheric pollutant, there are scarcely any limit values and environmental standards. In view of the fact that benzo[a]pyrene is incorporated by humans from different sources, it must be ensured that foodstuffs and drinking water are not polluted in any way by this substance.


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