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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]pyrène
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: | 178°C |
| Vapour pressure: | 0.7 x 10-6 Pa at 20-25°C |
| Solvolysis/solubility: | in water: 4.5 x 10-6 g/l at 15-30°C |
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 µg/l |
BaP + 5 other substances | acc. RIPPEN, 1989 | |
| Drinkw | D | L |
0.2 µg/l |
BaP + 5 other substances | acc. RIPPEN, 1989 | ||
| Drinkw | EC | G |
0.2 µg/l |
BaP + 5 other substances | acc. RIPPEN, 1989 | ||
| Drinkw | SU | (L) |
0.005 µg/l |
acc. RIPPEN, 1989 | |||
| Drinkw | WHO | G |
0.2 µg/l |
BaP + 5 other substances | acc. RIPPEN, 1989 | ||
| Groundw | D(HH) | G |
0.2 µg/l |
Closer investigation | acc. LAU-BW, 1989 | ||
| Groundw | D(HH) | G |
1 µg/l |
Rehabilitation investigation | acc. LAU-BW, 1989 | ||
| Groundw | NL | G |
0.1 µg/l |
Reference, Naphthalene | acc. TERRA TECH 6/94 | ||
| Groundw | NL | L |
70 µg/l |
Intervention, Naphthalene | acc. TERRA TECH 6/94 | ||
| Groundw | NL | G |
0.02 µg/l |
Reference, Anthracene + Phenanthrene | acc. TERRA TECH 6/94 | ||
| Groundw | NL | L |
5 µg/l |
Intervention, Anthracene + Phenanthrene | acc. TERRA TECH 6/94 | ||
| Groundw | NL | G |
0.005 µg/l |
Reference, Fluoranthene | acc. TERRA TECH 6/94 | ||
| Groundw | NL | L |
1 µg/l |
Intervention, Fluoranthene | acc. TERRA TECH 6/94 | ||
| Groundw | NL | G |
0.002 µg/l |
Reference, Benzo[a]anthracene | acc. TERRA TECH 6/94 | ||
| Groundw | NL | L |
0.5 µg/l |
Intervention, Benzo[a]anthracene | acc. TERRA TECH 6/94 | ||
| Groundw | NL | G |
0.002 µg/l |
Reference, Chrysene | acc. TERRA TECH 6/94 | ||
| Groundw | NL | L |
0.05 µg/l |
Intervention, Chrysene | acc. TERRA TECH 6/94 | ||
| Groundw | NL | G |
0.001 µg/l |
Reference, BaP | acc. TERRA TECH 6/94 | ||
| Groundw | NL | L |
0.05 µg/l |
Intervention, BaP | acc. TERRA TECH 6/94 | ||
| Groundw | NL | G |
0.0002 µg/l |
Reference, Benzo[ghi]perylene | acc. TERRA TECH 6/94 | ||
| Groundw | NL | L |
0.05 µg/l |
Intervention, Benzo[ghi]perylene | acc. TERRA TECH 6/94 | ||
| Groundw | NL | G |
0.001 µg/l |
Reference, Benzo[k]fluoranthene | acc. TERRA TECH 6/94 | ||
| Groundw | NL | L |
0.05 µg/l |
Intervention, Benzo[k]fluoranthene | acc. TERRA TECH 6/94 | ||
| Groundw | NL | G |
0.0004 µg/l |
Reference, Indeno[1,2,3-cd]pyrene | acc. TERRA TECH 6/94 | ||
| Groundw | NL | L |
0.05 µg/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-Württemberg 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.