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Polychlorinated biphenyls

DESIGNATIONS

CAS No.: 1336-36-3
Registry name: Polychlorinated biphenyls
Chemical name: Polychlorinated biphenyls
Synonyms, Trade names: PCB, Apirolio, Aroclor, Ascarele, Clophen, Delor, Fenclor, Inerteen, Kanechlor, Phenoclor, Pyralene, Pyranol, Pyroclor, Sovtol and many others
Chemical name (German):
Polychlorierte Biphenyle
Chemical name (French):
Polychlorure de biphnyle
Appearance:
The pure mono- and dichlorobiphenyls are colourless crystalline compounds; PCBs with more than 3 chlorine atoms are colourless liquids with moderate to high viscosity. All industrial mixtures are liquids.

Note: The group of polychlorinated biphenyls consists of 209 isomeric and homologous compounds.

BASIC CHEMICAL AND PHYSICAL DATA

Empirical formula: C12H10-nCln n=1-10, mainly n=2-7
Rel. molecular mass: 189-499 g
Density: 1.2-1.6 g/cm3
Boiling point: 320-420C
Vapour pressure: 0.2-133 x 10-3 Pa
Solvolysis/solubility: only slightly soluble in water

soluble in most organic solvents and in fat

Note: Polychlorinated biphenyls have a low vapour pressure, high viscosity, minimal water solubility, high dielectric constant, high thermal stability and resistance to chemicals.

Note:
Polychlorinated biphenyls have a low vapour pressure, high viscosity, minimal water solubility, high dielectric constant, high thermal stability and resistance to chemicals.

ORIGIN AND USE

Usage:
PCBs are used as coolants and insulating materials, transformer oils and hydraulic fluids, as plasticisers for synthetics and as impregnation agents for wood and paper. They possess almost ideal properties for electrical purposes and are likewise highly resistant to ageing.

In the European Community, the use of PCBs has been restricted to closed systems by regulation in 1976. In the USA the production of PCBs has been prohibited since 1977, in Germany since 1983.

Origin/derivation:
The chlorination of biphenyls with iron and iron chloride acting as catalysts produces an isomeric mixture which is subsequently distilled.

Production figures:

D (1980): 7,400 t (BMI, 1985)
D (since 1983): no production (BMI, 1985)
France (1980) 6,500 t (LORENZ & NEUMEIER, 1983)
Spain (1980): 1,250 t (LORENZ & NEUMEIER, 1983)

Toxicity

Mammals:
General: TDLo 325 mg/kg acc. UBA, 1986
Aquatic organisms:
Rainbow trout: LC50 2 mg/l (96 h) acc. UBA, 1986
Micropterus salmoides: LC50 2.3 mg/l (96 h) acc. UBA, 1986
American minnow: LC50 7.7-300 mg/l (96 h) acc. UBA, 1986
Catfish: LC50 8.7-139 mg/l (30 d) acc. UBA, 1986
Blue perch: LC50 84-400 mg/l (30 d) acc. UBA, 1986
Gammarus spec.: LC50/EC50 10-73 mg/l acc. UBA, 1986
Green algae: 0.1-300 mg/l inhibited growth acc. UBA, 1986

Characteristic effects:

Humans/mammals: The toxicological effects of PCBs on humans still have to be fully established. The Chemicals Law in the Federal Republic of Germany classes PCBs as being of low toxicity despite their proven carcinogenic and teratogenic effects in animal experiments (supposed to be carcinogenic for humans). As a general rule, the toxicity level increases with the chlorine content; the same effect is produced by the oxidation products of PCB which may be far more toxic than PCB itself. The risk of poisoning due to inhalation is normally slight on account of the low vapour pressure. On the other hand, skin contact and oral intake can have serious consequences. The main points of attack are the liver and the enzyme system. The usual symptoms of chronic poisoning are nausea, vomiting, weight loss, oedemas and pains in the lower abdomen; if the liver is seriously damaged, coma or even death may result.

Plants: PCB reduces the cell division rate and the CO2 fixing of algae. There is overall inhibition of growth. Population shifts are encountered with concentrations greater than 0.1 m g/l (phytoplankton and invertebrates) [LORENZ & NEUMEIER, 1983].

ENVIRONMENTAL BEHAVIOUR

Water:
PCBs ingress into surface water from various sources and by precipitation from the atmosphere.

Air:
PCBs are released into the atmosphere by evaporation, favoured by higher temperatures. They condense on aerosol particles and are thus widely spread. The evaporation rate for soil - as a function of soil texture - is greater than for water.

Soil:
Accumulation in humus layer with little mobility; following sorption, mobility by way of vapour phase. There is very little degradation; the persistence increases with the degree of chlorination.

Degradation, decomposition products:
Degradation due to hydrolysis is not to be expected since PCBs are stable even in the presence of strong alkalis and acids. Oxidative degradation involves considerable energy. Biotic degradation by microorganisms only occurs under aerobic conditions. Adsorption and/or transition to anaerobic areas totally inhibits degradation in soil. Mineralisation is possible under strong UV radiation.

Metabolites are hydroxy compounds, metafission products and chlorobenzenes. The degradation process ends in CO2 and HCl.

Food chain:
Some 25% of the PCBs assimilated by humans are taken in by inhalation and 75% through foodstuffs (UBA, 1986). Animal products are the main source, with fish supplying between 4 and 5% of the amount absorbed. The intake with drinking water is minimal.

PCB is stored in fatty tissue, milk and the liver.

ENVIRONMENTAL STANDARDS

Medium/acceptor Sector Country/organ. Status Value Cat. Remarks Source
Water Surface D

(G)

0.014 mg/l

  Freshwater acc. UBA, 1986
Air: Refer to information sheets 164-166 as regards environmental standards for air
Foodstuffs:   CDN

G

0.2-1.0 pg/(kgd)

ADI   acc. CRINE, 1988
  NL

G

4 pg/(kgd)

ADI   acc. CRINE, 1988
  USA

G

0.06 pg/(kgd)

ADI EPA acc. CRINE, 1988

The production of polychlorinated biphenyls has been banned in the USA since 1979; the use of concentrations > 500 mg/kg for transformers and electromagnets has been banned since 1985 (LORENZ & NEUMEIER, 1983).

Comparison/reference values

Medium/origin Value Source
Air 5-30 ng/m3 acc. BMI, 1985
Air 0.1-20 ng/m3 acc. PEARSON, 1982
Water:
Rain/snow 0.1-200 ng/l acc. PEARSON, 1982
Seawater 0.25-100 ng/l acc. PEARSON, 1982
Surface water 0.1-3000 ng/l acc. PEARSON, 1982
Soil/sediment 1-1000 mg/kg acc. PEARSON, 1982
Soil 0.05-0.1 mg/kg acc. BMI, 1985
Sludge 1-100 mg/kg acc. PEARSON, 1982
Plankton 0.01-2 mg/kg acc. PEARSON, 1982
Fish 0.01-25 mg/kg acc. PEARSON, 1982
Birds 0.1-1000 mg/kg acc. PEARSON, 1982
Aquatic mammals/amphibious creatures 0.1-1000 mg/kg acc. PEARSON, 1982
Human beings (fatty tissue) 0.1-10 mg/kg acc. PEARSON, 1982

Assessment/comments

PCBs are characterised by a high persistence and widespread use. Disposal is particularly problematic. Thermal decomposition in waste incineration plants at insufficient temperatures can cause considerable amounts of polychlorinated dibenzo-p-dioxins to escape into the environment. In addition, the question whether PCBs can be completely decomposed at high temperature remains to be fully clarified. Therefore, the use of PCBs must be restricted or limited to utilisation in closed systems. Sufficient substitute materials are already available.

Special sources: HUTZINGER, SAFE & ZITKO (1974); CRINE (1988).


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