State of knowledge report
Environment Australia, 2001
ISBN 0 6425 4739 4
Polychlorinated biphenyls (PCBs)
|Substance name:||Polychlorinated biphenyls (PCBs)|
54% chlorine: 11097-69-1
42% chlorine: 53469-21-9
|Molecular formula:||PCBs are a group of chemicals that contain many individual compounds with the same basic structure, known as congeners; 209 congeners are possible, but only about 130 are likely to occur in commercial products (IPCS 1993) which are mixtures. The chlorination of biphenyl (two benzene rings linked by a single carbon-carbon bond C12H10) can lead to the replacement of 1–10 hydrogen atoms by chlorine. The chemical formula can be represented as C12H10-nCln where n, the number of chlorine atoms, can range from 1 to 10.|
|Synonyms:||PCBs, chlorinated biphenyls, chlorobiphenyls, aroclor, clophen, phenclor, zanechlor, phenclor, pyralene.|
PCBs are a class of industrial chemical that contain up to 209 individual compounds. PCBs are either oily liquids or solids; they are colourless to light yellow in colour, with no known smell or taste.
Boiling point: 365–390°c
Freezing point: 10°C
Vapour pressure: 0.00006 mmHg
Boiling point: 325–366°C
Freezing point: -19°C
Specific gravity: 1.39
Vapour pressure: 0.001 mmHg
PCBs do not burn easily. Most are nonflammable, but, according to the 1996 Merck Index, aroclor 1242 (42% chlorine) has an open cup flashpoint of 176–180°C.
PCBs are nonflammable liquids, but exposure to fire results in the formations of black soot that contains PCBs, polychlorinated dibenzofurans, and polychlorinated dibenzo-p-dioxins.
PCBs are incompatible with, and react with, strong oxidising agents but are chemically stable under normal conditions. They are very resistant to a range of other chemicals, and they remain chemically unchanged even in the presence of oxygen or some active metals, at either high temperatures (up to 170° Celsius) or for long periods.
Individual, pure congeners of PCB are colourless, often crystalline, compounds, but commercial PCBs are mixtures of these congeners with a clear, light yellow or dark colour, and range from oily liquids to waxy or hard solids. They do not crystallise at low temperatures but turn into solid resins.
PCBs are practically insoluble in water; however, they dissolve easily in hydrocarbons, fats and other organic compounds, and fatty tissues readily adsorb them.
PCBs are good insulating materials. They have been used widely as coolants and lubricants in transformers, capacitors, and other electrical equipment. The manufacture of PCBs stopped in the United States in 1977 because of evidence that they build up in the environment and cause harmful effects. Products containing PCBs include old fluorescent lighting and electrical appliances containing PCB capacitors, old microscope oil and hydraulic fluids. PCBs were used in other products as diverse as hydraulic fluids, lubricants, adhesives, fire retardants, paints, plasticisers, inks, carbonless copy paper, caulking compounds and slide mounting oil for microscope slides. Other halogenated compounds may contain PCBs in small amounts as a contaminant (IPCS 1993).
Leaks from electrical transformers containing PCBs. Electrical equipment in which PCBs have been replaced may still contain traces of them.
Before 1977, PCBs entered the air, water and soil during their manufacture and use. Today, PCBs may be released into the environment from either hazardous waste sites that contain PCBs or from illegal and improper dumping of PCB wastes.
There are no known natural sources of PCBs.
There is no information available.
Consumer products that may contain PCBs
Old products listed below under 'Health effects' may contain PCBs.
How might I be exposed to PCBs?
Exposure may be through:
- capacitors in old fluorescent lighting fixtures and old appliances such as television sets and refrigerators, which may leak small amounts of PCBs into the air when they get hot during operation;
- eating food, including fish, meat and dairy products containing PCBs;
- breathing air near hazardous waste sites that contain PCBs;
- drinking PCB-contaminated well water; and
- repairing or maintaining PCB transformers.
By what pathways might PCBs enter my body?
PCBs can enter the body in three ways:
- absorption through the skin;
- inhalation of PCB vapour (at room temperature, the vapour concentrations of PCBs are not significant); and
- ingestion, if there is contamination of food or drink.
National Occupational Health and Safety Commission (NOHSC):
- TWA (eight-hour time weighted average) exposure limit in the workplace:
- 1 mg/m³ for PCBs containing 42% chlorine
- 0.5 mg/m³ for PCBs containing 54% chlorine.
- STEL (short-term exposure limit) (15 minutes):
- 2 mg/m³ for PCBs containing 42% chlorine
- 1 mg/m³ for PCBs containing 54% chlorine.
The absorption of these substances through the skin may be a significant source of exposure.
What effect might PCBs have on my health?
Chronic (long-term) exposure to some PCB formulations by inhalation in humans results in respiratory tract symptoms, gastrointestinal effects, mild liver effects, and effects on the skin and eyes such as chloracne, skin rashes, and eye irritation.
In Japan in 1968, people were affected by PCBs when they ingested rice bran oil that had been accidentally contaminated with kanechlor 400; this led to an outbreak of what became known as 'Yusho disease'. Symptoms included nausea, lethargy, chloracne, excessive eye discharge, visual disturbances, gastrointestinal disturbances and jaundice. The cooking oil was also contaminated with polychlorinated dibenzofurans. PCBs containing 42%and 54% chlorine are classified by the NOHSC as Category 2 carcinogens (substances for which there is sufficient evidence to provide a strong presumption that human exposure might result in the development of cancer).
Microbes degrade PCB molecules containing one, two or three atoms of chlorine relatively rapidly. Those with four atoms of chlorine degrade more slowly. The more highly chlorinated PCBs resist biodegradation. Since PCBs bioaccumulate in fat, PCBs may build up in fish and marine mammals and can reach levels thousands of times higher than the levels in water.
PCBs may be carried long distances in air. They can remain in air for approximately 10 days. In water, small amounts of the PCBs may remain dissolved, but the majority will settle into sediments by adhering to organic particles.
The Scheduled Waste Management homepage (http://www.environment.gov.au/industry/chemicals/swm/) at the Environment Australia website includes the following reports:
- Polychlorinated Biphenyls Management Plan;
- National Advisory Body on Scheduled Wastes: Monitoring of PCBs in Australia (September 1998);
- Identification of PCB-Containing Capacitors – An information booklet for electricians and electrical contractors (ANZECC 1997)
Australian Water Quality Guidelines for Fresh and Marine Waters (ANZECC 1992):
- Freshwater: maximum of 0.001 micrograms/L
- Marine waters: maximum of 0.004 µg/L.
These figures are being revised: the draft guidelines can be found at http://www.environment.gov.au/water/quality/nwqms.
PCBs are listed under the Rotterdam Convention of Prior Informed Consent (PIC), which covers international trade. Information on this convention can be found at http://www.pic.int and its links. PCBs are also listed in the Customs (Prohibited Import) Regulations.
The Victorian Department of Infrastructure has published a brochure titled PCBs in buildings (1998).
What effect might PCBs have on the environment?
PCBs occur globally and are very persistent, bioaccumulating up the food chain. They are toxic; for example, bats have been found to be susceptible to aroclor 1242 released from their fat during migration. PCBs reduce the capacity of sea mammals to reproduce.
Links to another web site
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