Polychlorinated Biphenyls

What are Polychlorinated Biphenyls (PCBs)?

Polychlorinated Biphenyls (PCBs) are chlorinated, often colorless compounds, manufactured synthetically. Depending on the number and position of the chlorine atoms in the molecule, the physical and chemical properties vary. This variation is also reflected for the toxicological properties of the different molecules.

PCBs were included in the initial list of the twelve POPs under the Stockholm Convention, which entered into force in May 2004. 

The production of PCBs is not allowed, and equipment containing PCBs shall not be exported or imported except for the purpose of environmentally sound management. The Stockholm Convention requires international action to eliminate the use of PCBs in equipment by 2025 and to manage PCB waste in an environmentally sound manner by 2028.

Properties

PCBs are fire resistant, have a low electrical conductivity, high resistance to thermal breakdown and a high resistance to oxidants and other chemicals.

As the characteristics of PCBs are quite advantageous from a technical point of view, PCBs can be found in a wide range of applications. 

Some PCB congeners as e.g. the PCB congener 118 are dioxin-like. Dioxin-like PCBs are co-planar; have a geometric configuration like 2,3,7,8-TCDD. Furthermore, dioxin-like PCBs are potentially the most hazardous. They have the same toxicity profile as dioxins and furans.

Some characteristics of PCBs:

• High heat stability
• Good heat conductivity
• Hardly inflammable
• Only poorly soluble in water, but well-soluble in fat
• Relatively good acid, alkali and chemical resistance 
• Stable against oxidation and hydrolysis
• Very small electrical conductivity
• Low vapour pressure

PCB in building materials can be categorised in primary and secondary sources of PCB: 

A primary source of PCB is a product to which PCB was intentionally added to improve its characteristics.

A secondary source of PCB is a product to which PCB was not intentionally added but that was later contaminated by PCBs from other sources (e.g. fogging effect). Both primary and secondary sources continuously emit PCBs and must therefore be considered when planning a clean-up of a building.

Usage and applications

PCBs were first synthesised in 1866, but it was not until 1929 that industrial production started. PCBs were manufactured worldwide by a small number of companies in mostly industrialised countries and often used as cooling and isolating agents in transformers and capacitors.

Globally, the PCB production peaked in the 1960s and 1970s. Between 1983 and 1993, the production of PCBs was stopped in many countries. In some countries it had already been regulated since the early 1970s.

It is estimated that approx. 1.5 million tonnes of technical grade PCBs were produced since the late 1920s , and open applications of PCBs accounted to approx. 25 % of this total production.

PCBs and substitutes like CPs were used in open applications in many industrial, public and private buildings as well as in hydro power, nuclear power and water treatment plants, military installations, the car and shipbuilding as well as the mining industry, and more.

Many buildings worldwide, especially those constructed or renovated between the 1950s and the early 1980s, contain PCBs in a wide variety of applications which emit PCBs into the environment. In buildings, PCBs can contribute directly to human exposure.

Many of these open applications are still in use today, and they are usually not detected and defined as hazardous waste at the time of disposal. PCBs in open applications often find their way into the environment.

Closed applications

In closed applications, PCBs were mostly used as cooling fluids in: 

• Transformers
• Capacitors
• Switches
• Light ballasts and small capacitors
  (for example in fluorescent lamps)

Partially open applications

• Hydraulic oils
• Heat transfer oils
• Lubricating oils

Open applications

Approx. 25 % of globally produced PCBs were used in open applications, such as: 

• Caulks/sealants
• Paints
• Varnishes
• Anti-corrosion coatings
• Cable sheaths
• Adhesives
• Flame retardants
• ... and many more

Risks

PCBs are a serious threat to human health and the environment. It has been demonstrated that PCBs cause a variety of adverse health effects. Among others, they are considered to be carcinogenic, immunotoxic and they affect reproduction and are therefore among the chemicals listed in the group of POPs regulated under the Stockholm Convention.

PCBs are carcinogens and endocrine disruptors. On the basis of sufficient evidence of carcinogenicity in humans and experimental animals, the IARC classified PCBs in 2013 to be a Group 1 carcinogen. Additionally, dioxin-like PCBs were also classified in Group 1.

Furthermore, there are a number of serious non-cancer health effects in animals, including effects on the immune system, reproductive system, nervous system, endocrine system and other health effects. The different health effects of PCBs may be interrelated. Alterations in one system may have significant implications on the other systems of the body.

Due to the persistence of PCBs and the lipophilic properties, PCBs are bioaccumulated and biomagnified. PCBs can be found in the environment, and in the food chain. The chemical is transported over long distances to regions where it has never been used or produced before. PCBs bioaccumulate in the fatty tissue of humans and other living organisms. Fatty animal-based foods like fish, meat and dairy products often contain PCBs. Particularly high PCB levels can be detected in fatty fish types like herring and salmon caught in the wild.

While the Stockholm Convention prohibits production, PCBs are still in use in many applications and stockpiled in many countries. Once released into the environment, PCBs remobilise and enter the ecological food chain, eventually contributing to human exposure via food intake. 

PCBs from open applications can be released into the environment by weathering and inappropriate removal of PCB containing materials. It is therefore important to identify these applications (diagnostics). A detection of PCBs in open applications is only possible if the (building) material is sampled, and analysed in a laboratory.

PCBs used in buildings can contribute directly to human exposure. Indoor air concentration is influenced by both primary and secondary sources of PCBs.

If PCBs are exposed to extreme heat or fire, highly toxic furans and dioxins may be formed and released.

Laws and regulations

The Stockholm Convention on Persistent Organic Pollutants (POPs) counts PCBs among the substances targeted for worldwide elimination. The existing PCBs and all equipment contaminated with PCBs have to be managed (PCB Management) and eliminated in an environmentally sound manner without producing hazards for humans or the environment by 2028.

PCB treatment or disposal technology must comply with the highest safety and environmental standards and must be capable of reducing the PCB contamination level of those pieces of equipment suitable for re-classification below the legally permitted level of 50 mg/kg as well as assure that the PCB level remains below that limit.

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