What are PCBs?

  • Definition of PCB

A PCB, or Polychlorinated Biphenyl, is a chlorine derivative, known more widely in France as the chemical compound pyralene. Internationally, it is one of the twelve POPs (persistent organic pollutants).

A PCB is one of the organochloride configurations, with 2 to 10 chlorine atoms attached to biphenyl, which is a molecule composed of two benzene rings.
They are viscous or resinous fluids, depending on their chlorine content, with low water solubility, clear or yellow in colour, and odourless.

structure-chimique-des-polychlorobiphenyles
Chemical structure of polychlorinated biphenyls

The chemical formula is: C 12 H 10-nCln where n=1-10 (and in principle n=2 to 7)
Relative atomic mass: 189 – 499 g

  • Uses of PCBs

PCBs began to be used as industrial products, mainly as dielectric fluids for transformers, from 1929 until the beginning of the 1980s.

They were obtained from biphenyl through the partial substitution of hydrogen atoms with chlorinated atoms.

While PCBs were recognised very early on as VERY GOOD ELECTRICAL INSULATING FLUIDS, their inflammable properties, physical and biological stability, plasticity, insolubility, relative innocuousness (at least for the time) and low production cost meant they were considered a “miracle product” and were put to good use during the height of industrial development.

There were two key uses for it:

  • In enclosed units: dielectric fluids (oil), mainly in transformers and capacitors. They were also found in certain electrical oil heaters or other electrical equipment.
  • Open sources: pesticide thinners, lubricants for turbines and pumps, cutting fluids for metal cutting, welding, adhesives, paints and carbonless copying paper, etc.

Such wide use gave rise to broad dispersion in the environment, with the most serious cases involving  unauthorised deposits or incidents involving the use of electrical equipment: vandalism, abandonment, explosion of transformers or capacitors, lack of maintenance, etc.

Between 1929, when they were first used commercially, and 1989, the total global production (excluding URSS) is estimated at 1.5 million tonnes.

  • Environmental and health risks associated with PCBs

PCBs have very little biodegradability with very long persistence.

Once released into the environment, PCBs can accumulate in the food chain. They can amplify within living organisms and withstand deterioration.
PCB compounds can be found in a wide variety of milieus and in all ecosystems: air, ground, water, sediment, and after transfer on plants, in animals and people.

There are two main sources of PCB pollution today:

  • recurrent sources from atmospheric fallout (dust, rainwater), run-off water in urban areas and waste from purification plants, resulting in persistent saturation of our societies.
  • one-off cases such as acts of vandalism, due to the appeal of copper contained in transformers, during accidental spillage, negligence or lightening flash on transformers or in the case of overvoltage.

The negative health effects of PCBs mainly relate to endocrine disease.

  • PCB waste disposal plans

France’s national plan for the decontamination and elimination of equipment containing PCBs had a deadline of 2010.

At national level, the Stockholm Convention stipulates a deadline of 2028.

PCB production was prohibited in France as a persistent organic pollutant in 1985, while in the US, PCB production has been prohibited since 1977 and in Germany since 1983.

In Europe, the use of PCBs in open sources such as inks and adhesives, paints, varnishes, etc. was banned in 1979.

In France, the use of PCBs in electrical appliances was banned in 1987.
After the application of various different regulations governing the banning, elimination and destruction of PCBs, a natinal plan for the decontamination and elimination of equipment containing PCBs was devised in the decree of 18 January 2001, which set a deadline of 31 December 2010 for the elimination of equipment containing PCBs in concentrations above 500 mg/kg.
A new text is being prepared to organise the gradual destruction, treatment and elimination of transformers and transformer fluids that still contain traces of PCBs.

At international level, the Stockholm Convention provides that equipment containing PCBs must be listed, labelled and decommissioned by 2025, and must be correctly stored before being eliminated in an environmentally sound manner by 2028.

  • PCB waste elimination methods

The safest means of elimination is still by incineration at 1200°C under strictly controlled conditions, followed by sudden cooling.

Trédi St Vulbas is the only plant in the world to receive official authorisation and approval to completely dispose of PCB waste (decontamination and incineration).

Given the chemical make-up of PCBs, the risk posed by their potential dissemination and amplification as a result of their ability to remain in the environment and to withstand time means that VERY SPECIFIC HANDLING is required.

Trédi St Vulbas, whose processes are based on these factors, IS AUTHORISED to DECONTAMINATE WASTE CONTAINING PCBs (capacitors, transformers, etc). Its operations and environmental impact are subject to strict controls on a regular basis, with the result that the plant has been designated as having the “Best Available Technology”.

If the PCB content is particularly low, and depending on the equipment’s history, certain transformers can be rehabilitated for reuse after decontamination. In other cases, some materials, such as metallic mass, can be recovered after decontamination.

The entire treatment chain from the moment the PCB waste is obtained through to its destruction is subject to strict controls. The Trédi St Vulbas plant has been ISO 9001, ISO 14001 and OHSAS 18001 certified for several years.