PCB, the polychlorinated biphenyls, are a group of 209 synthetic, chlorinated hydrocarbons. They are thermally stable, chemically inert and plasticising, and precisely these properties made them a sought-after additive in joint sealants, seals and paints. The same properties are the problem today: PCB practically do not break down in the environment. They are found worldwide, from Arctic ice to the deep sea, and in a building they sit where they were installed decades ago, and keep off-gassing.
In Austria, PCB-containing joint sealants were installed from about 1955 to the end of the 1970s, above all in precast-concrete buildings, office buildings and schools. Since 1993 the manufacture, placing on the market and use of PCB have been banned in Austria (BGBl. No. 210/1993); for electrical equipment already in use at the time, transition periods applied, depending on the type of equipment until the end of 1996 or the end of 1999. The joints from that period are often still there.
Where PCB sit in buildings
- Building joints: elastic sealing compounds between precast concrete elements, on facades, between floor slabs and external walls. The most common source.
- Window joints: sealing compounds around window frames, especially with the metal windows of the 1960s and 1970s.
- Expansion joints: in floors, car parks and industrial buildings.
- Paints and coatings: rarer, but possible, for example in anti-corrosion coatings.
The sealants are usually grey, beige or black and become hard and cracked over time.
Why PCB are dangerous
PCB off-gas continuously from the sealant into the room air over decades and accumulate in house dust. In the body they are fat-soluble, deposit in fatty tissue and are broken down only very slowly. The International Agency for Research on Cancer (IARC/WHO) classifies PCB as carcinogenic to humans (Group 1), and the dioxin-like PCB likewise; PCB cause malignant melanoma, and positive associations are described for non-Hodgkin lymphoma and breast cancer (IARC 2013, Monograph 107, published 2016). Alongside this, liver damage, a weakening of the immune system and disruption of the hormone system are described; children and pregnant women are considered especially sensitive. This classification describes the hazard of the substance, not the level of risk in a particular room, and it rests on the occupationally highly exposed. What counts in the specific building is the measured concentration; the reference value against which it is judged is an action value, not a line between harmless and harmful. That part of the PCB acts like the dioxins is no accident of naming but chemistry; the first fold-out sets it out.
For experts, or those who want to become one: 209 congeners, the dioxin-like PCB, and why they are so long-lived
A PCB molecule consists of two benzene rings joined by a single bond (the biphenyl skeleton), to which one to ten chlorine atoms can attach. From the possible positions arise 209 different individual compounds, the congeners. Technical PCB mixtures were never a single substance, but mixtures of many congeners with a certain degree of chlorination. The many chlorine-carbon bonds and the lack of points of attack make the molecules chemically inert and biologically hard to degrade; they are fat-soluble, accumulate in organisms and along the food chain, and are carried through the atmosphere as far as the Arctic. Persistence, bioaccumulation and long-range transport are the criteria by which PCB were taken into the Stockholm Convention.
A subset of the congeners has a special effect. If chlorine is absent at the inner, the ortho, positions, the two rings can turn freely into one plane; these planar and near-planar congeners, the dioxin-like PCB, bind like 2,3,7,8-tetrachlorodibenzodioxin to the aryl hydrocarbon receptor and trigger the same kind of effect, though with far lower potency. For them the WHO has, as with the dioxins, set up a system of toxic equivalency factors that relates their effect to that of TCDD. For the carcinogenic effect, IARC in 2013 drew on the entirety of the cohort data and classified both PCB overall and the dioxin-like PCB as carcinogenic to humans (Group 1); the related polybrominated biphenyls were classified as probably carcinogenic (Group 2A) (IARC 2013, Monograph 107; evaluated 2013, published 2016).
Why the source is not only the joint
A peculiarity complicates PCB remediation in buildings. From the sealant, the primary source, the compounds migrate over years into adjacent, porous components, into concrete, plaster and screed. These components thus become secondary sources that keep off-gassing even when the original joint has long been removed. A PCB remediation is therefore seldom done with cutting out the joint; often the contaminated surroundings must be assessed and remediated too. Anyone who removes only the visible joint and overlooks the secondary sources often does not reduce the room-air burden lastingly.
How PCB are determined
It begins with a material sample of the suspect sealant, a small piece of a few centimetres, examined in an accredited laboratory. Six indicator congeners are recorded, from whose sum the total content is extrapolated. If joints lie open over a large area or complaints exist, a room-air measurement completes the picture. Self-sampling of PCB-suspect sealants is inadvisable, if only because of skin contact, and large open joints should not be worked on oneself. How six congeners yield a total content and what the guide values mean is in the fold-out.
For experts, or those who want to become one: The six indicator congeners, the extrapolation and the guide values lowered in 2025
Determining all 209 congeners individually would be uneconomical. The analysis therefore restricts itself to six indicator congeners after Ballschmiter (PCB 28, 52, 101, 138, 153 and 180), which are regarded as representative of the whole congener spectrum. The total content is extrapolated from their sum: the convention common in Germany and Austria takes the sum of the six congeners times five as total PCB (total PCB = ΣPCB6 × 5). The factor of five also shows that the six indicator congeners make up only about a fifth of the total content, not the majority.
Austria has no binding limit of its own for PCB in indoor air; the German guide values of the Committee on Indoor Air Guide Values (AIR) serve as orientation. The committee lowered them markedly in 2025: in place of the former remediation-target value of 300 ng/m³ and the intervention value of 3,000 ng/m³ came a precautionary value (guide value I) of 80 ng/m³ and a hazard value (guide value II) of 800 ng/m³, each referring to total PCB (AIR 2025). Below the precautionary value the burden is regarded as tolerable in the long term; above it the source is to be sought and the concentration lowered; from the hazard value there is a need to act. The lowering rests not on the dioxin-like effect but on a more sensitive endpoint: the new value is derived from immunotoxicity, on the basis of the lowest effect dose in the most sensitive animal species, the rhesus monkey, whereas the old value rested on now-outdated liver findings. The reassessment became possible because the PCB fraction taken up by inhalation from the room air could be plausibly quantified for the first time. The former separate value for dioxin-like PCB was withdrawn in the process, because the new hazard value protects against them too (AIR 2025). In practice, the lowering means that rooms which were unremarkable under the old values may have to be reassessed.
The legal framework
PCB have been banned in Austria since 1993 (Ordinance on the prohibition of halogenated biphenyls, terphenyls, naphthalenes and diphenylmethanes, BGBl. No. 210/1993). EU-wide and internationally, PCB are covered as persistent organic pollutants under the Stockholm Convention. Under the European List of Waste, PCB-containing building materials are classified as hazardous waste once their PCB content exceeds the concentration limit of 50 mg/kg, and must then be disposed of accordingly (List of Waste 2000/532/EC; POP Regulation (EU) 2019/1021, Annex IV). For the assessment of indoor air, the German guide values of the Committee on Indoor Air Guide Values, lowered in 2025, serve as orientation (precautionary value, guide value I: 80 ng/m³; hazard value, guide value II: 800 ng/m³), since Austria has not set a binding value of its own (AIR 2025).
What to do
- PCB joints intact, no known room-air burden: document the joint and have it professionally removed at the next renovation. Because even intact joints keep off-gassing, in case of doubt, especially in rooms with small children, a room-air measurement gives information on the actual burden.
- Joints open, cracked or over a large area indoors: a room-air measurement is sensible. Above the precautionary value, identify the source, lower the concentration and remediate the joints.
- Remediation planned: PCB sealants and the contaminated adjacent components are to be removed under protective measures, and the waste disposed of as hazardous waste. Because the secondary sources in the concrete count too, the extent should be professionally established before work begins.
PCB rarely occur alone. In buildings of the 1960s to 1980s there is often also asbestos and old mineral wool insulation (MMF).
Sources
- AIR (2025): Committee on Indoor Air Guide Values (Ausschuss für Innenraumrichtwerte, Germany), guide values for polychlorinated biphenyls (PCB) in indoor air. Bundesgesundheitsblatt 68(2):201 to 218. Precautionary value (guide value I) 80 ng/m³, hazard value (guide value II) 800 ng/m³, referring to total PCB (ΣPCB6 × 5); previously remediation-target value 300 ng/m³ and intervention value 3,000 ng/m³; critical endpoint immunotoxicity. dguv.de
- IARC (2013): Polychlorinated Biphenyls and Polybrominated Biphenyls. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol. 107 (evaluated 2013, published 2016). PCB and dioxin-like PCB carcinogenic to humans (Group 1), based on malignant melanoma, with positive associations for non-Hodgkin lymphoma and breast cancer; polybrominated biphenyls Group 2A. ncbi.nlm.nih.gov/books/NBK361680
- PCB ban Austria (1993): Ordinance on the prohibition of halogenated biphenyls, terphenyls, naphthalenes and diphenylmethanes, BGBl. No. 210/1993. ris.bka.gv.at
- European List of Waste (2000/532/EC, consolidated): Commission Decision establishing a list of wastes; wastes containing PCB above the concentration limit of Annex IV of the POP Regulation (50 mg/kg, Regulation (EU) 2019/1021) are classified as hazardous; PCB-containing construction and demolition wastes such as sealants carry waste code 17 09 02*. eur-lex.europa.eu
- Stockholm Convention (2001/2004): Convention on Persistent Organic Pollutants (POP), PCB in Annexes A and C. pops.int
- Federal Environment Agency Austria: Polychlorinated Biphenyls (PCB), occurrence, persistence and POP regulation. umweltbundesamt.at
- ARGUK environmental laboratory: PCB indoors, primary and secondary sources (migration from the sealant into adjacent components). arguk.de
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