When you enter the roof structure of an old building and there is a musty, chemical smell, old wood preservatives can be the cause. From the 1960s into the early 1990s, roof structures, beams and timber cladding were chemically treated on a vast scale, usually with two active ingredients in combination: PCP (pentachlorophenol) against fungi and lindane (γ-hexachlorocyclohexane) against insects, often in a ratio of about ten to one. They were sold under names such as Xylamon or Xyladecor. In buildings from before the 1990s, treated timber is the rule rather than the exception.
Both substances off-gas from the wood over decades and accumulate in house dust, long after the last treatment.
Where treated timber sits
- Roof structures: the classic location. Rafters, purlins and collar beams were coated over the surface or treated in a dip bath.
- Timber-beam ceilings and half-timbering: in old buildings with visible wood.
- Cellar beams: moisture-exposed wood was treated especially intensively.
- Cladding and panelling: wall panelling and ceiling panels.
A sign may be a brownish, greenish or oily discolouration of the wood, sometimes also a sweetish, chemical smell, especially on warm days or in poorly ventilated rooms. But only an analysis gives certainty.
Why PCP and lindane are dangerous
PCP damages the liver and immune system and can trigger chloracne. The IARC of the WHO classifies PCP as carcinogenic to humans (Group 1), on the basis of non-Hodgkin lymphoma (Monograph 117). Particularly problematic: technical PCP contains dioxins and furans as impurities, highly toxic and persistent compounds.
Lindane is a neurotoxin, damages the liver and acts on the hormone system. The IARC has classified lindane as carcinogenic to humans (Group 1, Monograph 113) since 2015. It accumulates in fatty tissue.
Both substances are long-lived. In attic spaces with treated rafters, significant levels are still found in room air and house dust decades after application.
How to test for contamination
The process begins with a sample: wood shavings from the suspect component, supplemented by a house-dust or room-air sample, examined in an accredited laboratory for PCP, lindane and related substances. Only the analysis shows whether and how heavily it is contaminated and which measures are appropriate. Collecting samples yourself is inadvisable; this, like the remediation itself, should be left to professionals.
The legal framework
PCP has been banned in Austria since 1991 (BGBl. No. 58/1991); lindane has not been permitted as a wood preservative since the early 1990s. Both are listed EU-wide as persistent organic pollutants (POP) under the POP Regulation (EU) 2019/1021; PCP was additionally subject to a REACH restriction until early 2021. There is no binding limit for PCP or lindane in indoor air in Austria; German guide values are used for assessment. Treated wood that is removed is, depending on the level of contamination, hazardous waste.
What to do
- Treated wood in rarely used, poorly ventilated rooms (attic): do not use as a living space until clarified.
- Loft conversion planned: have it measured before the conversion. Contamination changes the approach and the costs considerably.
- Contamination confirmed, residential use: the most reliable solution is to remove the treated wood. Where that is not possible, planing off the surface or sealing can reduce off-gassing, accompanied by good ventilation. Which measure is appropriate depends on the findings and should be planned professionally.
Wood preservatives are one of several invisible legacies in the attic and old building. In buildings of the same period it is also worth looking at asbestos and old mineral wool insulation.
Sources
- IARC/WHO, Monograph 113 (2015): lindane as a Group 1 carcinogen; Monograph 117: pentachlorophenol (PCP) as a Group 1 carcinogen (on the basis of non-Hodgkin lymphoma)
- Prohibition of pentachlorophenol (PCP) in Austria, BGBl. No. 58/1991 (RIS, Gesetzesnummer 10010660); EU: POP Regulation (EU) 2019/1021
- Verbraucherzentrale NRW, „Holzschutzmittel Lindan": verbraucherzentrale.nrw
- allnatura.at, substance profile „Pentachlorphenol (PCP)"
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