Mending a bad reputation

Impregnated wood has an undeservedly bad reputation and has in fact been a safe material choice for years, believes Fredrik Westin, CEO of the Swedish Wood Preserving Association, which is behind the publication ‘An Environmental Handbook for Treated Timber.


Published 16 August 2023

Today's wood preservatives are water-soluble and use copper as the main biocide, as directed by the Swedish Chemicals Agency and the EU's biocide regulations. All wooden products produced in the Nordic region are also treated according to the rules of the Nordic Wood Preservation Council (NTR), which have been rigorously tested ‘in-field’ for at least five years. The wood impregnation process itself is always done in a sealed-off environment in order to avoid any potential external contamination.

In the past, pressure-treated wood products may have contained several harmful substances such as chromium, arsenic and creosote. CCA (Copper, Chromium, Arsenic) agents were no longer in use in Sweden by 2004, and were completely banned in 2007. Some products may still contain creosote, but these are highly restricted and may only be used for railway sleepers and utility poles, and not by private individuals. Yet even though it has been 20 years since CCA agents were last used in Sweden, the general perception that pressure-treated wood is dangerous has, in many ways, persisted.

"Impregnated wood in general has had a bad reputation. Many people think that impregnated wood is toxic and dangerous, which has led, in many instances, to it not being used in various situations. But now that we are increasingly talking about sustainability and thinking more from a longer-term perspective, organizations such as the Nordic Swan Ecolabel label have changed their position on impregnated wood. They believe it is better that we build with impregnated NTR wood than waste resources. There are clearly negative aspects associated with wood preservative treatment, because it uses substances that you should be very careful with. On the other hand, treated wood lasts four to five times longer and you can use local raw materials”, says Fredrik Westin, CEO of the Swedish Wood Preserving Association.


Fredrik Westin is CEO of the Swedish Wood Preserving Association and the Swedish Wood Preserving Institute, as well as General Secretary of the Nordic Wood Preservation Council. He is also a board member of the European Institute for Wood Preservation (WEI-EIO) based in Brussels.

Environmental Handbook

This summer the Swedish Wood Preserving Association published ‘An Environmental Handbook for Treated Timber’. The handbook, which is the result of months of research and work, is designed to provide a factual resource for producers of impregnated wood when talking with customers and authorities who have specific questions about environmental issues and regulations.

According to Swedish waste regulation classifications, treated wood manufactured with water-soluble copper-based wood preservatives is considered below the limit for what constitutes hazardous waste, and must therefore be sorted as mixed wood waste.

The impregnated wood products that Norra Timber produces have been manufactured according to the treated wood standards of NTR A and NTR AB, which means they are classified as non-hazardous waste by a considerable margin.

Impregnated wood also has a significantly longer lifespan than untreated wood, which facilitates recycling and is an important step towards reaching our environmental goals.

Careful use of Copper

Copper is classified as an essential metal, and humans, plants and animals all need a small amount of copper to enable cells to function properly. In the case of clam farming, for example, it is permitted to fertilize the soil with copper in order to boost growth. Too much copper, however, can be harmful, especially for aquatic organisms, which is why impregnated wood is not suitable for marine use. Both the global research institute RISE and the IVL Swedish Environmental Research Institute have investigated how much copper is leached from impregnated wood, and have concluded the amount is negligible from a health and environmental perspective. A study by the Swedish University of Agricultural Sciences shows that copper-based wood preservatives in, for example, growing boxes or plant support stakes do not generally affect root formation or any uptake of wood preservatives by the plants themselves.


In some wood preservative treatments the substances propiconazole and/or tebuconazole are used in very low doses. As there are currently no viable alternatives to these biocides, exceptions have been made to allow for their use within the EU. The quantities used are so small that it does not affect waste assessments, and in some cases the doses are so insignificant that even the Nordic Swan Ecolabel criteria discount them. They are, nevertheless, classified as toxic to reproduction and must be phased out when other viable equivalents are found.