The evaluation of an active substance or a biocidal product under the Biocidal Products Directive (BPD) requires that an environmental risk assessment is carried out. The risk assessment for wood preservatives includes scenarios for preserved wood (e.g. cladding on a house), in which the predicted environmental concentration (PEC) in soil is calculated, using an emission rate for the active substance from the treated wood. The emission rate is critical to the environmental risk assessment of preserved wood and ultimately to the risk mitigation measures required for the preserved wood in storage and in service. This document reviews the published literature concerning the estimation of emission rates from preserved wood, covering laboratory leaching tests, such as EN84 and OECD Guideline tests, and emissions from board and panel tests in outdoor exposure. The results are compared with the results from a modified EN84 test which explains the ‘exponential’ profile of results in laboratory leach tests, and a ‘single board’ outdoor exposure test which shows a ‘sawtooth’ profile. The results are also compared with the emission values which have been used in the Biocidal Products Directive evaluation of active substances and published in the Evaluation Reports. Proposals are made for the use of a harmonized approach and realistic emission rates in the Product Authorisation phase of the BPD.

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