Under the Biocides Directive Competent Authorities will be responsible in conducting risk assessment strategies for 23 product types, of which wood preservatives are only one. All of these groups show further diversity in terms of use patterns and the type of application method of the different chemical products used to control a variety of natural organisms. This increases the problem associated with predicting exposure to the environment from their use and more importantly their subsequent impact. Like most other biocidal product types exposure and emission scenarios have not been adequately developed for the purposes of realistic regulatory risk assessment scenarios for wood preservatives. The EU Commission have developed clearly defined technical guidance for data requirements but as yet there is no definitive risk assessment guidance to show how to use this data quantitatively in the risk assessment process. What is clear is that the use of predictive modelling will be pivotal to the environmental risk management strategies enshrined in the current Biocides Directive. There are many hundreds of models to choose from for predicting the fate of chemicals in the environment but from a regulatory point of view models need to be simple to use, result in realistic predictions and for practicality have a limited number of input parameters. For the purposes of the Biocides Directive fate models to predict exposure will be mathematically derived calculations based on agreed default parameters at European level. Decisions will be based on the modelistic approach of the predicted environmental concentration (PEC) and predicted no effect concentrations (PNEC) in the environment. Calculations are required to calculate a risk quotient (RQ) using the PEC:PNEC ratio. This is based on known rates of release and dilution factors in the environment. The PNEC can be calculated by dividing the EC50 or LC50 for the most sensitive species by an arbitrary safety factor (often 1000). This is to allow for the great uncertainty in extrapolating from laboratory toxicity data for one species to expected field toxicity to another species. It is proposed that the following assessment factors are used when reviewing data from laboratory testing: a) 1000 applied to the lowest L(E)C50 from base-set toxicity data (fish, daphnia and algae); b) 50 applied to the lower NOEC from long-term toxicity data from two species in two taxonomic groups; c) 10 applied to the lowest NOEC from long-term toxicity data from fish, daphnia and algae; d) if field data exist, they will need to be reviewed on a case-by-case basis. PEC values are likely to be derived for local as well as regional situations, each based on specific emission characteristics with respect to time and scale. To ensure PECs are realistic, they should be based on the information in the submitted technical dossier and on any other available and relevant information. Data on loss of the product from treated materials (leaching profile) is usually essential but this is largely product dependent. For instance, this would be essential for treated wood. Unfortunately many of the essential parameters, including specific emission characteristics have not been fully defined or evaluated for wood preservatives or other biocides. There will be particular problems of predicting environmental risk since it will be difficult for applicants to convince authorities that a product should be allowed on the market if the PEC/PNEC ratio is above 1. Careful and urgent discussions are needed at member state level to develop realistic emission scenarios for the wood preservative industry. The EU Commission is not ignorant of these issues. Furthermore the OECD recently hosted a workshop on Environmental Exposure Assessment to wood preservatives. A number of proposals for the future were made. It was clear that practices in the wood preservative industry were not uniform across all member states. A view from the workshop was that in the absence of firm information as to whether particular containment measures could be taken as read the regulators would always carry out a realistic worse case assessment. A key recommendation was the importance of a Europe-wide survey carried out with the help of industry to determine the level at which good practices are applied across member states. This could form the basis for future exposure assessments. Further information on the number of applications per day, quantity of wood treated at one time storage density on site, and storage duration would also be required for industrial timber processes. There was also a call for the development of standardised appropriate methods, to determine the release rate from stored timber. The potential for errors of judgement by regulators must b avoided. We must avoid the situation of overestimating or underestimating the impact on the environment of wood preservative use at all costs. This can only be achieved by accurate and reliable data. This presentation explores the measures that need to be adopted by industry and regulators alike in order that the Biocides Directive can be used as a tool to realistically assess the risks from the use of wood preservatives to the environment.

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