Alternative methodology for the environmental impact assessment of treated wood: the wood emissions ecotoxicology

IRG/WP 00-50161

P Marchal, H W Wegen, J Van Acker, E Melcher, R-D Peek, W J Homan, D Aston, D Rudolph, E F Baines

Preservative products and technologies are important for optimising the use of wood and wood products in our society. The regulations of their use under the european Biocidal Products Directive 98/8/EC will require an evaluation of the environmental impact of treated wood. The methodology currently used for this determination is the PEC/PNEC ratio. It consists of calculating PEC values (Predictive Environmental Concentration) from emissions test data using mathematical models and PNEC values (Predictive No Effect Concentration) from ecotoxicological tests, including a safety factor for the results obtained (the more ecotoxicological data available, the smaller the safety factor). This approach was developed for agrochemical industry and has been in use for a couple of years. Since the exposure scenarios for treated wood are different to the agro-chemicals compounds, there is an urgent need to provide a test methodology to be included in the technical guidance document of wood preservatives. For that case, we suggest applying a "wood emissions ecotoxicological methodology" which can be summarised as follows : a laboratory and/or pilot scale emission protocol for treated wood, resulting in realistic wood leachates, on which ecotoxicological tests can be performed. This suggests that a whole toxicity assessment of the leachate has to be performed : it is well known that wood matrix is a chemically complex structure and that natural compounds can leach from wood into the receiving environmental compartment. This means that chemical analysis of active ingredients alone will not take into account the complex mixture of organic and inorganic substances that a wood leachate represents (active ingredients, modified or metabolised active, tannins, salts …). The toxicity from modelled components can moreover be different from the whole toxicity of leached components complex from wood. Furthermore, it is very difficult in the standard methodology to take the chemical speciation and bioavailability of the released active ingredients into account. The result obtained from this methodology is a more realistic one than the PEC/PNEC ratio estimation and could allow a simple scale classification of the wood emissions' environmental toxicity. This method is complementary to the chemical analysis which has to be carried out in parallel on the active ingredients (especially if the leachate is ecotoxic). Further analysis could also be made (metabolite analysis , leachate biodegradation…) in order to go deeper into the environmental behaviour. If the leachate is not ecotoxic, the emission evaluation can be stopped at this stage. A decision flow chart will also be included in this paper.


Conference: 00-05-14/19 Kona, Hawaii, USA

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