1.2Het gebruik van verduurzaamd hout leidt tot een zekere emissie van actieve stoffen. Verweerder heeft de risico’s voor het milieu als gevolg van deze emissie onderzocht. Daarvan is een ‘Biocidal product assessment report related to product authorization under Regulation (EU) 528/2012’ d.d. 3 april 2015 (hierna: het rapport) opgesteld. Het rapport luidt, voor zover hier van belang:
p. 47
“(…) In the case of treated wood in service, the following emission scenarios have been run for use classes 3 and 4:
- (…)
- jetty in the lake as a representative for wood directly in contact with stagnant surface water (UC4);
- sheet piling in waterway as a representative for wood directly in contact with flowing surface water (UC4). (…)”
p. 49
“(…) The ESD applies a three compartment model in which equilibrium between water and suspended matter, and water and sediment is assumed. The corresponding concentration in water, suspended matter, and sediment are calculated according to the active substances’ organic carbon water partitioning coefficients (Koc). This however contradicts with the TGD where sediment is defined as freshly deposited suspended matter in flowing water and the concentration in sediment is based on the characteristics of and distribution constants for suspended matter. It is, however, still questionable if the ESD’s model is realistic for the bridge over pond and jetty in a lake scenario.
Direct exchange of active substances between water and sediment may be only relevant
for shallow water with sufficient resuspension as equilibrium is reached fast. However, due
to slow kinetics and stagnant boundary layers, it is unrealistic that in deeper waters the
concentration in sediment is in equilibrium with the concentration in the overlying water phase, especially for the initial assessment period. Moreover, the sediment layer is continuously buried under freshly deposited suspended matter. Sedimentation should be therefore taken into account, but the required models and parameters are not yet available.
Nevertheless, the sediment compartment cannot be ignored as sorption to suspended
matter only and subsequent PEC calculations for sediments according to the TGD result in
unrealistic high concentrations when biocides are released to stagnant water day after day.
To overcome this, the three compartment model for the ESD was still applied, but sediment (…) was based on the partition coefficient and density of suspended matter instead the corresponding values for sediment. (…)”
p. 64
“(…) The emission of copper from preserved wood applied in stagnant surface water as represented by a jetty in a lake will not increase the background concentration significantly. An exceeding of the PNEC is therefore not expected. (…)
The emission of copper of wood applied as sheet piling in a streaming water way, however, results in unacceptable risks for water and sediments.
p. 66
3 Decision
(…)
Tanalith E3462 has been applied for and evaluated as a fungicide, and insecticide. The authorization is granted for preventive protection of wood and constructional timbers in Hazard Classes 1, 2, 3 and 4a by vacuum pressure application. (…)”