Conclusion regarding the peer review of the pesticide risk assessment of the active substance Diuron

Diuron is one of the 52 substances of the second stage covered by Commission Regulation (EC) No 451/20001, as amended by Commission Regulation (EC) No 1490/20022. This Regulation requires the European Food Safety Authority (EFSA) to organise a peer review of the initial evaluation, i.e. the draft assessment report (DAR), provided by the designated rapporteur Member State and to provide within one year a conclusion on the risk assessment to the EU-Commission. On 19 September 2003, Denmark being the designated rapporteur Member State submitted in accordance with the provisions of Article 8(1) of the amended Regulation (EC) No 451/2000, the DAR on diuron to the EFSA. The peer review was initiated on 13 October 2003 by dispatching the DAR for consultation of the Member States and the notifier, The European Diuron Taskforce consisting of Bayer and Griffin. However, the task force has in the meantime been changed as DuPont de Nemours (France) S.A. has replaced Griffin (Europe) within the European Diuron Taskforce (DTF) by 5 November 2003. This has been reported to the Commission, the RMS and EFSA on 26 August 2004. The comments received on the DAR were examined by the rapporteur Member State. Remaining issues were evaluated in respective meetings with Member State experts. A final discussion of the outcome of the consultation of experts took place with representatives from Member States on 14 December 2004 leading to the conclusions as laid down in this report. The conclusion was reached on the basis of the evaluation of the representative uses as herbicide as proposed by the notifier which comprises spraying to control mono-and dicotyledonous weeds in pome fruit and vine at application rate up to 2 kg diuron per hectare in strip application. The notifier has applied for an amendment of the GAP after the expert meetings The new intended GAP is pre-emergence application of 1.5 kg a.s./ha in strips. The new intended GAP has not been taken into account by the RMS due to the late submission. Due to the fact of outstanding data a final comparability of the technical material from the different sources could not be conducted during the evaluation procedure. From an analytical point of view none of the three sources can be regarded as equivalent. Therefore the given minimum purity of 970 g/kg has to be regarded as a provisional value. No analytical method for monitoring purposes to determine residues of diuron in food of plant origin is available. In addition, the acceptability of the analytical method for the determination of residues in soil and ground water is depending on the residue definitions for monitoring purposes, which can be concluded only after the assessment of outstanding data in the fate and behaviour section. The necessity for an analytical method for food of animal origin cannot be concluded due to the fact that the risk assessment on food of animal origin cannot be finalised. The main toxicological effects of diuron are haemolytic anaemia and effects on the urothelial system. It is carcinogenic in rats and mice. The classification is toxic with the risk phrases T; R22, R40, R48/22, R48/23. Based on the available data the estimated operator exposure (German model, with standard PPE) exceeds the AOEL. Bystander and worker exposure is assumed to be negligible. The metabolism of diuron in plants is well understood and yields the metabolites DCPMU (3,4-dichlorophenyl-methylurea) and DCPU (3,4-dichlorophenylurea), which are of toxicological concern. It is noted that these metabolites can derive not only from diuron but also from other herbicides. As long as the investigation of the residue situation according to the critical GAP is not finalised, the risk assessment for consumers cannot be finally concluded, nor can MRLs be proposed. Soil degradation of diuron yields DCPMU and DCPU as major metabolites. Mineralisation is generally low but occasionally may reach levels up to 32 %. Non-extractable residues build up during the degradation. A photolysis in soil study is necessary to complete the assessment. Diuron is moderately to highly persistent in soil under aerobic conditions. Degradation of diuron is slower at lower temperatures and under anaerobic conditions. In multiple season field studies, a tendency of soil adaptation is observed with a faster degradation in the later years. The need for further soil degradation studies on metabolites DCPMU and DCPU has been identified during the peer review. Diuron, DCPMU and DCPU have medium to low potential for mobility in soil. Hydrolysis of diuron shows strong pH dependence being relatively rapid under acidic pH and stable at alkaline pH. Aqueous photolysis could contribute to environmental degradation of diuron. It is proposed to classify this active substance as "non-readily biodegradable" taking into account the results of the water sediment studies. In water sediment systems no metabolites are formed at levels above 10 % AR neither in the water nor in the sediment. Diuron was relatively rapidly adsorbed by the sediment. In the total system, diuron was moderately to highly persistent. Diuron PECsw and PECsed (initial) values used in the risk assessment are based on the spray drift values. The contribution from drainage and run-off was not assessed and should be taken into account by MS when these routes of surface water contamination are envisaged to be relevant. The Notifier is required to provide the existing surface monitoring data but this data requirement was not considered essential to finalise the EU risk assessment. The level of uncertainty in the available FOCUSgw modelling is too high to come to a conclusion regarding the risk of ground water contamination and new FOCUS modelling is needed (pending further data on degradation of DCPMU and DCPU). Therefore, the residue definition for ground water is still open. A high risk to birds and mammals from the use of diuron was identified. The lowest TER values are 8.8, 5.2 and 0.4 for the acute, short and long term risk to birds, respectively, and 5.1 and 0.7 for the acute and long term risk to small herbivorous mammals, respectively. These values are all below the corresponding Annex VI trigger values of 10 for both the acute and short term risk and 5 for the long term risk. Further data to address this risk is needed and the risk assessment can only be concluded when the outstanding data is evaluated. Using the lowest algae endpoint, the risk assessment indicates a high risk to aquatic organisms. Even with a buffer zone of 50 m, the calculated TER value (2.5) is below the respective trigger of 10. Additionally, a high risk to terrestrial plants was identified as the trigger is breached with a buffer zone of 50 m (TER = 3.58, trigger in the guidance document on terrestrial organisms is 5). Therefore, extensive risk mitigation measures (e.g. buffer zones above 50 m) or further data to address this risk to aquatic and terrestrial plants is considered necessary. For bees (pending confirmatory data requirement), non-target arthropods, soil micro-and macro-organisms, including earthworms the risk is considered low for the representative uses with regard to diuron and metabolites.