Peer review of the pesticide risk assessment of the active substance mesotrione


European Food Safety Authority
EFSA Journal
EFSA Journal 2016;14(3):4419 [103 pp.].
Conclusion on Pesticides
On request from
European Commission
Question Number
19 February 2016
7 March 2016
European Food Safety Authority (EFSA), Parma, Italy
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The conclusions of the European Food Safety Authority (EFSA) following the peer review of the initial risk assessments carried out by the competent authorities of the rapporteur Member State the United Kingdom and co-rapporteur Member State Belgium for the pesticide active substance mesotrione are reported. The context of the peer review was that required by Commission Implementing Regulation (EU) No 844/2012. The conclusions were reached on the basis of the evaluation of the representative use of mesotrione as a herbicide on maize. The reliable end points, appropriate for use in regulatory risk assessment are presented. Missing information identified as being required by the regulatory framework is listed. Concerns are identified.


Commission Implementing Regulation (EU) No 844/2012 (hereinafter referred to as ‘the Regulation’) lays down the procedure for the renewal of the approval of active substances submitted under Article 14 of Regulation (EC) No 1107/2009. The list of those substances is established in Commission Implementing Regulation (EU) No 686/2012. Mesotrione is one of the active substances listed in Regulation (EU) No 686/2012.

In accordance with Article 1 of the Regulation, the rapporteur Member State (RMS), the United Kingdom, and co-rapporteur Member State (co-RMS), Belgium, received an application from Syngenta Crop Protection AG for the renewal of approval of the active substance mesotrione. Complying with Article 8 of the Regulation, the RMS checked the completeness of the dossier and informed the applicant, the co-RMS (Belgium), the European Commission and the European Food Safety Authority (EFSA) about the admissibility.

The RMS provided its initial evaluation of the dossier on mesotrione in the renewal assessment report (RAR), which was received by EFSA on 23 February 2015. In accordance with Article 12 of the Regulation, EFSA distributed the RAR to the Member States and the applicant, Syngenta Crop Protection AG, for comments on 17 April 2015. EFSA also provided comments. In addition, EFSA conducted a public consultation on the RAR. EFSA collated and forwarded all comments received to the European Commission on 18 June 2015.

Following consideration of the comments received on the RAR, it was concluded that additional information should be requested from the applicant, and that EFSA should conduct an expert consultation in the areas of mammalian toxicology, residues, environmental fate and behaviour and ecotoxicology.

In accordance with Article 13(1) of the Regulation, EFSA should adopt a conclusion on whether mesotrione can be expected to meet the approval criteria provided for in Article 4 of Regulation (EC) No 1107/2009 of the European Parliament and of the Council.

The conclusions laid down in this report were reached on the basis of the evaluation of the representative use of mesotrione as a herbicide on maize, as proposed by the applicant. Full details of the representative uses can be found in Appendix A of this report.

The use of mesotrione according to the representative use proposed at EU level results in a sufficient herbicidal efficacy against the target weeds.

In the area of identity, physical/chemical/technical properties and methods of analysis, a data gap was identified for specifying two of the significant impurities on dry weight basis. Data gaps were identified for validation data of methods used in data generation.

Regarding the mammalian toxicology area, a number of data gaps were identified. The toxicological relevance of individual impurities present in the technical specification in comparison with the toxicity profile of mesotrione needs to be addressed. Interspecies comparative in vitro metabolism should be conducted to identify at least potentially unique human metabolites to mesotrione. As the genotoxic potential of metabolite AMBA could not be ruled out due to positive results obtained in an in vitro cytogenetic assay, and no in vivo genotoxicity testing was performed, a critical area of concern has been identified regarding consumer risk assessment; repeated dose toxicity would also have to be addressed for this metabolite. Mesotrione is proposed to be classified as Repr. 2 for development by the peer review (in contrast with the harmonised classification according to CLP Regulation) and adverse effects were observed on endocrine organs. Therefore, according to the interim provisions of Annex II, point 3.6.5 of Regulation (EC) No 1107/2009 concerning human health, mesotrione may be considered to have endocrine disrupting properties. As no study is available to investigate a potential ED mode of action, a general data gap has been identified such as level 2 and 3 indicated in the OECD Conceptual Framework to address this issue; this was identified as another critical area of concern.

The consumer dietary risk assessment could not be finalised with regard to products of animal origin considering the requested clarification of the genotoxic potential and the toxicological profile of AMBA. Furthermore, the consumer risk assessment from consumption of drinking water could not be finalised whilst the nature of residues in drinking water following water treatment had not been addressed.

A data gap was also identified for the determination of the residues in pollen and bee products for human consumption.

Enough information was available to finalise the exposure assessment in the environment. Nevertheless, a data gap has been identified for the applicant to address the substances of potential toxicological concern that could be derived from mesotrione and its metabolites under drinking water treatment procedure conditions to assess if the approval criteria in Article 4 of Regulation (EC) No 1107/2009 are satisfied.

In the area of ecotoxicology, a data gap and a critical area of concern were identified to further address the long-term risk for wild mammals. A data gap was identified to further refine the risk to aquatic organisms in the scenarios R2, R3, and R4. Data gaps were also identified for bees to provide information to further assess the risk to adult honeybees and honeybee larvae from exposure via guttation and via consumption of contaminated water. Effects on HPG development should be considered. Furthermore additional data would be needed to assess the risk to honeybees for relevant metabolites in pollen and nectar. The risk to non-target terrestrial plants was low with mitigation measures. A data gap was also identified to further address the sensitivity to mesotrione of dicotyledonous and monocotyledonous plant species.

mesotrione, peer review, risk assessment, pesticide, herbicide
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