Paradigm shift in the risk assessment of cumulative effects of pesticide mixtures and multiple residues to humans and wildlife: German proposal for a new approach

A paradigm shift is underway in the risk assessment of chemicals leaving behind the traditional ‘‘individual substance approach.’’ This simplified approach has long been criticized for not adequately taking into consideration the well-known occurrence of chemical mixtures in relevant exposure matrices (foodstuff, environmental media) and thus ignoring the ‘‘added risk’’ resulting from multiple exposure and associated mixture toxicity. More recently, the adequacy of this approach was also questioned from the political arena in Europe (Council of the European Union 2009; European Commission 2012). As a consequence, several reviews of the state-of-thescience as well as opinions on the implementation of mixture risk assessment in chemicals regulation have been delivered. Further, the principal request for taking the risk of mixtures into due account has been introduced in recently updated European chemicals legislations, e.g. for plant protection products (PPP) and biocidal products (BP). For PPP, regulation (EC) No 1107/2009 (European Commission 2009) requires in article 29 that ‘‘interaction between the active substance, safeners, synergists and co-formulants shall be taken into account’’ in the evaluation and authorization. This explicitly refers to marketed PPP, which are by origin technical mixtures containing one to several active substances plus typically several co-formulants. Consequently, the ‘‘mixture toxicity issue’’ for these technical mixtures is already mirrored in the standard data requirements for PPP. However, common agricultural practice comprises also the application of two or more PPP simultaneously (tank-mixtures prepared by the farmers directly before application) as well as the sequential application of several different PPP during the growing season (serial applications). Hence, there is well-justified concern for exposure of humans and non-target organisms towards ‘‘coincidental’’ pesticide (residue) mixtures resulting from common agricultural practice. Regarding human health risk assessment, a general and explicit request is laid down in the regulation (EC) No. 1107/2009, stating that PPP and their residues ‘‘[...] shall have no immediate or delayed harmful effect on human health, [...], taking into account known cumulative and synergistic effects where the scientific methods accepted by the Authority to assess such effects are available; [...].’’ With regard to the environmental risk assessment in the standard data requirements for PPP a quite similar sentence is included. While there are clear regulatory requirements on adequately considering the risk from exposure to PPP (residue) mixtures, often the lack of agreed and sufficiently specific technical guidance is the major obstacle for a consistent and adequate implementation of mixture risk assessment under regulation M. Streloke (&) Federal Office of Consumer Protection and Food Safety (BVL), Messeweg 11/12, 38104 Brunswick, Germany e-mail: martin.streloke@bvl.bund.de