No proof of synergy at environmentally realistic concentrations of prochloraz and esfenvalerate—A reaction on “Synergy in microcosms with environmentally realistic concentrations of prochloraz and esfenvalerate” by Bjergager et al. (Aquat. Toxicol. 101 (2011), 412–422)

Abstract

The aquatic microcosm study by Bjergager et al. (2011) on a mixture of the fungicide prochloraz and the insecticide esfenvalerate concluded that synergistic effects were found at environmentally realistic concentrations for these compounds and thus that current risk assessment procedures might underestimate the effects of synergistically interacting azoles and pyrethroids. Both prochloraz and esfenvalerate are registered in Europe and thus the relevance of the employed concentrations can be assessed against European surface water measurements and risk assessments procedures. A detailed comparison of the employed concentration of prochloraz in the microcosm study with the concentration deemed acceptable in the European Union and those actually measured in the aquatic environment demonstrate that the employed prochloraz concentration was about two orders of magnitude too high. Therefore, on basis of the data presented by Bjergager et al. (2011) it cannot be concluded that current European single substance risk assessment procedures are insufficiently protective and that synergism actually occurs at environmentally relevant concentrations.