title: The minimum detectable difference (MDD) and the interpretation of treatment-related effects of pesticides in experimental ecosystems.
abstract: In the European registration procedure for pesticides, microcosm and mesocosm studies are the highest aquatic experimental tier to assess their environmental effects. Evaluations of microcosm/mesocosm studies rely heavily on no observed effect concentrations (NOECs) calculated for different population-level endpoints. Ideally, a power analysis should be reported for the concentration-response relationships underlying these NOECs, as well as for measurement endpoints for which significant effects cannot be demonstrated. An indication of this statistical power can be provided a posteriori by calculated minimum detectable differences (MDDs). The MDD defines the difference between the means of a treatment and the control that must exist to detect a statistically significant effect. The aim of this paper is to expand on the Aquatic Guidance Document recently published by the European Food Safety Authority (EFSA) and to propose a procedure to report and evaluate NOECs and related MDDs in a harmonised way. In addition, decision schemes are provided on how MDDs can be used to assess the reliability of microcosm/mesocosm studies and for the derivation of effect classes used to derive regulatory acceptable concentrations. Furthermore, examples are presented to show how MDDs can be reduced by optimising experimental design and sampling techniques.
authors.affiliation: Alterra, Team Environmental Risk Assessment, Wageningen University and Research Centre, P.O. Box 47, 6700 AA, Wageningen, The Netherlands, theo.brock@wur.nl.
authors.forename: T C M
authors.initials: TC
authors.lastname: Brock
authors.forename: M
authors.initials: M
authors.lastname: Hammers-Wirtz
authors.forename: U
authors.initials: U
authors.lastname: Hommen
authors.forename: T G
authors.initials: TG
authors.lastname: Preuss
authors.forename: H-T
authors.initials: HT
authors.lastname: Ratte
authors.forename: I
authors.initials: I
authors.lastname: Roessink
authors.forename: T
authors.initials: T
authors.lastname: Strauss
authors.forename: P J
authors.initials: PJ
authors.lastname: Van den Brink
mesh_terms: D017753:Ecosystem; D004784:Environmental Monitoring / Q000379:methods / Q000592:standards*; D010575:Pesticides / Q000032:analysis*; D015203:Reproducibility of Results; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D010575:Pesticides; D014874:Water Pollutants, Chemical