Figure 5.

Schematic presentation of the tiered approach within the acute (left part) and chronic (right part) effect assessment for PPPs. For each PPP, both the acute and chronic effects/risks have to be assessed. The Tier‐1 and Tier‐2 effect assessments are based on single species laboratory toxicity tests, but to better address risks of time‐variable exposures the Tier‐2 assessment may be complemented with toxicokinetic/toxicodynamic (TKTD) models. Tier‐3 (population and community level experiments and models) and Tier‐4 (field studies and landscape level models) may concern a combination of experimental data and modelling to assess population and/or community level responses (e.g. recovery; indirect effects) at relevant spatiotemporal scales. All models included in such a tiered approach need to be properly tested and fulfil required quality criteria. RAC: Regulatory Acceptable Concentration; sw: surface water; ac: acute; ch: chronic; PEC: Predicted Environmental Concentration; twa: time‐weighted average