Fig. 1.

Schematic summary of the approach used to evaluate in vivo and in vitro effects studies for use in assessing human health risks related to exposure to nano- and microplastic particles. All criteria have equal weight, whereby studies receiving non-zero scores against all criteria would ideally represent studies that should be prioritized for risk assessment. Due to an absence of any study receiving non-zero scores against all criteria, however, the criteria highlighted in red represent the minimal information required for identifying a study as fit-for-purpose in the context of deriving a human health threshold value by participants of the Southern California Coastal Water Research Project (SCCWRP) Health Effects Workshop (https://www.sccwrp.org/about/research-areas/additional-research-areas/trash-pollution/microplastics-health-effects-webinar-series/. The ‘red’ criteria can be modified depending on the screening and prioritization purpose and should not be misinterpreted as representing criteria that are critical for determining the reliability and relevance of a study. Tables S1 and S2 provide guidance related to scoring each of the criteria