Highlights

• Hazard assessments of micro- and nanoplastics (MNPs) need more relevance and reliability.

• Experiments should include environmentally relevant MNP types and concentrations.

• Complex MNP-biota interactions are best addressed with array of test species, endpoints and durations.

• Analysis of MNPs and chemical additives in tests improves the reliability of the data.

• Soil and MNP physicochemical properties should be routinely analyzed in the tests.

Abstract

Micro- and nanoplastics (MNPs) are widespread emerging contaminants with many potential direct and indirect effects on soil ecosystems. Ecological soil MNP hazard assessment is thus crucial for a proper risk assessment and the development of environmental protection regulations. However, current hazard assessment testing approaches are hampered by the absence of guidelines, harmonization, and standard reference materials. This article discusses the need for improving testing approaches and provides specific recommendations to increase the relevance and reliability of ecotoxicity data. Our recommendations focus on environmentally relevant experimental designs, guidelines for MNP test materials selection and characterization, analysis of MNPs and additives in soil and biota, and a proposal for relevant soil physicochemical properties to be assessed during ecotoxicity testing. This article brings novelty to the field of ecological hazard assessment of MNPs in soil by providing specific recommendations much needed in this field.