Reproducibility, reliability, and regulatory relevance of plant visual injury assessments
Authors: Fellmann Sebastian , Duffner Andreas , Kirkwood Ashlee , Lopez-Mancisidor Patricia , Arnie Joshua , Krueger Henry , Hoffmann Gunther , Wolf Jeffrey , Kraetzig Gwendolin , Springer Tim , Isemer Rena 
Published: October 2023

The registration of herbicides in the European Union requires an assessment of risks to nontarget terrestrial plants (NTTPs). Regulatory plant studies are performed to determine risk-assessment-relevant endpoints (50% effect rate) for quantitative parameters, mostly biomass and survival. Recently, the European Food Safety Authority stated that endpoints for qualitatively assessed plant visual injuries (PVIs) such as necrosis, chlorosis, and so forth should be considered for the risk assessment as equal to endpoints derived from quantitatively determined parameters. However, the lack of guidance in the NTTP test guidelines on how to assess PVI and how to derive a statistically meaningful endpoint for PVI makes their use in risk assessments challenging. To evaluate and improve the reliability, reproducibility, and regulatory relevance of PVI assessments in NTTP studies, the PVI Working Group was formed in 2022 within the SETAC Plant Interest Group. In a first exercise, research needs, guidance gaps, and shortcomings in current methodologies were identified and are presented together with recommendations for a future, validated, and harmonized method for the assessment of PVI. Survey results revealed a high variability in how PVI are currently assessed, and that the reliability of these data is unclear. Under current conditions, the PVI data can rather be seen as supportive information instead of using the data for the statistically sound determination of a regulatory endpoint. Consequently, standardization and harmonization of procedures for the assessment of PVI are needed. An improved scoring methodology should be developed that allows for a precise, statistically sound endpoint determination. Regarding the regulatory relevance of PVI, further research is required to assess the biological meaning of PVI data and how this is connected to the regulatory requirements and protection goals. Last but not least, guidance is required on how to evaluate the historically available PVI data that are based on various assessment methodologies. Integr Environ Assess Manag 2024;20:915–923. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Key Points

The lack of guidance in the nontarget terrestrial plant (NTTP) OECD test guidelines on assessing plant visual injury (PVI) and deriving statistically meaningful endpoints contradicts the European Union's requirement to use PVI assessments for risk assessment of NTTPs. Under current conditions, the PVI data can rather be seen as supportive data instead of using the data for the precise determination of a regulatory endpoint. Further research is required to assess the biological meaning of PVI data and how this is connected to the regulatory requirements and protection goals. In the future, a more appropriate scoring methodology for evaluating PVI should be established, encompassing (1) a logically consistent scoring scale, (2) reproducible scores, (3) objective scoring, and (4) scores with distinct biological meaning that align with regulatory requirements.