Improvement in mixture risk assessment: A multi-national application of the Pesticide Risk Metric

Neelamraju, Cath A., Mann, Reinier M., Bainbridge, Zoe T., Mitchell, Hannah C., and Turner, Ryan D.R. (2025) Improvement in mixture risk assessment: A multi-national application of the Pesticide Risk Metric. Environmental Advances, 22. 100676.

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Abstract

Significant advancements have been made in the development of methods to assess mixture risk, with the hazard unit and concentration addition methods being commonly used for tier one screening risk assessments. However, a reduction in risk estimate uncertainty is required for higher tier assessments and targeted management action, particularly in the context of policy frameworks such as the European Green Deal, which aims to reduce the use and risk of pesticides that may pollute air, water and soil. This study proposes the Pesticide Risk Metric (PRM), an approach grounded in existing ecotoxicological methods for this purpose. By combining the species sensitivity distribution approach with the independent action model of joint toxicity, the PRM reduces uncertainty and provides more reliable risk estimates for individual toxicants and mixtures. The PRM method was applied to aqueous pesticide monitoring data from eight countries to demonstrate the utility of the method. Of the 706 sites, 61 (8.6 %) did not meet the annual average environmental quality standard (AA-EQS) for individual pesticide active ingredients, with Italy showing the highest number of exceedances. When assessed as a mixture, 359 sites (51 %) failed to meet the AA-EQS, with Italy and the Netherlands showing the highest annual average mixture toxicity. The primary contributors to mixture toxicity were insecticides (61 %), followed by other herbicides (32 %) and photosystem II inhibiting herbicides (6.1 %), with significant variation at the country and site levels. Fourteen pesticides contributed 99 % of the annual average mixture toxicity at the country level. The adaptability and reliable risk estimates of the PRM make it a valuable tool for second-tier risk assessment, further enhancing targeted policy and management decisions.

Item ID: 89888
Item Type: Article (Research - C1)
ISSN: 2666-7657
Keywords: Aquatic ecosystem, independent action, Mixture toxicity, Pesticide, Risk assessment, Water framework directive
Copyright Information: © 2025 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
Date Deposited: 02 Apr 2026 02:12
FoR Codes: 41 ENVIRONMENTAL SCIENCES > 4105 Pollution and contamination > 410599 Pollution and contamination not elsewhere classified @ 50%
41 ENVIRONMENTAL SCIENCES > 4104 Environmental management > 410402 Environmental assessment and monitoring @ 50%
SEO Codes: 18 ENVIRONMENTAL MANAGEMENT > 1803 Fresh, ground and surface water systems and management > 180301 Assessment and management of freshwater ecosystems @ 100%
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