Risk assessment for pesticide mixtures on aquatic ecosystems in China: a proposed framework

With over 12 000 registered mixture formulations in China, environmental risk assessment of co-formulated pesticide mixtures to aquatic ecosystems is of increasing interest to scientists, risk assessors, and risk managers. This study proposed a pragmatic approach based on widely accepted scientific concepts and strategies.

The proposed approach has three tiers, a preliminary Tier 0 stage, a Tier 1 stage, and a refinement stage as Tier 2, which are demonstrated with one case study. Because of the large number of co-formulated pesticide mixtures available in China, a unique Tier 0 stage is proposed with practicable criteria to identify mixtures requiring further evaluation. For Tier-1 assessment, exposure is assessed based on the application scheme and local scenarios in China. Hazard is evaluated using the concentration addition model as the default approach, which was developed a century ago and was adopted by the majority of the regulators globally. Given the unique characteristics of mixtures in the environment, data variability and ratio changes of active ingredients are also evaluated for hazard assessment. More accurate assessments with decreased uncertainties can be achieved by higher tier refinements in Tier-2, such as alternative models, consideration of co-formulants, and higher tier effect and exposure analyses.

Widely accepted concepts, methodologies, and criteria should be used for aquatic risk assessment for pesticide mixtures in China. To avoid unnecessary workload and a more accurate assessment, unique perspectives such as local agricultural practice, local scenarios and a preliminary screening stage (Tier 0) should be implemented. © 2019 Society of Chemical Industry.