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

Abstract

BACKGROUND: 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. RESULTS: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. CONCLUSION: 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.

Target Organ Toxicity in Rats After Subchronic Oral Exposure to Soil Extracts Containing a Complex Mixture of Contaminants

“…However, CBR assessments fail to consider that contaminants almost always occur in mixtures. In a CBR assessment, interactions among chemicals are not considered, which results in uncertainties pertaining to complex mixture assessments (Borgert et al 2001;Heys et al 2016;Chen et al 2020). Further serious complication occurs when unknown compounds from legacy contamination are present in the complex mixture.…”

Chemical Mixtures and Multiple Stressors: Same but Different?

“…The predictions of concentration addition and independent action converge in the case of mixtures with many chemicals at low effect levels, for example up to 10% of the total possible effect, where the effect is typically mortality (Escher et al, 2020). Given the frequent similarity in prediction accuracy and that data is often lacking to fit an independent action model (see below for details), the concentration addition model has been suggested as the standard tool for chemical risk assessment in different regions such as the European Union (Frische et al, 2014), the United States (Belden & Brain, 2018), and China (Chen et al, 2020). Comparative discussions on null model selection are largely lacking in ecosystem management focusing on multiple stressors.…”

A critical review of effect modeling for ecological risk assessment of plant protection products

“…If the MDR values are < 5, then the CA model applies since the additive MoA can be assumed. If the MDR val ues are > 5, there is a potential that synergistic MoA dominâtes (Chen et al, 2020). When the MDR value is > 2.5, high levels of uncertainty exist, and this decreases the applicability of the model to risk assessments (Belden and Lydy, 2006).…”

“…Regarding environmental monitoring and risks, mixture models hâve been used for many years to assess the risks estimated from monitoring data on envi ronmental concentrations (George et al, 2003;Schuler and Rand, 2008;Vaj et al, 2011;Chen et al, 2020). Cruzeiro et al (2016) measured 56 priority PPP belonging to distinct categories (insecticides, herbicides and fungicides) in 42 surface water samples.…”