Assessing the Effects of Pesticides on the Soil Microbial Community: Advances, Standardization of Methods and the Need for a New Regulatory Framework

Abstract

Upon their application pesticides end up in soil where they interact with the soil microbial community. Considering the pivotal role of soil microorganisms in ecosystem homeostasis and the growing evidence about their potential toxicity response to pesticide exposure, there is an urgent need to revisit the relevant regulatory framework. This is necessary in light of the enormous methodological and standardization advances in soil microbial ecology in the last 20 years and the outdated assessment scheme currently in place. In this chapter we highlight the key elements of a new risk assessment scheme including (a) the definition of microbial indicator groups like ammonia-oxidizing microorganisms and arbuscular mycorrhizal fungi (b) the parallel determination of the level and the duration of the exposure including transformation products (c) the need for implementation in environmental risk analysis of advanced and standardized tools. Based on all these a new tiered-risk assessment scheme is proposed. Emerging issues in soil microbial ecotoxicology are discussed including (a) the assessment of pesticide soil microbial toxicity at ecosystem level and (b) the assessment of the soil microbial toxicity of biopesticides, pesticide mixtures and pesticide transformation products on soil microorganisms. We conclude by highlighting emerging scientific questions that are expected to puzzle the soil microbial ecotoxicologists working with pesticides in the next decade.