Toxicity, bioaccumulation and metabolism of pesticides in the earthworm

Abstract

The toxic effects of pesticides on earthworms, one of the most important bioindicators in the terrestrial environment, are closely related to their body burden determined by uptake, metabolism and excretion processes. Not only the passive diffusion via the outer skin from a dissolved fraction of pesticide but also the ingestion of contaminated soil and food governs the uptake process, with each contribution controlled by either the hydrophobicity of the pesticide or the soil organic matter. Although the available information is limited, earthworms are likely to metabolize pesticides via hydrolysis and oxidation (Phase I) followed by conjugation (Phase II), and low bioaccumulation is observed as a result for most pesticides. The acute toxicity in the soil exposure can be partly explained by the dissolved fraction of pesticide in pore water, but the contribution of dietary uptake and metabolism should be further studied to correctly evaluate pesticide toxicity.