Accumulation and sublethal effects of triclosan and its transformation product methyl‐triclosan in the earthworm Eisenia andrei exposed to environmental concentrations in an artificial soil

Abstract

Municipal biosolids are increasingly used as a low-cost fertilizer in agricultural soil. Biosolids are contaminated by low concentrations (nanograms per gram dry wt range) of a large variety of organic contaminants, such as triclosan. The effect of exposure to low concentrations of organic contaminants on soil biota remains largely undocumented. We evaluated the sublethal effects of triclosan on the earthworm Eisenia andrei using an artificial soil amended with a nominal concentration of triclosan of 50 ng g dry weight soil. Using a 56-d reproduction test, we monitored the effect of triclosan exposure on adult earthworm survival, growth, and reproduction. The bioaccumulation of triclosan in earthworm tissue (adults and juveniles) and degradation of triclosan were monitored. The genotoxicity of triclosan was evaluated using a comet assay (DNA damage) on adult earthworm coelomocytes. Exposure to a low concentration of triclosan had no significant effects on adult earthworm survival and DNA damage but significantly stimulated growth (p < 0.05) by 2-fold compared with controls. It also significantly affected E. andrei reproduction parameters (p < 0.05), as evidenced by an increase in the number of cocoons and juveniles and a decrease in the mean dry weight of juveniles. The bioaccumulation of triclosan in earthworms was moderate (bioaccumulation factor ∼2). In biosolid-borne trials, the bioaccumulation of methyl-triclosan in earthworm tissues was higher than that of the parent compound triclosan. We conclude that exposure to low concentrations of triclosan in artificial soil can significantly affect the growth and reproductive performance of earthworms (i.e., E. andrei). More research is required with natural soils to assess triclosan bioavailability for earthworms. Environ Toxicol Chem 2018;37:1940-1948. © 2018 SETAC.

Triclosan: An Update on Biochemical and Molecular Mechanisms

“…On the other hand, TCS induced dose-responsive DNA damage in hemocytes of the zebra mussel D. polymorpha [88], and strand breaks in the digestive gland of U. tumidus mussels [114]. A similar dose-dependent DNA damage was also observed in the earthworm E. fetida [108, 109], but not in E. andrei [161].…”

Bioaccumulation and Toxicity of Organic Chemicals in Terrestrial Invertebrates

“…Personal care products can induce genotoxicity in terrestrial invertebrates. Some authors indicate that triclosan can induce DNA damage to earthworm coelomocytes (e.g., E. fetida; EC 50 8.9 mg kg À1 d.w.) [200], while others describe no effects [196]. Triclosan can also alter the transcriptional expression levels of some genes as described by Lin et al [200] for the heat shock protein Hsp70 gene in E. fetida (upregulation after triclosan exposure; EC 50 1.8 mg kg À1 d.w.).…”

“…Most of the recent studies focused on the antimicrobial agent triclosan and its main soil metabolite (methyl-triclosan), with special attention to earthworm bioaccumulation. For instance, Chevillot et al [196] assessed the bioaccumulation of these compounds in E. andrei exposed to both a triclosan-spiked soil (BAF 2.6 and 0.5 for triclosan in juveniles and adults, respectively; no detection of methyl-triclosan) and a soil amended with biosolids from a wastewater treatment plant containing triclosan (BAF 2.0-2.5 for triclosan and methyl-triclosan). Macherius et al [197] also evaluated the bioaccumulation of triclosan and methyl-triclosan in different earthworm species of a soil amended with biosolids.…”

“…This is, for example, the case of F. fimetaria and A. fulica exposed to triclosan [202,203]. However, there are also studies indicating no effects of triclosan on earthworm survival [196,198]. Besides the variable effects reported on survival, triclosan generally alters reproduction.…”

The comet assay in animal models: From bugs to whales – (Part 1 Invertebrates)

“…Besides coelomocytes as a somatic type of cells, there are also studies done on spermatogenic cells [212,213]. These species were used for the evaluation of several genotoxic agents present in soil and sediment [214,215] as well as for the genotoxicity of heavy metals [216], pesticides [217,218], radionuclides [219], peloids (natural muds) [220], flame retardants [221], naphthenic acid [222], nanomaterials [197,223,224], phthalates [225], PAHs [226] and organic compounds [227]. The DNAdamaging effects of both ionising [212,228] and non-ionising radiation [229] were also studied, indicating that both types of radiation are able to induce DNA damage and that the comet assay is a sensitive and rapid method for the detection of radiation-induced genotoxicity.…”