Ecotoxicity and genotoxicity of a binary combination of triclosan and carbendazim to Daphnia magna

Abstract

In the environment, chemical substances appear as complex mixtures and consequently organisms are exposed to a variety of chemicals from different sources (e.g. wastewater treatment plants, agriculture runoffs). When studying chemical mixtures, there are two conceptual models usually used to predict toxicity: the Independent Action (IA) and Concentration Addition (CA) models. However, deviations from these reference models can occur as synergism or antagonism, dose ratio or dose level dependency. The aim of the present study was to investigate the effects of triclosan and carbendazim, and their binary mixture to Daphnia magna. With this purpose, immobilisation, feeding inhibition, and reproduction were assessed as main ecotoxicity endpoints. In addition, in vivo genotoxicity of both chemicals was investigated using the comet assay. In the single exposure, carbendazim was more toxic to D. magna than triclosan. When daphnids were exposed to both single compounds, DNA damage was observed. Concerning mixture exposures, different endpoints followed different patterns of response, from additivity: IA model (feeding inhibition and reproduction data), to deviations that indicate interaction between chemicals inside the organism: dose level dependency (immobilisation data) and dose ratio dependency (DNA damage). This study showed that additivity does not rule the dose-effect relation in chemical mixtures of carbendazim and triclosan and interactions between both chemicals might induce generally higher toxicity than predicted based on single chemical exposures.

Multigenerational effects of carbendazim in Daphnia magna

“…The experiment lasted for approximately 34 wk, corresponding to 12 generations. This carbendazim concentration (5 μg/L) corresponds to the no‐observed‐effect concentration (NOEC) value determined for D. magna reproduction by Silva et al .…”

“…Carbendazim concentration in the ASTM medium decreased over time, with a decay rate (K 0 ) of 0.03/h (standard error 0.005), showing that only 18% of the initial concentration remained after 48 h (as also described in Silva et al [11]). Although this is a significant decay of the compound, the medium was changed 3 times a week (in the Dph_clean and Dph_CBZ populations) and every other day (in the reproduction tests), and therefore nominal concentrations were used for the LC/EC50 calculations, as advised by OECD guideline 211, Annex 6 [18].…”

“…Silva et al corresponding to 12 generations. This carbendazim concentration (5 mg/L) corresponds to the no-observed-effect concentration (NOEC) value determined for D. magna reproduction by Silva et al [11]. Both clean (Dph_clean) and contaminated (Dph_CBZ) isoclonal populations of D. magna were reared in similar conditions in 1-L glass vessels containing 25 daphnids, with medium renewal 3 times a week and daphnids fed with R. subcapitata at a concentration of 3 Â 10 5 cells/mL, supplemented with an organic extract (Marinure seaweed extract).…”

Passive dosing of triclosan in multigeneration tests with copepods – stable exposure concentrations and effects at the low μg/L range

“…We are not aware of any published data on triclosan toxicity for N. spinipes or any other harpacticoids. However, published median effective concentration values for the crustacean Daphnia are in the range of 200 mg/L to 400 mg/L; these were obtained in 24 h acute toxicity to 8 d subchronic toxicity tests [40][41][42]. The copepod populations in the present study were close to extinction in 2 out of 3 experimental replicates exposed to 21 mg/L at the end of the experimental period, whereas development inhibition was observed at as low as 4 mg/L after a period that was sufficient for completing juvenile development [23,24].…”

A comparison between the oxidation with laccase and horseradish peroxidase for triclosan conversion

“…[3,7,8] However, in many countries legislation, there is not a maximum allowable concentration for triclosan in STPs effluents. [9] The main concern about the presence of this microbicide in the environment is that it can contribute to the development of bacterial resistance. Resistance to triclosan can confer concomitant resistance to other antimicrobials because the action mechanism of triclosan is similar to that of clinically relevant antibiotics.…”