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

Abstract

Ecotoxicity testing is a crucial component of chemical risk assessment. Still, due to methodological difficulties related to controlling exposure concentrations over time, data on long-term effects of organic chemicals at low concentrations are limited. The aim of the present study was, therefore, to test the applicability of passive dosing to maintain stable concentrations of the organochlorine bacteriocide triclosan in the water phase during a 6-wk multigeneration population development test with the harpacticoid copepod Nitocra spinipes. Triclosan was loaded into silicone (1000 mg), which was used as passive dosing phase in the exposure vials. The distribution ratio for triclosan between silicone and water (D silicone-water ) was 10466 AE 1927. A population development test was conducted at 3 concentration levels of triclosan that were measured to be 3 mg/L to 5 mg/L, 7 mg/L to 11 mg/L and 16 mg/L to 26 mg/L. The results demonstrate that passive dosing is applicable for long-term ecotoxicity testing of organic chemicals, including during significant growth of the test organism population. Shifts in the demographic structure of the population during exposure suggest the most severe effects were exerted on juvenile development. Progressively lower development index values in the populations exposed to increasing triclosan concentrations suggest developmental retardation. The results further stress the need for chronic exposure during ecotoxicity testing in chemical risk assessment because even the most sensitive endpoint was not significant until after 7 d of exposure.

Transferring mixtures of chemicals from sediment to a bioassay using silicone-based passive sampling and dosing

“…This observation could be explained by a fairly low sorptive capacity of the PDMS for some of these chemicals due to their relatively polar properties, which also cause them to partition more readily into the water phase compared to g-HCH, PCBs and PAHs. To compensate for the losses of phenolic chemicals, a larger ratio of the mass of PDMS versus water volume might be needed, as was also observed by Ribbenstedt et al 25 These results support the applicability domain of the silicone-based system for semi-hydrophobic to hydrophobic chemicals and the possibility to retain a mixture composition within $50% for such chemicals.…”

“…The rst batch of water equilibrated with the dosing silicone polymer was discarded as elevated concentrations (above equilibrium partitioning) have been observed in the rst batch of water in a previous study, where chemicals were loaded from a methanol-water solution. 25 This was done as a safety precaution and might not have been necessary as a different loading method was used in this study than in Ribbenstedt et al 25 Analytes in the second batch of equilibrated water were extracted with 5 mL n-hexane aer addition of a mixture of labeled internal surrogate standards containing Danthracene, D-pyrene, D-benzo(a)pyrene, 13 C-PCB 28 and 13 C-PCB 52. The dosing polymer was extracted twice with 5 mL nhexane for 24 h, and the extracts were combined.…”

“…Passive dosing can overcome these challenges, while also avoiding the usage of solvent spiking during the test. [23][24][25] Passive dosing works on the reversed principle of passive sampling. The test chemicals are loaded into a dosing polymer, which acts as a quasi-inexhaustible source, and via equilibrium partitioning between the polymer and the exposure media a stable exposure concentration can be maintained throughout the test, even for hydrophobic chemicals.…”

Sediment biotesting in the Baltic Sea

“…Using widespread zooplankton species, biotests applying the epibenthic harpacticoid copepod Nitocra spinipes have been developed (Perez-Landa and Simpson, 2011), also in the Baltic Sea (Ribbenstedt et al, 2017). This organism has been extensively used to study the effects of a wide range of environmental contaminants using physiological, developmental and reproductive endpoints as well as responses in population growth and genetics (Ribbenstedt et al, 2017).…”

“…This organism has been extensively used to study the effects of a wide range of environmental contaminants using physiological, developmental and reproductive endpoints as well as responses in population growth and genetics (Ribbenstedt et al, 2017). Among snails, the freshwater gastropod Potamopyrgus antipodarum, which is a nonindigenous species in the Baltic Sea, has been shown to be a useful biotest species especially with regard to endocrine disruption (Duft et al, 2003) In addition to the use of whole organisms, molecular techniques for ecotoxicological biotesting have been developed.…”