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 (Dsilicone-water ) was 10466 ± 1927. A population development test was conducted at 3 concentration levels of triclosan that were measured to be 3 μg/L to 5 μg/L, 7 μg/L to 11 μg/L and 16 μg/L to 26 μg/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. Environ Toxicol Chem 2017;36:1254-1260. © 2016 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.
Highlights
Reliable ecotoxicological data are crucial for sound risk assessments of chemicals
AConcentrations are displayed for the first 10 mL of water equilibrated with silicone, and after termination of the exposure. conc 1⁄4 concentration; standard deviations (SDs) 1⁄4 standard deviation; RSD 1⁄4 relative standard deviation
Loading efficiency of triclosan on the silicone phase casted in the test vials was 82 Æ 6%
Summary
Reliable ecotoxicological data are crucial for sound risk assessments of chemicals. In environmental risk assessment, criteria for protection goals are generally focused on populations, communities, and ecosystems [1,2]. Adverse effects, which are detectable by long-term exposure to chemicals at low concentrations, are thereby rarely assessed. In ecotoxicity testing of organic chemicals, the test substance is added to the test medium in a solvent solution. This procedure works well for polar, nonvolatile, chemicals and chemicals that do not significantly degrade or transform during the test period. Many contaminants of environmental concern are hydrophobic or semihydrophobic These chemicals partition to organic matter in the test medium or to the walls of the test vial and, depending on their properties, may volatilize, leading to significant decrease in exposure concentrations.
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