Individual and combined toxicity of silver nanoparticles and triclosan or galaxolide in the freshwater algae Euglena sp.

With the widespread production and usage, silver nanoparticles (AgNPs) can be extensively found in the aquatic environment and co-exist with other pollutants for a prolonged time, leading to a more complex ecological risk in natural waters. In this work, the model freshwater algae Euglena sp. was selected to study the toxicity of AgNPs and explore their influences on the toxicity of two frequently detected personal care products, triclosan (TCS) and galaxolide (HHCB). The LC-MS targeted metabolomics was used to analyze the possible toxicity mechanism at the molecular level. Results showed that AgNPs was toxic to Euglena sp. upon 24 h exposure, but the toxicity decreased gradually as exposure times increased. AgNPs (<100 μg L-1) attenuated TCS and HHCB toxicity to Euglena sp., which could be attributed primarily to the decreased oxidative stress. Metabolomic analysis revealed that AgNPs induced a stress on algal defense system upon TCS exposure, but promoted the algal defense system upon HHCB exposure. Furthermore, DNA or RNA biosynthesis was accelerated in algae exposed to TCS or HHCB after the addition of AgNPs, implying that AgNPs may mitigate the genetic toxicity of TCS or HHCB in Euglena sp. These results emphasize the potential of metabolomics to reveal toxicity mechanism and provide new perspectives on the aquatic risk assessment of personal care products in the presence of AgNPs.