Nanoecotoxicity assessment of graphene oxide and its relationship with humic acid

The risk assessment of nanomaterials is essential for regulatory purposes and for sustainable nanotechnological development. Although the application of graphene oxide has been widely exploited, its environmental risk is not well understood because several environmental conditions can affect its behavior and toxicity. In the present study, the graphene oxide effect from aquatic ecosystems was assessed considering the interaction with humic acid on 9 organisms: Raphidocelis subcapitata (green algae), Lemna minor (aquatic plant), Lactuca sativa (lettuce), Daphnia magna (planktonic microcrustacean), Artemia salina (brine shrimp), Chironomus sancticaroli (Chironomidae), Hydra attenuata (freshwater polyp), and Caenorhabditis elegans and Panagrolaimus sp. (nematodes). The no-observed-effect concentration (NOEC) was calculated for each organism. The different criteria used to calculate NOEC values were transformed and plotted as a log-logistic function. The hypothetical 5 to 50% hazardous concentration values were, respectively, 0.023 (0.005-0.056) and 0.10 (0.031-0.31) mg L^-1 for graphene oxide with and without humic acid, respectively. The safest scenario associated with the predicted no-effect concentration values for graphene oxide in the aquatic compartment were estimated as 20 to 100 μg L^-1 (in the absence of humic acid) and 5 to 23 μg L^-1 (in the presence of humic acid). Finally, the present approach contributed to the risk assessment of graphene oxide-based nanomaterials and the establishment of nano-regulations. Environ Toxicol Chem 2018;37:1998-2012. © 2018 SETAC.