Original: https://doi.org/10.1016/j.enceco.2025.12.012
To identify nanomaterials that may pose environmental risks, bioaccumulation testing is required for regulatory assessment. However, applying the OECD fish bioaccumulation Test Guideline (TG) 305 to nanomaterials still requires additional clarification, especially regarding the best exposure method and whether small changes to nanomaterials—such as different surface coatings—affect their potential to accumulate in organisms.
In this study, OECD TG 305 was used to evaluate the bioaccumulation potential of cadmium telluride (CdTe) quantum dots (QDs), with extra considerations specific to nanomaterial testing. CdTe QDs were chosen because their use is increasing, they may enter aquatic environments, and little is known about how they accumulate in fish.
To examine how exposure route and coating affect bioaccumulation, the uptake and depuration behavior of two types of CdTe QDs—one coated with carboxylate groups and the other with polyethylene glycol (PEG)—was measured in rainbow trout (Oncorhynchus mykiss) using both aqueous and dietary exposures.
In the dietary exposure tests, fish were fed food containing 10 or 100 mg/kg of CdTe QDs for 28 days, followed by a 28-day depuration phase. These data were used to calculate biomagnification factors (BMFs).
In the aqueous exposure tests, fish were exposed to 4 or 40 μg/L of CdTe QDs in water for 28 days, followed by a 14-day depuration phase to calculate bioconcentration factors (BCFs).
Both CdTe QD types showed low bioaccumulation potential. Although PEG-coated QDs showed slightly higher uptake, overall biodistribution, uptake rates, and depuration patterns were similar between the two coatings.
Dietary exposure allowed reliable estimation of BMFs using both sequential and simultaneous calculation methods. In contrast, the aqueous exposures were complicated by dissolution of CdTe QDs in the aquarium water, and steady-state conditions were not reached within 28 days, making it difficult to calculate accurate BCF values.
Overall, this study provides important insights into how differently coated CdTe QDs behave in fish, assesses how well OECD TG 305 applies to metallic nanomaterials, and highlights considerations needed to generate regulatory-acceptable indicators of nanomaterial bioaccumulation potential.