Influence of carbon nanotubes on the bioavailability of fluoranthene

Concurrent with the increase in the use of carbon nanotubes (CNTs) in society is the rise of their introduction into the environment. Carbon nanotubes cause adverse effects themselves, and they have the potential to adsorb contaminants such as polycyclic aromatic hydrocarbons (PAHs). Although CNTs have a high adsorption capacity for PAHs and these contaminants can co-occur in the environment, few studies have characterized the bioavailability of CNT-adsorbed PAHs to fish. The goal of the present study was to characterize the bioavailability of fluoranthene adsorbed to suspended multiwalled-carbon nanotubes (MWNTs) in freshwater containing natural organic matter (NOM). Adsorption isotherms indicated that NOM influenced the adsorption of fluoranthene to MWNTs, although in the absence of MWNTs it did not influence the bioavailability of fluoranthene to Pimephales promelas. Pimephales promelas were exposed for 16 h in synthetic moderately hard water containing fluoranthene in the presence of different concentrations of NOM, and fluoranthene adsorbed to MWNTs in the presence of NOM. Bioavailable fluoranthene was quantified in each exposure through bile analysis using fluorescence spectrophotometry. By comparing the concentration of fluoranthene metabolites in the bile with the concentration of fluoranthene added to MWNT and NOM solutions, the relative bioavailability of fluoranthene adsorbed to MWNTs was quantified. Results indicate that approximately 60% to 90% of the fluoranthene was adsorbed to the MWNTs and that adsorbed fluoranthene was not bioavailable to P. promelas. The results also suggest that fluoranthene is not desorbed from ingested MWNT, and the bioavailable fraction is only the freely dissolved fluoranthene in the aqueous phase.