title: N-functionalized carbon nanotubes as a source and precursor of N-nitrosodimethylamine: implications for environmental fate, transport, and toxicity.
abstract: Hazardous byproducts may be generated during the environmental processing of engineered nanomaterials. Here, we explore the ability of carbon nanotubes with nitrogen-containing surface groups (N-CNTs) to generate N-nitrosodimethylamine (NDMA) during chemical disinfection. Unexpectedly, we observed that commercial N-CNTs with amine, amide, or N-containing polymer (PABS) surface groups are a source of NDMA. As-received powders can leach up to 50 ng of NDMA per mg of N-CNT in aqueous suspension; presumably NDMA originates as a residue from N-CNT manufacturing. Furthermore, reaction of N-CNTs with free chlorine, monochloramine, and ozone generated byproduct NDMA at yields comparable to those reported for natural organic matter. Chlorination also altered N-CNT surface chemistry, with X-ray photoelectron spectroscopy indicating addition of Cl, loss of N, and an increase in surface O. Although these changes can increase N-CNT suspension stability, they do not enhance their acute toxicity in E. coli bioassays above that observed for as-received powders. Notably, however, dechlorination of reacted N-CNTs with sulfite completely suppresses N-CNT toxicity. Collectively, our work demonstrates that N-CNTs are both a source and precursor of NDMA, a probable human carcinogen, while chemical disinfection can produce CNTs exhibiting surface chemistry and environmental behavior distinct from that of native (i.e., as-received) materials.
authors: Department of Civil and Environmental Engineering and ⊥Department of Chemical and Biochemical Engineering, University of Iowa , Iowa City, Iowa 52242, United States.
authors: Edgard M
authors: EM
authors: Verdugo
authors: Caitlin
authors: C
authors: Krause
authors: Kelly
authors: K
authors: Genskow
authors: Ying
authors: Y
authors: Han
authors: Jonas
authors: J
authors: Baltrusaitis
authors: Timothy E
authors: TE
authors: Mattes
authors: Richard L
authors: RL
authors: Valentine
authors: David M
authors: DM
authors: Cwiertny
mesh_terms: D002273:Carcinogens / Q000737:chemistry; D002700:Chloramines / Q000737:chemistry; D004128:Dimethylnitrosamine / Q000032:analysis / Q000633:toxicity; D004203:Disinfection; D004926:Escherichia coli / Q000187:drug effects; D006801:Humans; D037742:Nanotubes, Carbon / Q000737:chemistry*; D010126:Ozone / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity; D018508:Water Purification / Q000379:methods*; D014881:Water Supply / Q000592:standards
chemical_list: D002273:Carcinogens; D002700:Chloramines; D037742:Nanotubes, Carbon; D014874:Water Pollutants, Chemical; D010126:Ozone; C030816:chloramine; D004128:Dimethylnitrosamine