N-functionalized carbon nanotubes as a source and precursor of N-nitrosodimethylamine: implications for environmental fate, transport, and toxicity.
ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014;
48:9279-9287. [PMID:
25073818 DOI:
10.1021/es501578u]
[Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
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.
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