Fullerene nanomaterials are finding an increasing number of applications in energy and environmental technologies. However, substantial production and use of fullerenes will likely lead to environmental exposure with unknown consequences. In this study, aqueous suspensions of three types of fullerenes nanoparticles, C(60) fullerene, single-wall (SW) and multi-wall (MW) carbon nanotubes (CNT) were prepared by sonication and tested for reactive oxygen species (ROS) production and oxidation of benchmark organic compounds under ultraviolet (UV)-A irradiation. All three fullerenes formed colloidal aggregates in water. SWCNTs showed the highest ROS production and 2-chlorophenol degradation followed by MWCNT, and fullerene.