Abstract: A method of reducing side effects of damage in a human subject exposed to radiation includes administering to the human subject carbon nanotubes in a pharmaceutically acceptable carrier after or prior to exposure to radiation. A composition for reducing radical damage includes a carbon nanotube which is functionalized (1) for substantial water solubility and (2) with a radical trapping agent appended to the carbon nanotube forming a radical scavenger-carbon nanotube conjugate.