A group of South Korean scientists has identified the negative effects of magnetic nanoparticles on human cells, a finding that urges the development of new nanoparticles that are safe to humans, the science ministry said Wednesday. According to the study, led by Chae Kwon-seok and Jang Yong-min, both professors at Kyungpook National University, nanoparticles magnetize themselves under strong magnetic fields, which make the particles cytotoxic to human cells.