Abstract: This review illustrated the radiation effects on the environment in Japan, the improvements and applications of source identification by using radioisotope tracer, the resulted challenge on the environment and radiation dose estimation due to the released radioactive microparticles, and the regulations and current situation of food safety in Japan, after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. The FDNPP accident allowed the staffs in the nuclear industry, managers for the nuclear emergency, and the public to recognize the importance of nuclear security and nuclear emergency response again.