To provide a method for inhibiting a radical generation at the time when a zinc oxide powder absorbs light.

Zinc oxide coated with the oxide of a metal other than zinc has such characteristics that the probability of survival of HeLa cells in a culturing medium containing 1% surface coated zinc oxide is ≥90% of that in a culture medium containing no coated iron oxide when the HeLa cells are cultured in the culturing medium containing the zinc oxide and containing no zinc oxide after irradiation with ultraviolet rays. The generation of the radical by the coated fine powder zinc oxide is inhibited.