Gamma radiation is often used to kill living organisms, in a process called irradiation. It is unstable when exposed to ultraviolet light and gamma irradiation. Production of ozone is one of the potential dangers of ultraviolet germicidal irradiation. Such a lamp can then be used for ultraviolet germicidal irradiation. Cancer treatment by chemotherapy and irradiation kills target cells primarily by inducing apoptosis. This method is used for the ultraviolet (UV) blood irradiation (UVBI) by UV lamps. Vitamin D is produced by ultraviolet irradiation of ergosterol found in many fungi. Effects related to electron irradiation degradation are therefore more pronounced. This is performed using high-intensity chemotherapy and total body irradiation. In case of long wavelength irradiation, photons penetrate deep into the cell. APAF-1 cells are protected from apoptosis stimuli such as irradiation. Sterilization can be achieved through various means, including heat, chemicals, irradiation, high pressure, and filtration. Uranium-233 is produced by the neutron irradiation of thorium-232. Other methods of sterilizing foods include food irradiation and high pressure (pascalization). Packaging materials containing the food processed by irradiation must also undergo approval.