Cobalt-60 emits gamma rays that sterilize male insects and reduce insect population.
Gamma irradiation of processed food also destroys microorganisms. Cobalt-60 irradiation destroys parasites in pork (trichinosis) and chicken (salmonella). Gamma irradiation also increases shelf life without using preservatives.
According to IAEA.org, insects that are released in an SIT (sterile insect technique) program are not radioactive. The type of radiation used to sterilize insects is very similar to that used for medical x-ray procedures, to sterilize medical products and to irradiate foodstuffs.
The conclusion of all the studies on irradiated foods indicates that there are no levels of residual radiation nor of the production of biologically active compounds.
The radiation sources used to irradiate food and agricultural products (including insects) are restricted to: gamma rays from the radionuclides 60Co and 137Cs, and accelerator-generated radiation either as 10 million electron volt (MeV) electrons or 5 MeV X-rays (FAO 2003).
Insect sterilization also requires a much lower radiation dose, 100-300 Gy, (IDIDAS 2004; Bakri et al. 2005) than for food irradiation, 100 Gy to 60 kGy, (IAEA 2002a, b). Thus, the induction of radioactivity in insects irradiated for programmes that release sterile insects can also be "best characterized as zero".
Given the low levels of irradiation for insects, the small biomass of the released insects and their wide dispersal, there are no plausible grounds for concern about residual radioactivity, or radiation-induced toxins, in released insects.