Sterilisation by ionising radiation (ISO 11137)
Ionising radiation works by energy transfer (the absorption of energy by the target material). Ionisation occurs at room temperature. Treatment depth varies with the type of radiation. Ionising radiation causes breaks in the chromosomal DNA of micro organisms (at the cellular level), which results in their death.
Sensitivity to radiation varies considerably from one micro organism to another. This basically depends on the type of germ (the species or strain). Radiosensitivity is numerically evaluated using the D10 value. This corresponds to the radiation dose required to reduce the initial bacterial population to 1/10th.
Most bacterial species have D10 values below 10 kGy.
The more resistant bacteria (spore-forming bacteria) can have D10 values as high as
30 kGy.