Destruction of Bacillus anthracis strain Sterne 34F2 spores in postal envelopes by exposure to electron beam irradiation

Aims: To determine the irradiation dose necessary to reduce the populations of Bacillus anthracis spores in a dry medium in postal envelopes. Methods and Results: Bacillus anthracis Sterne 34F2 spores were dispersed in non‐fat dry milk and then placed into standard business postal envelopes. The spores were treated with a sequence of irradiation doses to determine the decimal reduction value (D10) in kiloGrays (kGy). The average D10 value was 3·35 ± 0·02 kGy. Conclusions: An irradiation dose of 40·2 kGy would be required to result in a process equivalent to the thermal canning process (12 D10 reduction) to eliminate Clostridium botulinum spores. Significance and Impact of the Study: Irradiation is an effective means of reducing or eliminating B. anthracis spores in a dry medium in postal envelopes.