Bacillus spores in the mail: "ironing" out the anthrax problem.

INTRODUCTION: Following a terrorist release of Bacillus anthracis spores through the U.S. Postal Service, it was suggested that decontamination of spores in mail envelopes could be accomplished at home by utilizing the steam heat from a household iron. This study investigated the use of a standard household iron, in a dry heat mode, for sterilizing mail envelopes laced with bacterial spores.
METHODS: The Bacillus subtilis var. niger spore, a more heat resistant spore, was used as a surrogate for B. Anthracis spores. Standard mail envelopes containing 2.1 x 10(6) spores were sealed and subjected to various levels of dry heat from a standard household iron for periods of 5, 10, and 15 minutes. Envelope contents were then cultured in soy broth for seven days to detect any bacterial growth, and in addition envelopes and contents were visually inspected for evidence of damage and readability of words.
RESULTS: At a temperature range of 160.01 degrees C - 204.5 degrees C for a period of 5 minutes, B. subtilis var. niger spores were effectively sterilized and, at 7 days, no bacterial growth was observed. No gross evidence of envelope damage was observed and the legibility of words was not compromised.
CONCLUSIONS: Dry heat from a common household iron is capable of destroying Bacillus spores in mailing envelopes without grossly altering the envelope or affecting the legibility of words.