This guidance reflects the current understanding of the unique environment that would be expected during the first week of a wide-area anthrax release, and is expected to evolve with changes to our understanding regarding exposure risk, scientific developments, and availability of new environmental monitoring techniques. This guidance is intended to support ongoing planning and preparation efforts, as well as to lay the basis for plans to protect all individuals who may respond. This planning guidance will be refined as the evidence base for determining exposure risk and the efficacy of protective measures is strengthened.