Addressing residual risk issues at anthrax cleanups: how clean is safe?

Area of Science:

• Environmental Science
• Risk Assessment
• Microbiology

Background:

• The 2001 anthrax attacks highlighted the need to assess inhalational anthrax risks.
• Effective cleanup goals require credible risk estimates for Bacillus anthracis spore contamination.

Purpose of the Study:

• To review existing data on Bacillus anthracis spore mortality in animals and humans.
• To analyze the impact of the 2001 inhalational anthrax cases on hazard identification.
• To evaluate the challenges in assessing exposure levels and performing robust risk assessments.

Main Methods:

• Review of mortality data from laboratory animals and human cases of inhalational anthrax.
• Analysis of factors influencing risk in exposed populations and uncertainties in dose-response.
• Examination of the current state of science for assessing Bacillus anthracis spore exposure levels.

Main Results:

• Existing data on Bacillus anthracis spore mortality and the 11 cases from 2001 were reviewed.
• Factors contributing to increased risk and uncertainties in dose-response analysis were identified.
• Significant challenges remain in robustly assessing exposure levels to Bacillus anthracis spores.

Conclusions:

• Robust risk assessment for Bacillus anthracis spore exposure is currently challenging due to data and methodological limitations.
• The findings support the U.S. Environmental Protection Agency's policy of zero Bacillus anthracis spore growth for effective site cleanup and reoccupancy.
• Establishing definitive cleanup criteria requires overcoming significant scientific uncertainties in risk assessment.