Secondary Aerosolization of Viable Bacillus anthracis Spores in a Contaminated US Senate Office
- Christopher P. Weis, PhD;
- Anthony J. Intrepido, MS, CIH;
- Aubrey K. Miller, MD, MPH;
- Patricia G. Cowin, MS, CIH;
- Mark A. Durno, BS;
- Joan S. Gebhardt, PhD;
- Robert Bull, PhD
- Author Affiliations: US Environmental Protection Agency National Enforcement Investigations Center, Denver Federal Center, Denver, Colo (Dr Weis); US Army Center for Health Promotion and Preventive Medicine, Aberdeen Proving Ground, Md (Mr Intrepido and Ms Cowin); US Public Health Service, Denver, Colo (Dr Miller); US Environmental Protection Agency Region 5, Cleveland Office, Westlake, Ohio (Mr Durno); and Naval Medical Research Center, Biological Defense Directorate, Silver Spring, Md (Drs Gebhardt and Bull).
Abstract
Context Bioterrorist attacks involving letters and mail-handling systems in Washington, DC, resulted in Bacillus anthracis (anthrax) spore contamination in the Hart Senate Office Building and other facilities in the US Capitol's vicinity.
Objective To provide information about the nature and extent of indoor secondary aerosolization of B anthracis spores.
Design Stationary and personal air samples, surface dust, and swab samples were collected under semiquiescent (minimal activities) and then simulated active office conditions to estimate secondary aerosolization of B anthracis spores. Nominal size characteristics, airborne concentrations, and surface contamination of B anthracis particles (colony-forming units) were evaluated.
Results Viable B anthracis spores reaerosolized under semiquiescent conditions, with a marked increase in reaerosolization during simulated active office conditions. Increases were observed for B anthracis collected on open sheep blood agar plates (P<.001) and personal air monitors (P = .01) during active office conditions. More than 80% of the B anthracis particles collected on stationary monitors were within an alveolar respirable size range of 0.95 to 3.5 µm.
Conclusions Bacillus anthracis spores used in a recent terrorist incident reaerosolized under common office activities. These findings have important implications for appropriate respiratory protection, remediation, and reoccupancy of contaminated office environments.
