Risk-based selection of respirators against infectious aerosols: application to anthrax spores

Area of Science:

• Occupational Health
• Infectious Disease Epidemiology
• Respiratory Protection

Background:

• Airborne pathogens pose significant risks, necessitating effective respiratory protection strategies.
• Estimating infection risk is crucial for selecting appropriate personal protective equipment (PPE).
• Previous risk assessments may not fully account for cumulative pathogen exposure effects.

Purpose of the Study:

• To present two methods for estimating infection risk when using air-purifying respirators against airborne pathogens.
• To compare the efficacy of different air-purifying respirators in reducing inhalation anthrax risk.
• To highlight the importance of considering cumulative dose effects in risk assessment.

Main Methods:

• Developed two distinct methods for infection risk estimation: one assuming no cumulative dose effect and another accounting for it.
• Utilized pathogen concentration, respirator penetration, infectious dose, breathing rate, and exposure duration as input parameters.
• Applied the methods to hypothetical scenarios involving Bacillus anthracis (anthrax) spores.

Main Results:

• Failure to account for cumulative dose effects leads to underestimation of infection risk.
• Anthrax spores demonstrate a cumulative dose effect, particularly for exposures close in time.
• Full-facepiece powered air-purifying respirators (PAPRs) predicted to be the most effective air-purifying device against anthrax spores.

Conclusions:

• Accurate infection risk assessment for airborne pathogens requires incorporating cumulative dose effects.
• While PAPRs offer superior protection, they may not eliminate all inhalation exposure.
• Post-exposure prophylactic therapy is recommended for unvaccinated individuals exposed to anthrax spores, even with respirator use.