Selecting Respirators for Control of Worker Exposure to Infectious Aerosols

Abstract

A method for selecting respirators for protection in infectious aerosol environments was developed, building on a procedure used to choose respiratory protection for environments containing nonbiological contaminants. Modifications in the traditional respirator selection method are proposed for situations where information on occupational exposure limits, toxicity, and airborne concentrations is absent. Toxicity is determined from risk rankings proposed by a variety of organizations. The nature of the activity allows assessment of source generation, which is combined with room volume and airflow to obtain a ranking of airborne concentration. Finally, concentration and toxicity ranks determine a minimum assigned protection factor, which corresponds to a respirator class. Case studies are presented to illustrate the proposed decision logic. For each situation, the procedure yielded choices that were both protective and reasonable. These results suggest that the procedure will be applicable to a variety of settings for a range of infectious organisms.

Issues Affecting Respirator Selection for Workers Exposed to Infectious Aerosols: Emphasis on Healthcare Settings

“…Once a decision has been made that respirators are needed to protect the health of workers, the process of selecting an appropriate respirator requires an understanding of the work activities associated with potential exposures, the health effects of overexposure, properties of the air contaminant (e.g., in healthcare settings, the characteristics and behavior of an aerosolized infectious disease agent), and worker and workplace factors that may affect how effective a respirator will be in protecting workers (Johnson, 2001;McCullough & Brosseau, 1999). In addition, consideration must be given to whether wearing a certain type of respirator will adversely affect a worker's ability to perform his or her tasks or will create a risk to the safety of the worker or others (e.g., the trailing hose of a supplied air respirator can be a tripping hazard).…”

“…Assigned protection factors range from 10 for fit-tested, air-purifying, half-facepiece respirators to 10,000 for pressure demand self-contained breathing apparatuses (American National Standards Institute [ANSI], 1992;McCullough & Brosseau, 1999; National Institute for Occupational Safety and Health [NIOSH], 1987;OSHA, 2003).…”

“…A method using expert opinion and a modification of the hazard ratio method was published to address respirator selection for healthcare workers exposed to infectious aerosols (McCullough & Brosseau, 1999). This approach, which could be termed a qualitative ranking method, uses qualitative rankings of airborne concentrations (instead of contaminant measurements themselves) and rankings of "toxicity" or risk (as surrogates for occupational exposure limits) to identify graphically the level of respiratory protection to which assigned protection factors could be compared.…”

Green Jobs: Definition and Method of Appraisal of Chemical and Biological Risks

“…Even ideal general ventilation does not reduce a worker's exposure if the workstation is located near the source, if there are projections, or if the worker blocks or protects the source by disturbing the ambient air flow profiles. A risk is always present in these situations and can never be reduced to zero by general ventilation in this additive model, as is the case in the models of McCullough and Brosseau (1999) and the CSA (2011), where ventilation divides the risk (Neesham-Grenon et al, 2013;Lavoie et al, 2013a,b).…”

“…But instead of using a list of risk phrases as used for chemicals, the CB model for biological agents is based on the international microorganisms classification in four risk groups according to their pathogenicity ( Attribution of hazard score Unlike the chemical toxicity assessment, the ranking of biological agents is subject to an international consensus (Public Health Agency of Canada, 2004), and the hazard score was divided in four bands according to the risk groups used in biosecurity. Green job titles and related occupations considered in this study reflect the reality Attribution of exposure As published before in the use of CB for the evaluation of biological risks, the exposure was based on two criteria, the level of the control over the agent (C) and the level of the exposure (E) (McCullough and Brosseau, 1999;CSA, 2011). The exposure to biological agents was appraised for each green job title.…”