Respirators, Recommendations, and Regulations: The Controversy Surrounding Protection of Health Care Workers from Tuberculosis

During the past 5 years, tuberculosis has reemerged as a major public health problem [1, 2]. Numerous nosocomial outbreaks of tuberculosis have been reported and have often involved multidrug-resistant strains of Mycobacterium tuberculosis [3-8]. In outbreaks of multidrug-resistant tuberculosis investigated by the Centers for Disease Control and Prevention (CDC), more than 100 health care workers have had tuberculin skin-test conversions, at least 17 have developed active multidrug-resistant tuberculosis, and at least 6 have died [8]. Because of concern about the risk for occupational acquisition of tuberculosis by workers in health care facilities, the various federal agencies responsible for the protection of these workers have issued recommendations, guidelines, and compliance memoranda outlining various protective measures. Each of these agencies has recommended some type of respiratory protective device to be worn by health care workers (Tables 1 and 2); at times these recommendations have appeared contradictory and have led to confusion. Our purpose is to describe both the evolution of these recommendations and the role of each federal agency in respiratory protection for health care workers. Table 1. Summary Comparison of Four Respirator Types Evaluated for Protection of Health Care Workers Potentially Exposed to Tuberculosis* Table 2. Summary Comparison of Three Types of Negative-Pressure Respirators The CDC Tuberculosis Guidelines The CDC is a nonregulatory federal agency responsible for developing practical guidelines for the prevention of disease transmission. In 1982, it published Guidelines for Prevention of TB Transmission in Hospitals, in which it recommended surgical masks for the protection of health care workers [9]. Because nosocomial transmission of tuberculosis was reported infrequently and surgical masks were used to protect patients from health care workers, to protect health care workers from patients, and as source control to contain droplet nuclei in patients with tuberculosis, there was little evaluation of the type of respiratory protection recommended to protect health care workers from tuberculosis. However, as the 1982 Guidelines for Prevention of TB Transmission in Hospitals was being revised in 1989 by representatives of the National Center for Infectious Diseases (NCID), the National Center for Prevention Services (NCPS), and the National Institute for Occupational Safety and Health (NIOSH)all of which are part of the CDCnosocomial outbreaks of drug-susceptible and multidrug-resistant tuberculosis began to be reported [3-8, 10]. In 1990, the CDC published Guidelines for Preventing the Transmission of Tuberculosis in Health-Care Settings, with Special Focus on HIV-related Issues [11]. The 1990 Guidelines stated that standard surgical masks may not be effective in preventing inhalation of droplet nuclei and recommended the use of disposable particulate respirators while acknowledging that the efficacy of particulate respirators in protecting susceptible persons from inhalation of tuberculosis has not been demonstrated. The term particulate respirator was defined as a disposable respiratory protective device designed to filter out particles 1 to 5min diameter; no specific reference was made to the three classes of filtersdust-mist, dust-fume-mist, and high-efficiency particulate aircertified under federal regulations (31 CFR Part 11) published in 1972. Use of the generic term particulate respirator implied that the use of any of these three filters would satisfy the 1990 guidelines. Dust-Mist and Dust-Fume-Mist Filters: 1992 NIOSH Draft Report In a 1992 draft report, NIOSH presented peer-reviewed data showing that the filters of certain dust-mist and dust-fume-mist respirators allowed significant leakage of small particles ( 2 microns). Public health concern about the data arose because these small particles are also likely to reach the lungs of workers. Occupational Safety and Health Administration Requests NIOSH Respirator Recommendation As more outbreaks of multidrug-resistant tuberculosis were reported, concern about occupational acquisition of tuberculosis increased. The Occupational Safety and Health Administration (OSHA), the federal agency with legislatively established regulatory responsibility for workplace safety and health, responded to complaints (mainly from workers in New York State) and did inspections relevant to occupational exposure to tuberculosis. In May 1992, OSHA Region II issued enforcement guidelines for such occupational exposure, in which it specified the minimal recommended level of respiratory protection to be that provided by dust-fume-mist respirators. In August 1992, OSHA formally requested NIOSH to state which respirators health care workers should be required to wear to prevent occupational acquisition of tuberculosis (OSHA requires use of NIOSH-certified respirators). A nonregulatory federal agency responsible for research and training in occupational safety and health, NIOSH also has a statutory responsibility to provide a scientific basis for criteria it recommends to OSHA, criteria that OSHA uses to develop workplace standards. In addition, NIOSH has regulatory responsibility for respirator certification. Response of NIOSH to OSHA Request In August 1992, NIOSH issued Recommended Guidelines for Personal Protection of Workers in Health Care Facilities Potentially Exposed to Tuberculosis [12]. Believing that it was legally mandated that recommendations should eliminate all risk for infection without considering cost or practicality, NIOSH recommended the use of NIOSH-certified, powered, half-mask respirators equipped with high-efficiency particulate air filters in areas where patients known or suspected to have tuberculosis were receiving care. In the most hazardous locations and during the most hazardous procedures (such as bronchoscopy and sputum induction), NIOSH recommended the use of NIOSH-certified, positive-pressure, air-line, half-mask respirators. It also recommended that all respirators be used in conjunction with an effective respiratory protection program [12-15]. These recommendations were made because many important factors, including the size of the infectious droplet nuclei, the concentration of bacteria released by infectious patients, the permissible (maximum) exposure limit, and the threshold (minimum) limit were unknown; the likelihood of faceseal leakage of nonpowered respirators was thought to be substantial; and the NIOSH respirator decision logic excluded the use of less effective respirators. The CDC Examines the Need for Revision of Its 1990 Tuberculosis Guidelines Transmission of tuberculosis from patient to patient and from patient to health care worker raised concerns about the adequacy of the CDC's 1990 guidelines. Thus, in October 1992, the CDC held a meeting to discuss whether the 1990 guidelines should be revised. The initial outbreaks of multidrug-resistant tuberculosis were discussed and follow-up data from one hospital were presented; these data showed that if the 1990 guidelines were fully implemented (including those requiring the use of source and engineering controls and molded surgical or high-efficiency laser surgical masks or dust-mist respirators), nosocomial transmission of multidrug-resistant tuberculosis from patient to patient or from patient to health care worker would cease [16]. Additionally, NIOSH presented their respirator recommendations and the rationale behind them. At the conclusion of the meeting, the Director of the CDC stated that although they need some revision, the basic thrust of the CDC 1990 Guidelines is about right. It has also been made clear that the 1990 Guidelines have not yet been widely put in place. He recommended wider implementation of the 1990 CDC tuberculosis guidelines and a reinforcement in the revised guidelines of the hierarchy of controls, health care worker education, and the role of source and engineering controls. A CDC Tuberculosis Guideline Working Group that included representatives from NCID, NCPS, and NIOSH was charged with revising the 1990 CDC tuberculosis guidelines. The CDC Publishes 1993 Draft Guidelines On 12 October 1993, the CDC published Draft Guidelines for Preventing Transmission of Tuberculosis in Health-Care Facilities, second edition, in the Federal Register for public comment [17]. The Draft Guidelines emphasized the hierarchy of controls needed to prevent transmission of tuberculosis. Performance criteria were outlined for personal respiratory protection in situations where administrative and engineering controls may not provide sufficient protection. Performance criteria for respirators were as follows: 1) the ability to filter particles 1min size with an efficiency of at least 95%; 2) the ability to be qualitatively or quantitatively tested for fit in a reliable way; 3) the ability to fit test health care workers with different facial sizes and characteristics; and 4) to ensure proper protection, the ability to have facepiece fit checked by the wearer each time the respirator is worn. These criteria were based on the characteristics of respirators that were used in conjunction with source and engineering controls in outbreak settings where the transmission of tuberculosis to health care workers had been reduced or terminated. The 1993 Draft Guidelines stated that some dust-mist or dust-fume-mist respirators might meet the performance criteria. In addition, evidence was obtained from two hospitals that had had outbreaks of multidrug-resistant tuberculosis; this evidence showed that implementation of a program satisfying CDC recommendations for source and engineering controls and including the use of dust-mist respirators that met the 1993 Draft Guidelines criteria terminated transmission of tuberculosis to health care workers. However, only high-efficiency particulate air filter respirators are certified by NIOSH (as required by OSHA) and