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.

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 CDC—nosocomial 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 5 microns in diameter; no specific reference was made to the three classes of filters—dust-mist, dust-fume-mist, and high-efficiency particulate air—certified 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 1 micron in 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 consistently meet or exceed the performance criteria. At the present time, there is no way for a purchaser to determine which dust-mist or dust-fume-mist respirators meet the performance criteria.

Compliance Memorandum on Health Care Workers Tuberculosis Protection

On 8 October 1993, OSHA issued a Compliance Memorandum outlining their enforcement policy on occupational exposure to tuberculosis. The policy relied on the hierarchy of controls presented in the 1990 CDC tuberculosis Guidelines and required the use of respirators in those situations in which the CDC found that engineering and other controls would be ineffective in preventing worker exposure. The Memorandum indicated that effective 6 January 1994, OSHA would issue citations and fines to health care facilities under their respiratory protection standard [13] for failure to use appropriate respiratory protection (for example, high-efficiency particulate air filter respirators, identified by OSHA as the minimum acceptable level of respiratory protection) and for failure to implement a complete respiratory protection program for affected health care workers [13-15].

Another concern raised by hospital personnel is the need for a training and fit-testing program for health care workers using respirators. The respiratory protection standard set by OSHA requires a NIOSH-certified respirator; when such a respirator is used to protect a worker, the law requires that a training and fit-test program be present. The Memorandum requires employees to wear respirators when entering areas occupied by or when doing high-risk procedures on persons with suspected or confirmed tuberculosis; respirators must also be worn by emergency medical-response personnel or others when they transport, in a closed vehicle, persons with suspected or confirmed tuberculosis. These employees must be covered by the respirator protection program.

Early in 1994, OSHA announced its intent to develop a standard for occupational exposure to tuberculosis. As this is being done, health care worker tuberculosis protection is currently being enforced under the October 1993 Compliance Memorandum and the general duty clause.

Effect of NIOSH Respirator Certification on Respirator Recommendations

The CDC could not recommend some respirators currently on the market (such as dust-mist and dust-fume-mist respirators), even though they are less expensive and possibly easier to use than high-efficiency particulate air filter respirators, because they did not meet, nor were they certified by NIOSH to meet, the 1993 Draft Guidelines performance criteria.

The Coal Act of 1969 gave respirator certification authority jointly to the Department of Health and Human Services and the Department of Labor [14]. Since 1972, NIOSH and the Mine Safety and Health Administration of the Department of Labor have been responsible for certifying respirators under this law. In the current NIOSH respirator certification program, high-efficiency particulate air filter respirators are tested with 0.3-micron particles (the most penetrating particle for filter material) and 99.97% of the particles must be filtered ( 0.03% penetration). In contrast, under the antiquated 1972 regulations, dust-mist and dust-fume-mist respirators are tested with silica dust and dust-fume-mist respirators are also tested with a lead fume aerosol. The silica dust test uses 40 to 50 mg of silica dust, 99% of which must be filtered ( 1% penetration is allowed). In the lead fume aerosol test, the maximum allowable filter penetration is also 1%. Penetrating particles are not sized in either test; thus, these respirators cannot currently be certified because they cannot be shown to prevent penetration of 95% or more of 1-micron particles as outlined in the 1993 Draft Guidelines.

Although some dust-mist or dust-fume-mist respirators may filter 95% or more of 1-micron particles, NIOSH and others have data showing that some currently available dust-mist or dust-fume-mist respirators allow unacceptable leakage of small (<2 microns) particles. Given the current certification process, it is impossible for the buyer to know whether a particular dust-mist or dust-fume-mist respirator meets the 1993 Draft Guidelines performance criteria.

Revision Proposed for NIOSH Respirator Certification Regulations

It has long been acknowledged that the current respirator certification process is antiquated. In 1985, the Mine Safety and Health Administration and the Office of Management and Budget agreed that NIOSH should be given primary responsibility for revising the respirator certification process. However, despite NIOSH's repeated attempts at revision, and despite their announcement in October 1987 of a Notice of Proposed Rule Making to comprehensively revise the certification process (proposed 42 CFR Part 84), the technical complexity of making a single comprehensive revision of the entire certification process precluded finalization. Consequently, NIOSH has adopted a modular approach to respirator certification revision. Seven modules have been proposed; the first would revise respirator filter penetration tests and remove the regulatory restrictions that currently impede marketing new generation respirators.

In the Federal Register on 24 May 1994, NIOSH published a Notice of Proposed Rule Making for new filter standards [18]. The new certification process includes the testing of respirators using particles of approximately 0.3 microns and will certify respirators at three levels of filter efficiency (99.97%, 99%, and 95%). This upgrade in the testing procedure would adequately assess a respirator's ability to filter very small particles and would enable certification of a broad range of respirators that provide the level of protection outlined in the 1993 Draft Guidelines. In May 1994, NIOSH reviewed the interim status of research and events subsequent to the 1992 NIOSH respirator recommendations. As a result, in June 1994, NIOSH announced that "in the place of the Institute's 1992 recommendation (powered air-purifying particulate respirators), NIOSH now recommends that workers exposed to patients with infectious tuberculosis wear respirators that meet the performance criteria CDC has outlined (the Draft Guideline respirator performance criteria)."

It is hoped that the revised certification process will result in the production of a wide variety of NIOSH-certified respirators that meet or exceed the Draft Guidelines performance criteria. Respirator manufacturers predict that these new respirators will be closer in cost, appearance, and convenience to dust-mist or dust-fume-mist respirators than to current high-efficiency particulate air-filtered respirators, yet the new models will have better worker-protection properties than do earlier dust-mist and dust-mist-fume equipment. All NIOSH-certified respirators in these classes would then be acceptable protection for health care workers against M. tuberculosis.

Conclusion

Top Conclusion Author & Article Info References

The current NIOSH Notice of Proposed Rule Making on respirator certification solves the problem of merging scientific and theoretical data into a sound approach to protecting health care workers from tuberculosis. The Tuberculosis Guideline Workgroup has reviewed the approximately 2700 responses to the 1993 Draft Guidelines published in the Federal Register. The final 1994 CDC tuberculosis Guidelines, incorporating modifications of the Draft Guidelines made on the basis of the comments received, was published in October 1994 [19]. The development of the 1994 CDC tuberculosis guidelines has been an evolutionary process that will not stop with publication. As the results of further research become available, the guidelines will continue to evolve to incorporate the most current scientific data. The goal of all parties involved in the recommendation and regulatory process remains the same: to prevent the nosocomial transmission of tuberculosis to patients and the occupational acquisition of tuberculosis by health care workers.