February 17, 1998 - Occupational Exposure to Tuberculosis

The American Society for Microbiology (ASM) appreciates the opportunity to comment on the proposed rule published by the Department of Labor, Occupational Safety and Health Administration on October 17, 1997 in the Federal Register entitled "Occupational Exposure to Tuberculosis". The ASM is the largest, single life science society in the world with an active membership of over 42,000. The ASM represents microbiologists who work in clinical, public health, industrial and research laboratories including those laboratories which detect and diagnose Mycobacterium tuberculosis (TB). Many ASM members are also engaged in infection control activities. ASM commends the Occupational Health and Safety Administration (OSHA) for its concerns for workers potentially exposed to Mycobacterium tuberculosis in an employment setting. ASM shares those concerns and will focus our comments on worker safety in the clinical and research laboratory setting.

Unfortunately, data regarding clinical laboratory safety are derived from many decades ago and antedate the implementation of the current recommendations. There are anecdotal publications that provide compelling evidence of hazards in autopsy suites and frozen section (histology) laboratories, but little contemporary data on the conventional laboratory setting. A preliminary survey conducted this year by the ASM suggested the likelihood that skin test conversions in laboratories are related to failure to adhere to current good laboratory practices and are not due to the facility design per se. ASM has proposed to extend that survey and CDC has agreed to participate in the design and evaluation of the survey instrument. With the availability of well-designed engineering controls such as biological safety cabinetry, most hazards can be contained if there are detailed hazard assessments that are tied to implementation of accommodating safety practices. However, working with culture-amplified organisms places laboratorians in a higher risk category than identified in the current proposed rule.

There are many instances, detailed in the ASM comments that follow, in which the draft OSHA standard misinterprets the intent f current laboratory guidelines and practices. The draft document paraphrases certain Centers for Disease Control (CDC) guidelines and calls for practices that, in some cases, can be extremely hazardous. ASM strongly encourages OSHA to consult with scientists with expertise in performing mycobacteriological tests safely as the agency proceeds to revise this draft standard. The ASM offers its' microbiological expertise and could provide OSHA with a list of individuals who are recognized for their expertise in this area. Enclosed is the table of contents of a recently published book "Laboratory Safety - Principles and Practices", Second Edition which provides OSHA a list of a number of experts with whom to consult. In addition, we have enclosed the chapter "Biosafety Precautions for Airborne Pathogens" which further details appropriate safety procedures when handling Mycobacterium tuberculosis in a laboratory setting.

The final publication of the OSHA standard, if not significantly revised, will have an enormous impact on laboratory workers and the visitors, patients and staff who breathe the air of the building in which they work. Although the same is true for those directly involved with patient care, the order of magnitude for a laboratory worker who works with organisms amplified by culture is much greater. It is imperative that OSHA not allow unsuspected hazardous procedures be written into regulation which will adversely impact laboratory workers.

The ASM has provided specific comments pertaining to particular questions posed by OSHA, elements of the preamble to the proposed standard, and comments on the proposed standards itself.

Laboratories, Page 54164, Column 1,
OSHA Query 1: Should OSHA require that specimens be labeled within the facility or when specimens are being shipped?

ASM Reply
: ASM does not recommend a separate warning label. Specimens to be delivered within the hospital should be treated universally as potentially containing Mycobacterium tuberculosis and should be in sealed containers that are leak-proof. These containers should be placed into plastic bags. The label should contain patient and test order information but no special hazard warning. The same specimen often is sent for other tests in bacteriology, histology, and cytology so a special warning would not make sense. Specimens to be shipped should be packaged and labeled according to current shipping regulations for infectious material.

2. Laboratories, Page 54164, Column 1
OSHA Query 2: Other than the recommendations in Biosafety In Microbiological and Biomedical Laboratories, do any other provisions need to be added?

ASM Reply
: The CDC/NIH recommendations that were used as a basis for the OSHA proposed rule are insufficiently specific in some cases. Thus, ASM suggests herein many enhancements that would be desirable. However, the recently published draft CDC guidelines for Mycobacterium tuberculosis laboratory safety utilizes a "one size fits all" approach and, therefore, is unsuitable for many laboratory circumstances. In the following comments, the ASM provides suggested alternatives including a plan to generate additional applicable data in collaboration with CDC.

3. Respirators, Page 54164, Column 2
OSHA Query 4: Should OSHA require a respirator that is more protective than the N95?

ASM Reply
: ASM believes that there are potentially some circumstances when working with culture-amplified organisms, spill cleanup for example, when the face seal leakage and the filter efficiency would compromise worker safety if an N95, or any negative pressure device, is worn. In such circumstances, room reentry might best be done wearing a HEPA filtration unit operating under positive pressure (PAPR). ASM also suggests that some research activities would not be made adequately safe by use of respirator-complemented BSL-3 practices and facilities. The respirator wearer and respirator type are not the sole consideration, but rather the safety of workers in adjacent spaces who are poorly protected by only the differential of negative air in the BSL-3 room. Better containment for high volume, high aerosolization activities would be indicated, e.g. sealed blenders.

4. Definitions, Page 54165, Column 2 & 3
OSHA Query 3: Is the distinction between clinical and research laboratories clear and should the distinction be made or should there be modifications?

ASM Reply
: Although an attempt has been made to distinguish research and clinical laboratories, the fit is imperfect, as further detailed in number 14, below.

5. Medical Surveillance, Page 54172, Column 1, Paragraph 1 & 2

ASM Comment
: OSHA stratifies skin test frequency with risk. For laboratorians who work in patient care areas in phlebotomy and in specimen management in TB and bacteriology laboratories, once per year skin test frequencies are suitable. For laboratorians in research settings where there is high volume and great aerosolization of culture-amplified organisms, a frequency of once per six months is deemed more suitable. As ASM will suggest throughout this reply, it is the degree of hazard that is the important factor and some laboratories in clinical settings may experience high risk, whereas; many research settings will not necessarily be high risk. See comment #14 below.

6. Health Effects, Background, AFB Test, Page 54174, Column 2, Paragraph 2

ASM Comment
: ASM suggests that the Acid Fast Bacilli (AFB) smear, when done correctly, is not nearly as quick nor as easy as indicated in the paragraph. The results of a smear that does not employ concentrated specimen cannot be relied upon for most applications. Thus, the test requires one or more hours to assure a reliable result. Reliable and positive results are directly related to the mycobacterial load. The judgment and skill level required to accurately assess the smear result are extremely demanding; and one of the harder, if not the hardest, judgments in TB laboratory work. The application of fluorescent versus vital stain and direct versus concentrated specimen should correlate to the urgency of the required result and the training and safety elements present in the testing facility. The smear result is only an adjunct to culture.

7. Health Effects, Hospitals - 1985 to Present, Page 54180, Column 3, Paragraph 2 & 3 and Page 54181, Columns 1 & 3

ASM Comment
: ASM commends OSHA for identifying the special hazards in autopsy and frozen section suites. For these laboratory settings, ASM believes that much more detailed safety precautions are necessary than are provided in the proposed rules. The frozen section suite is often in air space adjacent to surgery, which is maintained at positive pressure with respect to adjoining spaces. Thus, patients and operating room staff are at risk if frozen section operations continue to use freezing aerosols and operate without engineering controls on the microtome cryostat and/or the room air. The autopsy suite has long been recognized as hazardous and requires careful attention at a detail level not addressed in this document.

8. Health Effects Homeless Shelters Page 54186, Column 1, Paragraph 2 & 4

ASM Comment
: Phage typing results as a means to document epidemiology in TB outbreaks is an outdated method and of little utility. With the evolution of even better tools for epidemiologic typing of organisms, such as molecular techniques, laboratories should be required to bank one isolate of Mycobacterium tuberculosis per patient for at least one year so that typing tests may be done retroactively to determine epidemiologic links. CDC has demonstrated leadership in this area with the national surveillance system to perform restricted fragment length polymorphism (RFLP) analysis on all Mycobacterium isolates. This epidemiological procedure should be applied to all settings and not just to homeless shelters.

9. Preliminary Risk Assessment, Medical Laboratories, Page 54210, Column 2, Paragraph 2 & 3 and Page 54210, Column 3, Paragraph 1

ASM Comment
: The data cited by OSHA reflect safety outcomes experienced well before effective engineering controls were available to laboratories. ASM has conducted a preliminary survey which indicated that laboratories with careful oversight and good laboratory practices can be operated safely without skin test conversions. More data will be sought in collaboration with CDC. ASM does not wish to understate the relative hazards but also does not believe it prudent to cause fear that is not consistent with currently used practices and equipment.

10. Summary and Explanation of the Standard, Paragraph (a)(8), Scope, Page 54234

ASM Comment
: In your list of employees who may have occupational exposure to tuberculosis the ASM recommends adding "clinical microbiologists" to the ones mentioned.

11. What Would Be Required for Clinical and Research Laboratories? Page 54241 Chart 6 ASM Comment: ASM believes that Chart 6 is desirable with the following exceptions:

f) The term respiratory protection erroneously implies that respirators need only be worn until a task is completed rather than until the worker leaves the space at risk. ASM offers an alternative concept that is applicable to all comparable settings. ASM safety publications have named the concept "Respirator Rules." When invoked, Respirator Rules require a respirator to be worn by all present in the relevant space at negative pressure, except the infected patient if present. They require the usual fit testing and checking. They also require that a respirator be worn in the space until the space is deemed ventilated even if the source, patient or culture, is no longer present. (Ventilation to 99.9% removal would not be adequate for many circumstances when dealing with culture-amplified materials.)

h(2) The waste handling provisions specified in this proposed rule are inadequate for a TB laboratory. Waste that may be contaminated by aerosols should not be transported outside the laboratory until it has been autoclaved (steam-sterilized), unless there is a documented aerosol-proof container. Signs would not be sufficient for waste. ASM also suggests that rooms should be posted with Respirator Rules when necessary and these signs removed when respirators are not necessary.

12. Work Practices and Engineering Controls, Paragraph (d)(5)(vii) Page 54254, Column 3, Paragraph 3

ASM Comment
: The term isolation room in this document implies, by OSHA definition, patient rooms but not to a mycobacteriologist who uses the term to apply to the BSL-3 room. Whereas 99.9% removal may be sufficient for a patient room, if a spill of culture-amplified organisms has occurred in a TB laboratory, a greater order of magnitude of organisms in the room would require much greater removal efficiency to achieve equivalent levels of safety. This paragraph should specify that it does not apply to laboratories to insure that the rule is not followed by laboratories who have excerpted the document.

13. Clinical and Research Laboratories Page 54255 to 54257, Paragraph (e)

ASM Comment
: ASM addresses several elements in the paragraphs on these pages and in our other comments and will not reiterate all of them here. Of greatest concern is "that disposable items contaminated with respiratory secretions are not associated with transmission of Mycobacterium tuberculosis" and the allowance that such materials might be removed from the work area before decontamination. ASM considers this procedure potentially hazardous.

The requirement for a Class II BSC is overly restrictive when a Class I (or III) would provide equivalent (or superior) containment. The provision of chemical disinfection or incineration as alternatives to autoclaving is unsuitable. Exposure of workers transporting wastes is also likely and some of the devices that accomplish these alternatives may not be engineered to adequately contain laboratory aerosols. Autoclaving on-site in the laboratory should be the only method employed unless studies specifically demonstrate that aerosol hazards can be contained. "Empty" test tubes and pipettes contain high level aerosols and this would be extremely hazardous in a laboratory setting.

Page 54257, Column 1, Paragraph 1

ASM Comment
: Discussed in this paragraph are some possibilities of grave risk to the workers. The paragraph implies that a respirator would be necessary when a culture of Mycobacterium tuberculosis is centrifuged in an open centrifuge or when centrifuge containers are opened outside the BSC. Centrifuging in an open container or opening centrifuge containers outside a BSC are both completely unacceptable practices. This practice would be extremely hazardous to others in adjacent rooms and hallways as the engineering of negative air in a BSL-3 facility is insufficient to create a primary barrier for the outsider's protection and the face seal would not be adequate to protect the worker in the room if culture- amplified suspensions were being centrifuged.

14. Definitions, Clinical Laboratory, Page 54279, Column 1, Paragraph 2, Research Laboratory, Page 54281, Column 2, Paragraph 4

ASM Comment
: The definition of a "clinical laboratory", in contrast to a research laboratory, is (a) confusing, (b) overly restrictive and c) artificial in some instances:

a) The definition states that a clinical laboratory "conducts routine and repetitive operations for the diagnosis of tuberculosis". It is confusing because the term "clinical laboratory" generally applies to all sections of a medical diagnostic laboratory (in some contexts, it applies only to those sections that do work with specimens other than on tissue sections).

b) It is overly restrictive because it implies that the intent is to apply this definition only to the traditional mycobacteriology laboratory. This could exclude very important sections of the laboratory for which there are current data suggesting hazardous practices and high rates of skin test conversion, most specifically, the frozen section suite and the autopsy suite. It could also exclude from consideration the numerous potentially hazardous practices in a cytopathology section or a molecular biology section. It also excludes the traditional bacteriology, chemistry and hematology sections, which are at lower risk but do work with specimens that may contain mycobacteria. Of most concern with the latter would be the bacteriology laboratory that might not utilize a biosafety cabinet for work with respiratory specimens; we understand that some of the smaller bacteriology laboratories have not been induced to follow that safety practice. Finally, the phlebotomy team is often administratively part of the laboratory and bears a risk potential that is equivalent to health care workers in patient care areas. Similar consideration should be given to those who work in direct patient testing, specimen collection, etc., but who are not classified as laboratorians.

c) The distinction between clinical and research laboratories is artificial and may present a conflict. A mycobacteriology laboratory in a diagnostic medical laboratory may be conducting research that is hazardous beyond the usual practices in mycobacteriology. Furthermore, an outside researcher may be utilizing the mycobacteriology laboratory facility to conduct research that is hazardous. Some research may be only modestly hazardous and well contained with BSL 3 practices and BSL 2 facilities.

ASM Recommendation: ASM would propose that a better result would ensue if the risks (practices of the laboratory) were the key to determine safety provisions, rather than an artificial distinction among different laboratories, particularly one that excludes important segments of the laboratory health care team.

15. Definitions, Mycobacterium tuberculosis, Page 54280, Column 2, Paragraph 1

ASM Comment
: The term "Mycobacterium tuberculosis" is (a) insufficiently inclusive in some cases and (b) overly inclusive in others.

(a) The hazardous organisms include the human pathogens of the Mycobacterium tuberculosis complex and should be extended specifically to include the species "Mycobacterium bovis."

(b) Genetic variants (BCG) of Mycobacterium tuberculosis that are used for vaccines in humans and for therapy of some cancers are considered BSL-2 agents and should be excluded from this set of rules. OSHA Proposed Standard Cinical and Research Laboratories, Page 54286, Paragraph (e)

ASM Comment: The practices that are suggested are (a) insufficiently specific and (b) in some cases difficult, if not impossible for OSHA to assess.

(e-2-I) There is language in the document that suggests that "standard microbiological practices" be followed when, in fact, such standard practices are not specified in microbiology or are insufficiently safe for mycobacteriology.

(e-2-A) The laboratory is required to "minimize the creation of aerosols" when, in fact, many procedures, for which there is currently no known alternative, necessarily involve the creation of aerosols. It would be more desirable to require that the aerosol containment methods are sufficiently exacting to match or exceed the extent of the aerosol created.

(e-2-iii Containment Equipment) For centrifugation, it is suggested that the laboratory employ "sealed rotor heads" when in fact that specification would most likely be construed to include heads that are in actuality only splatter proof and not aerosol proof. The term "aerosol proof" should be substituted for "sealed."

ASM Comment: Undoubtedly, much of the problem is due to the change from a guideline format to a regulatory format and from a document generally applicable to many infectious agents to one intended for only Mycobacterium tuberculosis and related species. ASM suggests specific practices and risk practice guidelines that may be applicable to the regulatory arena, see below:

  1. Bacteriology laboratories should be required to employ bench top incinerators rather than open flames for sterilizing loops.
  2. No "hot-looping" of media should be allowed as it is now known that there may be microscopic colonies of Mycobacterium tuberculosis on routine bacteriology media and these may be aerosolized. This can be visually checked, seeking absence/presence of loop profiles melted into the agar surface.
  3. Bacteriology and cytopathology laboratories should be required to perform all manipulations of respiratory specimens within a biological safety cabinet whenever the specimen is opened.
  4. Aerosol proof rotor heads should be purchased for routine and cyto-centrifuge manipulation of sputum and other respiratory specimens. Where applicable, the O-rings should be inspected monthly and replaced annually or when visibly cracked. Records should reflect this process.
  5. All sonication should be conducted in a biological safety cabinet or device of equal or superior containment. Lidded tubes and presence of lysing reagents are insufficient to insure safety outside the BSC because of the extremely high hazard potential of lid seal leakage or the failure to add the lysing reagent. Or, for example, a few chips of solid colony could drop on the outside of a tube or test tube rack and be rendered extremely hazardous when sonicated.

Communications of Hazards and Training, Labels and Signs, Page 54290

ASM Comment: The specifications for waste disposal from the laboratory setting are inadequate and could represent a hazard to the laboratorian or to subsequent health care or contract workers who manage the waste. The wording "durable leak proof container, closed to prevent leakage, for transport from the laboratory" suggests that fluid material is the greatest hazard when in fact it is the "empty" test tubes, pipettes, etc, that contain aerosols that will diffuse out of a container that is not sealed that are most hazardous. Simple closure is insufficient to contain the truly hazardous "leakage" where aerosols are concerned. The emphasis on color coding is also hazardous because it implies that a color coded plastic bag might be used but in fact would readily release aerosols if the bag were compressed even though it might be "closed."

The sentence "Disposable items contaminated with respiratory secretions are not associated with transmission of Mycobacterium tuberculosis" is particularly hazardous because it occurs in a separate paragraph following the context in which it is intended. It is true that disposable tissues would not tend to release aerosols of Mycobacterium tuberculosis. However, disposable test tubes or pipettes appearing empty but containing a high-level aerosol of culture-amplified Mycobacterium tuberculosis, would be the source of extremely effective transmission that would not be easily detected and traced back to its source in the laboratory.

ASM Recommendation: Although it is possible that a container could be devised that would insure that no aerosols of Mycobacterium tuberculosis were released during storage and transport of laboratory waste, ASM would suggest that it is improbable that it would actually be effective when used by non-professionals, no matter how well it was labeled. There are two possible solutions. The first would be to require that all "empty" containers from the tuberculosis laboratory be filled with mycobactericidal disinfectant, while still in the biological safety cabinet so that all aerosols would be disinfected and/or purged and entrapped in the HEPA filter inside the cabinet. This would be a difficult practice to introduce and to enforce. The second would be to require that all mycobacterial waste being removed from the biological safety cabinet be contained in sealed, non-compressible containers and steam sterilized without delay by personnel who work in the laboratory and are trained for the job.

18) General Comments

The specifications for safety devices are insufficient.

Biological Safety Cabinet (BSC)
- The biological safety cabinet can represent a hazard if it is functioning improperly. The laboratory should be required to ascertain a frequency of certification that is relative to the risks, or performance characteristics detected by on-going documentation of monitoring of a magnehelic gauge or history of performance in the setting. There may be a necessity for in-laboratory monitoring and testing conducted between certifying visits, including face velocity, if the aerosols are prolonged or substantial, and smoke testing if the configuration of instruments in the BSC changes with time.

The BSC certifier should be personally certified by an agency with standards at least as demanding as those of the National Sanitation Foundation (NSF) and the instruments used for certification should be calibrated according to national standards. There should be documentation that the certifier's paperwork was assessed in the laboratory following the visit and any provisions or restrictions were followed. The degree of redundancy in the back-up power/battery should be in concert with the hazards, extent, and duration of aerosols. If there is an external exhaust fan, the belt should be part of a routine inspection and replacement program and the power should be backed up where risk is identified with greater aerosolization. There should be on-going continuous monitoring for failure of power or fan, e.g., tissue strips and/or alarms. Since onset of back-up power may be delayed if mechanical, review the need for instantaneous back-up when BSC is used to contain persistent or substantial aerosols.

UVGI - If ultraviolet lights are employed in the BSC or in the room, there should be a quality assurance program in place to monitor their efficacy.

Autoclave/steam sterilizer - The autoclave should be evaluated to assure that the air exhaust line is sealed and directed to a region outside the facility that does not represent a potential for entrainment or reintroduction. All autoclaves tend to exhaust their air as steam is introduced and are subject to these guidelines. Pre-vac autoclaves, intended for sterilization of wrapped, clean goods, may be contraindicated for use with mycobacteriology wastes unless the manufacturer certifies their safe application and their installation meets the above criteria.

Vacuum lines - If used for TB aerosols, vacuum lines should be pre-filtered or assessed for their ability to contain the aerosols safely.

2. Respirators - Respirator use may be indicated for some diagnostic laboratory work, depending upon the extent and duration of aerosolization occurring in the BSC but is only indicated for work in the BSL-3 room.

ASM does not believe that specimen management requires respirator use or work in a BSL-3 facility. In fact, there could be increased hazard to employees who normally spend many hours working with low risk specimens if they are required to work in the BSL-3 room where higher risk activities take place.

The use of minimally aerosolizing procedures with culture-amplified organisms, particularly those growing on solid culture media, is not likely to require a BSL-3 facility nor complementary respirators. With increasing volumes, numbers, or aerosolization of culture-amplified organisms suspended in fluid medium, there is a greater likelihood of a spill outside the BSC or of inadequate containment within the BSC. ASM is working with CDC to conduct a survey of practices that will reveal the recent history of problems so that some guidance might be available regarding the practices mostly like to require containment within a BSL-3 facility and/or complementary respirators.

Some research work can be adequately contained as described for clinical work, depending on the volume and extent of aerosolization. Aerosols of culture-amplified organisms exposed to efficient, high volume aerosolization devices, blenders, for example, would not necessarily be adequately contained in a BSL-3 facility unless the blender is completely sealed. Thus, the respirator would only protect the worker in the facility and not those in adjacent rooms or halls.

ASM Recommendation: ASM and CDC plan to collaborate to identify safety practices that OSHA might employ for different categories of risk. It is extremely critical that a set of "respirator rules" be followed, including the wearing of respirators for a given time period after the work is completed to allow the evacuation of the room. ASM is not convinced that the same exhaust time periods are applicable to spills of culture-amplified organisms, where the numbers of viable organisms may exceed those of sick, coughing individuals by many orders of magnitude. Therefore, the 99.9% exhaust calculations should not be employed for laboratories.

3. Education - Education and training is extremely important in the laboratory setting. The OSHA proposed standard should emphasize education and safety training more broadly and intensively.

ASM would suggest that a comprehensive, laboratory-oriented safety course be mandatory for supervisors and directors of TB testing laboratories. Special train-the-trainer courses that emphasize the unique nature of TB aerosol transmission should be routinely available and brought back, with yearly updates, to employees in the laboratories. ASM also recommends only utilizing appropriately trained, certified and educated personnel perform microbiological diagnostic testing, including mycobacteriological testing.

4. Sample Hazard Assessment, Attachment

A simple 2-page Hazard Assessment table is attached. Variations of this table have been published in a number of ASM safety books and manuals. It reflects the need to stratify practices with risks. ASM would like to work with OSHA to make such a concept applicable to the regulatory arena.

Thank you for considering our comments. The ASM would be pleased to assist OSHA as the agency continues to revise its proposed standards on the occupational exposure to tuberculosis. ASM members employed in clinical laboratories are the primary individuals who detect and diagnose patients with tuberculosis. Mycobacterium tuberculosis researchers, also members of the ASM, are the nation's best answer to permanently eradicating the dreadful scourge of Mycobacterium tuberculosis. In this regard, the ASM's highest concern is for the safety of these clinical and research laboratory workers.

All sonication should be conducted in a biological safety cabinet or device of equal or superior containment. Lidded tubes and presence of lysing reagents are insufficient to insure safety outside the BSC because of the extremely high hazard potential of lid seal leakage or the failure to add the lysing reagent. Or, for example, a few chips of solid colony could drop on the outside of a tube or test tube rack and be rendered extremely hazardous when sonicated.