# Assigned Protection Factors > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A06-6942 ## Record - **Collection:** Federal Register - **Document type:** Rule - **Published:** August 24, 2006 - **Citation:** 71 FR 50122 ## Text DEPARTMENT OF LABOR Occupational Safety and Health Administration 29 CFR Parts 1910, 1915, and 1926 [Docket No. H049C] RIN 1218-AA05 Assigned Protection Factors AGENCY: Occupational Safety and Health Administration (OSHA), Department of Labor. ACTION: Final rule. SUMMARY: In this final rule, OSHA is revising its existing Respiratory Protection Standard to add definitions and requirements for Assigned Protection Factors (APFs) and Maximum Use Concentrations (MUCs). The revisions also supersede the respirator selection provisions of existing substance-specific standards with these new APFs (except for the respirator selection provisions of the 1,3-Butadiene Standard). The Agency developed the final APFs after thoroughly reviewing the available literature, including chamber-simulation studies and workplace protection factor studies, comments submitted to the record, and hearing testimony. The final APFs provide employers with critical information to use when selecting respirators for employees exposed to atmospheric contaminants found in general industry, construction, shipyards, longshoring, and marine terminal workplaces. Proper respirator selection using APFs is an important component of an effective respiratory protection program. Accordingly, OSHA concludes that the final APFs are necessary to protect employees who must use respirators to protect them from airborne contaminants. DATES: The final rule becomes effective November 22, 2006. ADDRESSES: In compliance with 28 U.S.C. 2212(a), the Agency designates Joseph M. Woodward, the Associate Solicitor for Occupational Safety and Health, Office of the Solicitor, Room S-4004, U.S. Department of Labor, 200 Constitution Avenue, NW., Washington, DC 20210, as the recipient of petitions for review of this rulemaking. FOR FURTHER INFORMATION CONTACT: For technical inquiries regarding this final rule, contact Mr. John E. Steelnack, Directorate of Standards and Guidance, Room N-3718, OSHA, U.S. Department of Labor, 200 Constitution Ave., NW., Washington, DC 20210; telephone (202) 693-2289 or fax (202) 693-1678. For general inquiries regarding this final standard contact Kevin Ropp, OSHA Office of Public Affairs, Room N-3647, U.S. Department of Labor, 200 Constitution Ave., NW., Washington, DC 20210 (telephone (202) 693-1999). Copies of this Federal Register notice are available from the OSHA Office of Publications, Room N-3101, U.S. Department of Labor, 200 Constitution Ave., NW., Washington, DC 20210 (telephone (202) 693-1888). For an electronic copy of this notice, as well as news releases and other relevant documents, go to OSHA's Web site ( http://www.osha.gov ), and select “ Federal Register ,” “Date of Publication,” and then “2006''. SUPPLEMENTARY INFORMATION: I. General A. Table of Contents The following Table of Contents identifies the major preamble sections of this final rule and the order in which they are presented: I. General A. Table of Contents B. Glossary II. Events Leading to the Final Standard A. Regulatory History of APFs B. Non-Regulatory History of APFs C. Need for APFs III. Methodology for Developing APFs for Respirators A. Introduction B. Background C. Methodology, Data, and Studies on Filtering Facepieces and Elastomerics D. Alternative Approaches E. Updated Analyses F. Summary of Studies Submitted During the Rulemaking IV. Health Effects V. Summary of the Final Economic Analysis and Initial Regulatory Flexibility Analysis A. Introduction B. The Rule and Affected Respirator Users C. Compliance Costs D. Benefits E. Economic Feasibility F. Economic Impacts to Small Entities VI. Summary and Explanation of the Final Standard A. Definition of Assigned Protection Factor B. APF Provisions C. Assigned Protection Factors for Specific Respirator Types 1. APF for Quarter Mask Air-Purifying Respirators 2. APF for Half Mask Air-Purifying Respirators 3. APF for Full Facepiece Air-Purifying Respirators 4. APF for Powered Air-Purifying Respirators (PAPRs) 5. APF for Supplied-Air Respirators (SARs) 6. APF for Self-Contained Breathing Apparatuses (SCBAs) D. Definition of Maximum Use Concentration E. MUCs for Mixtures and Hazard Ratios F. MUC Provisions G. Superseding the Respirator Selection Provisions of Substance-Specific Standards in Parts 1910, 1925, and 1926 VII. Procedural Determinations A. Legal Considerations B. Paperwork Reduction Act C. Federalism D. State Plans E. Unfunded Mandates F. Applicability of Existing Consensus Standards List of Subjects in 29 CFR Parts 1910, 1915, and 1926 Authority and Signature Amendments to Standards B. Glossary This glossary specifies the terms represented by acronyms, and provides definitions of other terms, used frequently in the preamble to the final rule. This glossary does not change the legal requirements in this final rule, nor is it intended to impose new regulatory requirements on the regulated community. 1. Acronyms ACGIH: American Conference of Governmental Industrial Hygienists AIHA: American Industrial Hygiene Association ANSI: American National Standards Institute APF: Assigned Protection Factor APR: Air-purifying respirator Ci: Concentration measured inside the respirator facepiece Co: Concentration measured outside the respirator DOP: Dioctylphthalate (see definition below) DFM: Dust, fume, and mist filter EPF: Effective Protection Factor (see definition below under “Protection factor study”) HEPA: High efficiency particulate air filter (see definition below) IDLH: Immediately dangerous to life or health (see definition below) LANL: Los Alamos National Laboratory LASL: Los Alamos Scientific Laboratory LLNL: Lawrence Livermore National Laboratory MSHA: Mine Safety and Health Administration MUC: Maximum Use Concentration NFPA: National Fire Protection Association NIOSH: National Institute for Occupational Safety and Health NRC: Nuclear Regulatory Commission OSHA: Occupational Health and Safety Administration OSH Act: The Occupational Safety and Health Act of 1970 (29 U.S.C. 655, 657, 665). PAPR: Powered air-purifying respirator (see definition below) PEL: Permissible Exposure Limit PPF: Program Protection Factor (see definition below under “Protection factor study”) QLFT: Qualitative fit test (see definition below) QNFT: Quantitative fit test (see definition below) RDL: Respirator Decision Logic (see definition below) REL: Recommended Exposure Limit (see definition below) SAR: Supplied-air (or airline) respirator (see definition below) SCBA: Self-contained breathing apparatus (see definition below) WPF: Workplace Protection Factor (see definition below under “Protection factor study”) TLV: Threshold Limit Value (see definition below) SWPF: Simulated Workplace Protection Factor (see definition below under “Protection factor study”) 2. Definitions Terms followed by an asterisk (*) refer to definitions that can be found in paragraph (b) (“Definitions”) of OSHA's Respiratory Protection Standard (29 CFR 1910.134). Air-purifying respirator*: A respirator with an air-purifying filter, cartridge, or canister that removes specific air contaminants by passing ambient air through the air-purifying element. Atmosphere-supplying respirator*: A respirator that supplies the respirator user with breathing air from a source independent of the ambient atmosphere, and includes SARs and SCBA units. Canister or cartridge*: A container with a filter, sorbent, or catalyst, or combination of these items, which removes specific contaminants from the air passed through the container. Continuous flow respirator: An atmosphere-supplying respirator that provides a continuous flow of breathable air to the respirator facepiece. Demand respirator*: An atmosphere-supplying respirator that admits breathing air to the facepiece only when a negative pressure is created inside the facepiece by inhalation. Dioctylphthalate (DOP): An aerosolized agent used for quantitative fit testing. Elastomeric: A respirator facepiece made of a natural or synthetic elastic material such as natural rubber, silicone, or EPDM rubber. Filter or air-purifying element*: A component used in respirators to remove solid or liquid aerosols from the inspired air. Filtering facepiece (or dust mask)*: A negative pressure particulate respirator with a filter as an integral part of the facepiece or with the entire facepiece composed of the filtering medium. Fit factor*: A quantitative estimate of the fit of a particular respirator to a specific individual and typically estimates the ratio of the concentration of a substance in ambient air to its concentration inside the respirator when worn. Fit test*: The use of a protocol to qualitatively or quantitatively evaluate the fit of a respirator on an individual. Helmet*: A rigid respiratory inlet covering that also provides head protection against impact and penetration. High-efficiency particulate air filter (HEPA)*: A filter that is at least 99.97% efficient in removing monodisperse particles of 0.3 micrometers in diameter. The equivalent NIOSH 42 CFR part 84 particulate filters are the N100, R100, and P100 filters. Hood*: A respiratory inlet covering that completely covers the head and neck and may also cover portions of the shoulders and torso. Immediately dangerous to life or health (IDLH)*: An atmosphere that poses an immediate threat to life, would cause irreversible adverse health effects, or would impair an individual's ability to escape from a dangerous atmosphere. Loose-fitting facepiece*: A respiratory inlet covering that is designed to form a partial seal with the face. Negative pressure respirator (tight-fitting)*: A respirator in which the air pressure inside the facepiece is negative during inhalation with respect to the ambient air pressure outside the respirator. Permissible Exposure Limit (PEL): An occupational exposure limit specified by OSHA. Positive pressure respirator*: A respirator in which the pressure inside the respiratory inlet covering exceeds the ambient air pressure outside the respirator. Powered air-purifying respirator (PAPR)*: An air-purifying respirator that uses a blower to force the ambient air through air-purifying elements to the inlet covering. Pressure demand respirator*: A positive pressure atmosphere-supplying respirator that admits breathing air to the facepiece when the positive pressure is reduced inside the facepiece by inhalation. Protection factor study: A study that determines the protection provided by a respirator during use. This determination generally is accomplished by measuring the ratio of the concentration of an airborne contaminant (e.g., hazardous substance) outside the respirator (Co) to the concentration inside the respirator (Ci) (i.e., Co/Ci). Therefore, as the ratio between Co and Ci increases, the protection factor increases, indicating an increase in the level of protection provided to employees by the respirator. Four types of protection factor studies are: Effective Protection Factor (EPF) study: A study, conducted in the workplace, that measures the protection provided by a properly selected, fit-tested, and functioning respirator when used intermittently for only some fraction of the total workplace exposure time (i.e., sampling is conducted during periods when respirators are worn and not worn). EPFs are not directly comparable to WPF values because the determinations include both the time spent in contaminated atmospheres with and without respiratory protection; therefore, EPFs usually underestimate the protection afforded by a respirator that is used continuously in the workplace. Program Protection Factor (PPF) study: A study that estimates the protection provided by a respirator within a specific respirator program. Like the EPF, it is focused not only on the respirator's performance, but also the effectiveness of the complete respirator program. PPFs are affected by all factors of the program, including respirator selection and maintenance, user training and motivation, work activities, and program administration. Workplace Protection Factor (WPF) study: A study, conducted under actual conditions of use in the workplace, that measures the protection provided by a properly selected, fit-tested, and functioning respirator, when the respirator is worn correctly and used as part of a comprehensive respirator program that is in compliance with OSHA's Respiratory Protection Standard at 29 CFR 1910.134. Measurements of Co and Ci are obtained only while the respirator is being worn during performance of normal work tasks (i.e., samples are not collected when the respirator is not being worn). As the degree of protection afforded by the respirator increases, the WPF increases. Simulated Workplace Protection Factor (SWPF) study: A study, conducted in a controlled laboratory setting and in which Co and Ci sampling is performed while the respirator user performs a series of set exercises. The laboratory setting is used to control many of the variables found in workplace studies, while the exercises simulate the work activities of respirator users. This type of study is designed to determine the optimum performance of respirators by reducing the impact of sources of variability through maintenance of tightly controlled study conditions. Qualitative fit test (QLFT)*: A pass/fail fit test to assess the adequacy of respirator fit that relies on the individual's response to the test agent. Quantitative fit test (QNFT)*: An assessment of the adequacy of respirator fit by numerically measuring the amount of leakage into the respirator. Recommended Exposure Limit (REL): An occupational exposure level recommended by NIOSH. Respirator Decision Logic (RDL): Respirator selection guidance developed by NIOSH that contains a set of respirator protection factors. Self-contained breathing apparatus (SCBA)*: An atmosphere-supplying respirator for which the breathing air source is designed to be carried by the user. Supplied-air respirator (or airline) respirator (SAR)*: An atmosphere-supplying respirator for which the source of breathing air is not designed to be carried by the user. Threshold Limit Value (TLV): An occupational exposure level recommended by ACGIH. Tight-fitting facepiece*: A respiratory inlet covering that forms a complete seal with the face. II. Events Leading to the Final Standard A. Regulatory History of APFs Congress established the Occupational Safety and Health Administration (OSHA) in 1970, and gave it the responsibility for promulgating standards to protect the health and safety of American workers. As directed by the OSH Act, the Agency adopted existing Federal standards and national consensus standards developed by various organizations such as the NFPA and ANSI. The ANSI standard Z88.2-1969, “Practices for Respiratory Protection,” was the basis of the first six sections (permissible practice, minimal respirator program, selection of respirators, air quality, use, maintenance and care) of OSHA's Respiratory Protection Standard (29 CFR 1910.134) adopted in 1971. The seventh section was a direct, complete incorporation of ANSI Standard K13.1-1969, “Identification of Gas Mask Canisters.” The Agency promulgated an initial respiratory protection standard for the construction industry (29 CFR 1926.103) in April 1971. On February 9, 1979, OSHA formally applied 29 CFR 1910.134 to the construction industry (44 FR 8577). Federal agencies that preceded OSHA developed the original maritime respiratory protection standards in the 1960s (e.g., Section 41 of the Longshore and Harbor Worker Compensation Act). The section designations adopted by OSHA for these standards, and their original promulgation dates, are: Shipyards—29 CFR 1915.82, February 20, 1960 (25 FR 1543); Marine Terminals—29 CFR 1917.82, March 27, 1964 (29 FR 4052); and Longshoring—29 CFR 1918.102, February 20, 1960 (25 FR 1565). OSHA incorporated 29 CFR 1910.134 by reference into its Marine Terminal standards (Part 1917) on July 5, 1983 (48 FR 30909). The Agency updated and strengthened its Longshoring and Marine Terminal standards in 1996 and 2000, and these standards now incorporate 29 CFR 1910.134 by reference. Under the Respiratory Protection Standard that OSHA initially adopted, employers were required to follow the guidance of the Z88.2-1969 ANSI standard to ensure proper selection of respirators. Subsequently, OSHA published an Advance Notice of Proposed Rulemaking (“ANPR”) to revise the Respiratory Protection Standard on May 14, 1982 (47 FR 20803). Part of the impetus for this notice was the Agency's inclusion of new respirator requirements in the comprehensive substance-specific standards promulgated under section (6)(b) of the OSH Act, e.g., fit testing protocols, respirator selection tables with assigned protection factors, use of PAPRs, changing filter elements whenever an employee detected an increase in breathing resistance, and referring employees with breathing difficulties, either at fit testing or during routine respirator use, to a physician trained in pulmonary medicine (see, e.g., 29 CFR 1910.1025 (OSHA's Lead Standard)). The respirator provisions in these substance-specific standards reflected advances in respirator technology and changes in related guidance documents that were state-of-the-art information at the time when OSHA published these substance-specific standards. These standards recognized that effective respirator use depends on a comprehensive respiratory protection program that includes the use of APFs. In the 1982 ANPR, OSHA sought information on the effectiveness of its current Respiratory Protection Standard, the need to revise the standard, and recommendations regarding what revisions should be made. The 1982 ANPR referenced the ANSI Z88.2-1980 standard on respiratory protection with its table of protection factors, the 1976 report by Ed Hyatt from LASL titled “Respiratory Protection Factors” (Ex. 2), and the RDL developed jointly by OSHA and NIOSH, as revised in 1978 (Ex. 9, Docket No. H049). The 1982 ANPR asked for comments on how OSHA should use protection factors. The Agency received 81 responses to this inquiry. The commenters generally supported revising OSHA's Respiratory Protection Standard, and provided recommendations regarding approaches for including a table of protection factors (Ex. 15). On September 17, 1985, OSHA announced the availability of a preliminary draft of the proposed Respiratory Protection Standard. This preproposal draft standard included a discussion of the public comments received in response to the 1982 ANPR, and OSHA's analysis of revisions needed in the Respiratory Protection Standard to address up-to-date respiratory protection. The Agency received 56 responses from interested parties (Ex. 36), which OSHA carefully reviewed in developing the proposed rule. On November 15, 1994, OSHA published the proposed rule to revise 29 CFR 1910.134, and provided notice of an informal public hearing on the proposal (59 FR 58884). The Agency convened the informal public hearing on June 6, 1995. In response to the comments OSHA received on the proposal, the Agency proceeded to develop APFs. On June 15, 1995, as part of the public hearing, OSHA held a one-day panel discussion by respirator experts on APFs. The discussion included measuring respirator performance in WPF and SWPF studies, the variability of data from these studies, and setting APFs for various types of respirators that protect employees across a wide variety of workplaces and exposure conditions. OSHA also reopened the rulemaking record for the revised Respiratory Protection Standard on November 7, 1995 (60 FR 56127), requesting comments on a study performed for OSHA by Dr. Mark Nicas titled “The Analysis of Workplace Protection Factor Data and Derivation of Assigned Protection Factors” (Ex. 1-156). This study, which the Agency placed in the rulemaking docket on September 20, 1995, addressed the use of statistical modeling for determining respirator APFs. OSHA received 12 comments on the Nicas report. This report, and the comments received in response to it, convinced OSHA that more information would be necessary before the Agency could resolve the complex issues regarding how to establish APFs, including what methodology to use in analyzing existing protection factor studies. (See Section IV. Methodology for Developing Assigned Protection Factors in the June 6, 2003 NPRM, 68 FR 34044, for a detailed discussion of the Nicas report and the comments OSHA received.) OSHA published the final, revised Respiratory Protection Standard, 29 CFR 1910.134, on January 8, 1998 (63 FR 1152). The standard contains worksite-specific requirements for program administration, procedures for respirator selection, employee training, fit testing, medical evaluation, respirator use, and other provisions. However, OSHA reserved the sections of the final standard related to APFs and MUCs pending further rulemaking (see 63 FR 1182 and 1203). The Agency stated that, until a future rulemaking on APFs is completed: [Employers must] take the best available information into account in selecting respirators. As it did under the previous [Respiratory Protection] standard, OSHA itself will continue to refer to the [APFs in the 1987 NIOSH RDL] in cases where it has not made a different determination in a substance specific standard. (63 FR 1163) The Agency subsequently established a separate docket (i.e., H049C) for the APF rulemaking. This docket includes copies of material related to APFs that previously were placed in the docket (H049) for the revised Respiratory Protection Standard. The APF rulemaking docket also contains other APF-related materials, studies, and data that OSHA obtained after it promulgated the final Respiratory Protection Standard in 1998. On June 6, 2003, the Agency published in the Federal Register an NPRM titled “Assigned Protection Factors; Proposed Rule” (68 FR 34036) that contained proposed definitions for APFs and MUCs, a proposed Table 1 with APFs for the various respirator classes, and proposed revisions to the APF provisions and tables in OSHA's substance-specific standards. The NPRM announced that OSHA would be holding an informal public hearing in Washington, DC on the proposal. The public hearings were held over three days, from January 28-30, 2004. OSHA received extensive pre-hearing comments (Exs. 9-1 through 9-43 and 10-1 through 10-60), written hearing testimony (Exs. 16-1 through 16-25), post-hearing comments (Exs. 17-1 through 17-12), and post-hearing briefs (Exs. 18-1 through 18-9 and 19-1 through 19-8). Transcripts of the public hearings also were made and added to the APF Docket (Exs. 16-23-1, 16-23-2, and 16-23-3). It is from these public comments, exhibits, hearing transcript, and post-hearing submissions that OSHA has prepared these final APF and MUC provisions and revisions to substance-specific standards. B. Non-Regulatory History of APFs In 1965, the Bureau of Mines published “Respirator Approval Schedule 21B,” which contained the term “protection factor” as part of its approval process for half mask respirators (for protection up to 10 times the TLV) and full facepiece respirators (for protection up to 100 times the TLV). The Bureau of Mines based these protection factors on quantitative fit tests, using DOP, that were conducted on six male test subjects performing simulated work exercises. The Atomic Energy Commission (AEC) published proposed protection factors for respirators in 1967, but later withdrew them because quantitative fit testing studies, which the AEC used to determine APFs, were available for some, but not all, types of respirators. To address this shortcoming, the AEC sponsored respirator performance studies at LASL, starting in 1969. ANSI standard Z88.2-1969, which OSHA adopted by reference in 1971, did not contain APFs for respirator selection. Nevertheless, this ANSI standard recommended that “due consideration be given to potential inward leakage in selecting devices,” and contained a list of the various respirators grouped according to the expected quantity of leakage into the facepiece during routine use. In 1972, NIOSH and the Bureau of Mines published new approval schedules for respiratory protection under 30 CFR 11. However, these new approval schedules did not include provisions for determining facepiece leakage as part of the respirator certification process. NIOSH sponsored additional respirator studies at LASL, beginning in 1971, that used quantitative test systems to measure the overall performance of respirators. In a 1976 report titled “Respirator Protection Factors”, Edwin C. Hyatt of LASL included a table of protection factors for: single-use dust respirators; quarter mask, half mask, and full facepiece air-purifying respirators; and SCBAs (Ex. 2). Hyatt based these protection factors on data from DOP and sodium chloride quantitative fit test studies performed at LASL on these respirators between 1970 and 1973. The table also contained recommended protection factors for respirators that had no performance test data. Hyatt based these recommended protection factors on the judgment and experience of LASL researchers, as well as extrapolations from available facepiece leakage data for similar respirators. For example, Hyatt assumed that performance data for SCBAs operated in the pressure-demand mode could be used to represent other (non-tested) respirators that maintain positive pressure in the facepiece, hood, helmet, or suit during inhalation. In addition, Hyatt recommended in his report that NIOSH continue testing the performance of respirators that lacked adequate fit test data. To increase the database, Hyatt used a representative 35-person test panel to conduct quantitative fit tests from 1974 to 1978 on all air-purifying particulate respirators approved by the Bureau of Mines and NIOSH. In August 1975, the Joint NIOSH-OSHA Standards Completion Program published the RDL (Ex. 25-4, Appendix F, Docket No. H049). The RDL contained a table of protection factors that were based on quantitative fit testing performed at LASL and elsewhere, as well as the expert judgment of the RDL authors. In 1978, NIOSH updated the RDL specifying the following protection factors: 5 for single-use respirators; 10 for half mask respirators with DFM or HEPA filters; 50 for full facepiece air-purifying respirators with HEPA filters or chemical cartridges; 1,000 for PAPRs with HEPA filters; 1,000 for half mask SARs operated in the pressure-demand mode; 2,000 for full facepiece SARs operated in the pressure-demand mode; and 10,000 for full facepiece SCBAs operated in the pressure-demand mode. ANSI's Respiratory Protection Subcommittee (“Subcommittee”) decided to revise Z88.2-1969 in the late 1970s. During its deliberations, the Subcommittee conducted an extensive discussion regarding the role of respirator protection factors in an effective respiratory protection program. As a result, the Subcommittee decided to add an APF table to the revised standard. In May 1980, ANSI published the revision as Z88.2-1980 which contained the first ANSI Z88.2 respirator protection factor table (Ex. 10, Docket H049). The ANSI Subcommittee based the table on Hyatt's protection factors, which it updated using results from fit testing studies performed at LANL and elsewhere since 1973. For example, the protection factor for full facepiece air-purifying particulate respirators was 100 when qualitatively fit tested, or 1,000 when equipped with HEPA filters and quantitatively fit tested. The table consistently gave higher protection factors to tight-fitting facepiece respirators when employers performed quantitative fit testing rather than qualitative fit testing. The ANSI Subcommittee concluded that PAPRs (with any respiratory inlet covering), atmosphere-supplied respirators (in either a continuous flow or pressure-demand mode), and pressure-demand SCBAs required no fit testing because they operated in a positive-pressure mode. ANSI assigned high protection factors to these respirators, but limited their use to concentrations below the IDLH values. Pressure-demand SCBAs and combination continuous flow or pressure-demand airline respirators with escape provisions for use in IDLH atmospheres were assigned protection factors of 10,000 plus. In response to a complaint to NIOSH that the PAPRs used in a workplace did not appear to provide the expected protection factor of 1,000, Myers and Peach of NIOSH conducted a WPF study during silica-bagging operations. Myers and Peach tested half mask and full facepiece PAPRs under these conditions, and found protection factors that ranged from 16 to 215. They published the results of their study in 1983 (Ex.1-64-46). The results of this study led NIOSH and other researchers, as well as respirator manufacturers, to perform additional WPF studies on PAPRs and other respirators. NIOSH revised its RDL in 1987 (Ex. 1-54-437Q) to address advances in respirator technology and testing. The revision retained many of the provisions of the 1978 RDL, but also lowered the APFs for other respirators based on NIOSH's WPF studies. For example, the APFs were lowered for the following respirator classes: PAPRs with a loose-fitting hood or helmet (reduced to 25); PAPRs with a tight-fitting facepiece and a HEPA filter (lowered to 50); supplied-air continuous flow hoods or helmets (decreased to 25); and supplied-air continuous flow tight-fitting facepiece respirators (reduced to 50). In August 1992, ANSI again revised its Z88.2 Respiratory Protection Standard (Ex. 1-50). The ANSI Z88.2-1992 standard contained a revised APF table, based on the Z88.2 Subcommittee's review of available protection factor studies. In a report describing the revised standard (Ex. 1-64-423), Nelson, Wilmes, and daRoza described the rationale used by the ANSI Subcommittee in setting APFs: If WPF studies were available, they formed the basis for the [APF] number assigned. If no such studies were available, then laboratory studies, design analogies, and other information [were] used to decide what value to place in the table. In all cases where the assigned protection factor changed when compared to the 1980 standard, the assigned number is lower in the 1992 standard. In addition, the 1992 ANSI Z.88.2 standard abandoned ANSI's 1980 practice of giving increased protection factors to some respirators when quantitative fit testing was performed. Thomas Nelson, the co-chair of the ANSI Z88.2-1992 Subcommittee, published a second report entitled “The Assigned Protection Factor According to ANSI” (Ex. 135) four years after the Z88.2 Subcommittee completed the revised 1992 standard. In the report, Nelson reviewed the reasoning used by the ANSI Subcommittee in setting the 1992 ANSI APFs. Nelson noted that the Z88.2 Subcommittee gave an APF of 10 to all half mask air-purifying respirators, including quarter mask, elastomeric, and disposable respirators. The Subcommittee also recommended that full facepiece air-purifying respirators retain an APF of 100 (from the 1980 ANSI standard) because no new data were available to justify another value. Nelson noted that the Z88.2 Subcommittee approved the RDL's reduction to an APF of 25 for loose-fitting facepieces and PAPRs with helmets or hoods based on their performance in WPF studies. For half mask PAPRs, the ANSI Subcommittee set an APF of 50 based on a WPF study by Lenhart (Ex. 1-64-42). The ANSI Subcommittee had no WPF data available for full facepiece PAPRs, so Nelson indicated that the Subcommittee selected an APF of 1,000 to be consistent with the APF for PAPRs with helmets or hoods. The Subcommittee, in turn, based its APF of 1,000 for PAPRs with helmets or hoods on design similarities (i.e., same facepiece designs, operation at the same airflow rates) between these respirators and airline respirators. Nelson noted that the results from a subsequent WPF report by Keys (Ex. 1-64-40) on PAPRs with helmets or hoods were consistent with an APF of 1,000. According to Nelson, the Subcommittee used WPF studies by Myers (Exs. 1-64-47 and 1-64-48), Gosselink (Ex. 1-64-23), and Que Hee and Lawrence (Ex. 1-64-60) to set an APF of 25 for PAPRs with loose-fitting facepieces. Nelson stated that two WPF studies, conducted by Gaboury and Burd (Ex. 1-64-24) and Stokes (Ex. 1-64-66) subsequent to publication of ANSI Z88.2-1992, supported the APF of 25 selected by the Subcommittee for PAPRs with loose-fitting facepieces. Nelson also stated in his report that the ANSI Subcommittee had no new information on atmosphere-supplying respirators. Therefore, the APFs for these respirators were based on analogies with other similarly designed respirators (Ex. 135). The ANSI Subcommittee based the APF of 50 for half mask continuous flow atmosphere-supplying respirators, and the APF of 25 for loose-fitting continuous flow atmosphere-supplying respirators, on the similarities between these respirators and PAPRs with the same airflow rates. Nelson noted that the ANSI Subcommittee set the APF of 1,000 for full facepiece continuous flow atmosphere-supplying respirators consistent with the APF for SARs with helmets or hoods using the results of two earlier studies: a WPF study by Johnson (Ex. 1-64-36) and a SWPF study by Skaggs (Ex. 1-38-3). The Subcommittee used the design analogy between PAPRs and continuous flow supplied-air respirators to select the APF of 50 for half mask pressure-demand SARs and an APF of 1,000 for full facepiece pressure-demand SARs. Nelson stated, “The committee believed that setting a higher APF because of the pressure-demand feature was not warranted, but rather that the total airflow was critical” (Ex. 135). Nelson noted in the report that the Subcommittee selected no APF for SCBAs. In explaining the committee's decision, he stated that “the performance of this type of respirator may not be as good as previously measured in quantitative fit test chambers.” Nelson also observed that the ANSI Z88.2-1992 standard justified this approach in a footnote to the APF table. The footnote states: A limited number of recent simulated workplace studies concluded that all users may not achieve protection factors of 10,000. Based on [these] limited data, a definitive assigned protection factor could not be listed for positive pressure SCBAs. For emergency planning purposes where hazardous concentrations can be estimated, an assigned protection factor of no higher than 10,000 should be used. A new ANSI Z88.2 Subcommittee recently finished revising the ANSI Z88.2-1992 standard, in accordance with the ANSI policy specifying that each standard receive a periodic review. This revised ANSI Z88.2 standard is currently under appeal to the ANSI Board. C. Need for APFs When OSHA published the final Respiratory Protection Standard in January 1998, it noted that the revised standard was to “serve as a ‘building block’ standard with respect to future standards that may contain respiratory protection requirements” (63 FR 1265). OSHA's final Respiratory Protection Standard established the minimum elements of a comprehensive program that are necessary to ensure effective performance of a respirator. The only parts missing from this building block standard are the APF and MUC provisions that are being finalized in this rulemaking. In the standard the Agency recommended that employers in the interim “take the best information into account in selecting respirators. As it did under the previous standard, OSHA itself will continue to refer to the NIOSH APFs in cases where it has not made specific compliance interpretations” (63 FR 1203). In October 2004, NIOSH published its Respirator Selection Logic (RSL), an update of the 1987 RDL. The APF tables in the new RSL have not changed from those in the 1987 RDL. However, NIOSH stated in the forward to the 2004 RSL: “[w]hen the OSHA standard on APFs is finalized NIOSH intends to consider revisions to this RSL.” (Ex. 20-4.) The ANSI Z88.2-1992 APF table also has been a source for interim APFs while OSHA completed its APF rulemaking. However, the ANSI Z88.2-1992 respiratory protection standard was withdrawn by ANSI in 2003. While a revised ANSI Z88.2 standard has been written, the final ANSI standard has yet to be published since it is currently under appeal. Therefore, no ANSI respiratory protection standard with recommended APFs is available at this time. The draft APF table from the ANSI Z88.2 revision was submitted to the OSHA rulemaking docket (Ex.13-7-2), and was the subject of discussion during the public hearings on APFs. OSHA considered the draft ANSI table during its deliberations in this rulemaking. Throughout the Respiratory Protection Standard rulemaking, OSHA has emphasized that the APF and MUC definitions and the APF table are an integral part of the overall standard. A careful review of the submitted comments and information supports the Agency's conclusion that this final standard is necessary to guide employers in selecting the appropriate class of respirator needed to reduce hazardous exposures to acceptable levels. The final APF for a class of respirators specifies the workplace level of protection that a class of respirator should provide under an effective respiratory protection program. In addition, the APFs can be utilized by employers to determine a respirator's MUC for a particular chemical exposure situation. The final APFs must be used in conjunction with the existing provisions of the Respiratory Protection Standard. Integration of the final APF and MUC provisions into the reserved provisions of paragraph (d) completes that standard. With the addition of these provisions, appropriate implementation of the Respiratory Protection Standard by employers in their workplaces should afford each affected employee the maximum level of respiratory protection. III. Methodology for Developing APFs for Respirators A. Introduction In the proposed rule for Assigned Protection Factors (APFs), OSHA raised a number of issues or questions about its proposed methodology for deriving APFs (68 FR 34112-34113). OSHA asked for information on: (1) The evidence-based method used by OSHA in developing the proposed APFs; (2) any additional studies that may be useful in determining APFs that were not already identified by OSHA in the proposal; and, (3) statistical analyses, treatments, or approaches, other than those described in the proposal, available for differentiating between, or comparing, the respirator performance data. The vast majority of the comments in response to the NPRM addressed the use of WPF studies for establishing the APF for filtering facepiece half mask respirators. OSHA also received comments on the methodology and data it used for determining the filtering facepiece APF, and was provided with new studies on these respirators for consideration. OSHA's quantitative analyses for establishing the APFs for other classes of higher performing respirators drew little comment, and no new studies on these respirators were submitted. This section, therefore, focuses on methodology and new information relative to the APF for half mask air-purifying respirators. More specifically, Part C of this section contains a discussion of the comments about OSHA's proposed methodology for determining APFs for filtering facepiece half mask respirators, including comments on data analysis and study selection. In addition, OSHA is providing an overview of Dr. Kenny Crump's statistical analyses (Ex. 20-1) of the updated half mask database (Ex. 20-2). Comments about alternative approaches are discussed in Part D (“Methodology, Data, and Studies on Filtering Facepieces and Elastomerics”). The Agency's overall conclusions on methodology, and summaries of new studies submitted during the public comment process, are presented under Part E. Discussion of the comments and opinions regarding the APF for half mask respirators and the establishment of the APFs for higher performing respirators is included in Section VI, Summary and Explanation of the Final Standard. B. Background The Occupational Safety and Health Act of 1970 (“OSH Act”), 29 U.S.C. 651-678, enacted to ensure safe and healthy working conditions for employees, empowers OSHA to promulgate standards and provides overall guidance on how these standards are to be developed. It states: (5) The Secretary, in promulgating standards dealing with toxic materials or harmful physical agents under this subsection, shall set the standard which most adequately assures, to the extent feasible, on the basis of the best available evidence, that no employee will suffer material impairment of health or functional capacity even if such employee has regular exposure to the hazard dealt with by such standard for the period of his working life. Development of standards under this subsection shall be based upon research, demonstrations, experiments, and such other information as may be appropriate. In addition to the attainment of the highest degree of health and safety protection for the employee, other considerations shall be the latest available scientific data in the field, the feasibility of the standards, and experience gained under this and other health and safety laws. Whenever practicable, the standard promulgated shall be expressed in terms of objective criteria and of the performance desired. 29 U.S.C. 655(b)(5) [emphasis added]. A reviewing court will uphold standards set under this section when they are supported by substantial evidence in the record considered as a whole (29 U.S.C. 655(f)). In searching for the “best available evidence” upon which to base its rulemaking, OSHA is required to “identify the relevant factual evidence, * * * to state candidly any assumptions on which it relies, and to present its reasons for rejecting any significant contrary evidence or argument.” Public Citizen Health Research Group v. Tyson , 796 F.2d 1479, 1495 (D.C. Cir. 1986). OSHA has retained the multifaceted approach it used in the proposal to determine the APFs for classes of respirators. That is, the Agency reviewed all of the available literature, including the various analyses by respirator authorities, as well as quantitative analyses of data from WPF and SWPF studies. During revision of the overall Respiratory Protection Standard, the Agency used a similar approach when reviewing protection factor studies related to the effectiveness and necessity of a comprehensive respiratory protection program. The Agency did not use Effective Protection Factor (EPF) and Program Protection Factor (PPF) studies in its APF analyses since these measure deficiencies in respirator program practices. More specifically, EPFs are not directly comparable to WPF values because the determinations include the time spent in contaminated atmospheres both with and without respiratory protection. PPFs are affected by any deficient elements of a respirator program, including inadequate respirator selection and maintenance, poor user training and motivation, work activities, and inadequate program administration. Therefore, OSHA relied on WPF and SWPF studies, since they focus on the performance characteristics of the respirator only. During the APF rulemaking, OSHA reviewed the extensive literature on APFs and developed selection criteria for including studies and data in its quantitative analysis of respirator performance. This procedure ensured that only carefully designed and executed WPF and SWPF studies were included in the analysis. The Agency then used these studies to compile the NPRM's original database. The database was comprised of 917 data points from 16 WPF studies for half mask respirators (Matrix 1) and 443 data points from 13 studies for PAPRs and SARs (Matrix 2), conducted in a variety of American workplaces. OSHA made the studies, its selection criteria, the data, and its analyses available to the public electronically and through the rulemaking docket. In addition, the Agency encouraged the public to access this information and to reanalyze the data using methods of their choice. The Agency also sought submissions from the public of any additional studies for inclusion in its database. Four additional WPF studies of half masks were submitted during the public comment period following publication of the NPRM. Dr. Kenny Crump updated the Matrix 1 half mask database with these additional studies (Ex. 20-2) and reanalyzed the resulting 1,339 data points for half mask respirators (Ex. 20-1). Dr. Crump also performed a second quantitative analysis in which the 1,339 accepted data points (original NPRM database updated with data from the four new studies) for half mask respirators were combined with 403 data points from 12 studies that the Agency originally excluded from the analysis. This second analysis corroborated the original findings to the extent practicable. The results of both of these analyses provide compelling support of OSHA's conclusions regarding the appropriate APF for half mask respirators. The Agency believes that the database it constructed represents the best available data on APFs, and that its conclusions are based on substantial evidence. See Texas Independent Ginners' Association v. Marshall , 630 F.2d 398, 413 n. 48 (5th Cir. 1980), citing Industrial Union Dept., AFL-CIO-CIC v. American petroleum Institute , 448 U.S. 607, 661 (1980). In past rulemakings, OSHA's conclusions as to the best available evidence have been upheld as based on substantial evidence when it has relied on a body of reputable scientific evidence. See ASARCO v. Occupational Safety and Health Administration , 746 F.2d 483, 494 (9th Cir. 1984). OSHA need not accept all data presented to it as long it considers the data and rejects it on reasonable grounds. See id . Furthermore, each study relied upon by the Agency need not be a model of textbook scientific inquiry, and OSHA need not find one definitive study supporting its decision. Public Citizen Health Research Group , 796 F.2d at 1489, 1495. Rather, the Agency is justified in adopting a conclusion when the cumulative evidence is compelling. Id . at 1489, 1491, 1495. OSHA's conclusions are strongest when it has relied on multiple data sources that support each other, as it has in this rulemaking. C. Methodology, Data, and Studies on Filtering Facepieces and Elastomerics 1. Comments on the Methodology OSHA developed the proposed APFs through a multi-faceted approach. As it stated in the preamble to the proposal, “The Agency reviewed the various analyses of respirator authorities, available WPF and SWPF studies, and other APF literature.” It later concluded that “the APFs proposed by OSHA in this rulemaking represent the Agency's evaluation of all available data and research literature i.e., a composite evaluation of all relevant quantitative and qualitative information” (68 FR 34050). OSHA then asked the public if this method was appropriate to determine APFs. The methodology was supported by a number of commenters, including NIOSH (Ex. 9-13), the Department of the Army (Ex. 9-42), ALCOA (Ex. 10-31), and others (e.g., Exs. 9-1, 9-4, 9-14, 9-16, 9-22, 10-2, 10-17, 10-18, and 10-59). NIOSH stated: NIOSH agrees that the APF values resulting from this multi-faceted approach are reasonable indications of the level of protection that should be expected for each class of respirators. * * * The available data are not ideal because there can be considerable model-to-model variation and only a few models in each class have been evaluated. Given that lack of complete data, the approach taken by OSHA is the most appropriate currently possible. (Ex. 9-13.) The United States Army Center for Health Promotion and Preventive Medicine commented: The method of APF development used by OSHA is appropriate. OSHA reviewed available data, both published and unpublished; utilized technical reviews and summaries from subject matter experts outside-OSHA; weighed study findings and conclusions based on study shortfalls, as then state-of-the-art technical bias and procedural omissions; and used a conservative approach to maintain confidence that minimal risk of respirator selection and use errors will exist in worker protection from proposed APF use. (Ex. 9-42-1.) Nevertheless, some commenters did not agree with OSHA's approach. These participants included several labor organizations (Exs. 9-27, 9-29, 9-34, 9-40, and 10-37), trade associations (Exs. 9-24 and 10-27), and individuals (e.g., Exs. 9-17, 9-25, 9-33, 9-41, 10-33, and 10-42). Criticisms of OSHA's approach focused on the Agency's selection of WPF studies for its determination of the proposed APFs. Reasons given to support these criticisms included: The differences between the studies do not permit comparison of the studies; the study conditions are not representative of typical workplaces; the study data are too old; the data do not cover all configurations of filtering facepieces available; and, the analytical method employed by some studies was too sensitive. A few commenters (Exs. 10-34 and 10-47) recommended that certain criteria should be met before a WPF study is deemed acceptable for analysis. These criteria include: Exposures to small particle sizes; work time of at least four hours; moderate to heavy work rate; and, high temperature and humidity. Still others believed that OSHA should develop and perform SWPFs on a representative subset of all filtering facepieces or all configurations of filtering facepiece respirators and all respirator models, and establish APFs for all classes of respirators based on the SWPF study results (Exs. 9-41 and 10-27). A more detailed discussion of data issues is presented below. 2. Comments on Data and Study Problems Selection bias in WPF studies . Several commenters stated that the authors of WPF studies “cherry-picked” either the workplaces in which the studies were conducted or the individual tasks that were performed by workers chosen for monitoring (Pascarella, Tr. at 464; Faulkner, Tr. at 549 and 564-565). “Cherry-picking” is a common term for “selection bias.” Selection bias is a matter of concern when either workplace study participants or job tasks are selected for inclusion in the study in a manner that skews the results of the study away from the true value. Selection bias is a matter of concern for all scientific studies, not just WPF studies, and peer reviewers typically evaluate its effects before a study is accepted for publication in a peer-reviewed journal. Most of the studies included in OSHA's analysis of WPF studies were either published in peer-reviewed journals or were presented at the AIHCE, and met the criteria for respirator research studies accepted by the industrial hygiene community. The half mask database consists of 16 studies performed in a variety of workplaces over a range of years (from 1976 to 2004) by many different researchers. Therefore, it is highly improbable that these studies were subject to selection bias. OSHA could find no instance of selection bias either in its review of the scientific studies or its analysis of the data. Finally, OSHA repeatedly asked commenters who raised concerns about “cherry-picking” for specific studies in which selection bias occurred. In no case did the commenters provide any details to support their allegations. Observer effect in WPF studies . Several commenters (Shine, Tr. at 644 and Macaluso, Tr. at 652) stated that data from the WPF studies considered by OSHA were the result of a condition known as the “observer effect.” The observer effect occurs when the act of observing or monitoring test subjects causes their responses to differ from their usual (nonobserved) responses. In some of the WPF studies used by OSHA, the researchers stated that during the study, they were present to monitor the test equipment to ensure that the sampling equipment functioned properly, thereby increasing the usefulness of the results. In other WPF studies, the researchers did not indicate their presence during the study. The mere presence of an observer does not, in and of itself, presume that there will be an observer effect. For example, if the observer is a researcher who is monitoring the test equipment instead of a supervisor who is monitoring the workers' practices, the workers are unlikely to change their practices. Although the Agency repeatedly asked the commenters who raised this concern to identify specific studies in which the observer effect may have been involved, they could not do so (i.e., in no case did the commenters provide any example to support their allegations). In its own analysis of the WPF studies, the Agency was also unable to find any evidence of an observer bias. Representativeness of the data. A number of commenters expressed concern that the study data analyzed by OSHA were not representative of conditions found in the construction industry (Ex. 9-29, Building Construction Trades Department), or of workplace conditions in general (e.g., Exs. 9-34, International Union Operating Engineers; 9-35, Melissa Rich; 9-40, United Steel Workers of America; and 10-60, Paul Hewett). The bulk of these concerns are represented in the comments of Melissa Rich, a Department of Energy respirator program manager, who stated: The selection of the test sites for the cited APF proposed rulemaking WPF studies are not representative of the worksite for American workers. Many test sites chosen for these studies were selected on availability only. Moreover, key study attributes such as hot humid conditions, long work hours, and heavy workload were the exception, not the norm for most of the cited studies. Most test sites had ambient concentrations less than the OSHA half mask respirator maximum use limit (i.e., ten times the PEL). The various particle sizes, a critical issue in a WPF, cited in many of the APF proposed rule Workplace Protection Factor studies are so large that they do not penetrate the faceseal. Many respiratory protection studies have indicated that particles larger than two microns are less likely to penetrate the most important attribute of a respirator, the faceseal. Most of the APF proposed rule Workplace Protection Factor studies have a particle size greater than two microns. (Ex. 9-35.) The studies analyzed by OSHA consisted of a varied cross-section of workplaces and conditions. For example, workplaces included ship breaking, asbestos removal, aluminum and lead smelters, brass foundries, and aircraft painting and manufacturing. Two of the four new studies analyzed by OSHA involved concrete-block manufacturing. The authors of an aluminum smelter study (Ex. 1-64-24) noted that employees were required to rest in a cool area for 50% of each hour due to high heat, and a steel mill study (Ex. 1-64-50) and a primary lead smelter study (Ex. 1-64-42) both were conducted in the sinter plant and blast furnace areas. The asbestos study (Ex. 1-64-54) was conducted under high humidity conditions. Tasks performed by test subjects included welding and grinding, torch cutting, pouring molten metal, handling concrete blocks, and spray painting. Work rates for these studies, when provided, ranged from low to heavy. The purpose of a WPF study is to evaluate a respirator's effectiveness under actual workplace use conditions. Consequently, the contaminant concentrations and particle sizes contained in the analyzed studies were generated while the workers performed their normal job duties. With regard to concerns about particle size, Myers et al. (Ex.1-64-51) found particles larger than 10 microns inside the respirator facepiece. The Agency believes that accepting only WPF studies that are conducted at exposure levels close to 10 times the PEL, with particulates of two microns in size or less, would not be representative of the conditions found in the workplace. Studies based on such selective criteria would be more akin to a SWPF, rather than a WPF, study. OSHA has concluded that the data used in its analyses are applicable to other American work settings because a range of work rates and environmental conditions were represented, and many of the tasks performed by the test subjects are performed in a variety of workplaces, including construction. Accordingly, the Agency is not persuaded by comments suggesting that the studies were so narrowly focused that the data cannot be applied to other work settings. Sensitive analytical method. Several commenters questioned the use of sensitive analytical methods for the analyses of workplace exposures, sometimes accompanied by a recommendation to test respirators under controlled laboratory settings, and at sufficiently high concentrations to obtain inside-the-facepiece measurements (Ci) that can be assessed by less sensitive methods (e.g., Exs. 9-32, 9-35, 10-6, 10-37, and 10-49). The commenters believed that sensitive analytical methods (particularly PIXEA, proton-induced x-ray emission analysis) permit the determination of low Ci concentrations, resulting in high protection factors. In response to these comments, OSHA reviewed the seven half mask studies that used the PIXEA analytical method (Exs. 1-64-19, 1-64-51, 1-64-52, 1-64-15, 1-64-16, and 1-64-34) and found that six of the studies used the method to measure both the Ci and Co concentrations. The seventh study (Ex. 3-12) used PIXEA to measure the Ci concentration but used atomic absorption (AA) to assess Co concentrations because the respirator filters were overloaded. However, the Agency does not believe that this study provided inaccurate results. Under conditions of high Co concentrations, the AA method must be used because the PIXEA method would exceed its maximum measurement limits. Therefore, the PIXEA method would be unable to provide accurate Co data. Based on its review of these seven studies, the Agency found that the sensitive analytical method (i.e., PIXEA) allowed the investigators to quantify small amounts of contaminant that penetrate a respirator. This method permitted accurate assessment of Ci concentrations under conditions of low ambient concentrations, thereby permitting the use of actual Ci values in determining WPFs. Less sensitive methods would result in penetration values that are nondetectable or less than the limit of detection (LOD) for the analytic method, thereby requiring the study to discard these data or to correct for nondetected values using unvalidated statistical techniques. On the other hand, the sensitive analytical method was able to quantify low Ci concentrations, thereby enhancing the validity of the subsequent analysis by retaining the actual data and avoiding unvalidated statistical corrections. Craig Colton of 3M provided the following testimony in support of OSHA's conclusions: Some commenters also asserted that the use of analytical methods with low detection limits are a reason to invalidate some of the WPF studies. The claim is erroneously made that the analytical sensitivity affects the results from WPF studies. However, the actual amount of contaminant on the Ci sample is not changed by the analytical method. * * * Because the [Ci levels are] typically very small in a WPF study, the higher sensitivity of [the PIXEA method] is necessary to get the best data. * * * The WPF protocol from the AIHA Respirator Committee recommended the use of analytical methods with sensitive detection limits. * * * Use of less sensitive analytical methods for * * * [Ci] sample[s] that result in nondetect values are not meaningful for determining true exposure. (Tr. at 413-414.) In its post-hearing comments, 3M illustrated the value of sensitive analytical methods using the following example: [C]onsider three filters “spiked with 1 μg of silicon each and analyzed by three different methods [gravimetric, atomic absorption (AA), and PIXEA]. In the case of gravimetric and AA analyses, it is certain only that the silicon mass on the filter is between 0 μg and 10 [μg] or 0 μg and 5 μg respectively. However, PIXE[A] has sufficient analytical sensitivity to “find” the true value of 1 μg. Because the mass of contaminants on a Ci filter is typically very small in a WPF study, the higher sensitivity of PIXE[A] is necessary to get the best data. (Ex. 19-3-1.) Tom Nelson commented that “[t]he analytical method must be sensitive for a WPF study. For a half facepiece respirator[,] the detection limit should be at least 1/100 of the ambient concentration” (Ex. 18-9). Later in these comments, Nelson stated, “The [low-concentration Ci] samples are part of the distribution of WPF samples collected during a study. These represent true measures of performance.” Based on the evidence in the record, OSHA concludes that using sensitive analytic methods for assessing Ci samples is both necessary and appropriate. Specifically, the Agency sees no scientific basis for excluding WPF studies that used PIXEA, particularly when using the method to determine both Ci and Co. The Agency's review of the record evidence shows that a leading national organization representing industrial hygienists (i.e., the AIHA) recommends using sensitive analytic methods for assessing Ci samples. Furthermore, using sensitive analytic methods improves significantly the validity of data analyses by allowing studies to retain low Ci values, and by reducing substantially the need to use unvalidated techniques to correct low Ci values. Therefore, OSHA concludes that the data from the WPF studies used in its analyses are accurate, and that the availability of data with low Ci values improved the validity of the APFs derived from these analyses. Large particles. Several commenters (e.g., Exs. 9-33, 9-35, 10-6, 10-37, and 10-41) postulated that larger particles (greater than one or two microns) do not penetrate a respirator's faceseal. They believed that WPF studies having large particles in the Co concentration should be excluded from OSHA's analyses. They reasoned that these large particles were being measured as part of the Co but had no chance of being measured in the Ci, and consequently were inflating the WPF values. These commenters appear to be ignoring the possibility that half masks (both elastomerics and filtering facepieces) with faceseals that selectively filter large particles still are capable of providing an adequate level of protection. Nevertheless, OSHA notes that in one of the WPF studies used in OSHA's data analyses, Myers et al. found large particles (i.e., 10 microns in diameter) inside the facepiece, indicating that large particles are capable of penetrating a respirator faceseal (Ex. 1-64-51). Consistent with these results, Tom Nelson stated in his comments that “[t]he particle size of contaminants in the various WPF studies in the docket range from [about] 0.5 [microns] to 14 [microns] MMAD,” and that “particles much larger than those that would be predicted from laboratory studies have been found inside the facepiece in WPF studies” (Ex. 18-9). At the hearing, Nelson presented data showing that large particles enter half mask respirators, probably through breaks in the faceseal; moreover, these data demonstrate that no relationship exists between particle size and the WPF obtained for the respirator (Tr. at 146-148). The 3M Company addressed this point further, stating in its comments: Laboratory studies have shown that particle losses occur through fixed leaks. A faceseal leak is not accurately represented by a fixed leak, however. To perform these studies[,] assumptions were made regarding leak size, shape, and the particle size penetrating those leaks. These assumptions have been shown to be wrong. Myers has shown that large particles can be found inside the facepiece[,] much larger than could have occurred with the fixed leaks used by several researchers.[] As shown in Figure 1 [of the Myers et al. study], an analysis of particle size and the geometric mean WPF from a number of studies does not show any relationship between particle size and WPF. If the size of the particle played a role in faceseal leaks, a relationship would be evident. (Ex. 9-16.) Based on the evidence in the record, OSHA concludes that the data in its APF analyses for half masks were the same as particle sizes found in the workplaces represented in the WPF studies. Therefore, eliminating the study data from the Agency's analyses would be unnecessary and inappropriate. Probe bias. Probe bias refers to the misplacement of the sampling probe when taking measurements inside the respirator facepiece. Some commenters expressed concern that probe bias may have underestimated Ci in the half mask WPF studies analyzed by Dr. Brown (e.g., Exs. 9-17, 9-30, 9-35, and 10-42). These commenters suggested that OSHA reanalyze its database after applying a correction factor to account for probe bias. Tim Roberts provided a specific description of this concern when he testified: Respirator probe error is an issue. It's been better characterized for elastomeric type respirators than it has for filtering facepiece respirators, and we think that this needs some additional work as well, to characterize what that means when we put probes in different locations in elastomeric facepieces (Tr. at 208). Later in the hearings, Ching-tsen Bien questioned Craig Colton of 3M on Colton's experiences with probe location while conducting filtering facepiece WPF studies. Colton responded: [S]treamlining that you see is similar to that in the elastomeric half-facepieces. You see it streamlining from the leak up to the mouth and nose. And so what Dr. Myers indicated in his sampling bias—not really probe bias, but the sampling bias—was that location becomes important because if your probe is flushed with the facepiece, you can miss the streamlines. So his recommendation was that the probe needs to be ideally on the midline, between the mouth and the nose, and as close to the face as possible. And so that's what we attempt to do as best as you can with the products you end up testing to meet his recommendations. (Tr. at 455-456.) Colton also noted that, although some of his studies may show probes entering the side of the filtering facepiece, a probe extension was used to place the sampling inlet in the nose-mouth area (Tr. at 455-456). Tom Nelson explained the purpose of the probe location when he commented, “The sampling probe is placed so that it is close to the nose and mouth. This minimizes sampling bias” (Ex. 18-9). Warren Myers testified that, in unusual circumstances, the configuration of a half mask (including some elastomerics) requires placing the sampling probe on the side of the mask instead of the centerline between the nose and the mouth; in these cases, a study can control for sampling bias by randomly alternating the location of the probe on the right and left side of the mask (Tr. at 77). OSHA also reviewed the 13 half mask studies analyzed by Dr. Brown. The authors of nine of these studies specifically state that the probe was located in the area of the nose and mouth. While the remaining four studies do not specify the probe's location, no evidence from this rulemaking indicates that the sampling probes were inappropriately placed. Therefore, the majority of the WPF studies, along with the new studies included in the updated database, located the sampling probe in the nose-mouth area. Of the 1,339 data points in the updated database, approximately 220 of these points (about 16%) are from the four studies in which no information on probe placement was available. OSHA believes the sampling methodology that was used in these studies was consistent with comments indicating that the optimum location for a probe is at the centerline between the nose and the mouth. At this location, the probe will sample any streamlining that occurs between a faceseal leak and the nose-mouth area, thereby detecting the maximum Ci exposure level. In addition, no analysis was submitted indicating that the data from these studies, whether corrected for probe bias or excluded altogether, would have resulted in APFs that differed from the final APFs derived from this rulemaking. 3. Summary and Conclusion OSHA considered the comments addressing the data and study problems identified by commenters, but does not find that these comments merit rejection of the data or analyses. The studies OSHA analyzed were conducted on employees in actual workplaces who were performing their normal job duties. Consequently, the particle sizes, work rates, work times, and environmental conditions varied among these studies. The Agency has concluded that using data collected under these various conditions presents a more accurate picture of workplace use of these respirators and is a better measure of the protection provided by half mask respirators than data collected only from SWPF or other highly controlled studies. D. Alternative Approaches 1. Alternatives Based on Non-Compliant Respirator Programs Several commenters suggested alternative means for ascertaining APFs. While not completely disagreeing with OSHA's approach, Paul Hewett of Exposure Assessment Solutions Incorporated (Ex. 10-60) stated that OSHA should include EPF studies in its APF deliberations. He commented that EPF studies account for actual use conditions in that they factor in the time that the employee does not wear the respirator but is still exposed to atmospheric contaminants. He also believed that determination of an appropriate APF should represent respirator use in hot, strenuous jobs. Therefore, he recommended that “OSHA should factor in real world conditions and not rely exclusively on WPF and particularly SWPF studies” (Ex. 10-60.) OSHA noted in the proposal that the Agency would analyze only WPF and SWPF studies since they address respirator performance exclusively (68 FR 34045). This alternative approach already has been addressed above by the Agency in its discussion of the usefulness of WPF data. The Agency has no data in the record showing that EPF studies would improve, or even complement, its analyses. Therefore, OSHA is not convinced that EPF data would increase the validity of the APFs derived in this final rule. The discussion of an EPF study by Harris et al. (Ex. 27-11; 63 FR 1167) substantiates these conclusions. Ching-tsen Bien of LAO Consulting, Inc. (Ex. 18-5) wanted OSHA to enter into the record any available independent assessment reports (and applicable check lists) for the year prior to, and for the year of, each WPF study. Bien noted that the reports would have covered applicable program elements, and ensure that OSHA selected studies for its analyses that were in compliance with appropriate respiratory protection standards. He also requested that OSHA enter the “selection criteria, decision matrix for each study, and the review report for these studies to the H-049C Docket” (Ex. 18-5.) As stated in the NPRM at 68 FR 34046, the Agency evaluated all studies used in its analyses for compliance with the requirements of OSHA's Respiratory Protection Standard (29 CFR 1910.134), as well as for completeness of the data. The Agency also compiled a list of criteria (Ex. 5-5) for evaluating each study. Accordingly, OSHA evaluated each published article or each written study report to determine whether the test subjects were trained properly, fit tested, medically evaluated, and in compliance with the requirements of the OSHA Respiratory Protection Standard. The researchers performing these WPF studies ensured that fit testing was performed on the test subjects, trained them on doffing and donning the respirator, as well as the performance of user seal checks, on the selection of proper-sized respirators, and on the other elements of a complete OSHA-compliant respirator program. These researchers did not rely on the existing workplace respirator program, but instead performed the necessary actions to ensure that the test subjects in their WPF studies met the respirator program requirements. The WPF studies the Agency evaluated were either WPF studies that had been published previously, or were newly performed studies that were submitted during the rulemaking for inclusion in the OSHA database. OSHA did not perform these studies, and was not involved in the selection of the worksites being tested. Therefore, the Agency could not gather additional information on a worksite's respirator program that was in effect when a WPF study was performed, as Bien requested. Additionally, such information is irrelevant to the results of a WPF study since the researchers had to demonstrate compliance with the required respirator program before OSHA included the study in its database. 2. Alternatives Based on SWPF Studies The American Chemistry Council (Ex. 10-25) stated that OSHA's APFs should be based on SWPF studies, and that the APFs derived from this rulemaking should be used only as interim values until SWPF studies could be performed. OSHA notes that basing APFs on SWPF studies, rather than on WPF studies, was recommended by a number of commenters including Organizational Resource Counselors Worldwide (ORC) (Ex. 10-27), Paper, Allied-Industrial, Chemical & Energy Workers International Union (PACE) (Ex. 10-37), and others (e.g., Exs. 9-32, 9-41, 10-6, 10-49, 9-33, 9-35, and 18-5). These commenters expressed various concerns about the WPF studies, and stated that SWPF studies permit investigators to control a number of variables (e.g., particle size, contaminant concentration, environmental conditions) that cannot be controlled in WPF studies. SWPF studies use sensitive analytical methods, such as PIXEA, to obtain measurable Ci information. SWPF studies safely test a respirator in a high-concentration atmosphere (i.e., at the respirator's limit of protection) to generate enough penetration for the analytical method to quantify Ci results. OSHA agrees that SWPF testing permits an investigator to control factors such as particle size, contaminant concentration, temperature, and humidity. Accordingly, the Agency used data generated from all available SWPF studies in determining APFs. However, OSHA concluded that controlled SWPF studies alone are not representative of, nor can they be extrapolated readily to, typical workplaces. Standardized protocols for conducting such testing, or a methodology for extrapolating SWPF results to protection levels expected in the workplace, are not available. ORC stated, “We advocate development of a protocol based on a combination of laboratory testing and field trials for determining expected respirator performance” (Ex. 10-27). NIOSH also supported the use of both SWPF and WPF studies, noting, “NIOSH agrees that the APF values resulting from OSHA's multifaceted approach to analysis of existing data provide reasonable values for the level of protection that should be expected for each class of respirators” (Tr. at 102). NIOSH continued, “Given this lack of complete data, the noted model-to-model variation and the imperfection in protection level measurements, the approach taken by OSHA is the best currently possible based upon available data” (Tr. at 103). The Agency has concluded that its approach in using both WPF and SWPF studies is well supported by the rulemaking record and is appropriate for determining APFs specified in this final rule. 3. Model-Specific APFs The Organization Resources Counselors Worldwide (Ex. 10-27), the American Chemistry Council (Ex. 10-25), and the Pharmaceutical Research and Manufacturers of America (Ex. 9-24) urged OSHA to develop model-specific APFs. Under this recommendation, each respirator model would undergo testing and be assigned a unique APF. NIOSH did not support this approach. In response to questioning by OSHA, NIOSH stated: This morning's expert witnesses and the questions I think clearly identified that there is variability, and because of this variability, we believe that class APFs are more appropriate and consistent with the state of the art today. In order to achieve more precise data, much, much larger data sets, including the numbers of test subjects that would have to be involved to eliminate this variability, seems impractical based upon the state of the art today. So we are for these reasons supporting class APFs, not model-specific APFs. (Tr. at 120.) OSHA considered the use of SWPF studies in developing model-specific APFs. The Agency's review of the ORC SWPF study of PAPRs and SARs in the proposal (68 FR 34069) stated that ORC had recommended that “the [ORC SWPF] study methodology should be the basis for determining APFs for all respiratory protective equipment regulated by OSHA” (68 FR 34070). However, only a few SWPF studies are available that measured the performance of a few PAPRs and SARs. Model-specific SWPF studies for the remaining respirator classes have not been performed. In addition, the respirator protection community has not agreed on a standard protocol for conducting SWPF studies, or how the results relate to APFs. These issues would have to be addressed before it would be possible to use model-specific APFs. Also, insufficient data are available to set model-specific APFs, and developing the methodology and conducting the testing could take years. OSHA believes that completing the APF rulemaking with the information available now is necessary. Delaying this rulemaking to develop model-specific APFs will result in employers not knowing what respirators to select and, consequently, employees will not receive adequate protection. Based on the rulemaking record, the Agency has concluded it will determine an APF for each respirator class using information from existing WPF and SWPF studies. 4. Nicas-Neuhaus Model Several commenters (Paul Hewett, Ex. 10-60; Bill Kojola, AFL-CIO, Ex. 17-2; and NIOSH, Ex. 17-7-1) asked OSHA to consider a February 2004 article by Nicas and Neuhaus (Ex. 17-7-2) that applies a model for analyzing WPF data to establish APFs. The Nicas-Neuhaus article is based on the variability of WPFs (i.e., the variability between different test subjects, as well as the variability within a test subject resulting from repeated donnings of the respirator). APFs based on this Nicas-Neuhaus model require that WPFs for 95% of all workers be above the APF 95% of the time. However, the established method for deriving APFs used by OSHA, NIOSH, and ANSI sets the APFs at the 95% percentile of the between-subject WPFs. By controlling for within-subject variability, APFs based on the Nicas-Neuhaus model will always be smaller than APFs derived using the established method. To account for within-subject variability, the Nicas-Neuhaus model requires repeated measurements on each test subject which is not required by the established method. Consequently, most available WPF studies did not include multiple measures on individual test subjects, resulting in an extremely limited database for applying the Nicas-Neuhaus model. Nicas and Neuhaus were able to analyze only seven half mask respirator studies, comprising a total of 310 data pairs. In comparison, the database established and analyzed by OSHA for determining the final APFs contains 1,339 data pairs from 16 half mask respirator studies. Also, OSHA had rejected for its analyses several of the WPF studies used by Nicas and Neuhaus in developing their model because these studies did not meet the Agency's selection criteria. The Nicas-Neuhaus model is a significant departure from established and accepted practices used by the respirator research community, The Agency has concluded that there are insufficient data to fully evaluate the proposed model, and to incorporate it in setting APFs. 5. Other Alternative Approaches Sheldon Coleman recommended that OSHA select a panel from AIHA members to review the APF data and OSHA's APF determinations (Ex.10-40). OSHA believes this rulemaking has provided ample opportunity for comment from the public and professional associations. Further analysis would delay the development of the final APFs, and is unnecessary as the rulemaking record is sufficient to determine APFs. 6. Summary and Conclusion OSHA is relying on science, data, and established quantitative analyses to establish the final APFs for filtering facepiece and elastomeric half mask respirators, and is limiting its statistical analyses to those procedures that use the selected data to the fullest extent possible. Reliance on alternative approaches is not supported by the evidence in the record. The data to use such approaches are not currently available, and require either a different set of data or a standardized testing protocol that requires testing every respirator model. OSHA concludes that the available data and analytic methods used in determining the final APFs are appropriate. E. Updated Analyses 1. Review of the Original WPF and SWPF Databases In developing its proposed rule regarding APFs for respirators, OSHA contracted with Dr. Kenneth Brown to investigate possible approaches for evaluating respirator performance data from WPF and SWPF studies. To assist Dr. Brown in this evaluation, the Agency reviewed the available studies and created a database from these studies. In deciding which WPF studies to include in this database, OSHA evaluated studies with respect to compliance with the requirements of its Respiratory Protection Standard (29 CFR 1910.134) and the completeness of the data. In doing so, the Agency excluded WPF studies of gas or vapor contaminants due to the limited number of these studies and the difficulties in conducting and interpreting data from such studies (68 FR 34046). During the rulemaking, OSHA received new WPF data on half mask respirators. No new SWPF data were submitted for half masks, and no new WPF data were submitted for higher-performing respirators. In the NPRM, Dr. Brown initially divided negative pressure half mask air-purifying respirators (APRs) into five classes. Four classes of filtering facepiece half masks were derived based on whether a respirator had adjustable head straps, an exhalation valve, a double-shell construction, or a foam-ring faceseal. Elastomeric half masks were grouped together in a single fifth class. (See Ex. 5-1 for details on respirator class definitions.) In his analyses, Dr. Brown found no clear evidence of a difference in WPFs across these different classes. In particular, he found that elastomeric half masks performed substantially the same as filtering facepieces. From the original database of 917 WPF measurements for negative pressure half mask APRs, 36 WPF measurements (3.9%) were found to have an APF less than 10, and 96.1% at 10 and above. 2. Updated OSHA Database on APRs In the NPRM, OSHA asked if any more WPF or SWPF studies should be considered in setting APFs. Data from four additional studies were submitted for OSHA's evaluation during the comment period, and an updated half mask database was compiled using these studies (Ex. 20-2). During the post-hearing comment period, the 3M Company provided OSHA with data from two additional WPF studies of filtering facepiece respirators. One study (Colton and Bidwell, Ex. 9-16-1-1) measured the performance of three different types of filtering facepiece respirators used by 21 workers at a lead-battery manufacturing plant. One respirator (3M 8710) was approved under 30 CFR part 11, and two respirators were N95 particulate respirators (3M 8210 and 3M 8510) approved under 42 CFR part 84. Up to three WPF measurements were made with each worker on each respirator type, for a total of 143 WPF measurements. The data submitted to OSHA from this study are provided in Appendix A of Dr. Crump's report on the reanalysis of the half mask database (Ex. 20-1). The second set of WPF data provided by 3M Company was from a study by Bidwell and Janssen (Ex. 9-16) on the performance of a “flat-fold” filtering facepiece respirator conducted at a concrete-block manufacturing facility. Repeated measurements of WPFs were made on 19 workers, and each sample was analyzed for both silicon and calcium. A total of 73 Co and 73 Ci air samples were collected, for a total of 146 WPF measurements. Eleven of the 146 Ci measurements were non-detectable (all coming from silicon exposures). The third study added to the database was a WPF study by Colton (Ex. 4-10-4) on the performance of an elastomeric half mask respirator. This study had been submitted earlier to OSHA, but was not included in the NPRM database since it was received too late for inclusion in Dr. Brown's original analysis. The data from this study, conducted in the battery-pasting and assembly areas of a battery manufacturing plant, have now been added to OSHA's updated database. Also, three additional data points from a study by Myers and Zhuang (Exs. 1-64-50 and 3-14) were added to the updated database. These data were collected in a concrete-block facility while elastomeric half mask respirators were worn as protection against calcium and silicon particulates. The updated OSHA half mask database (Ex. 20-2), summarized in Table III-1, contains 1,339 WPF measurements—760 collected from filtering facepiece respirators, and 579 from elastomeric respirators. The database originally analyzed by Dr. Brown contained 917 WPF measurements—471 from filtering facepieces, and 446 from elastomerics. Table III-1.—Summary of OSHA WPF Database for APRs Respirator class Figure 1 No. Constituent sampled Author Exhibit No. Number samples per study Number samples per class Filtering Facepiece Respirators 1 1 Asbestos Dixon 1-64-54 26 474 1 2 Fe Myers 1-64-50, 3-14 21 1 3 Mn Wallis 1-64-70 69 1 4 Al Colton 1-64-15 23 1 5 Al Johnston 1-64-34 13 1 6 Si Johnston 1-64-34 15 1 7 Ti Johnston 1-64-34 18 1 8 Pb Colton & Bidwell 9-16-1-1 143 1 9 Si Bidwell & Janssen 9-16 73 1 10 Ca Bidwell & Janssen 9-16 73 3 11 Pb Myers 1-64-51, 3-12 19 162 3 12 Zn Myers 1-64-51, 3-12 20 3 13 Fe Colton 1-146 31 3 14 Mn Colton 1-146 32 3 15 Ti Colton 1-146 28 3 16 Zn Colton 1-146 32 4 17 Pb Colton 1-64-16 62 124 4 18 Zn Colton 1-64-16 62 Elastomeric Respirators 5 19 Asbestos Dixon 1-64-54 46 579 5 20 B(a)Pyrene Gaboury 1-64-24 18 5 21 Pb Lenhart 1-64-42 25 5 22 Pb Myers 1-64-51, 3-12 46 5 23 Zn Myers 1-64-51, 3-12 46 5 24 Fe Myers 1-64-50, 3-14 30 5 25 Cr Myers 1-64-52, 4-5 35 5 26 Ti Myers 1-64-52, 4-5 33 5 27 Cd Colton 1-64-13 68 5 28 Pb Colton 1-64-13 57 5 29 Pb Dixon & Nelson 1-64-19 42 5 30 Pb Colton 4-10-4 130 5 31 Calcium Myers 1-64-50, 3-14 3 Grand Total 1339 3. Variability of the APF Data Several commenters (Faulkner, Ex. 9-40 and Kojola, Ex. 9-27) criticized WPF studies because the studies demonstrated what they considered to be a high degree of variability of the data. However, it is inappropriate to describe the variability of the data with terms such as “high” or “low” because no recognized standard exists by which to characterize variability. The variability of the data should reflect the true variability in respirator fit and performance experienced by workers who wear respirators. It is reasonable to expect variability because respirator performance is determined by many factors, including: Respirator type, the workers' face shapes, work practices and effort levels, and workplace conditions such as temperature and humidity. Thus, the key issue is not whether the data have too much or too little variability, but whether the variability in the data reflects the true variability in respirator performance under actual workplace conditions. A logarithmic transformation was applied to the WPF data set to adjust for a skewed distribution and extreme outliers, both of which are common with ratio-based data. As Figure III-1 shows, when a logarithmic transformation is applied to OSHA's WPF database, the data closely follow a standard normal distribution. Therefore, OSHA's analysis of the data, which assumes that WPFs are log-normally distributed with a geometric mean of 307 and a geometric standard deviation of 7.1, appropriately accounts for the variability in the WPF data. EP24AU06.000 4. Analysis of Updated Database on APRs OSHA proposed an APF of 10 for negative pressure half mask APRs, including both filtering facepieces and elastomerics (68 FR 34096). Accordingly, the present analysis focuses on estimating this APF, particularly the percent of WPFs that are less than 10. Figure III-2 displays the 1,339 WPF values, grouped by respirator class, 1 study, and contaminant. Each column of data points in the figure corresponds to a row number listed in column 2 of Table III-1. This figure shows that more WPFs for elastomerics are less than 10 than was the case for filtering facepieces, even though a much larger proportion of these WPFs are from filtering facepieces. 1 Includes four of the five classes originally determined in the analysis conducted for OSHA by Dr. Ken Brown; no data were available for Class 2. Dr. Brown characterized disposable half marks according to combinations of the following four design characteristics: (1) Adjustable head straps, (2) presence of an exhalation valve, (3) double shell construction, and (4) foam ring liner. Class 1 has none of the four design characteristics. Class 2 has design characteristics (1) and (3). Class 3 has design characteristics (1) through (3). Class 4 has all four of the design characteristics. Class 5 consists of all elastomeric half masks. EP24AU06.001 Figure III-2 also shows that differences exist between WPFs measured in different studies, even among respirators of the same type. For example, both the Colton (Ex. 1-64-15, #4 in Figure 2) and the Colton and Bidwell (Ex. 9-16-1-1, #8 in Figure 2) studies were conducted by some of the same investigators, and both studies used Class 1 filtering facepieces. Nevertheless, all but one of the 23 WPFs in the Colton study (Ex. 1-64-15) are less than 40, while all 143 of the WPFs from the Colton and Bidwell study (Ex. 9-16-1-1) are at least 58 or higher. However, the Colton study evaluated respirators approved under 30 CFR part 11, whereas the Colton and Bidwell study evaluated respirators approved under 42 CFR part 84. Table III-2 shows the percentages of WPFs less than 10 by respirator class, along with the 90% statistical confidence intervals on these percentages. The exact confidence intervals are based on a binomial distribution for counts. The percentage of WPFs less than 10 is less than 5% for all four classes, and the 90% statistical confidence interval on this percentage excludes 5% for every class except elastomerics. Also, elastomerics had the highest percentage of WPFs less than 10 (4.5%). Over all classes, 38/1339, or 2.8%, of WPFs were less than 10 (90% confidence interval: 2.1%, 3.7%). The upper bound of this two-sided 90% confidence interval, 3.7%, is equivalent to a one-sided 95% upper statistical confidence bound on the true proportion of WPFs less than 10. This bound may be interpreted as follows: assuming the database is representative of workplace WPFs in general (more specifically, that the data approximate a random sample of WPFs from all workers who use respirators), when the true proportion of WPFs less than 10 is 3.7%, the probability of observing 2.8% or less (the observed percentage) would be 1 − 0.95 = 0.05. Thus, under these assumptions, it is unlikely that the true proportion of WPFs less than 10 is as high as 3.7% (and extremely unlikely to be as high as 5%). Table III-2.—Percent of WPFs Less Than 10 by Respirator Class Total n n < 10 Percent (90% Cl) Class 1 474 11 2.3 (1.3%, 3.8%) Class 3 162 0 0.0 (0.0%, 1.8%) Class 4 124 1 0.8 (0.0%, 3.8%) Class 1-4 (Filtering Facepieces) 760 12 1.6 (0.9%, 2.5%) Class 5 (Elastomerics) 579 26 4.5 (3.2%, 6.2%) Total 1339 38 2.8 (2.1%, 3.7%) In the earlier database analyzed by Dr. Brown, 3.9% of the WPFs were less than 10. By comparison, among the 422 WPFs added to the database, only 2/422 (0.5%) were less than 10. Thus, the new data indicate a higher level of protection by APRs. In addition to the 1,339 WPFs in the updated OSHA database, an additional 403 WPFs from 12 studies were coded by OSHA but were not included in either the present database or the one analyzed by Dr. Brown. These data were omitted for various reasons, including too few WPF measurements in a study and problems with the quality of the studies (i.e., study did not meet requirements of OSHA's Respiratory Protection Standard). In addition, as noted earlier, OSHA did not include data from studies in which exposures were predominantly to a gas or vapor. To determine the effect that excluding these data had on the results in Table III-2, the 403 WPFs were added to the updated data base of 1,339 WPFs (for a total of 1,742 WPFs), and the overall fraction of WPFs less than 10 was computed (Table III-3). The percent of WPFs less than 10 was 4.0% (90% confidence interval: 3.2%, 4.8%). Thus, even with no data exclusions, the overall percent of WPFs smaller than 10 is less than 5%, and the 95% statistical upper confidence bound is also less than 5% (i.e., 4.8%). Table III-3.—Comparison of Percent of WPFs Less Than 10 in Studies Used and Not Used by OSHA Total n n < 10 Percent (90% Cl) Used 1339 38 2.8 (2.1%, 3.7%) Unused 403 31 7.7 (5.6%, 10.2%) Both Used and Unused 1742 69 4.0 (3.2%, 4.8%) Consistent with the WPF studies used in its analysis, OSHA adopted the point estimate of the lower 5th percentile of WPF or SWPF data to establish APFs. Table III-4 shows the point estimate of the 5th percentiles of WPFs for different categories of respirators using the updated database. The 5th percentile of WPFs for filtering facepieces as a whole was 18.1, and for elastomerics it was 12.0. In both cases, the point estimate was above the APF of 10 proposed by OSHA. Since several commenters expressed concern about whether sufficient evidence is available to support an APF of 10 for filtering facepieces, OSHA also calculated 90% confidence intervals for each point estimate. (As noted earlier, the lower limit estimate of a two-sided 90% confidence interval is equivalent to a one-sided 95% lower confidence bound.) The lower 95% confidence bounds for the 5th percentile of WPFs exceeded 10 for all classes combined, and, with the exception of elastomerics, for each individual class. The confidence limits for the 5th percentiles were computed using the method for distribution-free confidence intervals of Hahn and Meeker (1991), as implemented in SAS (2001). Therefore, OSHA concludes that sufficient statistical evidence is available to justify an APF of at least 10 for filtering facepieces. Table III-4.—Fifth Percentiles of WPFs by Respirator Class 5th percentile (90% Cl) Class 1 14.8 (12, 18) Class 3 19.7 (15, 24) Class 4 27.0 (22, 49) Class 1-4 (Filtering Facepieces) 18.1 (15, 22) Class 5 (Elastomerics) 12.0 (7, 14) Total 14.7 (13, 18) 5. Comparison of Respirators Approved Under 30 CFR Part 11 Versus 42 CFR Part 84 Several commenters expressed concern that the majority of WPF and SWPF studies were conducted on respirators certified by NIOSH under requirements in 30 CFR 11, instead of the newer NIOSH certification procedure described in 42 CFR 84. While these commenters did not explain the basis of their concern, two major studies were submitted that examined the performance of 42 CFR 84-approved respirators. The 3M study by Colton and Bidwell (Ex. 9-16-1-1) evaluated one respirator approved under 30 CFR 11, and two respirators approved under 42 CFR 84. In this study, WPFs were measured on up to nine different occasions for 21 workers (143 total measurements), 17 of whom used each type of respirator on at least one occasion, with none of them using the same type respirator on more than three occasions. Thus, this study provides an opportunity for comparing the performance of respirators approved under the two standards. Table III-5 shows the performance of these three respirators using three methods: the proportion of samples with Ci non-detects, the distribution of the 30 smallest WPF values among the three respirators, and the geometric mean of WPFs. The two 42 CFR 84-approved respirators performed similarly with each of these methods, and they both performed better than the 30 CFR 11-approved respirator (see Table III-5). Table III-5.—Performance of the 30 CFR Part 11 Respirator (3M 8710) and the 42 CFR Part 84 Respirators (3M 8511 and 3M 8210) Inside-the-mask non-detects Dist. of 30 smallest WPF WPF geometric means 1 3M 8710 5/49 15 792 3M 8511 23/47 7 2506 3M 8210 19/47 8 2405 1 Modeled assuming log-normal distribution with non-detects set at detectin limit. The geometric means of WPFs of the 42 CFR 84 respirators were similar (2506 and 2405), and were significantly (p < 0.0001) higher than the geometric mean of the 30 CFR 11 respirator (792). This comparison was made using a repeated measures analysis that accounted for dependence among different samples collected from the same worker, assumed log-normally distributed WPFs, and set non-detects at the detection limit (which should minimize differences between the two respirator types). All three respirators performed well in this study, with the smallest of the 143 WPFs being 52, well above the APF of 10 proposed by OSHA. When the 146 WPF measurements from the Bidwell and Janssen study (Ex. 9-16) (that assessed the 3M 9211 respirator approved under 42 CFR 84) are added to the 94 WPFs from the Colton and Bidwell study (Ex. 9-16-1-1), 240 WPFs in the OSHA database are from 42 CFR 84 respirators. None of these WPFs was less than 10 (0/240). This finding, along with the evidence that 42 CFR 84 respirators performed better than 30 CFR 11 respirators in the same study, suggests that the new filtering facepiece respirators certified under 42 CFR 84 may perform better than the respirators relied on by OSHA for its analyses, which consisted mainly of respirators approved under 30 CFR 11. Because the respirators approved under 42 CFR 84 outperformed those respirators approved under 30 CFR 11, which were adequately protective, OSHA is confident current workers will be well protected by the respirators approved under 42 CFR 84. 6. Methodology of Evaluating Overexposure Another method to assess the appropriateness of an APF is to determine whether an overexposure occurs (Ex. 10-17). The Agency reviewed relevant studies on this subject cited by several commenters (Exs. 9-16, 9-22, and 10-17-1) to determine if such an analysis would provide useful information on filtering facepiece and elastomeric half mask respirators. Two major studies (Exs. 9-16-1-9 and 4-21) address the likelihood that half mask respirators will not sufficiently reduce occupational exposures to airborne contaminants. In the first of these two studies (Nelson et al. , Ex. 9-16-1-9), the authors evaluated the risk of overexposure for selected APFs using Monte Carlo simulation modeling. For a half mask respirator with an APF of 10, the calculations indicated a low risk of being exposed above an occupational exposure limit (OEL), with mean exposures being controlled well below an OEL. In the second article by Drs. Myers and Zhuang (Ex. 4-21), ambient (Co) and in-facepiece exposure monitoring data (Ci) from studies of worker exposures in foundry, aircraft-painting, and steel-manufacturing industries were compared with the OSHA PEL for single-substance exposures. The 5th percentiles of the protection factor (Co/Ci) data from each study were calculated. The authors used a new binomial analysis of likelihood of successes (no overexposure) and failures (overexposures). Their calculations indicate, for both half mask elastomeric and filtering facepiece respirators, that the <5% of workers who fail to achieve an APF of 10 are still being protected. OSHA considered Nelson's analysis along with the findings of Myers and Zhuang when it conducted its own analysis. Accordingly, the Agency was persuaded to quantify the probability of overexposure by applying the Myers and Zhuang binomial analysis to OSHA's updated database. OSHA's expert, Dr. Gerry Wood, performed the analysis and presented his results in a report (Ex. 20-3) described below. The updated OSHA half mask database (Ex. 20-2) used in this analysis contains 1,339 WPFs from studies with both filtering facepiece half mask respirators (760 WPFs) and elastomeric half mask respirators with cartridge filters (579 WPFs). This database also contains Co and Ci measurements (expressed in μg/m 3 ), with asbestos fiber counts converted as follows: 1 fiber/cm 3 = 30 μg/m 3 ); these measurements permit binomial analysis of overexposure through calculation of hazard ratios (HR). The following 8-hour TWA PELs were used to calculate HR = Co/PEL for this study (see Table III-6). Table III-6.—8-Hour TWA PELs Used to Calculate the Hazard Ratios Analyte PEL (mg/m 3 ) Benzo(a)pyrene 0.2 Lead 0.05 Zinc 15 Iron 10 Chromium 0.5 Titanium 15 Manganese 5 Aluminum 15 Asbestos 0.003 (0.1 fiber/cm 3 ) Silica 10 Cadmium 0.005 Calcium 15 Values for individual WPFs then were plotted against HR as illustrated in the figures of the Myers and Zhuang reference (Ex. 4-21, Figure 1, page 798, and Figure 2, page 799). The same reference lines and labels were used, but the scales were expanded to include all data in the OSHA database. Figure 1 below shows the plot of all data for both filtering facepieces and elastomerics. The line labeled CD represents WPF = 10; 38 (2.8%) of the 1,339 data points fell below this line and five data points (0.37%) fell within the triangle defined by the letters ABK; Myers and Zhuang (Ex. 4-21) label this triangle as “Inadequate Protection, Overexposure,” which corresponds to the region in which Ci exceeds the PEL. EP24AU06.002 Figure 2 shows the same plot for studies using filtering facepieces only. Twelve data points (1.6%) are below the WPF = 10 line. Two of these twelve data points equal WPF = 10 when rounded off to the nearest whole number. Only 2 (0.26%) of the points are within the ABK overexposure region. The data point in the A corner (from a study by Colton (Ex. 1-64-16, CL4.15.Pb)) represents a Co just above the lead PEL (HR = 1.20) that, with a WPF = 1.15 (almost no protection), gave a Ci = 1.04 * PEL; this value represents an inside-the-mask exposure just barely higher than the PEL. The only other data point in the over-exposure region is from the asbestos (PEL-0.1 fiber/cm 3 ) study by Dixon (Ex. 1-64-54, CL1.2.Asb) which corresponds to HR = 77, WPF = 47, and a Ci = 1.6 * PEL, (or 0.16 fiber/cm 3 ). EP24AU06.003 If the MUC is defined as MUC = APF × PEL, and an APF = 10 is assumed, then data points in the triangle labeled AHE represent overexposures. With one data point in this triangle, filtering facepieces are 99.4% effective in protecting employees at an APF = 10 and an MUC = 10 × PEL (i.e., 160 of 161 data points in the AGFE area, with an HR ranging from 1 to 10, are outside the triangle (AHE) that represents diminished protection). Figure 3 shows the same plot for the elastomerics. Of these 579 data points, 26 (4.5%) fall below WPF = 10. Three data points (0.5%) in the ABK overexposure triangle are from an asbestos study by Dixon (Ex. 1-64-54, CL5.2.Abs). However, no data points of 265 in the AGFE area fall within the AHE triangle, indicating that all of these respirators provided protection at APF = 10 × PEL. EP24AU06.004 Figures 4 and 5 demonstrate that both filtering facepiece and elastomeric respirators maintain the level of employee protection found in Figures 2 and 3, even when the data are plotted using the higher PELs specified by the older OSHA asbestos standard (pre-August 1994) and cadmium standard (pre-April 1993). The combined data for both Figures 4 and 5 show that filtering facepieces had only one data point of 160 (with an HR ratio of 1 to 10) in the overexposure area (i.e., the AHE triangle), while none of the 241 data points for elastomeric respirators fell into this area. Therefore, Figures 4 and 5 and Figures 2 and 3 demonstrate that both filtering facepiece and elastomeric respirators afford employees effective protection against two different exposure levels of asbestos and cadmium. BILLING CODE 4510-26-P EP24AU06.005 BILLING CODE 4510-26-C 7. Summary of Quantitative Analyses of the Updated Database First, OSHA's database includes the best available data. As part of the APF rulemaking process, the Agency conducted a metaanalysis of data collected from numerous scientific studies related to APFs. OSHA established criteria that were used to evaluate each study's design and data quality to assure that the database included only the most valid data. The Agency, at each step in the rulemaking process, called on participants to identify additional studies to augment the dataset or to discuss alternative methods of analysis. In response, a number of commenters expressed these concerns about the data analysis: The statistical treatment minimized the true differences between elastomeric and filtering facepieces, and there was too much variability in the data. In all cases, concerns raised by commenters about the composition of the dataset used in the metaanalysis, or the statistical methods used to conduct the analyses, were unsubstantiated by evidence submitted to the record despite repeated requests by OSHA for either specific examples or additional evidence. Second, the best available data support an APF of 10 for half mask elastomerics and filtering facepieces. The final APF half mask database consists of 1,339 data points from 16 different studies, which represents a data increase of 46% over the 917 data points initially available for analysis in the proposal. The full data set indicates: (a) The precise APF for filtering facepieces is 18.1, with a 90% confidence interval between 15 and 22; (b) the precise APF for elastomerics is 12.0, with a 90% confidence interval between 7 and 14; and (c) that a greater percentage of elastomerics failed to achieve an APF of 10 (4.5%) than filtering facepieces (1.6%). In both cases, fewer than 5% of the respirators failed to achieve an APF of 10, which is the maximum failure rate historically allowed by both OSHA and other standards-setting bodies. Third, OSHA substantiated its previous analysis by adding to its updated database 403 data points that were excluded originally because they did not meet OSHA's selection criteria and reanalyzing the database. This additional analysis also supports an APF of 10 for both types of respirators, with the results being highly similar to the analysis based on the best-available data. Fourth, new studies submitted during the rulemaking allowed OSHA to compare the performance of similar respirators that were certified under both NIOSH's old (30 CFR 11) and new (42 CFR 84) certification standards. The 42 CFR 84 respirators achieved a WPF that was better than the 30 CFR 11 respirators. This finding is significant because the majority of the WPF studies, and the only studies in OSHA's original data set, were conducted on respirators certified under 30 CFR 11. Thus, the improved performance of 42 CFR 84 respirators indicates that these respirators are likely to be even more protective of worker health than an APF of 10 as provided for in the final rule. OSHA also addressed the issue of overexposure among workers. In doing so, it reviewed the respirator literature and performed an analysis of overexposure risk using filtering facepiece or elastomeric respirators. Based on this risk analysis, OSHA concluded that workers participating in effective respirator programs had an extremely low risk of overexposure. In conclusion, the extensive quantitative analyses of the databases clearly indicate that both filtering facepieces and elastomeric respirators are capable of achieving an APF of 10. The results demonstrate that no statistical justification exists for assigning an APF of less than 10 to either of these two types of respirators. Finally, the results show that an APF of 10 is an underestimate of the true protection provided by both types of respirators. Therefore, the final APF of 10 determined by this rulemaking provides employees who use respirators with an extra margin of safety against airborne contaminants. F. Summary of Studies Submitted During the Rulemaking 1. Additional Studies Used in the Updated Analyses OSHA found the studies discussed in this section to be of sufficient quality for inclusion in its APF analyses. Bidwell and Janssen study (Exs. 9-16-1-1 and 9-16). J. O. Bidwell and L. Janssen of 3M gave a presentation at the May 2003 American Industrial Hygiene Conference and Exposition (AIHCE) on a workplace protection factor study they performed in a concrete-block manufacturing plant with workers using a NIOSH-approved N95 flatfold filtering facepiece respirator. The filtering facepiece respirator tested was the 3M Particulate Respirator 9211, approved by NIOSH under the 42 CFR 84 respirator certification standards. The authors measured silicon and calcium exposures to 19 workers in the bagging and block-handling areas of the plant. In the bagging area, workers placed bags over cement-dust chutes for filling, and then transferred the bags to pallets. In the other areas of the plant sampled by the authors, workers handled concrete blocks, swept and shoveled dust and block pieces into containers, and cleaned out mullers with chipping tools. The workers were informed of the purpose and procedures of, and their role in, the study, and were provided with instructions on proper donning, fitting, and user seal check procedures, as well as respirator operation. In addition, the workers had to pass a Bitrex® qualitative fit test that followed the fit test protocol described in OSHA's Respiratory Protection Standard prior to study participation. They also had to be clean shaven. They were observed by the authors in the workplace on a one-on-one basis throughout the sampling periods. The inside-the-facepiece sampling train consisted of a 25-mm three-piece cassette with a 0.8-micron pore-size polycarbonate filter with porous plastic back-up pads for collecting the inside samples. For sampling purposes, a Liu probe was inserted opposite the mouth near the midline of the respirator. It projected one centimeter into the facepiece. The sampling cassette was attached directly to the probe, and a cassette heater was used to prevent condensation of moisture from exhaled breath. Outside-the-facepiece samples used a 25-mm three-piece cassette with a 0.8-micron pore-size mixed cellulose-ester filter. The outside sample cassette also was connected to a Liu probe, and this combination was attached in the worker's breathing zone. Inside samples and outside samples were collected at a flow rate of two liters per minute. Respirators were donned and doffed, and sampling trains started and stopped, in a clean area. Field blanks were used to evaluate for sample-handling contamination, and manufacturer blanks were collected to determine background contamination on the filters. The inside samples were analyzed using proton-induced X-ray emission analysis (PIXEA), and the outside samples were analyzed by inductively coupled plasma (ICP) spectroscopy. For both calcium and silicon, the authors presented the range of Co, Ci, and the associated geometric means and standard deviations. Three sets of WPF results were determined: One for calcium, a second for silicon, and a harmonic mean for the combined calcium and silicon samples. Silicon was not detected on eleven of the Ci samples. However, by using 70% of the limit of detection as the inside mass, the authors were able to include these samples in the statistical analysis. No field-blank adjustments were made (i.e., no calcium or silicon detected), and no mention is made of adjusting the data for pulmonary retention of particles. In addition, three sample sets were invalidated as a result of equipment and procedural problems. The authors reported a mean WPF of 152, with a 5th percentile of 13, for the calcium samples; a mean WPF of 394, with a 5th percentile of 34, for the silicon samples; and a harmonic mean of the calcium and silicon samples of 206, with a 5th percentile of 20. The authors noted a difference in the WPFs measured for calcium and silicon (using the same respirator), and discussed a number of possible reasons for the difference (e.g., random sampling and analytical errors, possible non-uniformity of the challenge aerosol over time). The authors concluded, “The estimated WPF for this respirator model based on this study exceeds the APF of 10 assigned to this respirator class by ANSI Z88.2-1992 and proposed by OSHA.” They also stated, “The respirator provided an adequate level of protection and reliably provided workplace protection factors of at least 10 when properly fitted, worn, and used” (Ex. 9-16, page 40). Colton and Bidwell study (Ex. 4-10-4). C. Colton and J. Bidwell of 3M made a presentation on May 25, 1995 at the AIHCE comparing the workplace performance of two different types of HEPA filters on an elastomeric half mask respirator in a battery manufacturing plant. The HEPA filters and the respirator model tested were approved under the 30 CFR 11 respirator certification standards. The half facepiece respirator tested was the 3M 7000, available in three sizes. The HEPA filters tested were the 3M 7255 high-efficiency (mechanical) filter and the 3M 2040 high efficiency (electret) filter. The authors measured lead exposures for 19 workers in the battery-pasting and assembly areas of the plant because these areas had the highest lead exposures. The workers were informed of the purpose and procedures of, and their role in, the study, and were provided with instructions on proper donning and fitting procedures, as well as respirator operation. In addition, the workers had to pass a saccharin qualitative fit test performed using the fit test protocol described in OSHA's Lead Standard. Workers had to be clean shaven. They were observed in the workplace by the authors on a one-on-one basis throughout the sampling periods. For sampling purposes, a Liu probe was inserted opposite the mouth near the midline of the respirator. It projected one centimeter into the facepiece. The sampling cassette was attached directly to the probe, and a cassette heater was used to prevent condensation of moisture from exhaled breath. A Liu probe was also attached to the outside sample to ensure that particle loss for the outside samples would be similar to that with the inside samples. Inside samples and outside samples were collected at a flow rate of two liters per minute, and sampling times ranged from 56 to 200 minutes. Up to four samples were collected per day on each worker, each worker was sampled for two days, field blanks were used, and care was taken to avoid handling contamination. The filter for the first day was assigned randomly, with a worker using one filter type on the first day and the second filter type on the second day. The inside- and outside-the-facepiece samples were analyzed for lead by ICP spectroscopy. The authors presented the range of outside and inside lead concentrations, and the associated geometric means and standard deviations. Two sets of WPF results were determined: One for the 3M 2040 filter and a second for the 3M 7255. A total of 140 samples were collected—one sample was eliminated due to low mass loading, 10 samples were lost due to equipment problems, and 85 samples had inside-sample mass values that were non-detectable. Of the remaining 44 samples, one outlier was identified in the electret filter data set, leaving 22 sets for the 3M 2040 filter and 21 sets for the 3M 7255 filter. No field blank adjustments were reported (i.e., no lead was detected on the field blanks). The authors reported a mean WPF of 562 and a 5th percentile of 71 for the 3M 2040 filter-respirator combination, and a mean WPF of 1006 and a 5th percentile of 80 for the 3M 7255 filter-respirator combination. When no lead was detected for the inside samples, the WPF results were recalculated using the detection limit to represent the mass for these samples. From these recalculations, the authors identified one outlier in the electret filter data set and two outliers in the mechanical filter data set. They then calculated geometric means, geometric standard deviations, and 5th percentile WPFs for the 67 samples for the 3M 2040 filter and for the 59 samples for the 3M 7255 filter. The authors reported a mean WPF of 420 and a 5th percentile of 101 for the 3M 2040 filter-respirator combination, and a mean WPF of 549 and a 5th percentile of 138 for the 3M 7255 filter-respirator combination. The authors concluded that the performance differences between the two filter types were not statistically significant. Both filters provided 5th percentile protection factors above 10. No WPFs were less than 30. Under these workplace conditions, no difference was found in the level of protection provided by the electrostatic HEPA filter compared to a mechanical HEPA filter. Colton and Bidwell study (Ex. 9-16). C. Colton and J. Bidwell of 3M presented a research paper at the May 1999 AIHCE on a WPF study they performed in a battery manufacturing plant with workers using three NIOSH-approved filtering facepiece respirators. The filtering facepiece respirators tested were the 3M 8210 and 3M 8511, approved by NIOSH under the 42 CFR 84 respirator certification standards, and the 3M 8710 filtering facepiece, approved by NIOSH under the 30 CFR 11 respirator certification standards. The authors measured lead exposures for 21 workers in the battery-manufacturing and assembly areas of the plant. The worker job classifications tested were stackers, heat sealers, burners, and assemblers. The workers were informed of the purpose and procedures of, and their role in, the study, and were provided with instructions on proper donning, fitting, and user seal check procedures, as well as respirator operation. In addition, the workers had to pass a Bitrex® qualitative fit test with all three respirators, and they had to be clean shaven. They were observed in the workplace by the authors on a one-on-one basis throughout the sampling periods. The sampling probe was a Liu probe that was inserted opposite the mouth near the midline of the respirator. It projected one centimeter into the facepiece. The sampling cassette was attached directly to the probe, and a cassette heater was used to prevent condensation of moisture from exhaled breath. Inside and outside samples were collected at a flow rate of two liters per minute for 79 to 159 minutes. Three samples were collected per day for each worker. Field blanks were used, and care was taken to avoid handling contamination. The inside samples were analyzed for lead using PIXEA. Outside samples were analyzed by ICP spectroscopy. The authors presented the range of outside and inside sample lead concentrations, and the associated geometric means and standard deviations for each respirator model tested. Three sets of WPF results were determined: One for the 3M 8710, a second for the 3M 8210, and a third for the 3M 8511. Lead was not detected on five of the inside samples for the 3M 8710, 19 for the 3M 8210, and 23 for the 3M 8511. No field blank adjustments were reported (i.e., no lead was detected on the field blanks). The authors reported a mean WPF of 730, with a 5th percentile of 105, for the 3M 8710 respirator; a mean WPF of 955, with a 5th percentile of 73, for the 3M 8210; an [Text truncated at 120,000 characters. The full text is on the page linked above.] --- Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A06-6942. Public record. Not legal advice.