OSHA Won't Add Shorter Bitrex Qualitative Fit Test

The test is "not sufficiently accurate to include among the qualitative fits tests listed in Part II of Appendix A of its Respiratory Protection Standard," the agency said in its Federal Register notice.

Part I to Appendix A of OSHA's Respiratory Protection Standard (29 CFR 1910.134) lists four qualitative fit testing protocols that use these challenge agents: Isoamyl acetate; saccharin-solution aerosol; Bitrex (denatonium benzoate) aerosol in solution; and irritant smoke (stannic chloride). The agency was considering adding a fifth -- an abbreviated Bitrex qualitative test that was submitted in a letter from Dr. Michael L. Runge of the 3M Company with a copy of "Development of an Abbreviated Qualitative Fit Test Using Bitter Aerosol," a peer-reviewed article published in the Fall/Winter 2003 issue of the Journal of the International Society for Respiratory Protection describing the accuracy and reliability of the test protocol. In a Federal Register notice today, OSHA announced it will not add the test at this time because it does not consider it sufficiently accurate.

The abbreviated test is a variation on the current Bitrex qualitative protocol, which 3M developed in the early 1990s and OSHA approved for inclusion in the standard. Both protocols use the same fit-testing requirements and instrumentation, except test subjects' exercise times are reduced from 60 seconds to 15 seconds and the abbreviated protocol is used only with test subjects who can taste the Bitrex screening solution within the first 10 squeezes of the nebulizer bulb (referred to as Level 1 sensitivity).

The study involved 43 experienced respirator users performing seven of the eight specified fit test exercises (normal breathing, deep breathing, turning the head side to side, moving the head up and down, reading a passage, bending over, and normal breathing) while wearing half-mask respirators equipped with P100 filters.

OSHA proposed to adopt the abbreviated protocol in December 2007 and asked for comments; 22 commenters, including NIOSH, which certifies protective respirators, and ISEA and the AFL-CIO, responded. Several commenters said the proposed protocol would not reliably assess proper fit for filtering-facepiece respirators because the authors did not include them in the study design, and some said the 15-second time would not allow some of the exercises to be completed. While OSHA answered these comments, it agreed with the AFL-CIO and other commenters who said OSHA should not sanction the binary logistic-regression analysis used by the paper's authors as an alternate method for analyzing the study results. No commenter supported using binary logistic-regression analysis to interpret the study results; "These comments clearly indicate that this analytic technique is currently inappropriate for use in determining the sensitivity of fit-testing protocols. OSHA agrees with these comments, and believes that the technique requires additional validation before it will be acceptable for this purpose," today's notice states.

"The test-sensitivity value of 0.92 would increase substantially the number of employees who would pass the proposed protocol with improperly fitting respirators, thereby making the proposed protocol unacceptable for listing in Part I.B. of Appendix A of OSHA's Respiratory Protection Standard," it states. "In addition, using binary logistic-regression analysis as a substitute for the sensitivity-test criterion in ANSI Z88.10-2001 is premature because the analysis requires additional validation."

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