© 2005, All rights reserved, Roy McKay, Ph.D.
In the January 2005 issue of Industrial Safety and Hygiene News the following question was asked to a group of experts in respiratory protection: “With so many types of respirators to choose from, how do I know my workers are wearing the proper respiratory protection?”. One expert incorrectly stated that once the contaminant is identified, the exposure levels of the respiratory hazards in the workplace must be determined by air sampling or monitoring. This is incorrect. The current respiratory protection standard requires a hazard evaluation, however, it does not require air sampling or monitoring. There are several methods that can be used to satisfy OSHA requirements for identifying and evaluating the respiratory hazards in the workplace without air sampling.
OSHA requires fit testing for filtering facepiece respirators (ie, disposable dust masks) when required to be worn, yet not everyone believes in the value of fit testing these respirators. In particular, cost conscious health care administrators question the need to fit test filtering facepieces. For example, at the recent CDC Workshop on Respiratory Protection for Infectious Agents (see below) health care administrators wanted proof that fit testing enhanced respirator performance. To those of us who routinely protect industrial workers from respiratory hazards, this seems to be a rather silly question.
However, respiratory protection is a new concept for many in the health care setting. Their unfamiliarity with respiratory protection makes them question nearly every aspect of what we have done for years.
Researchers are familiar with the published literature that support the need and benefits of fit testing. Recently, I reviewed a report prepared for the U.S. Department of Energy by the Pacific Northwest National Laboratory evaluating the performance of a filtering facepiece respirator. In this study dated July 2001, researchers concluded that a significant and sustained improvement in fit factor was observed after initial fit testing, indicating that respirator wearers benefited from the knowledge gained from previous fit testing. The initial learning experience was found to increase the performance (fit factor) for subsequent testing. In summary, these researchers concluded that quantitative fit testing of filtering facepiece respirators (dust masks) provided a valuable learning experience that improves respirator performance during future use.
While reviewing articles for our ongoing research
with filtering facepiece respirators, I came across an interesting article by
James Dosman and colleagues from the Centre for Agricultural Medicine (Chest:
Volume 118:852, 2000). Their study objective was to evaluate the protective
health effects of wearing a properly fitted N-95 filtering facepiece
(disposable) respirator while working in a swine confinement facility.
Measurements included lung function testing, methacholine challenge, blood
counts, nasal lavage, and cytokine counts from serum and nasal lavage fluid.
Negative acute health effects were demonstrated when respirators were not worn.
However, quantitatively
fit testing N-95 filtering facepiece respirators prevented the acute health
effects among subjects not previously exposed to a swine barn environment. In
summary, fit testing and wearing filtering facepieces can help protect workers
in this environment.
The 1998 revision to the OSHA respirator standard (1910.13) defines a Quantitative Fit Test (QNFT) as an assessment of the adequacy of respirator fit by numerically measuring the amount of leakage into the respirator. In comparison, OSHA defines a Qualitative Fit Test (QLFT) as a pass/fail fit test to assess the adequacy of respirator fit that relies on the individual’s response to the test agent. OSHA accepted quantitative fit tests include generated aerosol, ambient aerosol (TSI PortaCount), and controlled negative pressure (OHD Fit Tester). OSHA accepted qualitative fit tests include isoamyl acetate, saccharin, Bitrex, and irritant smoke. When using any of these methods in the United States, be sure to follow OSHA accepted procedures and protocols since these may differ from those you may be using.
By the time most of you read this newsletter, approximately 50 compliance officers and staff with the Washington Department of Labor and Industries will have received specific training on respirator selection and the development of chemical cartridge change out schedules from Dr. McKay. If you want to know what they know, check out our March 2005 course offering in Park City, Utah. Details are provided below.
When using irritant smoke tubes for fit testing respirators according to OSHA protocols, never use an enclosure to contain the challenge agent. The use of an enclosure results in elevated concentrations of hydrochloric acid (HCl) which often exceed Immediately Dangerous to Life and Health (IDLH) levels. Since you don’t know if the respirator fits (and even if it does), you don’t want to expose any subject to high levels of HCl when wearing a negative pressure air purifying respirator. In addition, when following OSHA protocols with irritant smoke the subject must conduct all seven (7) fit test exercises for one minute each. The total test time for a successfully fitting facepiece is therefore seven minutes. When wearing a half mask respirator, the subject will need eye protection from the irritant smoke or they must keep their eyes closed for the entire seven minutes. This may not be easy for all subjects. In addition, if the subject needs to wear a half mask respirator at the workplace with conventional eye glasses for vision correction, it may not be possible to conduct the fit test with eye protection, since the fit test will need to be accomplished with the eye glasses in place. Otherwise, you won’t know if the half mask respirator fits with eye glasses at the workplace.
As many of you know, there is relatively little data to predict the cartridge service life for organic vapor cartridges at high relative humidities. In addition, mathematical models including those used in some predictive software programs may not accurately account for a wide range of humidities a worker may encounter. This is especially important since it has been observed that humidity has a greater effect on organic vapor cartridge performance at the lower airborne concentrations a worker is more likely to encounter. For a comprehensive review of this topic, read the article by Gerry Wood in the July issue of the Journal of Occupational and Environmental Hygiene, volume 1, pages 472-492, 2004.
Researchers from the University of Cincinnati presented their research and opinions at the CDC Workshop on Respiratory Protection for Airborne Infectious Agents, November 30 - December 1, 2004 in Atlanta, Georgia. Sergey Grinshpun, Ph.D. presented a paper on Respirator Performance with Infectious Agents: Studies with Simulants. In his presentation, Dr. Grinshpun shared results of a newly developed personal sampling device used for collecting bioaerosols within respirator facepieces. This device has already been used to measure Workplace Protection Factors (WPF) in the agricultural industry. Early results from these studies reported by Drs. Lee and Reponen indicate that the performance of filtering facepieces may differ with bioaerosols. Dr.Grinshpun also presented results from a new approach using unipolar ion emission to increase the protection factor of filtering facepieces. Dr.McKay presented a paper on the Evaluation of Respirator Fit Test Method. In his presentation the purposes of fit testing and common myths associated with fit testing were explored. In addition, Dr. McKay provided evidence that fit testing filtering facepiece respirators provides the wearer additional protection from respiratory hazards. In addition, the advantages of repeating the fit test on a periodic basis were explored (ie, providing an opportunity for the respirator wearer to demonstrate their ability to properly don the facepiece, conduct user seal checks, verify the correct facepiece is being used, demonstrate that an acceptable seal has been obtained, and that the respirator initially selected still fits).
OSHA requires the employer to have a written policy for changing out cartridges used for protection against gases and vapors. OSHA also requires the employer to include (in writing) the data or rational used to support the written change out policy. Relying solely upon odor and/or taste is not acceptable practice and may lead to an OSHA citation. Worse yet, an allegation regarding an unacceptable change out policy may lead to an even more costly lawsuit. So where does OSHA make this statement? Go to 1910.134 (d)(3)(iii)(B)(2) where it states:
“If there is no ESLI appropriate for conditions in the employer’s workplace, the employer implements a change schedule for canisters and cartridges that is based upon objective information or data that will ensure that canisters and cartridges are changed before the end of their service life. The employer shall describe in the respirator program the information and the data relied upon and the basis for the canister and cartridge change schedule and the basis for the reliance on the data.”
The July 23, 2004 issue of the MMWR reports that although deaths from certain occupational diseases caused by inhalation of mineral dusts have shown a significant decline over the last 30 years, the death rate for asbestosis continues to rise. New cases of asbestosis (a fibrosis of the lung caused by excessive exposure to airborne asbestos fibers) continues to appear even though the use of asbestos has declined substantially. These new cases are generally the result of exposures occurring many years ago. An editorial to this report reveals that asbestosis mortality peaks 40 - 45 years after initial occupational exposure to asbestos. Given the temporal pattern and latency associated with asbestos exposure, asbestos-related mortality is expected to increase for at least another decade. The bottom line is this disease is not going away as of yet. Adequate respiratory protection could have reduced the number of asbestosis cases. Perhaps we should remember this history as we consider our need to select respiratory protection for the various airborne agents used today. For more information regarding the MMWR report, go to:
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5328a1.htm.
Roy McKay, Ph.D.
Course Director
University of Cincinnati
www.DrMcKay.com