As part of its recent annual N95 Day respirator activities, the National Institute for Occupational Safety and Health (NIOSH) sought to bust several myths about respiratory protection, including the misconception that “respirators and surgical masks provide the same type and level of protection for the user.”1
This would certainly seem to be patently false based on lab studies, which show the greater effectiveness of a well-fitted N95 in filtering out aerosols and particles that could go through a surgical mask.
Indeed, NIOSH notes that, “Surgical masks are typically disposable, loose-fitting, and do not form a tight seal to the face. They are also not designed to capture a large percentage of small particles, which means that they cannot prevent the wearer from breathing in airborne particles that may be transmitted by coughs, sneezes, or certain medical procedures (i.e. aerosol-generating procedures). Because of these factors, healthcare workers using surgical masks will not be protected against exposure to airborne transmissible diseases.”
However, actually determining the comparative efficacy of respirators and masks in clinical studies is much more difficult. In a recent meta-analysis, researchers in Canada could find no difference in protection between masks and respirators.2 They reviewed three randomized clinical trials, one cohort study, and two case-control studies.
“No significant difference in risk of laboratory-confirmed respiratory infection was detected between healthcare workers using N95 respirators and those using surgical masks in the meta-analysis of the randomized trials,” the authors concluded. “It was not surprising to find that N95 respirators were generally more efficient filters with better face-seal characteristics than surgical masks when tested in the laboratory. However, transmission of acute respiratory infections is a complex process that may not be appropriately replicated by surrogate exposure studies.”
A contributing factor is likely that respirator use is compromised by a lack of adequate fit-testing, and workers may handle and readjust the equipment during use.
“N95 respirators are often considered uncomfortable for regular use, and improper wearing or adjustment of the respirator because of discomfort could lead to inadvertent face contamination, thus negating the potential protective benefit,” the researchers found.
This is somewhat reminiscent of the findings of PPE use during Ebola, which revealed that healthcare workers frequently donned equipment improperly and contaminated themselves removing it. However, the findings were strongly refuted by some occupational health professionals, including a member of the Hospital Employee Health editorial board.
“The absence of proof is not the proof of absence,” says Gabor Lantos, MD, PEng, MBA, president of Occupational Health Management Services in Toronto. “There is much evidence in the aerosol physics and bioaerosol literature of airborne spread from coughs and sneezes. There is a good reason why NIOSH has never approved surgical masks as PPE.”
Still, the authors concluded in the paper that “randomized controlled trials conducted in clinical settings represent the most valid information to evaluate the effectiveness of N95 respirators. They are more relevant to real clinical situations and report actual outcomes in healthcare workers, and therefore they are the best evidence on effectiveness to inform policy-making.”
HEH requested an interview with the contact author on the meta-analysis study, but had not heard back as this issue went to press. We asked the NIOSH authors of the respirator myth document about the implications of the meta-study. Responding jointly by email as one source were Deborah Novak, PhD, RN, and Ronald Shaffer, PhD, both of NIOSH’s National Personal Protective Technology Laboratory in Pittsburgh.
“We are aware of the meta-analysis published earlier this year,” Novak and Shaffer noted. “The article shares several similar themes as a paper3 with NIOSH co-authors that addresses this same topic. For example, both papers report that across many laboratory studies, N95 filtering facepiece respirators (FFRs) show less filter penetration, less face-seal leakage, and less total inward leakage than surgical masks and that randomized controlled trials (RCTs) are important. However, the RCTs completed to date have yielded inconclusive results because of limitations in experimental design and implementation. For example, study subjects failing to wear the assigned device during all times of potential exposure (i.e., poor compliance with the intervention) negate the superior fit and filtration properties of the FFR. Current studies such as ResPECT4 may be able to overcome some of these difficulties, but a complete face-fitting respirator vs. surgical mask clinical trial remains elusive.”
Indeed, in the recently published ResPECT study, the authors concluded, “While it may seem that N95 respirators should better protect healthcare personnel (HCPs) than medical masks against airborne infections in the workplace, this notion has not been validated by objective clinical evidence. Low tolerance to respirator wear among HCPs may prompt more frequent or longer periods of removal, compared to medical masks, to an extent that the benefits of higher levels of filtration and lower levels of leakage around the facial seal afforded by respirators are offset or subjugated.”
Novak and Shaffer of NIOSH say N95 use “will reduce inhalation exposures to airborne biological agents by a factor of 10 or greater when complete, effective respiratory programs are in place, including initial and annual fit-testing and proper donning on each use.”
Noncompliance with proper consistent FFR use is a major detriment to effective respiratory protection, they add.
“Selecting a respirator during fit-testing that provides a good seal against the face is essential — akin to finding the right size shoe for your foot,” the NIOSH researchers wrote. “Like with shoes, a ‘one-size-fits-all perspective’ does not apply to this device.”
In terms of preparedness, NIOSH also noted in the myths document that many hospitals do not have the HHS-recommended six- to eight-week supply of disposable N95s.
“The consequences could be very serious if a facility does not have an emergency preparedness plan to obtain necessary supplies to protect their employees, such as N95s,” Novak and Shaffer wrote. “Therefore, the best approach is to have an emergency preparedness plan in place, including access to needed supplies, in the case of an emergency.”
In addition, NIOSH recently posted a video on YouTube that may be useful in educating healthcare workers about how respirators work.
The five-minute video emphasizes that “a particle is a particle,” and employees facing biological agents are protected by the same N-95 worn by a construction worker exposed to dust. Whether the particle is “living” or “infectious” plays no role in how well it will be collected by a filter, the video explains. (The video can be viewed at: http://bit.ly/2doRDOS.)
“Pathogens in the air behave no differently than do all other particles of similar physical properties,” Lantos says. “Their infectious natures are of no consequence if they do not enter the body. There are numerous scientific experiments that demonstrate the superior protection offered by N95 respirators.”
- Preparedness through Daily Practice: The Myths of Respiratory Protection in Healthcare. DHHS (NIOSH) Publication No. 2016–109. March 2016: http://bit.ly/2cB80Sq.
- Smith JD, MacDougall CC, Johnstone J, et al. Effectiveness of N95 respirators versus surgical masks in protecting health care workers from acute respiratory infection: A systematic review and meta-analysis. CMAJ, published ahead of print March 7, 2016, doi:10.1503/cmaj.150835.
- Janssen L, Ettinger H, Graham S, et al. Commentary: The Use of Respirators to Reduce Inhalation of Airborne Biological Agents. Journal of Occupational and Environmental Hygiene 2013;10:8, D97-D103, DOI: 10.1080/15459624.2013.799964.
- Radonovich, JJ Jr, Bessesen MT, Cummings DA, et al. The Respiratory Protection Effectiveness Clinical Trial (ResPECT): A cluster randomized comparison of respirator and medical mask effectiveness against respiratory infections in healthcare personnel. BMC Infectious Diseases 2016;16:243 DOI 10.1186/s12879-016-1494-2.