THE COHEN GROUP
  Environmental Health & Safety Consulting Services

The Cohen Group Newsletter - Volume 8  Issue 1, Article 1.  January, 2006

With the outbreak of SARS (Severe Acute Respiratory Syndrome) in Asia in recent years and now the current concern over an outbreak of avian bird flu, greater attention is being focused on respiratory protection for healthcare workers and public health investigators. To prevent exposure to these airborne pathogens (and others such as tuberculosis), healthcare workers and others concerned with inhalation exposure should wear respiratory protection when in close association with either known or suspect infected persons. Too often, surgical masks are thought to provide sufficient protection against the inhalation of airborne pathogens when they are not intended for that purpose. This article will discuss the difference between surgical masks and N-95 respirators (disposable masks) that are truly designed for personal respiratory protection.

The U.S. Food and Drug Administration (FDA) provides information on its website (http://www.fda.gov/cdrh/ppe/) about personal protective equipment (PPE) that is regulated by FDA for use in patient care, including surgical masks and surgical N95 respirators. These items are considered by the FDA to be "medical devices" and therefore fall under their regulatory jurisdiction. The FDA states that a surgical mask covers the user’s nose and mouth and provides a physical barrier to fluids and particulate materials and can be identified as surgical, laser, isolation, dental or medical procedure masks with or without a face shield. An N95 respirator is fitted to the user’s face, forming a seal that provides a physical barrier to fluids, small particulates and aerosols. When a mask is both approved by the FDA as a surgical mask and certified by NIOSH as an N95 respirator, FDA calls it a "surgical N95 respirator."

The Centers for Disease Control & Prevention (CDC) provides guidance for the infection control in health care facilities. CDC documents state that respiratory infections can be acquired from exposure to pathogens contained in either droplets or droplet nuclei. When droplets are produced during a sneeze or cough, a cloud of infectious particles greater than 5µm in size is expelled, resulting in the potential exposure of susceptible persons within about 3 feet of the source person. Since these particles tend to fall out of the air rather quickly because of the relatively large size, indirect transmission (e.g., particle transport via the ventilation system) is not the primary concern. Rather, it is the respiratory protection of health care workers and other personnel within the near vicinity of the source person (the infectious particle cloud) that is important.

The use of air-purifying respirators in the health care setting is a relatively new, but important step forward in the efforts to prevent the transmission of communicable diseases such as TB. The level of protection a respirator provides is determined by the efficiency of the filter material and how well the facepiece fits or seals to the individual's face. A number of studies have shown that surgical masks will not provide adequate protection in filtering out the TB organism. Researchers at the University of Cincinnati recently performed a study to evaluate the efficiency of N95 respirators and surgical masks against viral particles and found the mean protection factors provide by the N95 masks to be four to eight times higher than those of surgical masks for particles smaller than 0.3 µm. This finding is borne out by quantitative fit testing of health care workers with N95 disposable masks done by The Cohen Group in 2005. Using quantitative test methods, we found much lower fit factors for a surgical mask when fit tested on the same individual, primarily due to the poor fit provided by the surgical mask due to its design, which prevents a secure seal at the respirator edges where the straps are attached (near the corners of the mouth).

Additionally, surgical masks are not respirators and therefore are not NIOSH certified and do not satisfy OSHA requirements for respiratory protection. Surgical masks are designed primarily to provide protection to the patient from the exhalations of the health care workers (e.g., surgeons and nurses in the OR) and to provide some level of protection to the worker against splashes and gross aerosols generated during surgical activities. They are not designed to filter out small particles, such as airborne viruses and other pathogens, and are not intended to provide respiratory protection to the user.

So it is important to always choose an N95 disposable respirator when considering respiratory protection from airborne pathogens. Don’t be fooled by the comfort and appearance of the surgical mask. They have their use in health care settings, but it is not the protection of your lungs.