Protection from Exposure to Biological Agents Such as Bacillus Anthracis The Centers for Disease Control (CDC) is the recognized authority on infectious agents, including appropriate precautions to protect individuals from exposure to these agents. Recent events have caused many to be concerned about biological agents, which could be used in a terrorist attack. CDC has published guidelines for protecting individuals who are concerned about potential exposure to Bacillus anthracis, the agent that causes the disease anthrax. The October 31, 2001 CDC Health Advisory specifically refers to situations where known exposure to Bacillus anthracis has not occurred. In the October 31, 2001 CDC Health Advisory, CDC strongly recommends engineering controls (local exhaust ventilation) administrative controls (limiting number of people potentially exposed), and good work practices (do not perform tasks that could cause agents to be airborne) as the primary means of preventing exposures to biological agents. Personal protective equipment, such as respirators, gloves, and clothing is secondary to the more reliable exposure reduction measures. Please note that the October 31, 2001 advisory focuses on situations where the infectious agents have not been found. If known infectious agents are found to be present in a location, the area is immediately evacuated and secured. The ventilation is shut down to prevent spread of contamination. People who were in the environment during the period of suspect exposure, regardless of whether or not they were wearing personal protective equipment, are isolated for decontamination and encouraged to seek medical evaluation and treatment. Emergency responder personnel in heavy duty protective gear (powered air purifying respirators with high efficiency filters, protective suits and booties, and gloves) enter the environment to characterize and define the extent of contamination and clean up the contamination. These highly trained professionals also evaluate the environment to determine when it is safe for unprotected personnel to re-enter the environment. The October 31, 2001 CDC Health Advisory recommends NIOSH approved N95 half mask respirators as the lowest level of respiratory protection for potential exposure to biological agents, such as Bacillus anthracis, in situations in which agents are not known to be present. The N95 is a filter class, with the letter N indicating durability of filter material and the number 95 denoting the efficiency level. N filters do not work well when oil could be present in the air. If oil is likely to be airborne, P type filters are best. The efficiency level indicates what percentage of the airborne particles the filter stops. So, 95 means that the filter stops 95% of the incident particles. A 95% efficient filter allows 5 particles out of every 100 particles (or spores in the case of Bacillus anthracis) through to the wearer’s breathing zone. A 100 type filter is really 99.97% efficient, thereby letting 3 out of every 10,000 particles pass through the filter. In addition to efficiency rating, another extremely important factor is how well the respirator fits a person. If the respirator does not fit well, particles can pass around the sealing surface of the respirator and get into the wearer’s breathing zone. People with facial hair cannot wear tight-fitting respirators; they need powered air purifying respirators with hoods for protection. The only way to be sure a respirator fits properly is quantitative fit testing, an objective measurement of the quality of fit of the respirator on a particular individual. To make sure that wearers are properly protected when wearing respirators, a work site specific respiratory protection program, which includes training on use, care, and maintenance of respirators, in accordance with the OSHA Respiratory Protection Standard, 29CFR1910.134 (U.S.) must be developed and implemented. In addition to making recommendations to prevent inhalation exposure, CDC recommends that the skin be protected to assure no cutaneous exposure. Good practice suggests that eyes also be protected with safety eyewear in these environments. The following table lists types of respirators, assigned protection factors (which provide relative level of protection, the higher the number the better, for the type of facepiece), and AOSafety® products that meet the criteria. The type of respirator recommended for a given exposure situation depends on various factors in the environment. The person responsible for health and safety of the people working in that environment is responsible for determining the most appropriate respirator for the situation.
For the most up-to-date information for recommendations on protection from exposure to biological agents, including Bacillus anthracis, click on http://www.bt.cdc.gov. |
