78 
So Dr. Barkley, you have already been introduced to us as the expert 
on containment, and I believe your official title is Director, Office of 
Research Safety in the National Cancer Institute. We welcome your de- 
scription of these facilities. 
DR. BARKLEY: Thank you, sir. I will not discuss at this time the 
procedures used by the NIH Biohazards Committee for review of intramural 
research programs involving recombinant DNA molecules. To continue the 
discussion of this morning, I will go directly into a description of the 
physical levels of containment that have been recommended in the committee's 
report . 
Safety guidelines for handling hazardous microorganisms have been 
recommended by a number of governmental agencies. The guidelines are con- 
sistent and each varies according to the actual risk potential of the agent 
handled. In general, the guidelines fall into three or four distinctive 
control categories. The objective of each category, however, is the same. 
That is, to reduce or eliminate hazards or health risks in the handling of 
hazardous agents by reducing or preventing exposures to that agent. The 
difference in the control categories is in the margin of safety that is 
provided in preventing exposures. 
Dr. Singer stated that the committee has drawn heavily upon the experi- 
ence of a number of people in formulating recommended physical control 
measures. Four principal sources have been used in the formulation. Most 
importantly, I think, is the booklet Classification of Etiologic Agents on 
the Basis of Hazard . This document which was prepared by the Center for 
Disease Control (CDC), PHS, DHEW, places microorganisms capable of inducing 
disease in man into four categories according to risk. Descriptions of 
physical containment necessary for the control of risks in each of the four 
categories are presented. Further description of guidelines are presented 
in the CDC "Lab Safety Manual." 
The other two documents are guidelines written by the National Insti- 
tutes of Health for biosafety in general and the National Cancer Institute 
for oncogenic viruses. 
Before describing levels of physical containment, it is important to 
understand two points. First, data on laboratory-acquired infections, 
collected by Dr. Pike and the late Dr. Sulkin of the University of Texas, 
indicate that the causative event which results in laboratory-acquired 
infections is unknown in 80 percent of all reported laboratory infections. 
Second, most microbiological procedures have been shown to possess the 
potential for creating aerosols. An aerosol creates two problems. An or- 
ganism suspended in air can gain entry into the respiratory tract of the 
laboratory worker through inhalation. Airborne organisms can also settle 
on work surfaces or objects and can be transferred to a site where an 
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