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With regard to the anticipated but speculative benefits of recom- 
binant DNA research, adherence to the Guidelines may postpone their 
realization. Certain experiments are prohibited. The Guidelines are 
binding on all NIH grantees and contractors as well as NIH intramural 
scientists and laboratories. The Guidelines serve as a model for all 
other Federally supported work and comparable activities in the private 
sector. All work with recombinant DNA techniques known by NIH to be 
occurring in this country is presently being carried out under these 
guidelines. 
1 . Impact on the Safety of Laboratory Personnel and on the 
Spread oF Possibly Hazardous Agents by Infected Laboratory 
Personnel 
The NIH Guidelines are directly concerned with reducing and 
eliminating exposures of laboratory personnel and all other persons to 
host cells and microorganisms containing recombinant DNA molecules. 
The degree to which the potential for exposures are reduced or 
eliminated corresponds to the assessed potential hazard of the 
experiments. The NIH Guidelines classify allowable experiments into 
four levels of potential hazard. And for each level of experiments, 
the Guidelines describe safe laboratory practices, containment equip- 
ment, and facilities (Section II). 
The four levels of physical containment are based on recommended 
methods for the safe handling of microorganisms that produce human 
disease of varying degrees of severity. The descriptions of these 
requirements were developed by a working group of biological safety 
experts representing the Center for Disease Control (CDC), the 
National Institutes of Health, the National Animal Disease Laboratories 
(Department of Agriculture), and the Frederick Cancer Research Center 
(FCRC) of the National Cancer Institute, NIH. Representatives from 
FCRC were previously responsible for directing the biological safety 
programs at Fort Detrick. The names of these experts are listed at 
the end of Appendix D of the NIH Guidelines. 
The protection of laboratory personnel is achieved through the use 
of host-vector systems that are not infectious to man as well as the 
use of safe laboratory practices and containment equipment. The 
capability of safe laboratory practices and containment equipment 
for protecting laboratory workers can be assessed by evaluating their 
effectiveness when used for the containment of human pathogens. The 
documented experience at Ft. Detrick for the 25-year period during 
which human pathogens capable of causing serious disease in man 
were extensively handled (while safe laboratory practices and equip- 
ment were improved) provides a basis for such an evaluation. 
