Attachment I, I^ge 6 
microorganisms currently used in rDNA applications are debilitated through 
genetic manipulation such that their ability to reproduce outside of a highly 
modified environment is severely curtailed. None of the organisms in current 
use have been shown to cause infection or disease in persons using rDNA 
techniques. Recent risk assessments suggest that the likelihood of infection 
by microorganisms containing rDNA is minimal. Despite those 
reassurances, there is residual, albeit unquantified concern that workers 
engaged in industrial applications of rDNA technologies may be at heightened 
8 9 
risk of colonization or infection by modified organisms. ’ The Working 
Group notes in that connection that the circumstances of potential exposure in 
industry will differ considerably in their scale from the usual exposures 
encountered in research laboratories. Also, the number of workers potentially 
exposed in industrial applications will be much greater than the number 
potentially exposed heretofore. 
The primary defense against colonization or infection of workers in rDNA 
applications will be provided by strict physical containment of organisms 
5 
containing rDNA. In the development and capitalization of industrial 
applications of rDNA techniques, exposure control and worker protection must 
be given equal emphasis as process integrity and product development. 
Experience gained by NIOSH in other sectors of the chemical and pharmaceutical 
manufacturing industries indicates that preplanned maintenance is a central 
aspect of exposure control. Facilities for containment of recombinant 
organisms must periodically, in accordance with a strict timetable, be shut 
down for scheduled examination and repair. Procedures for evaluation of 
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