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The conference reviewed progress in research on recombinant 
DNA molecules and discussed ways to deal with the potential bio- 
hazards of the work. Participants felt that most experiments on 
construction of recombinant DNA molecules should proceed, but that 
appropriate containment should be utilized until hypothetical hazards 
could be better assessed. The conference made recommendations for 
matching levels of containment with levels of presumed potential hazard 
for various types of experiment. It also recommended against the 
performance of certain experiments at that time. Some of these 
involved the intrinsic hazard of using organisms known to cause disease. 
Others involved hypothetical risks that seemed greater than reasonably 
necessary to permit knowledge about the new techniques to be obtained 
cautiously and prudently. The proscribed experiments included the 
cloning of recombinant DNAs derived from highly pathogenic organisms, 
of DNA containing toxin genes, and large-scale experiments (more than 
10 liters of culture) if recombinant DNAs are able to make products 
potentially harmful to man, animals, or plants. 
A report on the conference was submitted to the Assembly of Life 
Sciences, National Research Council, NAS, and approved by its Exec- 
utive Committee on May 20, 1975. A summary statement of the report (9) 
was published in Science, Nature, and the Proceedings of the National 
Academy of Sciences. The report noted that "in many countries steps 
are already being taken by national bodies to formulate codes of practice 
for the conduct of experiments with known or potential biohazard. Until 
these are established, we urge individual scientists to use the proposals 
in this document as a guide. 1 
Again, while many recombinant DNA experiments not subject to 
the moratorium continued after Asilomar, there is substantial evidence 
that the Asilomar recommendations were voluntarily observed throughout 
the world. In this regard it is noteworthy that the experiments rec- 
ommended for deferral in the Asilomar report (9) differ from those 
mentioned in the 1975 report of the NAS committee (see above and 
reference 8). Insofar as they relate to experiments with antibiotics, 
the experiments described as Type 1 by the NAS committee were not 
among those recommended for deferral by the Asilomar report. The 
Asilomar report stated: "Experiments extending the range of resistance 
of established human pathogens to therapeutically useful antibiotics or 
disinfectants should be undertaken only under moderate or high risk 
containment, depending upon the virulence of the organisms involved. " 
