194 MUTATIONS 



jecture that when the potentialities of chemical mutagenesis become 

 known, within a few years we will be facing the same kinds of questions 

 that have arisen regarding the radiation genetics of man. 



I see very little likelihood that this problem can be satisfactorily 

 studied in intact human populations. There are a few circumstances 

 where one group of human beings has been irradiated and suitable 

 controls exist. However, I find it difficult to visualize a satisfactory set 

 of observations on intact populations involving caffeine. It is going to 

 be difficult to set up one group of 300,000 drinking caffeine and a 

 strictly comparable group of 300,000 who do not drink caffeine. 



It looks to me, then, as if we are either forced to tissue culture 

 techniques or else we are going to be guided for a long time by the 

 results of screening tests on appropriate organisms. With respect to the 

 tissue culture approach, we have already mentioned the many prob- 

 lems here. While the breakthrough may come at any time, it might 

 be ten or fifteen years before all these problems are ironed out, so that 

 I would guess that if public concern over these problems does arise, it 

 will be the findings in microorganisms, Drosophila, and, conceivably, 

 the mouse that are going to be guiding us for the next ten years. The 

 question of the best combination of organisms to be used in forming 

 an opinion will be raised again and again. 



Goldstein: I would like to comment on some of these questions that 

 have been raised, particularly on something that Dr. Lederberg said 

 before. I don't want l)y any means to minimize the importance of 

 caffeine and I will soon summarize the evidence that suggests that 

 caffeine is the most important single compound for study. But the 

 reason I raised the question of screening was, as our Chairman just 

 suggested, that it is really quite accidental that caffeine came to our 

 attention as a mutagen. Among the very large number of compounds 

 to which human beings are exposed, both pharmacologically and other- 

 wise, it is conceivable, although it is a nightmare, that there may be 

 some which are really potent mutagens, about which one would want 

 to do something. After all, caffeine seems to be a rather weak mutagen 

 when you consider all the systems in which it has been tested. That is 

 the reason I raised the question of screening, and I'm sure it is not 

 going to be settled here, but this will be of concern, and I think that 

 some approach will have to be made to it. 



Let us now return to a brief consideration of Category III. I have 

 tried to include here (Table 3) all chemicals, both drugs and substances 

 in the environment, to which large parts of the population are exposed 

 for long periods of time, regardless of whether or not anything is known 

 about their mutagenicity. 



