The fact that the houses had been checked by radiation meters and found to be clean, and the fact that the half-life of iridium¹⁹² is only 75 days so that any trace of activity would disappear in a reasonably short time, did not dispel people’s fears. It is fortunate that no one was seriously hurt in this incident. But there is an important lesson we can learn from it: Ignorance may hurt more than radioactivity. That a house should lose its value in spite of the fact that its radioactive contamination has been removed, that a little boy should be shunned as though radioactivity were infectious like the plague—these are examples of suffering caused by one of the greatest sources of human misery: unreasoning fear. The greatest potentialities of fission products for the future might lie in still a different direction. Radioactivity can induce mutations. To what extent this is a danger we have discussed in an earlier chapter. In the hands of a breeder who tries to bring about changes in animals or plants radioactivity could become exceedingly useful. Of course it is true that most mutations are harmful. It is also true that artificial mutations have been produced for many decades. But now it is possible to place simple and cheap tools in the hands of many more people. Therefore the chances will increase to find among the many wrong mutations the few and decisive changes which lead to improvement. Do we dare to place dangerous materials in so many hands? We should not do so without making certain that only competent and responsible individuals will get radioactive materials. This can be done. Druggists have dispensed poison; doctors and biologists have bred in their laboratories the multiplying menace of germs. All this was done and is being done with safety and to the great benefit of all people. The use of radioactivity should be even more safe because this material is easy to detect. If poisons or germs become lost, they may be hard to find. Radioactive materials, however, give unmistakable evidence of their presence. It is, of course, never easy to find a needle in a haystack. But the chance to find it is much better if it is a radioactive needle. Radioactive by-products need not remain what they seem to be today: dirt and danger to be disposed of and hidden. But in the immediate future we shall incur some expense to keep radioactivity in a safe place. Some gaseous by-products like the long-lived krypton⁸⁵ (half-life: 10.4 years) might continue to give rise to real difficulties and to considerable expense. The trouble is, of course, that a noble gas like krypton will not be bound to any material by strong bonds. It may be inadvisable to let long-lived gases escape. On the other hand, their adsorption or their storage at low temperature or high pressure may prove to cost a considerable amount of money.