With your permission, a Cheann Comhairle, I propose to take Questions 31, 32 and 33 together.
The immediate possible danger from the recent nuclear tests, or from a continuance of such tests, lies in the deposit of radioactive iodine (Iodine 131) in quantities which would lead to a dangerous concentration of this substance in the thyroid gland. Iodine 131 deposited in the fall-out of nuclear explosions can find its way into milk and thus be ingested by humans. Obviously, with milk the vehicle for its transmission, the danger of excessive concentrations of this substance is greatest with babies fed almost entirely on milk. Radioactivity from Iodine 131 does not, however, remain a danger for very long after a nuclear explosion.
A longer-term danger from nuclear tests lies in the deposit of radioactive substances which do not decay rapidly, such as Strontium 90, Caesium 137 and Carbon 14. Of these Strontium 90 presents the most serious possibility of danger as it also may become a constituent of milk and be thus absorbed by humans. When ingested, Strontium may be laid down in the human bone. If this were to happen on a sufficient scale, serious harm could result, but this has not happened up to the present, nor does it appear that it will. The position, however, is being kept under review. Further tests at this stage would not be revealing since several months must elapse before Strontium from the recent nuclear tests reach our atmosphere. Testing will be resumed, if necessary, at the appropriate time. While the other two elements are potentially dangerous, there is at present no indication that they constitute a proximate danger.
The tests for radioactivity arranged by the authorities in this country are of two kinds. In the first place, routine measurements of air, rainwater and tapwater are continuously carried out by the Meteorological Service of the Department of Transport and Power. The object of these tests is to provide warning of any increase in total radio-activity.
The second type of test is designed to assess the content in milk of the potentially dangerous constituents, Strontium 90 and Iodine 131. Tests for Strontium 90 were carried out in 1960 and showed that the amount of that substance in milk was nowhere near the internationally recognised danger level.
At present, tests for Iodine 131 are being conducted. The results of the first set of these tests, which I published last week, showed that no danger existed for any section of the community. I again reassured mothers that there was no cause to change the feeding of infants. Further samples are being tested, but it is expected that a marked decrease in the level of iodine 131 will be apparent unless there is more large-scale testing of nuclear weapons.
In arranging for these tests for Strontium and Iodine I was glad to avail myself of the kind co-operation of the British Agricultural Research Council and have the tests carried out in the Council's Radiobiological Laboratory in Berkshire. This ensured comparability of the results with those from similar tests on British milk. I should like to take this opportunity to express to the House my appreciation of the co-operation of the British authorities in this matter.
The Deputies will appreciate from what I have said that there is no indication that any special measures are likely to be called for because of the levels of radio-activity resulting from recent tests. In the event of a future large-scale extension of nuclear testing, the Government is fully alive to the precautions which might be necessary and will advise the public on them should it become clear that they should be taken.