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Radium Emanation and Goitre Production.
(A negative result).
[Read before the Philosophical Institute of Canterbury, 3rd November, 1926; received by Editor, 31st December, 1926; issued separately, 8th November, 1927.]
Introduction.
While iodine deficiency in food, water, and air is recognized as the chief factor in the production of endemic goitre among human beings, it is not the only factor, since the percentage incidence of goitre varies greatly with sex, and also among individuals of the same sex, although the food supply is apparently identical.
It has been suggested that the presence of radium emanation might constitute another factor.
In 1925, before the Canterbury Philosophical Institute, Rogers read a paper on the occurrence of iodine and radium emanation in certain drinking waters in Canterbury. The object of his investiga-tion was to see if a statistical correlation exists between the emana-tion content of the water, and the goitre census as disclosed by the medical examination of school children in these areas, and to com-pare this with the iodine content.
While Rogers found a close relationship between goitre in-cidence and iodine content—the less the iodine the more the goitre—he also found, with one marked exception, that the goitre incidence was directly proportional to the amount of radium emanation. The exception was the town supply of Timaru, where no emanation was found, although the goitre incidence was high. It was considered likely, however, that the emanation would be lost during transit by open race from the Pareora River.
Farr and Florance in 1909, and Farr in 1912, drew attention to the emanation content of certain Christchurch artesian waters and to a parallelism between that content and mortality in trout in the egg and yolk-sac stages. Aeration by ripling, waterfalls, and spray-ing, reduces this mortality. By these means, not only are dissolved gases such as nitrogen and argon liberated, but there is also a gain in oxygen. Carbon dioxide varies only slightly.
Again, of those trout that survive, a considerable number develop a protusion of the eyeball, “pop-eye”. At a later stage some of the trout develop an enlargement of the thyroid gland, known to caretakers as “gill cancer”, especially where the fish are rather crowded. Several “gill-cancers” on microscopic examination, showed a cellular proliferation of the thyroid similar to that seen in the human thyroids of Graves Disease. Protusion of the eyeball also occurs in Graves Disease, but while “pop-eye” in trout is apparently due to a collection of gas at the back of the orbit, a similar causation has not been proved for human beings.
These facts suggested that direct experiments with emanation were desirable, since a correlation curve at best could not prove causation. A search of the available literature on the pharmacology of radium emanation and salts of radium, gave no hint that thyroid disturbances could be caused by these agents, but since no record of
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long-period experiments with large doses was found, it seemed possible that the thyroid effect may have been over-looked. It is sig-nificant, however, that in the fairly extensive literature of medical radiology, no record of goitre production could be found. The present report is merely a trial experiment on a total number of six rabbits. The experiment would have been continued with larger numbers had the results been encouraging, but it is believed that a more extended trial offers no hope of other conclusion than that reported here.
Procedure.
The radium emanation was obtained by courtesy of the Wellington Hospital Board from the Radon plant in Wellington. Roughly, it was calculated that, allowing for loss in transit, a total of approximately 150 millicuries was administered to each of five of these rabbits and 100 millicures to the sixth. Three of the rabbits were wild greys, three were white hutch rabbits, three were males, three were females. They varied from about two-thirds grown to full grown, but none were old rabbits. Three received their portion of the emanation in twelve weekly injections into the ear vein. The other three received the same amount by a stomach tube, except for one rabbit which died, probably of cardiac inhibition, while receiving the ninth dose. The ear rabbits received the emanation dissolved in 5 cc. of normal saline solution after crushing the capillary tubes containing the emanation underneath the solution. The stomach rabbits received the emanation liberated from the capillaries in 50 ccs. of saline solution. As radium emanation is very readily soluble, it was believed that the great bulk of the emanation would be present in the solution when prepared in this manner. Electroscope tests made by Mr. Rogers in the Physics Department of Canterbury College showed that practically no loss of emanation occurred during the above procedure.
Results.
The rabbits ate and thrived well and showed no abnormal symptoms. One became pregnant and produced three young rabbits, which are still healthy two months after the completion of the experi-ment. After thirteen weeks blood-counts and haemoglobin estimations were made and the animals were then killed. Four normal control rabbits were used to evaluate the changes that might be seen. Surpris-ingly, naked eye and microscopic examination of the main organs showed no abnormality, with the exception of a golden yellow de-generated liver in the case of the ex-pregnant female. The thyroids were neither altered in size as far as could be judged nor in micro-scopic appearances as compared with the controls. Certainly no appearances like those found in human goitre or in “gill-cancer” of trout were seen. The results were entirely negative as regards the production of thyroid abnormality or symptons referable to the thyroid gland.
When it is remembered that these experimental rabbits received doses enormously greater than they could possibly receive during normal life it does not appear possible that emanation could be an important factor in the causation of goitre, at least among rabbits. Further, although it is true that different species vary considerably
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in susceptibility to goitre production by iodine deficiency it is unlikely that the effect of massive doses of radium emanation would be remark-ably different among mammals. The effect of radium emanation on yearling trout is also being tested out, but the results are not yet ready for publication.