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Volume 57, 1927
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An Examination of the Radon and Iodine-Content of certain Christchurch Artesian and other Waters, with respect to the Incidence of Goitre.

By M. N. Rogers, M.Sc.
(Communicated by Dr. C. C. Farr, F.N.Z. Inst.)

[Read before the Philosophical Institute of Canterbury, 5th August, 1925; received by Editor, 8th December, 1925; issued separately, 8th March, 1927.]

The present research arose from the observation that Christchurch which has a particularly pure artesian water supply with a radium emanation content far above the ordinary (Farr and Florance, 1909), has also a high incidence of goitre. The emanation-content of the water is ten or twenty times that of any other New Zealand samples so far tested. It was therefore thought worth while to investigate the possibility of a connection between the radioactivity and the goitre incidence. Later an examination for iodine in the drinking waters was also made, for this element is known to be of fundamental importance for the functioning of the thyroid gland.

Canterbury affords excellent opportunities for investigating the connection between water-supply and the prevalence of goitre; for the water is obtained from artesian wells and the goitre varies markedly within so small an area that other conditions may be considered as approximately the same. The drinking waters which serve certain selected localities were examined both for emanation and for iodine, and the results tabulated against the endemicity.

The Examination for Radioactivity.

The samples of water for examination of radioactivity were collected by suction into evacuated flasks so that no emanation was lost by splashing. About one-half litre of water was employed for the examination, and the emanation from this quantity generally increased the “natural leak” of the electroscope by about 40 times.

The electroscope employed was a brass box, and the leaf system was a short sulphur column supporting a thin brass strip and gold-leaf. The leaf potential was about 200 volts and the “natural leak” constant at 4.4 divisions per hour, and this leak could usually be neglected.

The electroscope was first evacuated and then connected with the flask. Each solution was boiled for half-an-hour, air being bubbled through at intervals to sweep over the gas into the electroscope. The gas was carefully dried by concentrated sulphuric acid.

The following are the results of the examination tabulated against the goitre incidence:—

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Locality Radioactivity Goitre
Waltham 229 59
West Christchurch School 150 75
Boys' High School 210 75
Girls' High School 160 75
Sydenham 280 70
Heathcote 38 14
Woolston 84 52
Timaru 0 70

It will be noticed that the relations between the two columns do not suggest any definite conclusions about the theory of radioactive causation. The fact that no radium emanation is present in the Timaru drinking water weakens the theory, and shows at any rate that if radium emanation is a cause of the disease it cannot be proved by simple examinations of the drinking water. In order to test the point further, four gallons of water from Timaru were boiled to one litre and stored for a month. The growth of radium emanation was very small, and showed that the dissolved radium itself must be a very minute quantity. For the waters other than Timaru a fair correlation can be established.

Obviously a more direct way of examining the influence of the emanation would be to administer known quantities of it directly, and after a convenient period observe the resulting effects. Work along these lines is now being undertaken by Drs. Milligan and Pearson at the Christchurch Hospital.

Examination for Iodine.

The value of experimental results in showing any relation between the presence (or absence) of iodine and the prevalence of goitre is limited, because our knowledge both of the sources of iodine and in the exact tabulation of goitre incidence is so uncertain. Iodine, though absent from the soil, may be present in drinking water or foods, and until we are more or less satisfied about all such possible sources of supply, our conclusions will be less valuable than we could wish.

In a small country like New Zealand we may assume that the kinds of food consumed do not vary greatly, so that foreign sources of iodine can hardly be responsible for the marked variation in goitre in different districts. Therefore, should it often occur that in places where the soil and drinking-water possess a low iodine content there is at the same time a low goitre incidence, it would be necessary for those who hold the iodine theory to indicate either (a) Other sources of supply, or (b) Alleviating circumstances. At the same time, should the iodine-content of either soils or waters be high the incidence should be low.

The second reason why relations experimentally established must be uncertain, is that our tables of goitre incidence are drawn up from observations on children of different ages and sexes whose environments may be very different and who may possess the disease in at least four different degrees of development, viz., incipient, small, medium and large.

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The present contribution confines itself to an analysis of the Christchurch Artesian waters.

Method of Estimation of Iodine

The method of estimation of iodides consisted essentially of the distillation of the iodine into a starch-iodide solution after removal of nitrates and of other salts. The quantities were estimated by colorimetric comparison with standards of known strength. Several other methods were looked into, but the method adopted appeared after investigation to be the most satisfactory and yielded consistent and satisfactory results.

Preparation of Starch Iodide.—The starch was prepared by dissolving about one gram of “soluble” starch as a paste in 50 cc. of hot water and allowing it to cool. To three cc. of this were added three drops of a solution containing½ grm. per c.c. of pure potassium iodide solution. Into this was distilled the iodine from the solution under examination.

A diagram of the distilling apparatus is shown below. It was all glass, consisting of a thistle-funnel sealed into the neck of a small distilling flask. The steam was condensed as shown, and the iodine liberated was absorbed in the starch-iodide-solution. In the following description it is to be understood that the iodine estimated is of the order 10—5 grms.

Oxidizing Agents.—Several oxidizing agents for the liberation of the iodine were tried, ferric chloride eventually proving most satisfactory. Chromates and permanganates liberated bromine too readily, while potassium ferri-cynade decomposed on heating, and any blue colour present in the starch-iodide solution was, in this case, immediately destroyed. In fact an excess of iodine added to this starch solution, which contained HCN dissolved, failed to give any blue coloration.

The ferrichlorid contained a minimum of 0.005 grms. cc. In distilling, the flask contained not more than 20 cc. of solution, so that two or three minutes' boiling served to obtain the whole of the iodine. With much higher dilution the iodine was liberated very slowly.

Influence of other salts.—It was found necessary in dealing with such small quantities of iodine to remove any excess of other salts present in the sample. In the case of sodium chloride for instance, 2.0 grms. in 20 cc. allowed only a trace of the iodine to be liberated. With 1.4 grms. about one-half the iodine was liberated, while 0.7 grms. did not prevent the liberation of the iodine.

In the case of other compounds, e.g., caustic potash, ammonium chloride, the same inhibiting action was observed when these are present in excess.

A distillation was also made with potassium bromide. It was observed that a trace of bromine was liberated if there was present more than 0.05 grms. of potassium bromide in 20 cc. of solution. Such a quantity is about 1,000 times the usual quantity of iodine observed, and it has been assumed that in the samples tested there has been considerably less than this amount of bromide present. The method

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used to remove the other salts and described in the next paragraph will not eliminate small quantities of potassium bromide, but the maximum quantity of salts remaining was never as great as 0.05 grms., so that the possibility of interference from bromides was negatived.

The excess of other salts was removed by successive precipitations, with absolute alcohol. (Note: Solubility of sodium iodide in absolute alcohol at 10° is 46%, of potassium iodide only 4%.)

Ignition.—After the removal of the salts the solution was evaporated to dryness in a platinum dish, and ignited. As any trace of organic matter may destroy the test, it is necessary to maintain the ignition at a dull red for several minutes. If the solution, on taking it up with hot water, is not clear, it must be again evaporated and ignited.

Nitrites.—In comparing the results obtained by distillation of tap-water with the results given by other methods, the quantity of iodine came out far too high. This was found to be due to traces of nitrite remaining after ignition.

The first method employed to overcome this difficulty was to remove the nitrite before precipitation. This was done by boiling the solution for several minutes with excess of ammonium chloride until the test for nitrite failed. The ammonium chloride was then removed by boiling with potassium hydroxide, the cooled solution made just acid with dilute hydrochloric acid, and finally alkaline again with two drops of potassium hydroxide. The salts were then removed as before.

This method proved satisfactory provided no nitrates were present; but if there were any, their partial decomposing during ignition produced further nitrites.

In order to overcome this difficulty the removal of the nitrite was left until after the ignition. It was found that, if the final solution after ignition was boiled for 5 or 10 minutes in small volume with three or four drops of ammonium chloride solution, the nitrite was completely destroyed. The small quantity of ammonium chloride did not prevent the distillation of the iodine, 10 drops of the particular ammonium chloride used allowed a complete distillation.

Verification.—Test experiments showed that the method was capable of consistent results. Samples (kindly prepared by Mr. J. Packer, lecturer of the chemical laboratory) containing nitrites, nitrates, iodide, solium chloride (excess), sulphates, small quantities of potassium bromide and sodium oleate (an unsaturated compound) as organic matter, were examined. The following results were obtained:—

Quantity in Unknown Solution Quantity Estimated
8 × 10—5 grms. 8.5 × 10—5
6.5 × 10—5 grms. 6.5
4.2 4.0
2.0 1.8

The estimation thus appears to be quite satisfactory over this range, and the colorimetric comparison accurate to within 5–10%,

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provided the quantity of iodine is not too large. It is possible to detect four parts per million of iodine with this method.

The following example will illustrate the general method employed:—

Four gallons of water from Heathcote reservoir were made alkaline with sodium carbonate solution, and evaporated to about one litre. The precipitated carbonates were filtered off and washed, and the evaporation of the filtrate was continued in a large evaporating dish until salts began to crystallize out. The solution was then poured into three times its volume of 96% alcohol and left for two hours. It was then filtered and washed five times with 96% alcohol, five drops of potassium hydroxide were then added and the alcohol distilled off. A current of air was maintained through the liquid during the distillation to prevent bumping. The evaporation was then continued and the solution again precipitated, this time with absolute alcohol. After standing and filtering, two drops of potassium hydroxide were added and the process as before continued. After three precipitations the salts were removed and the solution was evaporated to dryness, covered with a watch glass, and the residue ignited at a dull red for about two minutes. The organic matter was plentiful but was completely destroyed. On taking up with 10 cc. of distilled water the solution was clear. A few drops of it were then tested with an acid-starch-iodide solution, and a blue coloration showed the presence of nitrite. This was completely destroyed after boiling the solution (volume 5 cc.) for five minutes with four drops of ammonium chloride solution. The sample was then placed in the distilling flask and 10 cc. of ferric chloride solution (equivalent to 0.05 grms.) being added, the iodine was distilled into 3 ccs. of starchsolution containing three drops of potassium iodide. The iodine liberated was greater than 7.5 × 10—5 and less than 8 × 10—5 grms., which gives a value of 7.7 × 10-5 grms. The iodine content was, therefore, 4.3 × 10-9 grms. cc.

The following table shows the goitre-incidence tabulated with the corresponding iodine-content of the water.

Source Goitre-Incidence Iodine-content of Water grms. cc. Remarks
New Brighton 47 2.9 x.10— [ unclear: ]
Heathcote 14 4.3
Granity 25 2.0 Rainwater on sea coast.
West Christchurch 75 .6
St. Albans 59 Less than .2
Woolston 52 1.0
East Christchurch 69 1.2
Blackball 81 1.4 Rainwater; organic matter large.
Westport 46 1.0 River water.
Christchurch Tap Water 63 .2
Lyttelton 40 3.8
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Although the results are few, the figures seem to show that where the iodine is above 2 × 10-9 grms. the goitre-incidence is reduced. The results also indicate that other factors must be taken into consideration, for the water-supplies of Lyttelton and Heathcote have the same source, namely Heathcote, but the goitre-incidence is different.

Mr. Carter's examination of the soils gives the comparative iodine-content of the Heathcote as 15 and of the Lytellton as 9. This small difference could hardly affect the question.

The fact that Blackball, which is several miles from the sea, 1.5 × 10-6 grms. cc. This is about 1000 times that obtained for the iodine-content of the air, it seems possible that the rainwater has obtained its iodine from this source. Gautier (Bull. Soc. Chem., 1899 (3) 21, 456–463) has found that air from the sea contains about 0.017 mg. of iodine in 1,000 litres. A rough idea of the influence of this quantity may be obtained by assuming that on condensation of the water-vapour from this air to form rain, the iodine is removed in the solution. It will also be necessary to assume a constant supply of iodine from the sea. Under these conditions the rain-water would contain

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0.017 × 76 × 22/1000 × 1000 × 18 grms. of iodine, which is equivalent to 1.5 × 10—5 grms. cc. This is about 1000 times that obtained for the Granity rainwater, so that, although the assumptions made may not be permissable, yet the iodine in the air should not be entirely neglected.

McClendon and Hathaway (Journ. Am. Med. Assoc., 1668–72, 1924) found the iodine-retention to be about 0.012 mg. per day. Assuming that, in different ways, a person takes in three litres of Heathcote drinking water per day, the iodine obtained could be 3,000 × 4 × 10—9, which is 0.012 mg. per day.

The above investigation was carried out at the suggestion of Dr. C. C. Farr, under a grant from the New Zealand Institute.

In conclusion, I have to thank Dr. Farr and Dr. H. G. Denham for much encouragement and advice during the research, and Mr. J. Packer for advice in working up the method of iodine estimation. I have also to thank Dr. Telford, Dr. Fenwick and others who kindly obtained for me the samples of water, and supplied me with figures relating to goitre among school children in Canterbury.

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