Milk contamination with 131I by nuclear test

In order to examine the variation of 131I concentration in milk of cows fed on the pastures contaminated with 131I by nuclear test, 131I was intravenously or orally given in a form of Na131I to cows and goats, that were secreting milk, and the results were observed. The blood concentration of 131I which was given orally reached the peak within two hours. 131I in the blood became maximum in the milk of cows after about one hour, while in goats it became maximum a little later, after about one and a half hour. All the blood 131I once entered into the thyroid gland and moved into the milk. Twenty to thirty per cent of the given 131I transfered from the blood into the milk, and the concentration in the milk decreased less than 0.1% seven to ten days after the administration. More than 90% of 131I was excreted as feces, urine and milk, and the other remained in the thyroid gland. However, the measurement value of this experiment differed from that of the nuclear test by the Chinese Communists. It was caused by the difference of absorption between natural 131I and a chemical form, Na131I. (Kanao, N.)