Highly
radioactive isotope of
iodine, widely distributed by
radioactive fallout in the 50s and 60s. When the
fallout landed in
grasslands it was eaten by cows and concentrated in
milk. When the milk was drunk by children, the i-131 went to their
thyroids and caused
tumors.
Ernest Sternglass published a study that estimated that upwards of 375,000 US children were killed as a result of atom bomb tests. Certainly fear of such results resulted in the Test Ban Treaty signed by JFK