In the 1950s and 1960s, several nations conducted tests of nuclear warheads in the atmosphere. It was

Question:

In the 1950s and 1960s, several nations conducted tests of nuclear warheads in the atmosphere. It was customary, following each test, to monitor the concentration of strontium-90 (a radioactive isotope of strontium) in milk. Why would strontium-90 tend to accumulate in milk?