• Tritium is a radioactive isotope of the element hydrogen. It is naturally produced in the upper atmosphere when cosmic rays strike air molecules and as a byproduct in nuclear reactors that produce electricity. Exposure to it and other radiation increases the risk of developing cancer.
• Strontium-90 is a fission byproduct of uranium and plutonium. Large amounts were produced in the 1950s and 1960s during atmospheric nuclear weapons tests.
Source: Environmental Protection Agency“