Sources of radioactive nuclides, illustration. The radioisotopes shown here are produced by nuclear fission, in the fallout from nuclear power station accidents (upper left) and from nuclear weapons testing (upper right). They are taken up by plants and animals on land and at sea, with cows, algae, zooplankton and fish shown here. Both food chains (via milk for cows) can result in the radiation affecting humans. The isotopes shown here are caesium-137 (Cs), iodine-131 (I), and strontium-90 (Sr). All can cause cancers in humans. For this illustration without labels, see image C047/4530.