deteriorated since the time. the radiation expert has led seven expeditions to fukushima. >> i think there was probably some exposure on the uss ronald reagan. saying some manifests to many people any radiation is going to be dangerous. that is actually not the case. >> he says it has navy's calculation suggest the radiation exposure was about the same as taking a transatlantic flight or not very much. he says health effects to cause cancer take years and decades to show up. these illnesses have happened two soon to have been as a result of the exposure at fukushima, he says. >> you have exposure then there's a pause before health effects colonel. >> what -- effects come.