| Kept secret until after the war, they were respectively called americium and curium. |
| Some like americium, iodine 129 or cesium 135 can remain several hundred millenia. |
| Although plutonium isotopes and americium 241 will persist perhaps for thousands of years, their contribution to human exposure is low. |
| Internal contamination with plutonium, americium, or curium can occur through a variety of routes including ingestion, inhalation, or direct contact through wounds. |
| Those that do not, such as technetium and americium, have been substituted, respectively, by rhenium and neodymium, which have similar traits. |
| Metallic californium has been prepared and is structurally similar to metallic americium, curium, berkelium, and most lanthanoid metals. |
