Hi, Dr. Z! This story came up in my feed about some guy at Hanford who got a huge dose of Am-241 but, contrary to expectations, didn’t die. Can you explain what happened? Thanks!
Yeah – this was a good one! So good, in fact, that there was an entire issue (October 1983) of the scientific journal Health Physics devoted to this one accident. A colleague of mine was involved in responding to this event, and a few others I know well were involved as well. So let me give the summary paper a quick read…and here’s what happened.
Almost exactly 48 years ago (August 30, 1976) a Hanford worker, known in the scientific literature only as Case 246, was working with Am-241 in a glove box when a chemical reaction caused an explosion. The explosion blew the glove box apart, sending shards of glass, nitric acid, and “gram quantities” of Am-241 (1 gm of Am-241 contains about 4 Ci or about 150 GBq of radioactivity, and microgram quantities can be fatal).
Immediately following the explosion Case 246’s contaminated clothing was removed and his face and eyes were rinsed to remove his skin contamination, then he was transported to an emergency decontamination facility. At the facility, he was administered a compound called DTPA to help remove the Am-241 from his body; decon personnel also scrubbed him down with soap and water to remove the contamination from his skin. Doctors treated the nitric acid burns and removed fragments of glass and other materials from his face and upper back.
Further studies and radiological surveys showed that the man’s face was heavily contaminated and that he’d had an uptake of about 1 mCi (40 MBq) of radioactivity. This is about 1000 times more than what regulations permit in a year – and it’s about four times higher than a fatal dose in the absence of medical intervention. Without the DTPA there’s little chance that Case 246 would have survived for very long. With it, he lived for more than a decade.
What’s interesting is that, in spite of this being far and away the highest intake of Am-241 ever recorded, Case 246 experienced very few health effects from his high radiation exposure; only reduced counts in his platelets (cells that help the blood to clot) and leukocytes (white blood cells, which help the body to fight off infection) were felt likely to be related to radiation exposure – which makes sense when we remember that the blood-forming tissues are among the most sensitive to radiation.
The DTPA therapy, which went on for several years, likely removed over 99% of the Am-241 from the body before it could lodge in the patient’s bones or organs; this is likely what saved his life. But even with that, enough americium remained in the body to give some huge doses to the liver (800 rads), lungs (160 rads), and bones (52,000 rad to the bone surface, 1800 rads to the whole bone). But, while the dose to the bone was frighteningly high, the mineral bone is fairly radiation resistant, and the alpha particles emitted by Am-241 can’t penetrate into the interior of the bone to affect the bone marrow. I should mention, too, that the reason these doses could be determined is that, after his death, the patient’s family generously donated tissue samples to the US Transuranium Registry to help scientists learn as much as possible from this unique event.
With such a high radiation dose it might seem counterintuitive that the man didn’t develop cancer. I was surprised at first, then read in a 1995 paper about the accident that, using risk factors developed by the National Academies of Science, there was a 12.5% chance that this would happen. Part of the reason is likely due to the relatively short time between the exposure and the patient’s death – a decade is a long time to survive after such a high radiation exposure, but not considering that radiogenic cancers can take a few to several decades to appear. On top of that, most of the radiation dose to the body was from alpha radiation, which would have been almost entirely shielded by the bone. Yet another factor might be the relative lethality of alpha radiation to living cells – cells that are killed by the alpha radiation can’t go on to become cancerous.
Case 246 passed away due to cardiorespiratory failure on August 17, 1987, just two weeks shy of the twelfth anniversary of the accident, following a history of coronary artery disease that preceded this accident.