From Marie Curie to the Demon Core: When Radiation Kills

Cherenkov radiation glowing in the core of the Advanced Test Reactor at Idaho National Laboratory. (Credit: Argonne National Laboratory) When we hear the word “radiation,” we tend to think of atomic bombs (like the ones that fell on Hiroshima and Nagasaki), or environmental mishaps like the three-eyed fish living outside Springfield's nuclear power plant on The Simpsons. But radiation – a term that refers to the transmission of energy through waves and particles – is not always a destructive force. “The word radiation is a lot broader than people realize,” says Johnathan M. Links, a medical physicist and professor at Johns Hopkins School of Public Health. “When people say radiation, what they usually mean is ionizing radiation, which has sufficient energy to eject electrons from atoms. Non-ionizing radiation doesn't have that capability, and that's an important distinction. When you eject electrons from atoms you can break chemical bonds, and that's what leads to the microscopic and macroscopic damage that radiation causes.” By breaking those chemical bonds inside our bodies, ionizing radiation can destroy or damage critical components of our cells, leading to injury, and at high enough doses, death. And low-level exposure can damage our DNA, potentially creating harmful mutations down the road. Human beings are exposed to radiation everywhere in our environment: Heat up leftovers in the microwave or turn on a lightbulb, and you're getting a dose of non-ionizing radiation. But even ionizing radiation – the kind that's capable of causing cellular damage – is everywhere, from the soil to the foods we consume. Each year, human beings are exposed to 300 millirads of naturally-occurring ionizing radiation, what’s called “background radiation.” Exposure to ionizing radiation over time (even in small doses) increases the risk of developing cancer. But the amount of background radiation we're exposed to yearly is so small, human beings would have to live for thousands of years before it could do any damage. However, when humans are exposed to very large amounts of ionizing radiation in a short period of time, Acute Radiation Syndrome (ARS) occurs. “There's a very noticeable threshold for developing radiation sickness, and in big round numbers that threshold is around 100 rads,” says Links. (For context, a mammogram is only 0.4 rads, or approximately 7 weeks of background radiation exposure.) People exposed to 100 rads start to show signs of ARS, which include fatigue, nausea, vomiting, diarrhea, and seizures – and the higher the dose, the more likely death is to occur. “Depending on the dose, you could die in 2-3 weeks as the blood-forming cells in your bone marrow shut down, or you might die in a matter of days because your GI tract is affected and you can't absorb nutrients,” Links says. Generally speaking, anything over 600 rads is considered a lethal dose. And it’s happened before, although such incidents are fairly rare. Whether it was because the effects and sources of radiation weren’t fully known or because of an unfortunate accident, human beings have encountered deadly doses of radiation before. Here are five of the most notable incidents.