By Debbie Koenig
Tense and often terrifying, HBO’s miniseries Chernobyl dramatizes the disaster that took place at the Soviet nuclear power plant in April 1986. In gruesome detail, we see employees and emergency workers accidentally exposed to massive amounts of radiation, and the aftermath of acute radiation sickness.
To find out how exposure to radiation affects our bodies, we spoke with Fred Mettler, Jr., MD, MPH, an expert in radiation who was the Health Effects Team Leader of the International Chernobyl Project, and the United States representative to the United Nations Scientific Committee on the Effects of Atomic Radiation for 28 years. Our interview has been edited for clarity and length.
WebMD: How does radiation sickness work—how does it enter our bodies, and what does it do?
Mettler: It typically comes from penetrating radiation, gamma rays or x-rays that get absorbed by your body. When radiation is absorbed it deposits energy in your cells. If the energy is high enough it kills the cells.
Not all parts of your body are equally sensitive—brain cells are very resistant, but your bone marrow and gut are very sensitive. With a low- to medium-level exposure, it’ll knock out your bone marrow. In a few days to a few weeks without treatment, you won’t make any more white blood cells to fight infection. That’s the lower end of the spectrum.
Raise the dose a bit higher, and radiation can start knocking out the lining of your gut. You’ll get diarrhea, with fluid and electrolyte loss. You’re much worse off—plus you’ll also have those bone marrow issues. As you raise the dose you affect still more systems in your body.
Remember that in accidents, most people aren’t standing facing one way the whole time. They’re peering around corners, turning this way and that. The exposure becomes a lot more complicated, with some parts of the body getting more than others.
Radiation that doesn’t penetrate deeply can kill off your skin. What happened to a lot of guys at Chernobyl was their bone marrow dropped out so they couldn’t fight infection, and they also had burns all over. With big burns you’re subject to infection. The germs get in through your skin, and you don’t have the wherewithal to fight that.
WebMD: How much radiation exposure does it take to kill someone?
Mettler: The radiation level from the natural background in the U.S. is around three millisieverts, which is an indication of the relative damage to our bodies. To get into acute radiation sickness, you need well over one sievert. That’s 1000 millisieverts, more than 300 times as much. For example, if you got 100 full-body CT scans at once, that would be enough to get you to the lower bound of mild acute radiation sickness. But if you spread it out over time your body has the ability to repair itself, like with radiation treatments for cancer that are spread out over weeks. An exposure all at once is worse.
With the Chernobyl emergency workers, one or two survived receiving up to eight sieverts. Nobody’s been able to survive getting over 10 sieverts in a short time, even with the best medical care. All your systems are in trouble at that level, with kidney failure, lung failure, intestinal damage, and no bone marrow.
If you get just the bone marrow failure, usually you can bring people through that. In Chernobyl 134 people had acute radiation sickness, but only 29 died. Over 100 made it.
WebMD: What are the symptoms of radiation poisoning?
Mettler: If you get high doses to your skin, above 3 sieverts in a short time, you’ll see reddening of the skin within a couple hours. The other thing you get pretty early is nausea and sometimes vomiting. One of the guys I saw at Chernobyl was a fireman who had his battalion called up. They were told, “Stand here, we may need you,” right next to the reactor building. They stood there a couple hours, not doing anything. Eventually a doctor came around and asked how they were doing. One said they’d just had lunch but there must be food poisoning, because they were starting to vomit. The doctor made them leave immediately. He saved their lives.
WebMD: Is radiation exposure contagious?
Mettler: At Chernobyl the guys were covered in radioactivity—they had radioactive dirt all over them. It’s like dealing with a kid who comes in from playing in the mud: If you take your clothes off before coming into the room, it takes care of 90% of the problem. Then you rinse off. The people who were in the dispensary taking care of the Chernobyl workers got some exposure, since the dirt gives off gamma rays. But their doses were a little less than a CT scan. After the workers were cleaned up, there was nothing contagious about any of this.
We put people with acute radiation sickness in reverse isolation to protect them, not because they’re contagious—they don’t have any bone marrow to fight infection, so they can’t be near germs.
WebMD: Is there a cure?
Mettler: At lower levels of exposure, one of first things you do is give antibiotics. If you can kill the bugs in your gut to begin with, that will keep you from absorbing them if you lose the lining of your gut. If your platelets go down and you start bleeding, they can give you platelet transfusions. The other thing they can do is to provide the drugs called CSF, colony stimulating factor, which they give to some patients undergoing radiation or chemotherapy treatment for cancer. That stimulates the production of blood cells. If you have enough of your bone marrow left and get CSF, you’ll probably make it.
WebMD: What role does iodine play?
Mettler: Iodine is a big component of what happens in a nuclear reactor. If radioactive iodine vapor comes out in an accident you can’t see it or feel it, but you can absorb it through your skin or inhale it. Or it settles down on the grass, cows eat the grass, and then kids drink the milk. When you take iodine into your body it goes right to your thyroid gland. Radiation to thyroids, especially children’s, causes thyroid cancer.
But if you take potassium iodide three hours before exposure, it’ll block 100% of the radioactive iodine from going to your thyroid. The potassium iodide fills up your whole thyroid, so the radioactive type passes right through. Even if you take potassium iodide at the same time as you’re exposed to radioactive iodine, it’ll help a lot. But 24 hours later, it won’t do much of anything—that radioactive iodine is already in your thyroid.
Potassium iodide protects your thyroid, but it doesn’t help bone marrow or anything else. It won’t protect you against radiation sickness.
WebMD: How long does it take to recover?
Mettler: That depends on the dose. People with bone marrow problems come back within two to three months. One thing that doesn’t happen right away is cataracts—most people with acute radiation sickness get them. But that’s not a big deal, since they’re easily fixed. Most of the Chernobyl guys were transiently sterile, but that was temporary. A bunch of them had kids later on.
There’s been a lot of research done about the possibility of genetic mutations, hereditary effects. There’s no evidence at all that anything like that occurs in humans, even after large studies of children of cancer survivors who were treated with radiation. We think it’s possible, but we’ve never seen it—not even in atomic bomb survivors.
WebMD: What about the increased risk of developing cancer?
Mettler: Before we did studies at Chernobyl, we needed to know how much cancer the surrounding areas had to start with. But they didn’t have any cancer registries. It turns out that in most of these rural villages, when someone died the death certificate was filled out by unqualified people. Nobody knew if it was lung cancer or pneumonia—the records were disastrous. So we compared Ukraine to Poland, which shares a border. The cancer rates in Ukraine were one-quarter what they were in Poland. Only after Chernobyl did the affected countries start realistic cancer registries.
Some people have reported a fourfold increase in cancers, but without accurate records to begin with that’s unreliable. We expected to see a clear increase in leukemia, but the papers are contradictory and it really hasn’t been definitively found. We don’t know why.
For comparison, in Japan during World War II, the average dose from the bombs was 230 millisieverts. Scientists followed over 80,000 survivors for 60 years and found that there were only about 500 excess cancer deaths.