Understanding Acute Radiation Exposure Effects
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Understanding Acute Radiation Exposure Effects

By Dr. Zoomie

Hi, Dr. Zoomie – I was watching the Chernobyl series and it made me wonder if they got it right with what happens to people who are blasted with a large dose of radiation in a short period of time. It looks pretty serious.

Hmmm…let’s start with the easy part – getting blasted with a high dose of radiation in a short period of time is pretty serious; depending on the dose you receive it can make your blood cell counts drop, it can make you sick, you can get radiation burns, and it can even kill you – so many of the health effects that the TV series showed can actually happen. But here’s the thing – it takes a fairly high dose of radiation to cause the more dramatic effects, and they take much longer to manifest themselves than what most people would think, and certainly much longer than what you saw in the miniseries. That’s the short version – let’s take a little more in-depth look for some of the details.

First, when we talk about acute (short-term) radiation exposure and its effects we’re talking about radiation exposure that takes place in less than about a day. So being exposed to, say, 100 rem in a few hours will give a person radiation sickness, but a person receiving that dose over the course of a year will not. The reason for this is that the body has the ability to repair radiation damage; if the exposure takes place over an extended time the damage will be repaired more or less as it occurs and not enough cells will be affected to cause illness. And with that as a prelude, lets see what some of those effects are.

One of the effects of radiation exposure is damage to our chromosomes and, after an acute radiation exposure of about 1 rem we can see slightly more chromosomal aberrations if we have access to a specialized laboratory that can perform that sort of analysis.

As the radiation dose reaches about 25 rem it starts to affect the blood-forming organs. Some properties that make cells more susceptible to radiation damage are

  • having a rapid rate of cell division (which gives less time to repair the DNA damage),
  • being relatively unspecialized (which means that more genes are active in the cells),
  • having a long reproductive lifetime (giving them more time to accumulated DNA damage and to pass it on to their progeny cells), and
  • being in an environment with higher than normal levels of oxygen (because oxygen enhances radiation’s effects on the DNA).

The cells that produce our blood cells meet two of these criteria fully and are inclined towards a third; a dose of 25 rem will do enough damage that they slow down the production of new blood cells for a while so we see blood cell counts start to drop after several days and they remain depressed for a few weeks or months. And here, please note the time frame – it takes a few to several days before we see the most sensitive cells in the body start to be affected by this level of radiation exposure; to see changes in a shorter period of time requires a lot more radiation.

The health effects mentioned so far won’t be noticed by anyone other than the laboratory technician who’s doing the analyses or the physician who reviews the reports – the person exposed won’t feel a thing. That starts to change when the dose gets to about 100 rem, which is when the exposed person will start to feel weak or lethargic, nauseous, and might start to vomit. But the progression of symptoms is more complex than one might expect. Say I’m responding to a radiological accident and I receive a dose of 100 rem or so in a short period of time. I won’t feel sick right away, but after a few hours I might start to get nauseous, and a few hours later I’ll start to recover. That’s not the actual radiation sickness, though; that’ll hit a few weeks to a few months later. So here, again, we see that the health effects take more time to show themselves than most of us would expect.

As the dose continues to increase the health effects start to get more severe; any dose higher than about 250 rem has the potential to become fatal, although the odds are very much in favor of survival, even without medical care. But at a dose of about 400-500 rem the odds of survival fall to about 50% without medical treatment; at this point it’s opportunistic infections that are the primary cause of fatality, largely due to the loss of the white blood cells that help us to fight disease. With medical care the odds of survival improve considerably, although a person might be hospitalized for up to a few months.

At higher doses things start to get a bit grim; a dose of 700-800 rem, even with the best medical treatment, will be fatal about half the time and a dose of 900-1000 rem is invariably so, usually taking weeks to a few months before the person exposed succumbs.

That’s what the books say – what about real life?

In 1999 there was a nuclear criticality accident in Tokaimura Japan, where three workers were exposed to high levels of radiation in a very short period of time.

  • The lowest-dosed worker received 300 rem. He was hospitalized with radiation sickness for about three months before being released.
  • A second worker received about 1000 rem. He was hospitalized for seven months as the medical staff tried valiantly to treat his symptoms and save his life before he died of multiple organ failure.
  • The final worker received a dose of about 1700 rem, surviving for 83 days before dying of his injuries, including the loss of his immune system, in spite of the best efforts that could be made on his behalf.

This was an exceptional case – in the last 80 years there have been fewer than 100 people who have died of acute radiation exposure (not counting medical radiation therapy misadministrations and other errors) and 27 of those were exposed during accidents on nuclear submarines in the Soviet Navy decades in the past.

This is what happens when the entire body is exposed – what’s called whole-body exposure. But what happens when only part of the body is exposed? Well…that part of the body suffers, but the person survives. This is, after all, the idea behind radiation therapy for cancer – to deliver a destructive radiation dose to the tumor without damaging healthy tissue, and leaving the patient alive and healthy. I have met a few people who were missing fingers from reaching into the very high dose-rate x-ray beam produced by an x-ray diffractometer (a device that uses x-rays to understand how atoms are arranged in crystals). Dose rates in these beams can be in the thousands of rem per minute so it doesn’t take long to receive a dose strong enough to cause irreparable damage.

The most common radiation injuries, though, are skin burns. In a medical setting these can happen if a patient is exposed to excessive “beam time” during fluoroscopy; radiation cancer therapy can cause skin burns as well. In a nuclear power setting small skin burns can occur if a “hot” particle lands on a worker’s skin, especially if it’s emitting beta radiation (due to the short range of a beta particle in tissue all of the decay energy is deposited in a relatively small volume of tissue). On a larger scale, two Fukushima workers received beta burns on their lower legs due to wearing leaky boots while wading into what turned out to be leaking reactor coolant laced with fission products due to fuel damage. I had a chance to meet the physician who treated the men; he told me that they both had second-degree burns on their lower legs, which he treated the same as any other second-degree burns.

So this is the bad news – acute high levels of radiation can cause injuries, illness, and even death.

And here’s the good news – it takes much more radiation to cause these problems, which usually take longer to manifest themselves than what most people think. So much radiation, in fact, that we only see, on average, one or two cases annually outside of medical treatments. And if we subtract the incidents on now-retired submarines from a nation that no longer exists the rate goes down to less than one annually. So – yes, radiation can be deadly. But most of the time it isn’t.

Oh – and as far as the Chernobyl TV series goes…it’s not very accurate in its portrayal of the health effects of acute radiation exposure. In particular, they showed symptoms (e.g. skin burns) showing up far more rapidly than experience has shown us and manifesting themselves in a more dramatic fashion than we know to be the case.  And – yes – I know…dramatic license. To which I’d counter that it seems to me that a nuclear reactor explosion, meltdown, and fire ought to be fairly inherently dramatic, just telling the story the way it happened. I’m not quite sure why a good writer would feel the need to embellish.