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Tuesday, June 19, 2007

Another danger of radiation

After I posted about Chernobyl yesterday, this is a good time to reflect on an even greater danger of the modern age, by way of another story. This story too has a moral that deals with the nature of science and society - but it's not a happy one.

Sure, it's dramatic when a nuclear reactor explodes and spreads radioactive dust for thousands of miles, killing as many as tens of thousands with cancer. But there are smaller dangers of our radioactive age that may turn out to be even greater.

In 1985 in Goiânia, Brazil, a radiation clinic moved to a new location. Against international and Brazilian regulations, they left a radiotherapy machine in the old building. The machine contained a single tube of cesium chloride made with the radioactive isotope Cesium-137. Cesium-137 emits gamma rays, a highly dangerous form of radiation that can pass through lead and can wreak havoc on human tissue and DNA.* The source at Goiânia had contained enough cesium to create about 50 million radioactive decays per hour. If you stood one meter away from it for one hour, you would receive a radiation dose of about 4.5 grays (all figures from the Wikipedia article).** What would that dose do to you? Probably nothing but irrevocably increase your cancer risk - which is hardly nothing. But if you spent about three full days one meter from the source, your risk would go up to this level:
Severe radiation poisoning, 35% fatality after 30 days (LD 35/30). Nausea is common (100% at 3 Sv), with 50% risk of vomiting at 2.8 Sv. Symptoms onset at 1 to 6 hours after irradiation and last for 1 to 2 days. After that, there is a 7 to 14 day latent phase, after which the following symptoms appear: loss of hair all over the body (50% probability at 3 Sv), fatigue and general illness. There is a massive loss of leukocytes (white blood cells), greatly increasing the risk of infection. Permanent female sterility is possible. Convalescence takes one to several months.

Back to
Goiânia. Brazil has a huge population of squatters that move into abandoned buildings and desperate poor people who scavenge abandoned buildings for scrap metal to sell, to make a few extra centavos. Inevitably, on September 13th, 1987, two men salvaged the radiation therapy machine for scrap. Their names were Roberto dos Santos and Wagner Mota. They both later developed extensive radiation burns, and one had to have his arm amputated.

They tried to open the casing of the cesium source, but were unable to. They did, however, break the opaque window to see the source emitting a strange and beautiful blue light. dos Santos and Mota sold the source to Devair Ferreira, a junkyard owner, who intended to make a ring for his wife, Maria, with the mysterious and beautiful substance.

You probably see where this is going. Ferreira had two of his employees break into the casing to get at the source. Both later died of radiation poisoning. Ferreira showed the source to his brother, Ivo, who scraped some of the dust onto the floor of his home. Ivo's daughter,
Leide das Neves Ferreira, ate meals off the floor. She died on October 23rd and was buried in a lead coffin, sealed with concrete.***

Meanwhile, Devair Ferreira sold the casing of the source for scrap metal, spreading the radiation poisoning around the community. Fortunately, no deaths have been directly traced to the scrap metal, but it's impossible to tell how many people will develop cancer later in life as a result.

Over the next few days, the Ferreiras showed the cesium chloride to many of their friends, and many of them became sick. No one knew why. On September 28th (15 days after the source was found), Maria Ferreira suspected that the mysterious substance might be the cause and took it to a local clinic. The doctor there correctly suspected what had happened. Soon after, the International Atomic Energy Agency was called.

On October 23rd, Maria Ferreira died of radiation poisoning, although she may have saved many other lives by correctly guessing the reason her friends were getting sick.

A massive environmental cleanup started throughout the city of Goiânia, which caused some level of panic in Brazil. The Wikipedia article has more information about the cleanup. The IAEA concluded that the danger is largely gone.

What makes this such a sad story is that these were truly innocent victims. I talked about Dinesh D'Souza yesterday, who is the kind of person who will viciously attack the methods and conclusions of science but would gladly accept radiation therapy if he had cancer, and gladly posts his diatribes on a computer without a word of gratitude for Alan Turing.

No, the people at
Goiânia didn't know any better. Brazil is in a fairly unique situation as a country, straddling the first and third worlds in such a way as to make the Goiânia accident most likely. The country is rich enough to have modern medical care including radiation therapy, but poor enough that there are millions of uneducated poor people who can survive only by scavenging scrap metal from hospitals. A nearly identical accident happened with a truck driver in Mexico in 1983 and thieves in Estonia in 1994.

And that leads to the question of science and society. Who was responsible for the deaths of Maria Ferreira,
Leide das Neves Ferreira, and the two junkyard workers? Certainly the owners of the clinic who left the machine, who were later charged with criminal negligence. Certainly the education system and media in Brazil should bear some responsibility for creating a society where people can't recognize the radioactivity symbol.

But do Henri Becquerel and Marie Curie bear some responsibility too? I think they do. Some people might argue that they are too far back on the chain of causes - after all, Curie died 53 years before the Goiânia accident. But, as scientists are always quick to point out, basic research can have applications that could never be predicted at the time. The positive future applications are nearly always used as support for basic research. But you can't take credit for the good and disown the bad. Once you bring something into the world, you take responsibility for it.

Many of the scientists working on nuclear energy understood this. Henry Kendall founded the Union of Concerned Scientists, and other scientists fought to get nuclear programs controlled by the Department of Energy rather than the Department of Defense.

In an age where we have millions of desperately poor people, a few committed terrorists, and radioactive samples in abandoned buildings all over the former Soviet Union, we should understand this too.

*[Pedantic note for youse physicists]Cesium-137 doesn't emit gamma rays directly; rather, it decays by beta decay into Barium-137m, which is metastable and has a half-life of only 2 minutes. Barium-137m decay is responsible for the gamma ray emissions.[/Pedantic note]

**For what follows, I'm assuming that 1 gray = 0.01 sievert for gamma decay, which is suggested by the Wikipedia article on radiation sickness, which gives Q = 1 for photons and N = 0.01 for skin (which I assume equals external exposure). Someone please correct me if these are the wrong values.

***I may be confusing you with all these Brazilian names, especially when so many of them are named "Ferreira," but I think it's important that these people are remembered.

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Anonymous Anonymous said...

Interesting post. I'd like to make a few comments...

First, if the figure of 4.5 Gy/hr (at 1 m) is correct, then this is already a dangerous high dose.

(From Hall, Radiobiology for the Radiologist, 2000)

3-5 Gy leads to the hematopoietic syndrome. Death would follow in several weeks due to damage to the bone marrow (which produces blood). LD50/60 is about 4 Gy (I believe without treatment), but I think one should survive if you get treatment.

Above 10 Gy (or two hours, if your figure is correct), survival is highly unlikely due to the gastrointestinal syndrome. Radiation damage will kill the lining of the gut, resulting in internal bleeding, dehydration, and inability to digest. Death should happen in a few days. (Hall says no one has survived more than 10 Gy, but I think I've heard about at least one case--not sure.)

Roughly 100 Gy or more will result in death within hours (cerebrovascular syndrome). Immediate nauseau is followed by seizures and coma within hours.

The above is for (adult) whole-body, gamma doses (measured in Gy). The equivalent dose is the dose times a weighting factor (depends on the radiation type: for example, gamma-rays are 1; neutrons, 10-20 depending on who's arguing and which biological endpoint is relevant). ED is measured in Sieverts.

Finally, the effective dose is the equivalent dose to each tissue multiplied by a tissue weighting factor, which takes into account the relative weights of different tissues. Skin has a weighting factor of 0.01, while gonads have a weighting factor of 0.20, colon has 0.12, etc. (The total weighting factors of all tissues add up to 1.0) Effective dose is also measured in Sieverts.

The weighting factor for skin, as in the post, is correct. However, gamma-rays are highly penetrating, and for all practical purposes, exposure to cs-137 is going to be a whole-body dose. So there is no point in looking at the dose to any organ (in any case, we would have to add in the doses to the other organs as well).

Finally, effective dose is useful in the field of radiation protection, which means basically the issue is cancer induction. This is not a useful concept when looking at acute effects; it is useful when considering long-term effects over large populations.

(Another way of looking at acute doses: an acute sub-lethal dose -- in other words, if you barely manage to survive a near-10 Gy dose -- will raise your risk of developing fatal cancer from about 10% to about 20%.)

To sum up, I think that you should just stick with units of Gy for your post (for whole-body gamma doses, the radiation weighting factor and tissue weighting factor are each 1, so there's no point in discussing Sv).

But I think this is an interesting post! There are some lessons to be learned from the Gioania tragedy, as with other radiation accidents.

Wednesday, June 20, 2007 6:56:00 AM  
Anonymous Anonymous said...

(Finished my last post before reading all the way to the end... let me defend the early pioneers of radiation physics.)

Within a short time of discovering x-rays, Roentgen realized the medical implications. (The famous x-ray of his wife's hand, for example -- "Honey, come stick your hand in front of this machine I've been building the basement...") I've heard that he chose not to patent his discovery, so that everyone could benefit (ie, no one could ever control a patent for x-rays).

Marie Curie in turn developed a portable x-ray device to aid in treatment of WWI casualties, and I *believe* she herself (and her daughter?) spent a lot of time operating these devices.

As for Becquerel (whom you mentioned in the post), I have alas not much to say. Charged-particle radiation is used in some cancer treatments, but if his work had direct medical impact, I'm not aware of it. Perhaps some other commenter will step up to defend his name!

You speak of responsibility for the radiation accident... I can't say that I immediately agree with you (although I am considering it carefully), but I wanted to add another perspective as well. The early pioneers were attempting to develop technology with the explicit purpose of helping people. Let us at least weigh that in the balance as well.

Wednesday, June 20, 2007 7:06:00 AM  
Blogger bay-of-fundie said...

Good post. I remember reading about this event years ago.

I'd lay the blame almost entirely on the clinic for not properly handling the stuff in the first place, and for having inadequate disposal procedures.

I disagree about going back and blaming the early radiation researchers. They aren't responsible for how the technology is used.

If somebody is researching nuclear physics with the intent to make a bomb, he is responsible in part for all of the destruction his bomb creates.

If somebody invents a reckless technology, such as genetically-modified crops, and releases it into the wild without adequate safeguards, he is responsible for any unintended consequences of his work.

But I fail to see how somebody who is doing pure research can be responsible for a later invention based upon that research. Nobody can forsee all of the possible applications of a new discovery.

By the way, I am flattered that you link to one of the graphics on my site, but I would have preferred it if you had linked to the article containing the graphic. That would give the reader context. That particular article is one of my funnier ones, so you shouldn't deprive your readers. After all, I won't hold you responsible for any inventions people make based upon the content of my article. The link is:

Thursday, June 21, 2007 12:56:00 AM  
Blogger Slag said...

Thanks for the interesting and insightful comments, all.

Anonymous, thanks for the feedback and the information about radiobiology. I'm certainly no radiobiologist, so I appreciate the help.

A quick tutorial for those not familiar: Grays (Gy) are a measure of how high a radiation dose a person has received; Sieverts (Sv) are a measure of how much damage the radiation is likely to cause, which depends on how the dose was received (ingestion is more dangerous than skin exposure, for example) and on the danger of the radiation type (gamma rays are most dangerous). As Anonymous points out, gamma rays are the most dangerous, so exposure is most damaging.

Bay of Fundie, thanks for providing the link to the your post. Sorry, I should have linked to it earlier. Everyone should read it. But, I wouldn't be so hard on the people asking about the fridge magnet. People are associating the radioactive sign with danger, and they want reassurance that the product is safe. But that's exactly what we want them to think! People should be afraid of the radioactive sign! And it doesn't help to call them morons for having a reasonable, if misplaced, fear.

For both of you, thanks for the comments on the pioneers of the study of radioactivity. Anonymous, I didn't know that Roentgen decided not to patent the x-ray machine, and I think that's lovely.

I think you're both right that the blame rests almost entirely with the Goiânia clinic, and that radiation therapy has saved many, many times more lives than it has cost.

My point was that if we (scientists and defenders of science) want to take credit for the beneficial applications of basic research, we must also own up to some share of the blame for the harmful applications, and we must do our best to make sure that the benefits always outweigh the harms. That's why I think the Union of Concerned Scientists is such a good idea.

I raise this point not to criticize science, or scientists. I want to be a defender of science; I just want to be a careful defender of science.

Thursday, June 21, 2007 6:43:00 AM  
Anonymous Anonymous said...

I agree: a careful defense of science is appropriate. Thank you for letting me offer a different perspective on the moral implications of the radiation pioneers' work.

In your reply to my comment, you had said gamma dose is the most dangerous. I think I would disagree, but the topic gets complicated very rapidly. For the same *whole-body* dose, alpha particles or neutrons would be far more dangerous than gamma dose (radiation weighting factor of about 20, so the equivalent dose for alpha/neutron would be 20 times than for gamma).

But then there's the question of shielding.

Alpha radiation is easy to shield, so it's trivial to protect people from it. Gamma radiation is hard to shield, but neutrons are probably even harder. On the other hand, there's probably no common source of neutron radiation. Other than large scientific facilities, and nuclear reactors, both of which will be well-shielded, the only common source of neutrons is the high-energy radiation in cancer therapy (the neutrons are a side-effect, but they are the reason linear accelerators are put in massive concrete vaults with a "maze" to enter). So you probably won't encounter neutrons.

But alpha sources are common-including natural sources (ie, rocks), as well as manufactured sources, such as the mantles for camping lanterns. Alpha radiation from natural sources won't penetrate even the dead layer of your skin. So as long as you don't ingest an alpha source, or get it in your contact lenses, alpha radiation can't hurt you. If you ingest it--perhaps by breathing in radon if you live in a basement (disclaimer: there's still a lot of argument about the actual effects of natural levels of radon in homes, and it may not be as dangerous as some people think) or by breathing in uranium dust if you're a mine worker--well, then the alpha radiation will damage your lungs, and that's very bad.

So is gamma radiation more dangerous than alpha radiation? Beats me!

Thursday, June 21, 2007 7:23:00 AM  
Blogger bay-of-fundie said...

This goes one step beyond the radioactive magnet:

Thursday, June 21, 2007 9:14:00 AM  

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