Friday, June 26, 2009

It does matter what you do with your old equipment: Goiânia’s dance with cesium-flavoured death

This is a story with two subjects. On the one hand, we have another blatantly irresponsible organization failing to take the most basic safety precautions; on the other, we have the deadly results of ignorance. It’s far from the only tale of its kind; the list of radiological accidents in developing or less-developed countries is depressingly long.

In order to explain how Goiânia happened, we need to touch briefly on the nature of the machine that started the disaster. Radiotherapy for cancer can take many forms: teletherapy (now known as external beam radiotherapy), where the source of radiation is outside but focused on the body; brachytherapy, where sealed radioactive sources are placed inside or next to the part of the body needing treatment; and systemic or unsealed source radiotherapy, where a soluble radionuclide is injected or ingested into the body. Mostly when people think of radiotherapy they think of external-beam/teletherapy machines with the rotating gantry and patient couch.

These days EBRT is mostly performed using linear accelerators, which produce a powerful beam of beta radiation (electrons) or X-rays with the push of a button and do not require dangerous radioactive source capsules, but in the early days of teletherapy they didn’t have that option. The two most common radioactive substances used as teletherapy sources are cobalt-60 and cesium-137. Both of these will kill you quite quickly if you pick them up in your hands: the machines using them rely on massive lead shields to limit the radiation to a controlled, collimated beam. The cesium-137 source in the Goiânia accident was filled with highly soluble, highly dispersible powder, rather than pellets of metallic solid material. This would prove to be important.

The unit involved in the accident was a Cesapan F-3000, a 1950s Italian design containing what was probably a source capsule manufactured in America in the seventies. It would have looked a little something like this (images from IAEA report). The rather ominous-looking head was capable of moving up and down on its support pillar and rotating through a couple of horizontal axes, and contained the source capsule in a rotating assembly that could move to line up the window in the capsule with the radiation aperture in the head, as illustrated here. The window in the shielding of the capsule, through which radiation could escape, was made of iridium. According to the International Atomic Energy Agency (IAEA) report, the source itself was of standard international dimensions and potency.

This machine was left in the derelict premises of a private radiotherapy clinic in Goiânia, capital of Goiâs State, Brazil, after the partnership that owned it dissolved toward the end of 1985; a cobalt teletherapy unit from the same clinic premises was removed and transferred to a new facility, but the cesium unit stayed where it was. We aren't sure why.

Vagrants used the gutted building to shelter in; wildlife came and went, and the Cesapan F-3000 stood there growing quietly more obsolete. It is perhaps surprising that it remained unmolested for two years before enterprising locals considered its potential scrap value.

On September 10, 1987, two men, A and B, began to try to dismantle the machine. It took a while and several attempts, but by September 13 they'd managed to extract the rotating assembly from the massive shielding of the radiation head. Outside this shielding, the unprotected source was giving off 465 rads an hour, or 4.65 Gray if you want to be modern about it. For comparison, the accepted annual radiation dose for non-nuclear-workers in the USA is between 1 and 5 millisieverts, or ~ 0.001 to 0.005 Gray.

They put the assembly in a wheelbarrow and took it to A's house; A had suggested salvaging the machine for scrap in the first place. That day, both of them began to vomit; over the next few days, B developed diarrhea and edema of his hand, which subsequently would develop into a burn corresponding to the size and shape of the window in the source capsule. They attributed their symptoms to something they'd eaten, and in fact when B saw a doctor he was told his symptoms were due to a food allergy and he was to take it easy for a week.

The real horror begins

In the days between September 13 and September 18, A had been tinkering with the rotating source assembly, which he'd dumped under a mango tree in his yard. He was trying to get the source capsule free of the assembly. At some point he managed to break the iridium window of the source with a screwdriver.

He thought that perhaps the intensely radioactive cesium thus exposed might be gunpowder, and tried to light it.

On the 18th he managed to get the breached source free of the rotating assembly, and sold the whole mess to a third man, C, who owned a junkyard nearby. That night, C went into the garage where the bits were stored and noticed that the stuff in the broken capsule was emitting a blue glow, and brought the capsule into his house to show it to his wife. Because it was so pretty and so strange, they thought it might be valuable, or have supernatural powers, and invited their friends over to have a look. On the 21st one of these friends dug out some of the powder with a screwdriver and took it away with him to give to his family and friends. Quite a few of them rubbed it on their skin like body glitter. C received a total dose of 7Gy and survived. His wife (5.7 Gy) would not.

I know this reads like a horror novel. It gets worse.

More people were (unsurprisingly) suffering the symptoms of acute radiation sickness: C's vomiting wife was examined at a local hospital, diagnosed with food poisoning, and sent home to rest. Her mother came over to take care of her, and took home a dose of 4.3 Gy.

Two of C's employees were tasked with removing lead from the remnants of the assembly, and worked on it from September 22 to 24. Directly exposed to the breached source capsule, they would be among the four victims who did not survive.

The last of the four fatalities was C's six-year-old niece, whose father had visited C and taken away some of the glowing powder. This was left on the table and handled by the family during meals. The little girl had played with the powder and put her fingers into her mouth. According to one source, when international medical teams arrived to treat the victims, they found her in an isolated room in the hospital because the staff were afraid to go near her.

On the 23rd, B was admitted to hospital: his skin lesions were diagnosed as related to some exotic disease, and on the 27th he was transferred to the Tropical Diseases Hospital.

The authorities finally become aware of the accident

After doing its damage to C's friends and family, the source and rotating assembly were sold to a second junkyard. The sudden epidemic of vomiting and diarrhea among their acquaintances was not lost on C's wife, who became convinced that the glowing powder from the capsule was responsible for all the sickness. On the 28th, ten days after the source was transferred to C's ownership, she and one of C's employees went to collect the remains of the source and rotating assembly from the second junkyard, put it in a plastic bag, and took it by bus to a hospital, spreading contamination as they went. The employee and C's wife presented a doctor, P, with the source in its bag, and she told him that it was "killing her family."

By now the employee who had carried the bag was developing a serious radiation burn on his shoulder, where it had rested, and he and C's wife were sent to the Tropical Diseases Hospital, where B and several other contamination victims had been sent for treatment. One of the doctors at the TDH was beginning to suspect that in fact the nearly identical symptoms of this whole cohort of patients could have been caused by radiation, and he contacted a colleague who had independently been contacted by Dr. P. Dr. P had initially thought that the bag contained bits from X-ray apparatus, and became wary of it, moving it outside the facility (and thus probably saving his own life).

The doctors at the TDH had another look at the patients, with the mysterious bag's contents in mind, and agreed that it would be a good idea to contact the state department of the environment; when they did, it was recommended that a medical physicist examine the package.

On the 29th they found a medical physicist, W. He found a radiation monitor used for uranium prospecting, which had a range of 0.03–30 microgray/hour, and set off for the hospital where the source was currently located: quite some distance away he noticed that the monitor was pegged no matter where he pointed it. He assumed it was malfunctioning and went back to fetch a different one, which showed exactly the same thing as soon as he turned it on.

At this point W realized that something was desperately wrong. At the hospital, Dr. P had become sufficiently concerned about the source in its bag that he had called the fire department, which had arrived and was preparing to chuck the whole thing into a handy river; W arrived on the scene just in time to prevent this. He convinced them to evacuate the hospital and make sure no one else got near it, and after talking with Dr. P they set off together to C's junkyard–where the monitor again read off the scale.

The official response begins

W, among others, managed after some effort to notify the secretary of health. Once the authorities had been convinced that yes, in fact, this was a huge deal and would require evacuation of a large number of people, steps began to be taken with considerably greater speed. The physicist and physician at the radiotherapy clinic's new location were notified, and the source was tentatively traced to the abandoned clinic and the cesium unit.

Civil defense forces were notified; the TDH was informed that a number of patients were contaminated; the known sites of contamination were resurveyed with equipment from the radiotherapy clinic; an emergency receiving and decontamination facility was set up in a local stadium. W, the physicist who had initially discovered the contamination, was contacted by an individual who had intended to cut up the source for C with an oxyacetylene torch (but had luckily forgot), who explained several useful details to the investigation.

International teams were sent in to decontaminate and treat the victims of the disaster. There is not a great deal that can be done in cases of radiation sickness: therapy consisted of dealing with the acute period of bone marrow suppression and subsequent immune deficiency, treating the burns, removing radiation from the body (decorporation), and general support. It's rather terrible to consider that many of these patients recontaminated their skin repeatedly by sweating; the cesium in their bodies found its way out in everything. Chelation with Prussian blue helped a significant number of the victims, a point which recalls the hopeless suggestion of treating Louis Slotin with methylene blue after his deadly exposure to plutonium criticality.

The final count of persons with significant contamination, out of the hundred thousand screened, was two hundred and forty-four. Most of those were lucky and received fractionated doses--spread over a long time period, giving the body's tissues a chance to attempt to recover from the damage. Some were not. The dead of Goiânia had to be buried in lead coffins surrounded by concrete.

Cesium didn't just destroy people in Goiânia, it destroyed property and livelihoods. Seven houses had to be demolished, so badly contaminated they could not be made safe. Topsoil was removed by the ton. In total 85 houses had to be decontaminated.

More than anything Goiânia stands as a blazingly vivid example of the importance of keeping sources secured. A number of factors conspired to make this accident as deadly as it was: criminal negligence on the part of the radiotherapy clinic which failed to remove and secure the capsule from the teletherapy unit, the nature of the radioactive material--its mysterious and magical blue glow entranced people, significantly increasing the scope of the disaster, and its powdery nature was easily dispersed and easily soluble--and the remote location of the disaster site. But the lesson of Goiânia applies to all source capsules, not just cesium in remote and unsophisticated locations.

Sadly, it's not a lesson that's been learned particularly well. In the years since Goiânia, unsecured radiation sources have caused at least four radiological accidents around the world. In Samut Prakarn, Thailand, a disused cobalt-60 teletherapy head was partially dismantled, taken from an unsecured storage location, and sold as scrap metal–in February of 2000. It's still happening. It will continue to happen as long as those in charge of radiation sources fail in their responsibility to keep them secure.

In many ways the eighties were a great time for death by radiation. You had Chernobyl, you had the 1983 Ciudad Juarez accident in Mexico–eerily similar to Goiânia–you had the Therac-25 linear accelerator deaths; but it hasn't stopped. People need to pay more attention to things that have happened, if they want to live very much longer; and people who take the responsibility to treat their fellow humans with lethal radiation must take the responsibility to prevent their fellow humans from dying of it.

Information in this article is from the IAEA report on the incident, available at www-pub.iaea.org/MTCD/publications/PDF/Pub815_web.pdf, and from Wiki.

2 comments:

  1. Fascinating!! This is quickly becoming one of my favorite blogs ever. Keep up the good work!

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  2. Thank you! Appreciate the feedback, and I'm glad you're enjoying it.

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