Twenty years ago or so the late Dennis Evans told me a story about some cops who thought that they would tell a “white lie” to protect society (I have no idea where this vile story occurred or if Dennis had made it up or not). What happened was these boys in blue raided a drug dealer’s hotel room. They find some packets of cocaine. Then to make sure that the man went away for longer they plant some extra packets of cocaine. I imagine that they wanted to make sure that the judge sent the vile coke dealer away for decades rather than just sending him to HMP holidaycamp for a few years.
The core thesis of the prosecution was that the man was a cocaine dealer who was mixing cocaine with sugar to turn a larger profit and that all the packets had come from a common source. The fact that different packets had different sugar levels made it look like the dealer was mixing purer cocaine with sugar to make a less pure grade.
The police’s expert issued a report on on cocaine content of each packet where he/she lumped all the adulterants together. It is a common habit for people in the illegal drug trade to mix illegal drugs with other materials to increase their profit. So it should not be a total shock for the police to have observed some evidence of such behaviour.
Dennis was contracted as an expert witness for the defence, he retested the cocaine and made a point of measuring the different sugars (glucose, fructose, sucrose etc) in the cocaine batches. He found a purer packet which the police claimed was the parent of the less pure cocaine contained a sugar which did not appear in the less pure packets.
Armed with this information the defence was able to prove that the story that the police were telling was false. They showed that someone (the police) had planted at least one packet in the room. They then suggested to the jury that all the cocaine had been planted in the room. The man then was acquitted on all charges and walked away from the court, I imagine without a stain on his vile character.
While some people might think “I have nothing to do with drugs” and “I am not a policeman” so this story has nothing to do with me. I would say that these people are being very foolish, this is a cautionary tale about telling a “white lie” to get the job done. This is an example of testilying and the vile perils it brings.
It is better to tell the truth about something even if you think by exaggerating that you will be more likely to get the outcome that you want.
Before we go any further I would like to make something clear to those of you who are not regulars here on my blog, I have to agree with the greens, antinuclear lobby or whatever you want to call them or be called yourself (if you are a member of the antinuclear lobby) that the Chernobyl and Fukushima events are horrible. These are events which need to be avoided where possible, and if total avoidance is not possible then these types of events need to be mitigated to eliminate the threat to the general public.
My (or your) revulsion at serious nuclear accidents is not however a license to exaggerate or attempt to use these events to score cheap political points. Frankly those who use these events for selfish ends disgust me just as much as the 19th century mill owners who thought it was quite reasonable to force young children to work in dangerous factories, clean chimneys or go down the coal mine.
My loathing of serious nuclear accidents is one of the reasons why I devote time and energy doing research on trying to prevent a nuclear accident causing harm to the general public. In order to protect ourselves against reactor accidents we need to understand them, part of the quest to understand them involves a quest for truth and an insight. During this quest I am doing my best to share whatever grains of truth I uncover with others, and also to point out silly ideas when I find them. One of the things which irks me is when people exaggerate the consequences of an event, the fact that an event is horrible is not a license to lie. To me the exaggeration of the event is as wrong as a person falsely claiming that it is less bad than it really is.
It has been claimed that the cesium from the Chernobyl accident causes heart disease in adults and children, the core of the idea is that cesium goes into the heart and that the radioactive cesium then damages the heart. Next the person falls down dead from heart disease or at least becomes in invalid.
We need to ask ourselves if the radioactive cesium is able to damage the heart, some time ago (2008) a Yann Gueguen et. al. published a paper (Cardiovascular Toxicology, 2008, 8(1), 33-40) in which they exposed rats to cesium in their drinking water. The amount of cesium was 150 Bq per day for three months. Now the rats weighed 560 grams, which means that they were drinking 267.85 Bq per kilo. Now if we scale this up to a 75 kilo man then he would have drinking 20 kBq per day. As each year has 365.25 days then this 75 kilo ratman will be drinking 7.338 MBq of cesium each year.
We are making the assumption that the cesium behaviour in rats and humans is the same and that the same dose / activity coefficient should be used for both species.
Based on my ALI as a classified radiation worker which is 1.5 MBq of cesium-137 (oral), the rat man will be drinking 4.9 times the ALI which is based on a 20 mSv dose. So the 75 kilo ratman will get a 97.84 mSv dose from the cesium. So this amount of cesium is a very large amount of cesium.
I hold the view that if a member of the general public is getting a 98 mSv dose from an nuclear accident which happened decades ago that something is deeply wrong. This is a dose which is far in excess of what I am allowed to be exposed to at work. So while this study might be an interesting one it is set at a level of cesium which I think is too high.
I suspect that some differences between rats and humans exist, I have checked and the biological half life of cesium in rats is shorter (11 days) than it is in humans (B. Le Gall et. al., Biochimie, 2006, 88(11), 1837-1841). So rats are able to get rid of cesium from their bodies faster than humans can. The estimates for the biological half life of cesium in humans range from about 1 month to 4 months. If we take the UN’s estimate that biological half life to be 100 days then we can compare rats and humans.
I have done some calculations for rats and humans and based on the difference in the biological half life I think that cesium should be 9.1 times less toxic to a rat than it is to a human. So we should revise down out doses for the “rat man”. If we take this correction factor then the rat man used in this experiment if it had been a human would have had a 10.78 mSv dose (0.8 MBq intake)
Now I think a key part of the reasoning behind “chernobyl heart” is the idea that the cesium goes into the heart, I was looking in the literature at animal studies where the experimental animals were fed cesium-137. I found a second paper (Jean-Marc Bertho et. al., Radiation and Environmental Biophysics, 2010, 49(2), 239-248) where mice were contaminated with cesium-137 (20 kBq per litre) in their drinking water.
This paper stated that human exposure to cesium-137 in contaminated areas is in the range 20 to 2100 Bq per day, which works out as giving a worst case amount of 767 kBq per year. While I think that this amount of cesium is a large amount in the general public’s diet it is well below my ALI (Annual Limit of Intake) and far below the level which I worked out by scaling the rat up to the 75 kilo “rat man”.
The mice were feed the cesium in their diet from the age of four weeks onwards, I looked at the intake of the these mice and the females drank 465 Bq per week and the males drank 507 Bq per week. As the female mice (at 20 weeks) had a
weight mass of 23 grams and the male mice had a weight mass of 30 grams we can make a first guess of what human level of exposure we are considering.
The 75 kilo “mouseman” would be getting 1.27 MBq per week while a 65 kilo “mousewoman” would be getting 1.31 MBq of cesium per week. This will work out as 66 MBq per year for the mouseman and 68 MBq per year for the mousewoman. This is a lot of radioactivity.
We are assuming here that the biological half life of cesium in mice is the same as it is in humans and that all other cesium biochemistry and biophysics is the same in both species. Again if we work out the biological half life of cesium in mice it works out being shorter than it is in humans. Using the data from J.M. Llobet et. al., Journal of Environmental Contamination and Toxicology, 1998,61, 289-296 it appears that the biological half life in mice is about 7 days. Thus based on the different biological half-lives the cesium will be 14 times less harmful to mice than men.
So micemen will now be getting an intake of 4.7 MBq per year. This is still a lot of cesium-137 to get in your diet.
Now back to the paper of Bertho, the important thing in this paper is that no clear signs of damage to the mice were seen. Also if you read the paper the radioactive cesium content of the heart (in Bq per gram) is less than the kidneys and the normal muscles of the mice. This paper makes me think that we need to take great care when we consider the possible link between chernboyl cesium and heart disease. This is because the cesium does not seem to be localizing inside the heart in the same way as iodine localizes inside the thyroid.
The next thing to be careful of is the fact that cesium-137 (together with its daughter barium-137m) emits three different forms of radiation. The average beta decay energy of cesium-137 is 188 keV, this is quite a low average beta energy when compared with yttrium-90 (933 keV) and phosphorus-32 (695 keV) but it is about the same as Sr-90 (196 keV). But it is a bit higher than carbon-14 (49 keV). So we can safely assume that some of the beta energy of the cesium which is in the heart will be deposited in the heart.
But 662 keV of the decay energy of the cesium will be in the form of gamma rays, even if the cesium is in the heart then much of this energy will escape from the heart. On average 363 keV of energy will fly away in the form of neutrinos. These are particles which are unlikely to interact with a slab of lead as think as the earth. So I think we are safe to assume that only part of the decay energy of the cesium which is in the heart will be delivered to the heart tissue.
Also bear in mind that the beta and gamma radiation are both low LET (Linear Energy Transfer) radiations. This means that ionization tracks formed by these radiations are long and diffuse, as a result these radiations are less able to damage living tissues. The issue of self repair needs to be considered, the background of radioactivity in a normal human body together with cosmic rays causes all tissue to be subject to ionizing events. The damage from most of these are repaired by the cells.
I think it would be a good idea if those who are making statements supporting the idea that cesium-137 causes cardiac damage to people should address the issues of how much cesium is in the heart and how much of the radioactive decay energy of the cesium is delivered to the heart.
Also they should consider the natural radioactivity (carbon-14 and potassium-40) which is in a normal clean and uncontaminated human body.
Well that is all for now, I will return with more of my thoughts later.
Filed under: cesium, chernobyl, fission products, Fukushima, radiation, radioactivity, radioactivity in food | Tagged: environment, politics, science | Leave a Comment »