The paper from the primary scientific literature I will discuss today was written by the Finnish scientists Iisa Outola, Ritva L. Saxén, Sirpa Heinävaara of the Finnish Radiation and Nuclear Safety Authority.
The paper is published in the Journal of Environmental Radioactivity and the abstract is available here Journal of Environmental Radioactivity, Volume 100, Issue 8, August 2009, Pages 657-664
Among fission products released either by nuclear weapons or resulting from Chernobyl, the two most problematic may be cesium-137 and strontium-90. Both elements have half-lives short enough to have very high specific activities and long enough that they can persist for quite some time. The half-life of Cs-137 is about 30 years, the half-life of strontium-90 is about 28 years.
I have written extensively on cesium in this space - I'm very fond of the chemistry of this fascinating element which is often glossed over as if its chemistry were simple and predictable and unexciting although, in fact, cesium's chemistry is anything but simple and predictable. Though I could still say more about cesium, I won't, other than to remark that the main risk of cesium-137 is very much involved its similarity to the important biological element potassium.
Calcium is, of course, also a very important biological element, both structurally and biochemically, and a problem with strontium-90 is that it's biological chemistry is almost identical - not exactly identical but very similar - to that of strontium. Thus ingested Sr-90 tends to accumlate in teeth and bones, for instance.
(A major nutcase named Ernest Sternglass collected huge quantities of baby teeth for several decades in the just passed century - including possibly some from kids I more or less grew up with - trying to prove that the Millstone Nuclear Power Plant in Connecticut was going to lead to beaucoup deaths among babies on Long Island. Predictably he gathered a lot of attention from people who were convinced he must be telling the truth, because they, like him, regarded science as something involved with seeing only what one wants to see. Serious radiobiolgists and health physicists never took Sternglass seriously.
Everyone on Long Island will die, by the way. I know lots of people on Long Island who did, in fact, die already. I, however, am still alive, even though I grew up on Long Island, where much of the drinking water leaches through garbage dumps.)
Sr-90 when isolated from a matrix in a relatively pure form, reaches radioactive equilibrium with its daughter nuclide Yttrium-90, Y-90, after about a month. In pure Sr-90, the concentration of Y-90 actual rises for about a month, reaches a maximum level, and then declines.
Y-90 is sometimes used in radiomedicine, although probably not on the same scale as Tc-99m. Y-90 is most often obtained from radiostrontium, by allowing the radiostrontium to decay to equilibrium with its decay product and then "milking" it out of the mixture of radioelements.
Anyone who has Sr-90 in their bones - and this almost certainly after the 1950s and 1960s open air nuclear tests includes everyone on earth - also has Y-90 in their bones, and for that matter, the stable decay nuclide, zirconium-90.
Everyone on earth will die.
However, the radiation from Sr-90 and Y-90 is qualitatively different from radiation from materials like Cs-137 inasmuch both Sr-90 and Y-90 are pure beta emitters. Beta particles are not very penetrating even though they are quite energetic. They can be stopped by light shielding, a piece of plywood maybe, or even a few centimeters of air. (However, beta particles in contact with heavy metals like lead can actually generate x-rays or even gamma rays.)
The fact that beta rays are not penetrating has lead - especially in former times - to their use in portable power devices. The Soviets were particularly wide practioners of this sort of thing. They powered a whole bunch of light houses - light buoys might be a better term - along the Arctic Ocean's Russian coast in the last half of the twentieth century with Sr-90 batteries, which could be expected to produce power for half a century at least.
Then they forgot where these bouys were, so they never could go back to collect them. This may or may not be a scary thought. It depends on how you see things. A good rule of thumb - not necessarily absolute but reasonable - is that any radionuclide is effectively nonradioactive after 10 half-lives have passed. A particular radionuclide in a particular chemical setting, say a radioisotope thermoelectric generator - an RTG - is of course designed not to escape quickly, and if it does escape, unintentionally, it is further subject to dilution by the radius of diffusion. In the case of the Soviet RTG's they may represent some risk for up to 280 years, after which all of the strontium now in them will be zirconium. It is not clear to me at least, if any of the strontium will ever leach out of the RTG's or if anyone will ever be injured by any of them. Probably they are less risk than if the Soviets had installed diesel powered light buoys.
Maybe you are concerned about the lost Soviet light buoy RTG's, but I think we have more important things to worry about, the epidemiology, for instance, of the benzene released by the recent Gulf Oil disaster, for instance, although I guarantee almost everyone will forget about that far greater human risk in short order.
Nevertheless, everyone in Russia will die.
By the way, I wrote about the Karachi Harbor Tasman Spirit oil disaster in this space in a diary in 2008, called Largest Human Exposure Ever: Health Effects Tasman Spirit Accident. The title was correct in 2008. It is obviously not correct now, although I assure you that there will be less concern in five years with the epidemiology associated with Alabama and Louisiana's recent benzene exposure from unrestricted release of crude oil than there will be with Chernobyl in 5 years. People will still be talking about Chernobyl in 5 years, and everyone will have completely forgotten Louisiana and Alabama and BP in 5 years. The process is already under way.
Everyone in Karachi will die. Everyone living on the North Shore of the Gulf of Mexico will die.
So what about the Finnish fish?
Here are some excerpts of the paper cited above:
Global nuclear weapons tests carried out in the 1950s and 1960s and the Chernobyl nuclear accident in 1986 introduced man-made
radionuclides into the Finnish environment, the most important being long-lived 137Cs and 90Sr. 90Sr originating from nuclear weapon tests was rather evenly distributed over the country. The accumulated deposition of 90Sr in Finland in 1985 has been estimated at 1100 Bq/m2 (Aaltonen et al., 1990). The Chernobyl accident, on the other hand, resulted in very uneven deposition of radionuclides in Finland. The highest 90Sr deposition, 590 Bq/m2, was detected in 1986 in central Finland (Aaltonen et al., 1990). The fallout pattern for Chernobyl 90Sr is not known in detail because, as a pure beta emitter, 90Sr cannot be directly measured and requires laborious analytical separation. The pattern for 137Cs, a gamma emitter and the main contributor in fallout in terms of long-term exposure, has been well studied (Arvela et al., 1990). 90Sr, a nonvolatile nuclide, did not follow 137Cs, a volatile nuclide, as suggested by the 137Cs/90Sr ratio, which varied from 3 to 67 in different areasof Finland (Aaltonen et al., 1990).
This is pretty much what I've already said above, without the sarcasm and without reference to Soviet era buoys, or the regrettable Soviet practice of discarding used nuclear fuel from submarines directly, without treatment, into the Artic ocean.
The authors go on to tell us that 10% of Finland is covered by lakes and streams and that fishing is a very common practice in Finland. Reportedly the average Finn eats about 14 kg of freshly caught fresh water fish a year. Moreover, 90Sr, both from Soviet nuclear weapons testing on the Artic Ocean island of Novaya Zemlya and from Chernobyl can be accumulated in fish.
(I have written about Soviet nuclear weapons tests on Novaya Zemlya in this space in a diary called Every Cloud Has A Silver Lining, Even Mushroom Clouds: Cs-137 and Watching the Soil Die.)
Anyway.
Quoth the authors of the Finnish Fish paper:
...studies have demonstrated that the bioaccumulation of 90Sr by fish is affected by many physical, chemical, biological and ecological factors, including the 90Sr deposition, feeding habits of the fish, weight of the fish, trophic characteristics of the lake, Ca concentration in water and other chemical and hydrological characters of the lakes as well as the quality of their drainage basins. A considerable proportion of 90Sr is transferred by runoff from land to water courses (Salo et al., 1984; Egorov et al., 1999) and 90Sr is mainly transported in the form of mobile compounds with a low molecular weight (Salbu et al.,1992). Besides radioactive decay, 90Sr is removed from lake water primarily by outflow and sedimentation...
Strontium forms insoluble carbonates, phosphates and sulfates, whereas cesium tends to form very few insoluble compounds, and most of those compounds are fairly exotic, the ferricyanides for instance. Since dangerous coal waste often contains significant amounts of the dangerous pollutants sulfuric acid, a source of sulfates, and carbon dioxide, a source of carbonates, you would think that strontium would tend to precipitate because of dangerous coal waste dumping in earth's atmosphere. But this is not the case, because besides strontium, calcium is involved and controls the activity of sulfates and carbonates more actively than dilute but radiotoxic strontium. Since surface waters always contain some calcium - without which everything on earth would die - it also contains some strontium where strontium is distributed. By contrast, the far more soluble cesium has a notable tendenancy for adhesion to particulates in soil and sediment, making it actually less mobile than strontium. Thus, claim the authors the dominant anthropogenic radionuclide in surface waters is not cesium, but is, in fact, strontium.
The authors examined fish in 15 Finnish lakes.
Here is what they found out.
The average 90Sr activity concentration in edible parts of thesampled fish was, respectively, 20 and 60 times higher in vendace (non-predators) and perch (intermediate) than pike (predators), as summarised in Table 3. The lower concentration observed in pike was due to the preparation of the fish for consumption, i.e. the removal of the skin, head, bones. Only the head and entrails were removed from perch and vendace, while the spine and smaller bones were left in the sample. Consequently, perch and vendace samples contained more bones and thus more calcium. 90Sr is an analogue to Ca and its accumulation in different organs follows that of Ca. The lowest Ca concentrations were measured in pike, which concurrently had the lowest 90Sr concentrations (Fig. 2). When the 90Sr activity concentration was calculated in relation to the weight of calcium in ash, the highest levels were detected in non- redatory vendace (mean 2.2 Bq/g of Ca in ash), which were approximately twice as high as those measured in predatory pike and intermediate perch (mean 1.2–1.4 Bq/g of Ca in ash; Table 3).
A Bq is the decay of one atom.
Let's cut to the chase though. The authors write this, giving some sense of risk.
- Radiation dose via fish.
The integrated internal radiation dose via consumption of fish was estimated to be 18 mSv during 1987–1997. This was calculated assuming a consumption of 3 kg of fish per year, 1 kg each of vendace, pike and perch (edible parts), and the dose coefficient of 90Sr via ingestion for an adult person 2.8 X 108 Sv Bq-1. For dose calculation, fishingwas assumed to take place in the lake where the 90Sr concentrations in fish were among the highest measured (L. Vehkajärvi). Since 90Sr accumulation in muscle tissue is low, its contribution to the human dose is low, even though the dose coefficient of 90Sr via ingestion is higher than that of 137Cs. The corresponding estimation for the radiation dose caused by 137Cs from the same lake was 1.8 mSv in the same time period, being 100 times higher than that of 90Sr. A small number of hunters consumes much more freshwater fish (41 kg/year) than people on average (Markkula and Rantavaara, 1997) and can be regarded as a critical group. The consumption figure of this group with the same assumptions as mentioned above leads to an internal dose of 0.24 mSv via 90Sr in fish in 1987–1997. The average annual dose from all sources in Finland is 3.7 mSv/year.
The bold is mine.
Thus if you assume the very worst case - and why not assume the worst if the contaminant is nuclear and not, for instance, oil- all of the people who eat the most fish fishing in the most contaminated lake, the radioactive exposure is raised from natural background by 6%.
Everyone in Finland will die.
You may therefore raise your radiation risk by eating lots and lots and lots and lots of Finnish fish - more than the average Finn in fact - although it is not clear that it would be as much as you may get if you fly alot. The worst plane to fly in from a radiological point of view was the old and now unavailable Concorde. I flew on the Concorde, and I was born and raised on Long Island. Somehow I seem to be still alive.
I will die. I'm not wishing bad on you, but I feel compelled to point out, so will you die. Neither of us, me the writer, you the reader, are immortal and so it is a worthy task to ask ourselves if the world will ultimately be better or worse not because we have died, but because we have lived.
It is not clear to me that the Chernobyl exposure is necessarily higher than the nuclear testing exposure, by the way.
There is no evidence that Finnish life expectancy has been falling since 1986. In fact Finnish life expectancy is rising fish or no fish. If you don't believe me, look it up.
Commercial nuclear power has been operating for more than 50 years. In that period, during which more than 400 nuclear power reactors have operated the number of events in which the entire nuclear inventory of a large reactor at the end of a fuel cycle has been exposed to the enviroment is still one.
People want to view Chernobyl in isolation from its alternatives, but Chernobyl is not the worst energy disaster of all time. That distinction belongs to the renewable energy accident at Banqiao in 1976, which killed hundreds of thousands of people unambiguously in a matter of days.
It is not clear to me, at least, in an epidemiological sense that Chernobyl will prove to be a disaster on the scale of the BP disaster this past year, although no one will pay attention to the latter and there is a subset of people - anti-nukes - who, with clearly selective attention, can't stop talking about the former.
No one will ever again build an RBMK nuclear reactor - they will build other kinds of reactors and people will also build coal plants - the latter taking place as all the while oblivious types mumble all sorts of wishful thinking about sequestration and so called "renewable" energy. The coal plants will kill people even if they just operate normally, never mind accidents. The nuclear plants, based on the history of the last 50 years, have a much lower probability of harming anyone than the coal plants. The probability is not zero, but it is low, possibly as low as is achievable for any form of energy.
Nuclear power need not be perfect, or even risk free to be vastly superior to everything else. It merely needs to be vastly superior to everything else, which clearly and unambiguously it is.
But if you're really concerned about radiation risks, try not to go fishing in Finland and eating 41 kg of Finnish fish, if that's what you were thinking of doing, and by all means, don't fly there.
Have a nice day.