Guest Post by Geoff Russell. Geoff is a mathematician and computer programmer and is a member of Animal Liberation SA. His recently published book is CSIRO Perfidy. To see a list of other BNC posts by Geoff, click here.
A recent Nature column raised the prospect that the legacy of radiation leaks at Fukushima Daiichi nuclear power plant would be decades of caesium-137 contamination around the plant. After reading this opening, I expected a hysterical beat up similar to that which prompted my last BNC piece. I was wrong. The author is the editor of a substantial book on the aftermath of the Chernobyl disaster and his Nature column ended with a clear and hopeful message summed up in a concluding anecdote about an elderly couple living near a heavily contaminated lake in Belarus. They were growing their own food and eating highly radioactive fish and doing just fine. They were survivors rather than victims. They had aligned their perception of risk with the numbers. The alternative is like the smoker who is terrified of air travel.
The rest of this piece is devoted to doing some risk perception re-alignment but I need to begin with a covering paragraph.
Nothing in this piece should be taken to imply that nuclear reactors should be allowed to become cheap and nasty because we can live with the consequences. Modern reactors with passive safety features are extremely safe and should reduce in price with appropriate modular mass production techniques. There is no need for corner cutting.
There will be two parts to this post. The first part is about the similarities and differences in the way radiation and food shred your DNA and the second describes the practical consequences with a little case study of Japan.
Part I: What exactly does radiation do to your cells?
Caesium-137 (Cs-137) has recently hit the headlines like some kind of scarlet pimpernel. Caesium here, caesium there, where will caesium next appear. Road blocks on Japanese roads now forcibly protect the public against caesium here and caesium there. It causes cancer. So do sake, bacon and steak, but I don’t notice road blocks on Tokyo bars or McDonalds.
Here’s a picture of what Cs-137 radiation does to your DNA. These come from a recent paper comparing damage from a range of sources and this particular picture is of damage caused by Cs-137.
The right hand image looks a little like a comet. Hence the name comet assay. First some cells were exposed to radiation and then they were chemically busted open to expose the DNA material from the cell nucleus. DNA is normally in coiled braids and when the braids are unbroken, they stay globbed up in a ball like the image on the left. On the right, busted strands of DNA are streaming out of the glob. It’s a bloody mess. The cell in this image was hit with 10 Grays. The unit used in most Fukushima publicity has been Sieverts. For the moment, just think of a Gray as another name for a Sievert. So 10 Grays is 10 Sieverts or 10,000 milli-Sieverts. A person receiving a full body dose of just half this amount would have a 50/50 chance of being dead within a couple of months.
What’s the difference between a full body 10 Gray dose and a cell being hit by 10 Grays? Don’t worry about it … just accept that this cell nucleus took a monster hit. Imagine blasting a water melon with a shotgun but instead of a shot cartridge with 200 pellets, you are using something with 100,000 really tiny pellets. That’s about what happened to this cell nucleus … the 100,000 is an approximately correct number, I didn’t just make it up!
Just to be clear. If the cell hadn’t been busted open by curious researchers, but was in a living person, the DNA would be still in the nucleus and cellular machinery would be either re-stiching the DNA strands or calling it quits and telling itself to suicide … cell death.
What, for comparison, does “low dose” radiation look like? Definitions vary, but small doses are like putting a few tiny pellets into that melon with perhaps a single pellet hitting the cell nucleus. You’d never see the damage with a comet assay. Over the course of a year background radiation and naturally occuring isotopes in your body do this, on average, once to every single cell in your body.
Comet assays are relatively crude but pretty simple and very widely used. The top images were made using a form of the test that gives particularly clear images. The degree of damage is judged by the length of the tail … long tail, more damage. Typically, an image would have hundreds of blobs and the degree of comet-ness of each would be categorised and counted according to standard protocols. A lucky researcher might have some image recognition software for the job. Otherwise tedium is ensured.
Here’s another pair of comet assays.
The scaling isn’t quite the same, and the method is a little different, but I think you get the picture. In this pair, both images have a tail, but one is much longer than the other. Remember, long tail … more damage. The image on the right looks like a massive radiation dose. It definitely doesn’t look like “low dose” with one or at most a few pellet tracks through the cell nucleus. This is massive damage.
What were these cells hit with and how much? Was it caesium here or caesium there? Or perhaps something from an exotic isotope of strontium, iodine, plutonium or americium?
None of the above … this damage was caused by milk. Yes, cow’s milk.
Not actually whole milk, just the milk protein casein. These particular cells are from the colon of a rat, but human cells would look no different. The left cell is from a rat fed a diet with 15 percent protein and the right is from a rat fed 25 percent protein. For people, a diet of 15 percent protein is fairly normal in a place like Australia, and at least double the amount required. At the recommended amount, there would be even less DNA damage. 25 percent is the amount that the National Health and Medical Research Council says you should stay below … which is rather less than the 31 percent of the CSIRO Total Wellbeing Diet. And yes, … rats were harmed in the production of both images.
It’s pretty simple really … more protein equals longer tail equals more DNA damage. All proteins will do this, but not all to the same degree. Red meat produces more and even longer comets than either casein or chicken but I couldn’t find a red meat research paper with pictures so I’ve used a casein picture. Most papers don’t have any pictures, just the DNA damage scores.
Is this DNA damage dangerous? Might it lead to cancer? The CSIRO certainly seems to thing so, along with everybody else working in cancer research. These particular images are from tests on a form of corn starch which the CSIRO has patents on. They want patent protection so they can charge a premium price to sell the starch to people to reduce the DNA damage done by the foods that the CSIRO tell people to eat as part of their famous high red meat, high protein diet. I’m not sure how the marketing will work, but advertising packets of starch to reduce red meat DNA damage probably won’t lock in high levels of CSIRO research funding from Meat and Livestock Australia.
Food damage, radiation damage …
Just two months after the massive release in April 1986 of radiation during the reactor explosion at Chernobyl, Russian scientists made rapid estimates of the probable extent of consequences to determine public health requirements. They needed to calculate if the affected regions need more hospitals, doctors, nurses and so on. The 1986 knowledge base was built on four decades studying survivors of the atomic bombs in Japan, together with patients receiving diagnostic radiation therapies. They identified thyroid cancer as a special case and estimated that (see para 90ff in 2008 summary ):
The increased incidence of cancers due to radiation exposure would not be significant from the point of view of organizing health care, although some effects on some population groups at specific periods of time might be detected using epidemiological methods;
They also predicted:
Psychological trauma caused by the accident would affect millions of people.
Such a laid back estimation of the medical outcomes will seem astonishing to people like myself brought up on anti-nuclear propaganda. My point in displaying the comet assays was to try and graphically demonstrate that cigarettes, foods, alcohol and radiation are surprisingly similar in their impacts and that modest radiation doses are merely bit-players next to cancer’s true super stars.
Consider the numbers. A 500 milli-Sievert dose of radiation isn’t a modest dose, it is a large dose. It is about double the reported average dose of the helicopter pilots who flew over the stricken Chernobyl reactor dropping stuff to cover the reactor core. Is this the kind of dose that would see people slough their skin and muscles and bleed out internally as hopefully infamously claimed by Crikey journalist Guy Rundle? What is the probability you would get cancer over the next couple of decades? According to Mayo Clinic experts, if you expose 250 people to a dose like this then, on average, one will get cancer during their lifetime as a result. In a world cancer frontrunner like Australia, about 80 of the 250 will get cancer anyway. It isn’t even clear that the single cancer from the radiation would be over and above the 80. This is possible if the person got leukemia, which has a short latency period. Otherwise the radiation damage might just mean that instead of getting cancer at 60, a person gets it 2 months earlier.
Why is radiation such a wimp?
Warning: this section is a little speculative … based on evidence, but with a speculative leap above and beyond!
Part of the reason that radiation is a relative wimp in the cancer stakes, is its randomness and and lack of accomplices. DNA damage is normally repaired. It’s what cells do. If the damage can’t be fixed, then the cell gets put in the garbage. Thrown out. Even when the damage isn’t fixed, or disposed of, it doesn’t go on to become a cancer without plenty of help. Radiation alone doesn’t cause cancer, it needs mates. People with a rare condition called Laron’s syndrome have a deficiency in a protein receptor required to assist a damaged cell along the pathway to becoming fully cancerous. So, far, nobody with this condition has been found with cancer … among all 230 known cases. These people, like the rest of us, get plenty of DNA damage but no cancer. By comparison, when people eat red meat, a cocktail of other chemical changes are induced some of which are required for DNA damage to become cancerous. Most of the time the DNA damage is still fixed, but if not, some of the help needed to turn mere damage into cancer is on-hand.
Australian Nobel Laureate Elizabeth Blackburn has been working with preventative health medical experts to show what happens to the pattern of genetic activation in cells when people change their diet and lifestyle. This is the beginning of an explanation of why some people get cancer remissions when adopting vegan diets and more exercise. Here and here are a couple of early results. Diet and exercise can make huge changes in the pattern of gene expressions in every cell in your body. In the figure below (from the second linked paper) you can see huge changes in which genes are on and off as a result of diet and lifestyle (stretching and exercise) changes. Some genes thought to promote cancer are turned off and others though to suppress cancer are turned on.
Radiation, as a cancer cause, is on its own. Just a random damage. It might hit a cell where other cancer growth conditions are satisfied … or not.
Now let’s switch focus from cell damage to people. In particular the people of Japan.
Part II: Cs-137 in your soil, or red meat on your plate, which is more dangerous?
Even before the mechanisms started to be understood, medical scientists knew that diet and other lifestyle factors caused most cancers. When people migrate and adopt the habits of a new country, their disease patterns follow suit. When in Rome, dine like a Roman, die like a Roman. It works the other way round as well and Japan is an excellent example. Over the past 60 years, the Japanese have adopted some of the diet and lifestyle habits of another culture. Consequently their disease patterns have changed. It takes a couple of decades for cancer rates to change, but they do. I’ll focus on bowel cancer primarily because its change in Japan has been well documented and its main causes are fairly well known.
Japanese bowel cancer rates
In the 1950s, just after World War II, Japan moved toward the diet of the victors. Consumption of milk, meat, eggs and fat climbed. The following graph is redrawn from a paper on bowel cancer in Japan. The y-axis is an index, not a quantity. It will look pretty weird to those without a technical background. Briefly, milk consumption went up 20-fold, which doesn’t say much because there wasn’t much milk in the traditional Japanese diet. More significant was an almost 10 fold increase in meat and a halving of rice and potatoes. Those who have been sold the advertising pseudo science on carbohydrates making you fat might like to reflect on the rising rates of obesity in Japan as elsewhere with rising protein intakes and falling consumption of carbohydrates. (Hint: scam)
Of all these possible dietary changes that might cause bowel cancer, the World Cancer Research Fund (WCRF) and American Institute for Cancer Research (AICR) have found convincing evidence of a causal relationship for just two foods: red and processed meat. There are other cancers that these foods might also cause, but the evidence on bowel cancer is quite solid. Epidemiologists rarely say X causes Y and when they do, without caveat, as in the case of red and processed meats, you’d better believe it.
Sure enough, a couple of decades later and Japan is seeing the payoff for its expansion in red and processed meat intake. The graph shows the rising wave of bowel cancer. It’s tempting to call it a tsunami, but it kills even more people each and every year than the horror of March 2011. There are about 43,000 deaths and just over 100,000 new cases of bowel cancer each year in Japan. Bowel cancer rates now match stomach cancer rates which is the traditional big cancer in Japan and thought to be a result of too much salty food.
Japan buys plenty of beef from Australia, but the per-capita beef consumption is still quite low with the most popular red meat in Japan being pig meat. Forget the advertising, from an epidemiological perspective, pig meat is just another red meat, except when it is treated with various additives and made into processed meat. I don’t have data on Japan, but am confident that, as in Australia, the difference in male and female bowel cancer rates mirror the significant differences in male and female red meat consumption. South Korea, also with a growing red meat intake shows the same pattern.
The traditional Japanese bowel cancer rate, down around 10 per 100,000 per year, is at a level still found in many parts of the world and there is little difference between male and female rates. This traditional rate is mainly down to a couple of genetic predispositions. The massive increase is down to red and processed meat, inactivity and obesity, in that order.
Leukemia compared with bowel cancer
Radiation as a carcinogen is well demonstrated above certain doses and the main cancers involved are thyroid and leukemia. The thousands of thyroid cancers around Chernobyl after the 1986 accident were prevented by simple measures in the rest of Europe, and should be preventable where ever contamination with iodine-131 occurs. Leukemia from caesium-137 is more intractable so that’s what I’ll focus on.
Currently in Japan, the age standardised rate of leukemia is about 4.3 per 100,000 people per year (averaged over both sexes). The age standardised rate for bowel cancer is about 7 times higher at 31 in 2008 (averaged over box sexes). Australia, is even higher with an average over both sexes of 39 with men up at 46 and women down at 32.
If the whole of Japan was blanketed in the kinds of levels of Cs-137 seen around Chernobyl and experienced a similar rise in leukemia levels, what would happen? Firstly, what actually happened after Chernobyl? A number of Chernobyl leukemia studies were reviewed in 2005. Those involving the general population are less clear cut than those involving clean up crews, sometimes called liquidators, who received much higher exposure. Let’s concentrate on those. One study of 168,000 Russian liquidators found a 77 percent increase in leukemia. How big is this? A recent Taiwanese study found a similar sized risk increase in leukemia associated with eating cured meat in young people under 20. Cancer researchers have only recently begun to look at dietary connections with leukemia because there isn’t any obvious mechanism to drive it. If this connection were eventually proven, would cured meats be banned? Would people lay down in front of meat delivery trucks to save their children the horrors of cured meat? Would local councils call themselves “Cured Meat Free” and block transport of cured meat on their roads? As a vegan, I’d certainly back such a move, but I doubt the anti-nuclear movement is consistently anti-cancer.
But, back to the liquidators. Not only did the liquidators have a higher exposure than ordinary people but the researchers included types of leukemia not thought to be caused by radiation. Another study found an increase of 150 percent in leukemia among a cohort of 71,870 liquidators with a radiation dose estimated at 150–300 mSv. How big a dose is this? It’s similar to the doses experienced by helicopter pilots flying over the Chernobyl reactor dropping material on the reactor core. A third study of Ukrainian cleanup crews found a doubling of leukemia. So, three studies of liquidators, three rates of leukemia increase … all well below a tripling of leukemia.
So, let’s suppose the whole of Japan was covered in caesium-137 to give everybody a dose similar to the helicopter crews flying over the Chernobyl reactor core. Let’s further suppose that there was subsequently a tripling of leukemia rates throughout the whole of Japan.
What are we up to? I’ve postulated a ridiculous worst case scenario over a ridiculously large area causing a rate of leukemia way above anything actually measured. The result would be that leukemia would rise to about 13 cases per 100,000 people per year. This is about half the rate of bowel cancer increase that has afflicted the country as a result of shifting from their traditional diet to one with more red and processed meat. It’s about a third of the male rate of bowel cancer.
Comet assays, as described above have been used to test DNA damage in lymphocytes of children from Chernobyl who have ingested low doses (up to 3 mSv) Cs-137. As expected, there was no difference in the DNA damage between these children and a matched control group. A 2002 review found no overall increase in childhood leukemia but left open the possibility of localised increases.
Oh, I almost forgot …
Food and lifestyle changes in Japan haven’t just caused a wave of bowel cancer far in excess of anything even remotely possible from a disaster far worse than Chernobyl. Those changes have also driven a similar rise in other cancers, particularly the most common cancer in women, breast cancer. Japanese women used to have about one seventh the rate of breast cancer of US or Australian women. I don’t have a nice chart for this, but the rate in Japan has risen to well over half that of the US. The age standardised incidence rate in Japan is now 42 per 100,000 women per year compared to 76 in the US and 85 in Australia. The cause(s) of this increase aren’t as easy to pin point as with bowel cancer. However, as with all cancers, getting taller is a marker. Increased protein, whether animal or vegetable made people taller in the middle of last century in western countries. The effect leveled off in about 1970 in the US, so as meat consumption continued to rise, people just spread out instead of up. On average cancer rates increase about 10 percent for each extra 5cm of height. Similarly, fatter and more inactive people get more cancer also.
In addition, high calcium diets are also considered by WCRF/AICR as a probable cause of prostate cancer, currently sitting at about 22 per 100,000 per year in Japan compared to 82 in the US and 104 in Australia. Australian dairy exports and marketing are Asian focused with Simon Crean, for example, very publicly salivating at the thought of selling Aussie milk to 1.5 billion Chinese.. About 75 percent of the world’s adults, including most Asians, don’t have the enzymes to break down lactose and get various gastrointestinal problems from drinking milk but can still usually eat yogurt and hard cheese where most of the lactose has been pre-digested by bacteria. If WCRF is right about high calcium diets, then, as with bowel cancer, the expansion of such diets will again cause far more cancer than anything that even the worst of nuclear power accidents might deliver.
Just a final note. Japan is still a relatively low-cancer country. Average red meat and dairy intake is still quite low. The rises I’ve discussed above (liver cancer is up also) have still only brought Japan’s age standardised all-cancer rate up to about 200 new cases of cancer per 100,000 per year compared to about 314 in Australia (360 for men and 274 for women). But attention to detail and perseverance should see them one day challenging us near the top of the table.
Reference: Most references are hyperlinked, but general background on radiation comes from the IARC site (monographs 75 and 78). Hopefully I haven’t misrepresented any of it!