News and Comments about Life
A lot has been said and written about the negative effects of radiation on our body and the environment, either by ordinary background levels or by the most feared emissions coming from nuclear plants or nuclear wastes. It might as well be that such alerts and warnings are far too exagerated, and that a low dose of radiation could even prove beneficial to our health. Radiation is the best example of an excessive enhancement of the ‘better safe than sorry’ theory, an attitude positive in its root but that has grown too much and is now threatening to suffocate technological development.
Too much of anything can be harmful to the human body. Take water, the most unharmful drink of them all. Dietologists, health terapists, doctors are eager to arn us we should drink two liters of water a day, to satisfy our body’s need for that precious ingredient. If we were to drink more than that, though, we would start feeling strange and odd, heavy and full. Twenty liters of water at once would kill. Another example is carbon monoxide. In the brain it performs a useful function as a signal transmitter. Above a certain level, though, it becomes deadly. Many drugs work fine in the right dose, but are lethally poisonous in larger amounts. It’s the principle of hormesis, the idea that biological organisms generally react favourably to low exposures to toxins and other stressors. In other words, a limited dose of a pollutant or toxin that exhibits hormesis has the opposite effect of a large dose.
First discovered by the German pharmacologist Hugo Schulz (1853–1932) towards the end of the nineteenth century, hormesis has been later largely ignored, because of Schultz’s links and connections with homeopathy. This is unfortunate because there is a wealth of evidence for hormesis. The best recent source is a 2009 publication, Hormesis: A Revolution in Biology, Toxicology and Medicine (Springer, 2009), which comprises a series of articles edited by Mark P. Mattson and Edward J. Calabrese.
How does hormesis work? When an organism is exposed to harmful influences, a number of compensatory mechanisms come into play. Their goal is to counter the influences at that particular juncture, but also to prepare the body for possible repeats in the future. The immune system is just one such mechanism. This is the main reason why patients about to be given an anaesthetic will be asked about drinking and smoking habits, for example: such informations are important because the livers of smokers and drinkers have adapted and break down the anaesthetic more efficiently. Hgher doses of the anaesthetic should then be necessary to reach the goal.
Hormesis was also the reason why many well known rulers of the past, even in pre-Christian times, used this to arm themselves against would-be poisoners taking small doses of poisons like arsenic: science has found out that a repeated exposure to arsenic results in accelerated availability of heat shock proteins (HSP), or in greater amounts. HSP are special proteins that can chaperone other proteins and protect them from damage.
Oxygen gives us another interesting example of how hormesis works. About three billion years ago, life on earth discovered the photosynthesis trick: Cyanobacteria gradually pumped oxygen into the oceans and the atmosphere. Evolution succeeded so well that nowadays we can’t do without oxygen. At at the same time, though – as Charles L. Sanders explains in Radiation Hormesis and the Linear-No-Threshold Assumption (Springer, 2010) clearly sho -, our cells are constantly battling against oxygen damage. It’s estimated that the DNA in each of our cells is damaged twice per second. Most of this damage results from the creation of highly reactive broken molecules, so-called ‘free radicals’.
Compared to this, the damage caused by radioactive radiation is small. Depending on the method of calculation used, the wear and tear caused by oxygen is a hundred to a million times greater than the damage resulting from ordinary background radiation. Almost all of this damage is repaired, and a large repair crew of enzymes is constantly at work.
Exxposure to radiation is said to be a major cause for cancer: a subject Sanders’ book deals with in great detail, focusing – as its title indicates – on the Linear-No-Threshold-hypothesis (LNT).
LNT is the generally used method to estimate radiation damage, and more particularly the risk of radioactively induced cancer. A very simple method, whereby all radiation doses a population has been exposed to are added up and then divided by 20 to give the number of cancer deaths. So, for example, if 100 million people are exposed to 1 millisievert per year for twenty years the calculation would be as follows: one hundred million times 1 millisievert per year times 20 years equals two billion millisievert, which equals 2 million sievert. Dividing 2,000,000 by 20 gives 100,000. This is the number of cancer-related deaths you can expect.
A method of calculation subject to critics and criticisms, indeed: why this division by 20? What is it based on? Well, it dates back to some of the earliest tests on survivors of the atom bombs of Hiroshima and Nagasaki. A group who had been given an average of 1 sievert each in a single dose showed a percentage of people contracting cancer of 38 percent instead of the 33 percent observed in a comparable non-exposed group. So 1 sievert means 5 percent more people die of cancer. This single piece of data forms the basis for the calculation 1 sievert = 5 percent (1/20) extra cancer risk.
But this is a nonsensical calculation. Incremental exposure is less damaging than a dose that is given all at once. Just like regularly running or fasting moderately. In other words, the phenomenon of hormesis is totally ignored.
This very mechanisms of incremental exposure can be applied to radioactivity. In Ramsar in Iran the soil produces a lot of radon, and the background radiation there reaches values of up to 700 millisievert per year. According to the LNT hypothesis, living there for 20 years would lead to about 100 percent of the people dying of cancer, but the villagers there seem to suffer from nothing except a slightly more active immune system.
So what can we conclude from all of this? The LNT–hypothesis is extrapolated to include low doses, but there is no proof for it at all. LNT makes it actually easier to impose strict regulations on the use of nuclear energy. Rules which are extremely costly, but easy to check. A situation not dissimilar to that in the early days of the automobiles. The British authorities were so afraid of the (admittedly potentially lethal) risks posed by cars on the roads that they stipulated (in 1865) that a man with a red flag should walk in front of these so-called road locomotives. It was only in 1896 that the law was relaxed slightly and the maximum speed for automobiles increased to that of bicycles (22 km/h).