Enki23 has given you a very good basic description of the situation. Most cancer cures are in fact carcinogenic themselves. It is known, for instance, that nurses who provide chemotherapy to patients, have very high cancer rates.
Contrary to popular opinion, radiation may not be the primary cause of cancer. It is important to understand that life evolved in the presence of radiation because 1) the planet overall is radioactive, 2) significant quantities of high energy radiation do penetrate the earth's atmosphere where it interacts with living tissue. Some people feel that the "linear hypothesis" in which the risks associated from radiation at low levels can be extrapolated from data collected from organisms subjected to high level radiation (atomic bomb survivors are among the most studied set of human organisms so studied) is nonsense. I am inclined to agree. There is some evidence, albeit controversial, that low level radiation exposure is good for you.
Neither can it be said that all cancer mechanisms are identical. Soot particles may cause cancer because they are planar on a molecular level. This allows them to fit in the grooves on nucleic acids and effect transcription, a process that can lead to cancer induction. Many cancer drugs, irinotecan for instance and cisplatin, work by exactly the same mechanism as soot, but they preferentially kill cancer cells as opposed to normal cells.
Other carcinogenic chemical compounds work by binding to regulatory proteins. Some metals are carcinogenic because they mimic other metals in metal co-ordinating proteins in a way that slightly modifies the effects of these proteins.
Carcinogenesis from radiation generally relates to the breaking of chemical bonds, particularly in nucleic acids, but also in proteins and other biomolecules. When radiation breaks a chemical bond, it can do so in two ways, heterolytically, in which two charged particles result, or homolytically, in which two neutral particles, each having a highly reactive unpaired electron which is generally referred to as a free radical. Of these two types of cleavage, it is probably the case that homolytic cleavage is the most problematic. Free radicals will sometimes cause chemical chain reactions. (Indeed many polymerization reactions such as are used to make plastics are free radical chain reactions.) A chain reaction in a cell can lead to the alteration of a base pair in a nucleic acid, resulting, say, in the methylation of a adenosine. This can under the right circumstances mimic the mechanism of many cancer drugs, which is to interfere with DNA transcription through chain termination. It can also lead to conformational changes that change the reactivity of the DNA molecule.
Depending on the location and type of cell involved, this can either kill an undesired cell (a cancer cell) or cause a normal cell to mutate into a cancer cell. It is important to note that not every interaction in which DNA is damaged results in a cancer cell. The most probable outcome of DNA damage, for cancer cells and normal cells alike is apotosis, cell death. In fact, the probability of cancer cells forming and surviving is very, very, very low. This is why we exist.
Smokers, for instance, usually smoke for many decades before actually getting cancer - it took my father almost 50 years to be killed by smoking but kill him it did. It is safe to say that the mechanistic opportunity to generate a cancer cell existed every day of his smoking life, just as the mechanistic opportunity to develop cancer from radiation exists at all times for all individuals since we are all radioactive. (This is because we all contain potassium, a radioactive element that is essential to life.) Not all smokers develop cancer. The comedian George Burns, for instance, existed almost continuously in a cloud of tobacco, and yet lived a long life. He was a centegenarian when he died. What we are saying when we discuss the risks of cancer and smoking is that one's
probability of getting cancer is higher, not that getting cancer is inevitable. This distinction is important and is generally missed by our risk illiterate public.
Some people argue on epidemiological grounds - although they are widely disputed on religious grounds - that low level radiation helps to stimulate the natural repair mechanisms that exist on a cellular level. This, it is argued, can have health effects that are beneficial. I am agnostic on this issue because I recognize that epidemiological inferences can be complicated by hidden variables.
I don't know if one should actually desire to be irradiated to a certain point. I attempt to sensibly - although not hysterically - to minimize my own exposure. Although I have worked appreciably with radioisotopes in the past, I still ride on airplanes and sometimes go to high altitudes. I get dental xrays. I sat with my son when he had a huge series of full body x-rays when he was 4 years old in connection with a Barium study of his alimentary tract. These practices expose me to higher levels of radiation than I would otherwise experience. On the other hand, I do try to mitigate the radon problem in my basement, which is measurable and real.
As for the effects of large unintentional releases of radioactivity I can say that when Chernobyl exploded, I expected huge numbers of injuries to occur in Kiev, a very large city not far from the plant. In fact, despite being near the
worst nuclear accident in history - probably the worst nuclear accident that is possible - Kiev is still a vibrant city where millions of people still lead useful lives. There has not been wide scale death at unusual rates in the city. Therefore my fears were unrealized. This outcome lead me to change my views of nuclear energy entirely.
One of the front lines in discussions of radiation effects is the Sellafield reprocessing plant in the UK. One can read on the Greenpeace site (I think) that everyone is Sellafield will die (this is actually true - although not for the implied reasons - because of the now famous leaky pipe or because of the mere existence of the reprocessing plant.) One can read elsewhere that Sellafield workers have abnormally
low cancer rates.
(Note that there was a Chernobyl type graphite fire reactor accident near Sellafield in 1957, in a weapons production reactor there: This certainly represents a complicating factor.)
We have heard recently a great deal about this recently discovered leaky pipe at the Sellafield reprocessing plant in the Cumbria Lake district in the UK. It would seem that the folks who keep raising this issue expect that everyone in Cumbria will die from this "tragedy," about which they obsess, apparently to distract themselves from real issues like global climate change. They want nuclear energy banned because the pipe has leaked.
Actually though, everyone in Cumbria has NOT died from this leaky pipe, although - as mentioned - surely everyone in Cumbria will die sooner or later. In fact, Cumbria, a beautiful place, remains a popular tourist attraction:
http://www.virtual-lakes.co.uk/menuphoto2.htmHere is link of some stock photographs of Cumbria, including one of a so called "nuclear waste" container at Sellafield:
http://www.stockphotography.co.uk/store/app/f.asp?PT=148Note that the grass immediately adjacent to the container is not dead, even though it depends, like all eucaryotic life, on DNA for its existence. In fact none of the vegetation in the picture is dead. There are not huge piles of dead human bodies on the container either, even though some very stupid people have remarked that so called "nuclear waste" is "dangerous" because you may die if you stand next to it. The container just sits there, more or less doing nothing. This small container, probably the result of powering millions of homes for periods of years, should be contrasted with mercury, lead, carbon dioxide and other coal related pollutants, which certainly
are doing something.
Whether or not radiation can be good for you - whether it is good for you under some circumstances and bad for you under others - is not actually the point. Even if it bad for you
all of the time, we have to ask ourselves how bad it actually is in comparison to its alternatives. It is very clear based on experience that the risks associated with radiation are vastly over-estimated by an increasingly stupefied public, while the risks associated with other energy related technologies are vastly understated.
Thanks for asking.
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