I was talking to my husband and a few friends and was surprised to find that they did not know what was radioactivity and the possible health effects (which left me quite frustrated, as I had gone through radiotherapy before and so was very sure that at least my husband should have known the risk that I was exposed to.) Anyway, I took for granted that most people should know, so I was also quite shock when I heard some of questions asked.
My husband remarked that this was because the biological effects was in the A-level syllabus and I had taught it and so I knew, but I should "enlighten" those who did not take Physics through my blog....anyway I will try my best and present the following as a FAQ in parts. (so that it can be slowly published).
[I have to note that much of these were taken from a set of lecture notes I prepared for A-levels two years ago and takes references from many websites, so not all the work are my original work, though I consolidated most.]
(Picture Taken from stock.xchng at http://www.sxc.hu/. H-Bomb by Sergey Lebedev.)
What is radiation?
The main danger from radiation is the damage it does to the cells in your body.
Most of this damage is due to ionization when the radiation passes, although if levels of radiation are high there can also be damage due to heating effects as your body absorbs the energy from the radiation.
Types of ionizing radiation includes :
- alpha particles (Helium nucleus)
- beta particles (electrons and positrons)
- gamma rays
- X-rays, and
- neutrons
Gamma rays, x-rays, as well as neutrons are known as indirect radiation, as they affect the cells in the body by transferring energy to neighbouring atoms. This causes the atoms to become excited and they can produce secondary electrons and photons that can continue to transfer the energy to nearby atoms.
So what are the harms associated with exposure to these radiation? Does a person continue to radiate radiation after he has been irradiated?
To understand this, we need to make distinction between internal exposure vs. external exposure as well as irradiation and contamination.
Internal Exposure vs. External Exposure
There are two ways in which people can get exposed to radiation exposure :
- Internal Exposure,
- External Exposure
o External Exposure is exposure of radiation sources outside the body.
Internal exposure can continue if the radioactive material remains in the body. In contrast, external exposure will not occur again once the radiation has penetrated the body.
Outside the nuclear and scientific community, there is a general misunderstanding that everything exposed to ionizing radiation is contaminated and dangerous forever. This is not the case, and there is a big difference between something being irradiated and something being contaminated.
Contamination vs. Irradiation
o Irradiation:
When something has been irradiated, the irradiation stops as soon as the source of ionizing radiation has been removed. The same can be said about the energy of ionizing radiation.
However even the irradiation has stopped, the biological effects of the irradiation may still occur if un-repaired cell damage has been inflicted.
o Contamination:
When contamination occurs, the source of the ionizing radiation itself is transfered, such as when radioactive isotopes in solid, liquid or gaseous forms are introduced into the environment.
When something has been contaminated with radioactive isotopes, it will remain radioactive until the radioactive isotope has decayed to a safe level.
Hence, from above we see that although one is irradiated by radiation, you do not become radioactive after that and become the source of radiation. This is why food exposed to microwaves do not emit microwave or food that has been treated with X-rays to lengthen their shelf lives are not sources of X-rays themselves.
However, for the case of Japan, as the nuclear reactors are spewing out particles that are radioactive, the particles can be inhaled by people or get attached to the clothes, the bodies or the vehicles that are passing through. Furthermore, the fall out will land in the water, on the soil etc. Those people and objects that have particles attached to them or have inhaled the particles, consumed the particles or "drank the particles" would therefore continue to emit radiation. This is why people are advised to wear mask and stay indoors. And food from the sources needs to be scanned as the fishes and subsequently the produce may contain high amount of radiation.
This is the principle we use for carbon dating. Carbon-14 is a radioactive isotope that is continually ingested and inhaled by animals and plants. Due to biological decays and its radioactive decay, the proportion in a living material is more or less fixed and hence there is a stable amount of radiation we emit. When however a living thing die, we stop taking in Carbon-14. That is why the radioactivity reduces and by looking at the reduction, we can date back the once living artifacts to the year it "died".
I hear that the winds are blowing the steam, the fallout of the explosions into the sea? So is the problem solved?
That depends on how you see it, if the fallout goes towards the sea, the radioactive particles will deposit into the ocean, this means that marine life will get a greater exposure to the radiation and will also ingest a greater amount of radioactive particles. This goes for the same if the steam and smoke gets carried by the winds into the atmosphere, this means the area that is exposed to the radioactive particles are greater but will also mean more distributed and evened out.
Some people are actually hoping for rain, as the precipitation will keep the affected area more confined, but this means the distribution is also more concentrated.
Coming up next
(1) Can we therefore make the radioactive isotopes non-radioactive by chemical reactions etc.?
(2) You mentioned alpha particles, but I also know that alpha particle can be stopped by paper,so out of the radiation which is less harmful, and what are the impacts of each type of radiation?
(3) Some people say swarthing iodine the bodies will help prevent the radiation from harming the body, is it true? If it is not true, then why are the governments buying iodine pills?
(4) How do we know that a person has been irradiated, are there visible signs e.g. glowing etc?
(5) What are the short term and long term biological effects of exposure to radiation?
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