Physical mutagens are different types of radiation whose effect on cells depends on phases of the cell cycle. Cells are more sensitive during division because of the chromosomes being condensed.
Radiation is energy. It can come from unstable atoms that undergo radioactive decay, or it can be produced by machines. Radiation travels from its source in the form of energy waves or energized particles. There are different forms of radiation and they have different properties and effects. Depending on whether it ionizes the surrounding matter it can be divided into ionizing and non-ionizing radiation:
Non-ionizing radiation has enough energy to move atoms in a molecule around or cause them to vibrate, but not enough to remove electrons from atoms. Examples of this kind of radiation are radio waves, visible light and microwaves.
Ionizing radiation has so much energy it can knock electrons out of atoms, a process known as ionization. Ionizing radiation can affect the atoms in living things, so it poses a health risk by damaging tissue and DNA in genes. Ionizing radiation comes from x-ray machines, cosmic particles from outer space and radioactive elements.
Ionizing radiation is further divided into alpha, beta, gamma and x radiation based on the amount of energy they posses. Alpha and beta radiation are not major causes of disorders in our body, but radiation can pass through our skin and tissues, even through sebstances/materials much denser as aluminum and concrete - which, although useful when used in moderation, can cause many problems. Radiation poisoning, ie radiation sickness occurs after exposure of the body to X or gamma rays which damage the organism by penetrating the skin and absorbing or storing energy in the cells.
How much radiation is safe?
Chances are you won`t have to worry about the amount of radiation you are exposed to during your lifetime. The amount of radiation is measured in sieverts- 1sv is enough to cause complications, while 10sv can kill us. But the usual doses we are exposed to measure in millisieverts, so there is no reason to panic. Every year we are exposed to radiation of 2.4milisv only from natural radiation, while, for example, scanning our breasts exhibits radiation of 6.8milisv.
While there's no magic number of how many X-rays are safe in each year, the American College of Radiology recommends limiting lifetime diagnostic radiation exposure to 100 mSv, which is the equivalent to about 10,000 chest X-rays, but only 25 chest CT scans.
If we converte the measure unit to grays (Gy) we can observe just how much effect ionizing radiation can have on the mutation rate. Irradiation of 30 cGy (0.01 Gy) doubles the degree of mutability of the gene. Exposure to large amounts of this radiation leads to disease such as radiation poisoning and cancer, because radiation causes the structure of our cell or DNA material to change, leading to chromosome fragmentation, structural and numerical aberrations etc. Problems arise when the cell replication repair mechanisms correct these mutations in the wrong way, forming mismatches, which can affect our body in many ways.
To explain this let`s look at some examples:
Our cells contain water - H2O, which is an important component of our whole organism. If chemical bonds are broken these elements can be reformed as O2, H2 or O2H2 - hydrogen peroxide - which is highly reactive and responsible for inducing mutations. What changes radiation will cause depends primarily on the amount of radiation, but one thing is for sure - no dose of radiation is healthy. Radiation has a cumulative effect, where each additional dose adds on to the existing one. As we mentioned before, infrequent radiation for determining the existance of other, more prevalent medical concerns is not harmful in itself, but frequent exposure to small amounts of radiation, for example when using a solarium, is harmful and can oftentimes cause cancer.
Exposure to large amounts of radiation suddenly causes acute poisoning, which is divided into 4 phases:
Prodormal- where the symptoms are vomiting, diarrhea and anorexia
Hidden, ie the disappearance of symptoms which deceives the victim into thinking she`s doing better. This period can last up to several weeks before the third phase occurs
Manifestation of the disease - which we will talk about soon
Recovery or death
What exactly are the effects of large exposure to radiation?
Let's say someone is exposed to radiation equal to 125 X ray scans of the abdomen at once, as a result symptoms of the lowest degree of radiation poisoning would present themselves. Radiation penetrates and destroys bone marrow cells by damaging their DNA. This means the suspension of production of blood elements (white and red blood cells, and platelets) and is followed by infection or blood loss. Transplantations of the bone arrow are possible if a match is found, the chancess of success are still 50%.
An amount of radiation equivalent to that of 1250 X ray scans at once destroys the cells of the gastrointestinal tract, meaning that the body can no longer absorb nutrients - causing an electrolyte imbalance, dehydration and worse. After this organ system dies off, there is no help for us - death is inevitable.
What happens to our body when exposed to the amount of radiation equivalent to 2500 x ray scans, is not entirely clear, but the results can not be good. Scientists speculate that there would be swelling of our cardiovascular and central nervous systems due to filling up with fluid caused by the enormous damage done to the cells. In less than three days the brain loses control of the body and that's it. Since radiation affects cells at the atomic level, treating this poisoning is extremely difficult, and it leaves us only with the possibility of treating symptoms these diseases cause. A lot of our knowledge on this topic originates from the catastrophic consequences of the Chernobyl radiation and the bombing of Japan during the second world war. Although doctors tried to document everything they could about the victims, there is still a veil of mistery that surrounds the topic - one that we can only hope will vanish as times goes on and scientific research progresses. But for now lets just hope we wont need thisknowledge in the near future or ever.
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