About radiation, part 2: How it may affect the human body

Most of the radiation around us comes from Radon.

Radon (Rn) is a gas, which in itself is harmless, but when it decays, it emits ionizing radiation, primarily in the form of alpha particles.

The most frequently occuring isotope of Radon is Rn-222, which is formed as the Uranium in the bedrock decays, and thus Radon exists naturally in the ground. It can also exist in building structures and even in drinking water, the latter due to the bedrock surroundings of the groundwater.

Especially Radon in residential buildings is in some countries a problem: As you just read, the gas itself isn't dangerous, but during decay, the Polonium ions 218 and 214 are formed. These stick to dust and smoke particles which then stick to the lungs when inhaled. Inside the lungs, the chain of decay continues, and this alpha decay causes damage to the breathing organs and increases the risk of lung cancer to develop.

Smokers, ex-smokers and passive smokers are for clear reasons exceptionally exposed to these risks. A non smoker; i.e an individual who has never smoked, the risk of Radon induced cancer is approximately 0,41%, but for an active smoker, the risk lies at about 9,7%. World wide, Radon is estimated to cause 3-14% of the total number of cases of lung cancer, and in Sweden, the number of cases is approximately 500 per year.

Now with these numbers dealt with, and a brief introduction to that ionizing radiation may induce cancer, the next logical question should be about how and why it happens.

The cell nucleus, containing the DNA molecule, is very sensitive to radiation, so exposed to such, it may lead to an uncontrolled division of cells, which in turn may lead to cancer. The cells that divide fastest, for example the cells of the bone marrow and the mucus membranes of the digestive organs, which are constantly regenerated, are more easily affected by ionizing radiation than for example brain cells. With the knowledge of ionizing radiation have accumulated to this day, it's been calculated that a one time exposure to a dose of 20 mSv increases the risk of developing cancer with 0,1%. It may take up to 20 years before cancer induced by low doses of radiation occur.

May I now bore you with some information about some of the fallout elements of the Chernobyl disaster and how they affect the human body? I thought not, here goes.

Iodine-131 has a half life of only 8 days and the human body's absorption of it can be blocked by ingesting Iodine pills. Absorbed Iodine is concentrated to the thyroid and when the Iodine is radioactive, the decay causes damage to the thyroid, but by taking supplements such as mentioned Iodine pills, providing the body with a maximum amount of Iodine, which reduces the uptake of the element.

However, the younger an individual is at the time of exposure, the greater are the risks of developing thyroid cancer. Children and teenagers, who are not fully physically developed, take more damage  from Iodine-131 than adults, who doesn't seem to show any significant difference in tyroid disease, compared to an unexposed group of equvalents.

In Kiev, Iodine supplements were handed out to the population 14 days after the disaster. By this time, they were pretty much useless.

Caesium-137 is a radioactive isotope of Caesium, which is formed by nuclear fission, and having a half life of 30 years, it means that areas exposed to Chernobyl fallout are still more or less contaminated.  Caesium-137 hasn't existed "naturally" on Earth for many billion years, but the occurance of the element in modern times,  is caused by man and  Caesium-137 is evenly distributed in the body, although with a higher concentration in muscular tissue, differently from...

Strontium-90, which goes straight to the skeleton and teeth, as the human body absorbs it as if it was Calcium. Calcium and Strontium have chemical similarity, but this unstable isotope of Strontium may induce bone cancer and other bone related disorder and diseases.

Ironically enough, Strontium-90 is used in cancer therapy, due to its long half life (28 years) and beta emission.
Photo from http://www.freeinfosociety.com

Lets now summarize in what other ways radiation may affect the human body.

The blood system
Even relatively low doses of radiation may inflict a reduction of  lymphocytes (white blood cells). These have the function of keeping the body clean from infections and without them, this part of the individiual's natural physiological defence is reduced, and the individual simply becomes more exposed to infections. For example flu like symptoms in a person who's been exposed to radiation, may be indicating a reduction as such, and the symptom can sometimes last for up to ten years. Patients with an insufficient amout of lymphocytes in their blood system are more susceptible to leukemia (blood cancer).

The brain
is due to its none reproductive cells, was  believed not to be affected by radiation, but  when it comes to absorption of high doses, as for example the cases of the firefighters and liquidators I mentioned in my previous post, damage to the central nervous system was recorded, and nowadays we also know that there's a connection between high doses of radiation and brain tumours.
The heart
Moderate doses of radiation may cause damage to capillaries and thereby also the heart. As the small blood vessels burst, the blood isn't transported properly to the heart, which increases the risk of cardiac arrest, which was the cause of death for many liquidators.

The reproductive organs
Ionizing radiation doesn't only affect the vital organs of the human body, but also the reproductive systems, (which  due to that also the cells of these divide very fast) are very susceptible to radiation damage. Many victims of radiation poisoning become sterile, males in particular. Radiation also affect fetuses and after the Chernobyl disaster a large number of abortions were obtained throughout Europe, due to fear of the radiation from the Chernobyl fallout. Among the deleterious effects on fetuses are miscarriage, birth defects, mental retardation, growth retardation (whilst still in uterus) and development of cancer.

The skin
Chernobyl firefighter, Photo from http://www.sxolsout.org.uk/
Ionizing radiation can inflict burns often refered to as gamma or beta burns. Beta radiation isn't able to  penetrate deeply into the body but manifest like shallow skin burns, but if exposed to intense beta radiation, indications of burns manifest in 24-48 hours with an itching or  burning sensation, and after 7-21 days, the actual symptoms appear as erythema, increased pigmentation, then desquamation/epilation and skin lesions. 
Concerning victims of the Chernobyl disaster, this was a serious issue. Of 115 liquidators treated in Moscow, 30% had severe burns covering signifigant areas of the body surface. This exposure was often caused by radioactive water (and recently there's been similar cases in Fukushima, Japan) Some firefighters suffered internal beta burns after inhalation of massive amounts of radioactive smoke and out of the 28 first deaths, 16 liquidators and firefighters had skin injuries listed among the causes. 
The skeleton 
The non growing portions of the bone are relatively resistant to radiation, but for growing individuals such as children and teenagers, large doses of radiation may retard the growth and development of the bones, and the bone marrow, where blood cells are formed, is generally at a greater risk of being damaged, inducting leukemia. and bone cancer. Exposure to Strontium-90 means an increased risk.

The thyroid
Also the thyroid is very susceptible to radiation and thyroid cancer is the most frequently occuring consequence. Above, I mentioned how the exposure to Iodine-131may affect especially young individuals, but if you want more in-depth information, a good article is to be found here.

Ionizing radiation affect more or less the entire body in different ways, but all of them lead to damage, disease or death. I'd like to spend more time digging further into this, but I'm afraid I do not have that time.

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