How ionising radiation affects our bodies

Developing foetuses are, of course, incredibly susceptible to radiation

Inhaling or swallowing radioactive material delivers the source of radiation directly to your cells, increasing the risk of cancer developing in the tissues where they accumulate.

In adults, strontium accumulates mainly on the surface of bones, but in children it can be incorporated into the growing bone itself. The beta radiation given off as the radioactive atoms decay into more stable forms can damage the bone marrow and lead to bone cancer.

What does radiation from a nuclear disaster actually do to our bodies? ABC Science

By Bernie Hobbs , 25 Apr 16, “……..long-term exposure to low doses of radiation increase the odds of getting cancer, while a single high dose will quickly cause immediate damage to cells and tissues — a process used effectively to kill tumour cells in radiation therapy.

Very high doses like those experienced by workers at the site of nuclear accidents (several thousand times higher than the background radiation level) cause extensive damage, resulting in a range of symptoms known collectively as radiation sickness. Extremely high doses can kill in days or weeks……What is nuclear radiation?

The high-energy radiation given off by radioactive decay can take the form of very high speed particles (electrons in the case of beta radiation; two protons and two neutrons in alpha radiation) or waves (gamma or X-rays).

Regardless of the form it takes, all nuclear radiation has enough energy to strip electrons off atoms and molecules that it interacts with, earning it the name ionising radiation.

It is this electron-stripping (ionising) property that does the damage to our cells and tissues.

As well as generating heat, the removal of electrons can break chemical bonds. When that happens in a molecule of DNA it can cause mutations, which can lead to cancer down the track. And ionising a protein can mess with its shape and function — not something you want in the molecules that coordinate most of the chemistry in our cells.

Those effects are compounded when water molecules (H₂O) in our bodies are ionised into the high energy free radicals OH^– and H⁺, which can go on to attack other nearby molecules and cells.

Our bodies are full of water, and almost all cells have DNA, but some cells and tissues are more susceptible to damage from nuclear radiation than others.

Which cells in the body are most affected by radiation?The cells and organs that are most affected by nuclear radiation are the ones that are actively reproducing, because the DNA is more exposed when the cell is in the process of dividing.

Blood cells have the highest turnover rate in our bodies, so the tissue where they are produced — the rapidly dividing cells of the bone marrow — is the most susceptible to radiation damage.

The damage to bone marrow in high doses — and complete destruction of it in very high doses — impairs our immune system by not replacing our white blood cells.

Long-term exposure to lower doses can lead to cancerous DNA mutations in the marrow, which can lead to the blood cancer leukaemia in people exposed through work or location………

Developing foetuses are, of course, incredibly susceptible to radiation, ……

Exposure to external radiation is one thing, but ingesting radioactive particles takes the damage to another level.

What happens if you breathe in radioactive particles or swallow contaminated food or water?

Inhaling or swallowing radioactive material delivers the source of radiation directly to your cells, increasing the risk of cancer developing in the tissues where they accumulate.

Radioactive iodine (iodine-131) blown into the atmosphere by the 1986 Chernobyl explosion caused a large number of cases of thyroid cancer in people who drank contaminated milk. (Having been released in the clouds of radioactive material following the explosion, the iodine — a by-product of nuclear fission reactions — landed on fields where it was swallowed by cows).

Iodine is essential for the normal function of the thyroid gland, and with its knack for attracting iodine the gland gets a concentrated dose of iodine-131 when contaminated milk is drunk. Thankfully, thyroid cancer is treatable by removal of the gland, although a lifetime of hormone supplements follows. With a half-life of just eight days, the level of radioactive iodine fell off quickly after the accident, so the risk of exposure dropped within weeks of the disaster.

Not so with the radioactive isotope of caesium-137, which has a half-life of 30 years. Caesium is very soluble in water, so when it enters our bloodstream via contaminated food or water it ends up spreading throughout our bodies, and concentrating in muscle tissue in particular. Our bodies eventually turn over these tissues, but it takes three months to reduce the amount of caesium in our muscles by half, so the long-term exposure to beta and gamma radiation increases the chances of cancer developing in those tissues.

With a half-life of 29 years, strontium-90 joins caesium-137 as a long-lasting source of harmful radiation after nuclear accidents.

Strontium is chemically very similar to calcium, so if you ingest food contaminated with radioactive strontium isotopes like strontium-90, it ends up wherever calcium normally would — primarily in the bones.

April 25, 2016 - Posted by Christina Macpherson | 2 WORLD, radiation, Reference

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