Hoax about nuclear radioactivity?

The general perception is that radioactivity is almost entirely due to anthropogenic activity where in fact only 13% is derived by human activity and 87% is natural. 12 % of human derived radioactivity are utilised in medicine (e.g. X – rays) and only less than 1% is actually caused by nuclear accidents, leaks, nuclear bombs and their testing. Radioactivity has been shown to cause detrimental effects on humans it may lead to change of DNA and cancer; it can also interact with electrons in molecules in cells causing ionisation which can result in alteration of important molecules in tissue. Radioactive particles like α could get inhaled or get ingested and β, γ particles could penetrate through and cause health problems.

Natural sources on Earth leading to radioactivity are mainly isotopes of radon (222Rn & 220Rn)(50%); gamma rays cause roughly 14%; food and drinks – 12%; and cosmic rays – 10%. Rn is thought to not be problematic when outside but a modern issue with it is that Rn could get trapped within homes especially as keeping heat inside homes. Once Rn has leaked into a building it concentrates in the lower levels as it is heavier than air. It could enter buildings in various ways where CO2 is one of the major gases transporting Rn. Usually it is derived by respiration of soils which gets incorporated by CO2 and carried into homes.

Some rocks may also be radioactive  as they contain uranium (U) rich minerals such as uraninite, brannerite and carnotite. Generally, the most radioactive rocks are “hot” granite, some black shales, coal, fly ash (used in some building materials), some sandstones, limestones and gneisses where only black shales are not problematic as they are very fine grained, well lithified (sealed) therefore it will be difficult for Rn to escape from the decay of U in time. Rn can easily escape from U-rich granites as the one in south west England due to the fact they are well-jointed and permeable.

Study undertaken in N. Caroline, USA shows that Rn is soluble in water where water extracted from U rich gneisses which breaks down to Rn isotopes was transported into the shower air increasing the radioactivity 96 times above the average Rn concentration for the USA.

It is important to understand the natural radioactivity in order to appreciate the little influence humans have. However, accidents such as Chernobyl and Fukushima have caused severe health issues around the world.

 

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Denitsa Tarnovska

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