Understanding the Basics of Radioactivity
Radioactivity is something most of us are familiar with, either through popular culture or a broad understanding of nuclear power, but the specifics as related to this scientific phenomenon are not as often understood. There is actually a natural level of radiation all around us at all times that originates from a few different sources. In addition to natural radioactive materials existing in the ground, common substances such as potassium and carbon contain radioactive isotopes – plus there’s cosmic ray gamma radiation from space and radon gas from the atmosphere! With radiation around us at all times, in this article we take a look at the different ways that radiation can affects humans.
Because radiation is a complex topic, we’ll try to break its measurement down as an amiable chemistry tutor in Adelaide (or wherever you may be from) would. Radiation absorption is measured in two different ways: grays, for non-biological matter and sieverts (Sv) for biological matter. Grays units are measured as a joule of energy per kilogram of mass but for biological tissue, it will depend entirely on the type of radiation involved and how much damage that radiation does to the affected cells. To find the dose in sieverts, grays are multiplied by some “quality factor” (i.e. the type of tissue irradiated and for the type of radiation). For example, in the case of electrons or gamma-rays, it is 1, but if measuring alpha particles such as those given off by the radioactive decay of uranium, the figure becomes a 20 – quite the increase! Although the amount of background radiation is related to a wide variety of factors, such as the type of soil and rock, altitude, latitude and diet, the average Australian is exposed to 1.5 mSv each year from natural sources. Interestingly, because rocks like granite contain higher levels of uranium, areas that contain higher concentrations of this rock will have a mSv of up to 5. This is reflected in places like Cornwall or Aberdeenshire in the UK, and background radiation can grow to 50 mSv per year in places like northern Iran.
The effects of radioactivity on human health
Most are well aware that radiation can have a negative effect on the body, but the complexity of this is sometimes not understood. Negative health effects related to radiation can act over the short- and long-term and also at shorter and greater distances. Generally, radiation causes health problems by killing cells in the body, the extent of the damage linked to the dose of the damage and the length of time in which the dose is spread out. Receiving 1 Sv in a single day can cause symptoms of radiation poisoning, such as nausea and damage to organs such as bone marrow and lymph nodes. These effects are amplified when ramped up to 3 Sv with the added possibility of developing an infection due to a reduced number of white blood cells in the body. In these cases, survival is likely with treatment –but not guaranteed. Larger doses can cause some far more severe side-effects, such as haemorrhaging, sterility and the peeling off of skin, and untreated doses of more than 3.5 Sv are fatal.
Radiation is all around us
Considering the horrific effects radiation can have in large doses, it’s often surprising to think about it being all around us constantly – especially when its concentrated in something as harmless as granite. Although the majority of us will have to deal with the negative effects of radiation, it’s certainly some food for thought and further education!