# If radium has such a long half-life, how can radon possibly be a threat to us?

If the probability is so low that a radium atom will decay into radon at any given time (the half-life is over 1600 years), then there will be a low amount of radon produced, granted it will be produced for a long time. If this is so, how can radon possibly be dangerous to us?

• Isn't chemistry all about electrons? How can this be on-topic? – Peter Mortensen Dec 7 '14 at 1:37
• Radioactivity is a part of nuclear chemistry. – Emu27 Dec 7 '14 at 2:06

There are two factors here:

1. Radon is a gas and can thus enter the body very easily, through inhalation.
2. $\ce{^222Rn}$ and its first 4 decay products are extremely radioactive, with halflives of miliseconds to a few days, releasing alpha and beta radiation.

When the two are combined, we have a problem. Even if the quantity is low, inhaling radon places an extremely radioactive substance at very close proximity to the cells in one's lungs. Normally, alpha and beta radiation are relatively harmless as they cannot penetrate tissue very well, but now they have direct access. All it takes is one mutation in the wrong place to cause lung cancer.

To give you an idea of what a difference these make, the volumetric activity which is one guideline for needing to mitigate radon accumulation in a house is around 800 $\mathrm{Bq/m^3}$, which corresponds to only 141 fg of radon per cubic metre of air. This isn't like a uranium mine or something, but at this level, a certain increased risk of cancer is expected. Apparently some study found a 50% increased risk at a much lower level ~150 $\mathrm{Bq/m^3}$, too.

N.B. a becquerel (Bq) is a reciprocal second—1 Bq means one atom of the radioactive substance disintegrates every second.

• This makes sense but I'm wondering if you are able to answer a followup question. Some areas in Montana actually have Radon-therapy mines and things of this sort also exist in Europe. Do you (or someone else) know if these are actually beneficial to health because Radon levels are so much lower, or because the period of exposure is so much shorter than it is for people who come in contact with Radon in their home? Thanks – Emu27 Dec 7 '14 at 1:14
• I found a paper about the Montana mines. As far as I know, it's quackery and it certainly sounds like a bad idea. Certainly nothing new. For a while, early last century, devices for adding radioisotopes to drinking water were a health fad. When a better understanding of radioactivity and its health effects was reached, they were banned and these devices mostly disappeared. Apparently this kind of thing hasn't totally died out. – Michael DM Dryden Dec 7 '14 at 1:23
• I think it would be interesting to conduct an official study regarding the potential side effects that these mines have on patients later into life. If the results turned out to match your hypothesis, it could prevent a lot of sufferers of arthritis and bronchitis from worsening their conditions by getting cancer later on. – Emu27 Dec 7 '14 at 2:30
• If I remember right, the decay products of radon are solids instead of gases? So radon atoms that decay in your lungs will deposit radioactive matter in the lungs that can't get back out. – user137 Dec 8 '14 at 16:53
• @MichaelD.M.Dryden And while lead is toxic by itself radioactive or not I doubt you'll get enough lead through radon to be a problem. – user137 Dec 8 '14 at 18:20