Bbrhuft t1_jcaeg0n wrote
Radon-222 decays via several steps, a decay chain leading to non-radioactive, Lead-210. A lot of the radon decay products, Lead-214 and Bismuth-214, ends up coating dust particles and sold surfaces, a phenomena called Radon Daughter Plate Out. So the daughter atoms aren't usually free floating in the air, but usually more than 90% ends up sticking to dust particles and solid surfaces.
>A small fraction of radon progeny, typically 0.1 or less, remains unattached and in dynamic equilibrium with attached particles. Generally, dustier atmospheres are associated with smaller values of unattached fraction and higher concentrations of radon due to additional radiation emission from dust.
This is the decay chain for Uranium-238, which includes Radon-222
Radon-222 initially decays to Polonium-218, via emitting a positively charged Alpha particle. The resulting Polonium-218 atom, with a half life of 3.1 minutes, is electrically charged and it is attracted to charged dust particles and sold surfaces where it quickly decays to Lead-214 and Bismuth-214, formimg a radioactive coating, a major source of radiation exposure from indoor Radon gas.
These two isotopes, in comparison to other isotopes of the randon decay chain, have relatively long combined half life of just over 20 minutes.
Radon Plate Out can be demonstrated using a balloon. If you have a building or better still, a basement with a slight radon problem, and leave an electrically charged balloon in the room for an hour or so, then measure it with a Geiger Counter, you'll often find the balloon becomes radioactive due a coating of Lead-214 and Bismuth-214, from attracting Polonium-218 directly and radioactive dust particles.
The Plate Out on glass is very sticky, I keep a Radium dial WWII compass safely sealed in an air tight jar. The inside of the jar gets coated with radon plate out, rubbing the glass with a wet tissue removes some of the contamination, the tissue gets contaminated, but most of the activity is stays stubbornly stuck to the glass.
It's possible some of plate out might have formed some sort of electrostatic bond, perhaps Van Der Waals force.
I can also measure the decay of the contamination:
The isotopes have an average half life of just over 20 minutes, so it's decay noticed quite quickly (using a Radiascan 701a connected to logging software on my PC).
boundless88 t1_jcajyn2 wrote
So does that mean my basement with it's slight radon problem is entirely covered in radioactive particles? How do you even clean that out and make the space usable / liveable after taking radon mitigation steps?
Bbrhuft t1_jcamrpd wrote
Having high radon levels in a basement area, a little above the recommended levels, shouldn't be a problem as you don't spend much time there, unlike a bedroom or living room.
Also, if you have a clothes drier in your basement and a Geiger Counter, a fun experiment involves measuring the radioactivity of the lint caught in the dust trap. It can sometimes be extraordinarily radioactive.
It doesn't work for me, as my clothes dryer is in a well ventilated room.
Also, the most effective way for society to reduce the risk of lung cancer from indoor radon exposure is to reduce rates of tobacco smoking.
Most people who get radon linked lung cancer are current and former smokers, as smoking reduces the lung's capacity to repair DNA damage caused by ionizing radiation. Smokers are almost 9 times more likely to develop radon linked lung cancer than never-smokers.
>The BEIR VI model also purports a significant synergism between radon exposure and smoking in lung cancer risk. On the basis of BEIR VI, the EPA estimates that, at a radon level of 4 pCi/L, the lifetime risk of radoninduced lung cancer death for never-smokers is 7 per 1000, compared with 62 per 1000 for ever-smokers.
Lantz, P.M., Mendez, D. and Philbert, M.A., 2013. Radon, smoking, and lung cancer: the need to refocus radon control policy. American journal of public health, 103(3), pp.443-447.
RadWasteEngineer t1_jcat6nk wrote
Commercial tobacco is also fertilized with mined phosphate fertilizers that are naturally Rick in uranium decay series elements, including Po-210. It also turns out that the tobacco plant has an unusually high affinity (uptake factor) for polonium, and the leaves become enriched in polonium. Smoking those leaves is the most effective exposure pathway: inhalation. Put all that together and voilà: cancer.
Bbrhuft t1_jcaunob wrote
That's interesting. I always wondered where the Polonium-210 came from. I have a radioactive apatite from Brazil. In this case it contains radioactive thorium, but yes apatite (phosphate ore) can also contain uranium.
RadWasteEngineer t1_jcavmk1 wrote
Uranium decays to thorium decays to radium decays to radon, and so on. So any or that contains uranium will contain this huge suite of decay products as well.
What's especially interesting to me about tobacco is that it selectively removes polonium from all the others and puts it in the hapless smoker.
Bbrhuft t1_jcayi93 wrote
Wow, so it's biologically concentrating Po-210 like how Chernobyl mushrooms concentrate Cesium-137, or radioactive galena...
This will interest you. Here's a sample of radioactive galena I have from the Kateřina Coal Mine, Radvanice, Czech Republic.
Here's a close up photo...
https://www.mindat.org/photo-1144820.html
It looks like a bismuth specimen, due to its odd formation process, deposition from hot gas.
The Kateřina Coal Mine was a bizarre combination of a coal and uranium mine, that caught fire in the 1960s or 70s. Fumes from the burning coal seams deposited galena in cracks, which ended up contaminated with radioactive Lead-210, half life 22 years.
The specimen was likely collected in the 1990. The entire site was rehabilitated about 15 years ago, it's now a nice green park. Big difference from the hell scape of a burning radioactive coal mine.
RadWasteEngineer t1_jcaz3dh wrote
Yes, bioconcentration.
That's amazing about the burning coal mine forming galena from the lead. Nature is incredible.
Apotropaic_Sphinx t1_jcb5i4y wrote
Yeah, my furnace filter gets slightly radioactive after a few months. Very minor but it’s detectable above background level.
GammeldagsVanilj t1_jcaq7y8 wrote
>How do you even clean that out and make the space usable / liveable after taking radon mitigation steps?
If you've taken radon mitigation steps (such as barriers against radon infiltration from the ground, overpressure in the building or increased basement ventilation from non-radon air sources) then the remaining already deposited decay products on surfaces in the basement should be negligible. Just vacuum the place.
GypsyV3nom t1_jcaorwb wrote
If you've already taken radon mitigation steps, you're good. The big danger from radon is inhalation, you really don't want any radioactive decay to occur inside your body. The radioactive dust can likely be removed through simple cleaning activities, and isn't that dangerous if it remains outside your body. Radon's decay chain exclusively produces alpha and beta particles, which your skin can easily block.
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