“You can’t see, smell or taste radon in your home. But that doesn’t mean it isn’t there.”
From the case of Singapore in my previous post, let’s move into something a little more intimate to all of us… radiation pollution at HOME!
What is radon?
Radon is a radioactive, colourless, odourless, and tasteless gas, and it is the leading environmental cause of lung cancer deaths in the U.S., which kills 21,000 people each year. According to the Environmental Protection Agency of the U.S., radon gas on dust particles upon inhalation may lodge in the airways of the lungs. When the radionuclides decay, they expose lung tissue to damage. They state that “there is no safe level of radon, any exposure poses some risk of cancer”.
Radon comes from the natural decay of uranium that is found in nearly all soils. It typically moves up through the ground to the air above and into houses through cracks and other holes in the foundation.
Harley (1990) indicates that when radon is released into an enclosed space, it cannot disperse, and continued release results in a marked buildup in concentration. This is especially so in the case of mines and indoor/enclosed areas, where the major source of radon is the soil under and immediately around the building.
From the figure above, various pathways include cracks in solid floors (1), cracks in walls (3), gaps in suspended floors (4) and water supply (7)
Radon pollution is made worse due to the increasing popularity of underground residences/basements. In a move to achieve greater energy savings, home have also been constructed with higher insulated and sealed structures. This minimises any air exchanges from within to outside the home, and increases the likelihood of the accumulation of radon gas.
Case of the Reading Prong
The Reading Prong, a geologic formation extending from Pennsylvania to New Jersey and New York is an area that received great public attention in the 1980s. Rocks of the Reading Prong are characterised by elevated concentrations of uranium, upon decaying produces radon gas that is a hazardous source of indoor pollution in structures constructed on the Prong.
Prior to this, radon in the environment was considered of little risk because it easily dispersed in the atmosphere. Testing in homes began only in mid-1980s: an engineer with a Pennsylvania utility set off radiation alarms when he entered a nuclear plant. Tests at his home above the Reading Prong found radon levels far above that allowed in uranium mines.
Why radon concerns us
According to Hill (2010),
- Radon-222 has a half-life of 3.8 days, so it may be breathed out of lungs before it decays
- Its solid radioactive daughter elements e.g. polonium-218 and polonium-214 that results from the decay of radon-222 are far more dangerous
- Polonium-214 has a half-life of less than 1 SECOND thereby can decay in the lungs when inhaled (emits alpha particles which can damage the DNA in lung cells)
- Polonium-218 and 214 attach themselves to tobacco particles, meaning that smokers and people in homes with smokers bear the brunt of the risk
Some thoughts of mine:
While doing research, I realised that little about indoor radon pollution has been talked about in the case of Singapore. In the U.S. however, indoor radon pollution is a far more widely discussed topic. The EPA provides plenty of information – from “A Citizen’s Guide to Radon” and even contacts for households to obtain radon test kits. From my research, it turns out that there is a geography to the presence of radon gas: rocks with higher concentrations of uranium are likely have higher concentrations of radon gas. These rocks include light-coloured volcanic rocks, granites, dark shales, sedimentary rocks. Layers of these rocks underlie various parts of U.S., while in Singapore, our geology mostly involves sand, silt, gravel or clay. While little has been studied on the potential for radon pollution in Singapore, this is only my conjecture as to why radon pollution is not widely discussed.
Thanks for reading!
Gang, C. J. (2012, July). Geology of Singapore. Retrieved March 21, 2015, from http://www.comp.nus.edu.sg/~a0083545/ssa2215/sg-rock-formation.pdf
Harley, N. H., & Harley, J. H. (1990). Potential lung cancer risk from indoor radon exposure. CA: a cancer journal for clinicians, 40(5), 265-275.
Hill, M. K. (2010). Understanding Environmental Pollution.
U.S. Geological Survey (1995, October 13). The Geology of Radon. Retrieved March 21, 2015, from U.S. Geological Survey: http://energy.cr.usgs.gov/radon/georadon/3.html
U. S. Environmental Protection Agency (2014, January 14). Basic Information. Retrieved March 21, 2015, from Radon: http://www.epa.gov/radon/aboutus.html