1. What is radon?
Radon is a colorless, odorless, tasteless radioactive gas that is widely present in nature such as air, water, and soil. It is produced after several steps of radioactive decay of uranium (U-238) and thorium (Th-232). It is a natural radioactive substance that exists anywhere on Earth that is not perceived by human senses. It is known to cause lung cancer when continuously exposed to high concentrations.
2. How much radiation does a person naturally receive?
According to a 1988 report by the “United Nations Science Committee” on the effects of atomic radiation1, the average radiation dose a person receives in nature is 2.4 mSv (240 mrem) per year. Of these, half are exposures related to radon. It is also said that this value is about 1.3 mSv.
3. What is the exposure limit for radon?
The exposure limit refers to the lowest level of radon concentration that should not be exposed beyond that in order to prevent the health effects of radon in healthy people. Exposure limits for radon concentrations vary slightly from country to country. In the United States, 148 Bq / m3, in Canada, 200 Bq / m3, and in Sweden, the standard for new homes (200 Bq / m3) is lower than that of existing houses (400 Bq / m3).
4. How dangerous is radon to the human body?
The World Health Organization (WHO) said radon is the leading cause of lung cancer after smoking.2 3 to 14% of lung cancer cases are caused by radon. According to the US Environmental Protection Agency (EPA), about 21,000 people, or more than 10% of Americans’ lung cancer deaths per year, are attributed to radon.3 This is higher than the risk of death from drowning and fire, and higher than death from drunk driving.
According to EPA’s “A citizen’s guide to Radon,” smokers are more likely to develop lung cancer from radon.4 If 1000 smokers live in an indoor space where the radon concentration of 4 pCi / L, which is the standard for regulation, is maintained for a lifetime, about 62 people are at risk of lung cancer. On the other hand, non-smokers are said to have about 1/10 of the risk.
5. How does radon gas enter the residential space?
As mentioned earlier, radon is everywhere in the atmosphere. Radon gas introduced into the room may accumulate and increase the risk. It is known that 80 to 90% of the radon in the room comes from radon gas generated from soil or ground rocks through cracks in the floor or walls of buildings. In addition, radioactive materials such as radium contained in construction materials (2 to 5%), or radon dissolved in groundwater (1%) may be introduced. Once introduced into the room, radon does not easily escape and continues to accumulate.
The concentration of radon in a poorly ventilated building is tens to hundreds of times higher than in outdoor environments. In general, the path through which radon gas is introduced is as follows.
6. How to reduce the indoor concentration of radon gas?
The easiest way is ventilation. Periodic indoor ventilation can significantly reduce the concentration of radon. Repairing a building’s cracks can help reduce the concentration of indoor radon in existing buildings. If it is not enough to prevent cracking, radon discharge pipes can be installed in the soil under the building to collect radon gas in the soil and discharge it outside the building without going through the room. In addition, if the pressure of the indoor air is artificially increased higher than the lower part of the building through the air inflow device, radon gas cannot enter the room due to the pressure difference.
When building a new building, consider the following radon reduction construction method from design.
- After laying gravel in the soil, install a radon discharge pipe.
- Place plastic sheet and seal it so that there is no gap.
- When the radon discharge pipe is installed to go straight up from the basement to the top of the building roof, radon gas generated from the soil does not accumulate in the room and goes out into the atmosphere.
- For the purpose of increasing the reduction efficiency, a ventilation fan may be additionally installed.