Hanoi: Radon toxic gas?

The concentration of harmful radon gas in houses is one of the civilized living standards that are increasingly concerned by many countries. Hanoi began to pay attention to this standard.

Standard of civilized life

The more civilized people are, the greater the demand for quality of life is. The more society develops, the more new standards of quality of the population appear and the more they are concerned and demanded by the community.

According to that rule, in recent years, in many developed countries, people have begun to care about the radiation background of the environment in which they live, paying special attention to the concentration of Radon in their homes, and watching that is one of the standards of civilized life.

Gone are the days when people still thought the radioactivity was far away, nothing to do with themselves. Now it is different, many people know that, around us, everywhere, are radioactive, they exist right from the time when the earth formed, human beings are born, and have a certain influence on your health. people.

Radioactive isotopes are found in all types of rocks, water, air, food, in the space of houses and in every part of a human being. They are mainly natural radioactive elements Uranium, thorium and decay products, ie their children, grandchildren, grandchildren . (also radioactive isotopes). In addition, there is another radioisotope - Potassium K-40 is found in vegetables, fruits and the human body.

Radon sugar penetrates in the house (red).(Illustration)

It is these radioactive substances that continuously emit radiation (particles) of radiation, such as alpha, beta, gamma . These types of radiation cannot be seen, but every second of every minute is projected on the body with a total dose of irradiation. , can be harmful if a certain limit is exceeded. The higher the radiation dose, the greater the harm. The average irradiation dose for residential areas in countries around the world, in general, ranges from 2.1 to 2.5 in mSv units.

Many people have hesitated, worried or even refused to live in a geographic location where the radiation dose exceeded the average value of the world, such as those near the Urani mine.

In Hanoi, according to the survey results by the expert group (NQ Long, TT Mai, DV Thang, NT Hau) of the Institute of Nuclear Science and Technology, the above irradiation dose is also approximate to many countries. Thus, it can be affirmed that the natural radioactive environment in Hanoi is normal, or in other words, the standard of general radioactive environment in the Capital can be considered good.

Something about Radon

- Radon radioactive elements (symbol Rn), including radioactive isotopes Rn-222, Rn-220 and Rn-119, are produced during the decay of the Uranium and Thorium parent nuclei.

- In particular, the radioactivity of the largest Rn-222 is due to its half-life of 3.8 days, enough time to move from where it appears to the lungs and survive for a long time in the muscle. human being.

- Rn-220 and Rn-119 have a shorter half-life, only 55 seconds and 4 seconds.So the danger is less.

However, the total irradiation dose mentioned above is not all. More interesting is a natural radioactive element - Radon (symbol Rn). It is the concentration of new Radon that greatly affects human health. Radon concentration in a room, a house has become one of the essential living standards of modern people.

Radon - ' hidden enemy '

The major effect of Radon on health is primarily because Radon is a special gas, a gas, not just an inert gas but a radioactive gas . Being chemically inert gas, when born, radon atoms are not bound to other matter atoms in host objects, such as construction materials, rock and other minerals, so they are easy to escape. through cracks and tiny holes in soil layers; stones, walls and floors then diffuse into the air, into rooms of houses, from which humans can breathe into the lungs.

Eventually Radon nuclei decay into a series of descendant nuclei, the most dangerous of which is the radioactive isotope Polonium Po-218.

P-218 decays alpha with a half-life of 3.05 minutes, enough for some breathing cycles in the human respiratory system, and they can be stored at the alveoli.

At alveoli, Po-218 alpha decay. Very high energy alpha particles will bombard the alveolar cell nucleus, causing chromosomal defects, negatively impacting the cell division mechanism. On the other hand, the nuclei when decaying will be recoiled, this backward energy can be enough to break down protein molecules in alveolar cells.

Radon emits radiation.(Illustration)

As a result, the probability of causing cancer by Radon is quite high. The risk of developing lung cancer due to radon irradiation depends on the amount of radon we breathe. The more radon in the air, the greater the harm. In addition, the harm is greater if the time we breathe in the air contains Radon longer.

With all the above characteristics and harms, it is clear to Radon that human health is a 'hidden enemy' . Radon plays the most important role in natural radioactivity, contributing a dose of 50% to more than 80% of the natural radiation dose mentioned above. Determining the concentration of radon gas is very important for the purpose of monitoring and warning of lung cancer risk to the community.

Data sources collected by many laboratories around the world show that: outdoors, the concentration of radon is usually measured in an average of about 10 units of Bq / m ³ (Berquerel is a unit of radioactivity, written turn off Bq). In bedrooms, basements, mineral deposits . Radon concentrations can range from 20 to 10,000 Bq / m ³ , or more. The main areas of high concentrations of Radon are in houses made of materials with high uranium content, a non-airtight sealing room, basements of large buildings . and especially in mining mines. Uranium waterfall.

Currently, Vietnam has not recommended the limited level of Radon required to intervene to lower, while many developed countries have legal regulations. In European countries that level is 200 Bq / m ³ . As for the US, this standard is stricter, according to the US Environmental Law, allowing Radon gas in houses less than 75 Bq / m ³ .

Radon concentration in Hanoi?

In the framework of a research project chaired by Hanoi Department of Science and Technology, the concentration of Radon radioactive gases in many places, outdoors and in the Hanoi (old) area has also been surveyed by the research team. on the Institute of Nuclear Science and Technology.

The concentration of outdoor radon gas in 231 different locations was measured. The result of determining the average concentration of Radon in Hanoi is 17 units Bq / m ³ . The lowest measuring place is 4 units Bq / m ³ and the highest measuring place is 58 Bq / m ³ .

Most important is Radon in houses. The research team placed radon tracking in 40 rooms in Hanoi city for 3 consecutive months, twice in 2007 and 2008. The results showed that the concentration of Radon in the lowest place was 7.2 Bq. / m ³ , where the highest is 138 Bq / m ³ and the average is 38.3 Bq / m ³ (In countries around the world and the region is about 26 Bq / m ³ ).

Measure the concentration of Radon gas in the bedroom
(Photo: Dang Thanh Luong)

Survey results of indoor radon concentration (and outdoor) this time were higher than the previous survey, in 1996, by the topic group KC.09.18. This increase is related to the development of home density, the appearance of many tall buildings and more common in the use of closed rooms. All of these factors increase the amount of Radon from construction materials emitted and store them long in rooms.

Anyway, the Radon survey data in Hanoi can be considered as equivalent to those in the countries of the world and in Southeast Asia, which has not caused any concern for the community. Residential Capital.

Of course, it is worth noting the relatively high concentration of radon (138 Bq / m ³ ) in a Hanoi room, which exceeds US standards. This is probably not the only case of high radon toxicity, because only a very small number, 40 rooms in Hanoi were surveyed. There will be many rooms, houses with Radon concentrations exceeding 138 Bq / m ³ above.

This poses the need to continue surveying with a further density of rooms, with houses built of different materials, different textures, different elevations, different geographical locations. In order to have more complete and more accurate conclusions.

And from there draw meaningful conclusions, make useful recommendations for the community in the Capital. Starting from Hanoi and gradually expanding to other localities. Accompanying the increasing trend from the minimum living standards of a period of worrying about " rice " to higher living standards of our civilized era.

Radon measurement

a / Radon measurements outdoors with live alpha meters.

- Using Alpha Guard gauge (Genitron firm), read standard with Rn 101 liter standard chamber (Genitron firm), with standard Rn (Standard Reference Materrial 4973).
- Depend on many factors such as weather, temperature, humidity, pressure . measurement results vary from 4 Bq / m ³ to 58 Bq / m ³ , an average of 17 Bq / m ³ with fluctuations in the range 9 Bq / m3.

b / Measure the concentration of radon in the home by nuclear trace method.

- Hanging traces of stains (in plastic materials and sensitive to alpha) in the room, radon beams of Radon will project and stain continuously for three months, then use chemical treatment to show stain and count on the microscope vi.
- From stain density (stain density / cm ² ), calculate the concentration of Radon in the room,
- The results show that the average concentration of radon in the house in Hanoi, in 2007 and 2008, is 38.3 Bq / m ³ .