Radiation: the culprit of Thach Son cancer village?

With the most modern methods and analytical equipment, the domestic science group has contributed to delineating the culprit causing Thach Son 'cancer village' (Phu Tho).

The group of domestic scientists published data and conclusions on this issue in the journal 'Nuclear Science and Technology Information', No. 1 and 2, 2010 / * / of the Atomic Energy Institute Vietnam (Ministry of Science and Technology).

Hundreds of brick kilns discharge smoke causing harm to the environment in Thach Son commune, Lam Thao district
- Phu-Tho.Photo: Employee.

Environmental problem

In recent years, Thach Son commune in Lam Thao district, Phu Tho province has suddenly been noticed with a strange name - ' cancer village ' because of the number of people suffering from dangerous diseases is much higher than normal. That situation caused public opinion to raise questions regarding the presence of so many years in the area of ​​Thach Son and Chu Hoa communes (collectively referred to as ' Thach Son village ') in some factories such as phosphorous superphosphate. Phat Lam Thao, Pin - Vinh Phu Battery, many brick kilns close .

The question is, do these industrial establishments disperse harmful health pollutants to people such as toxic chemicals or radioactive substances?

This article does not mention the first type of culprit, only seeking answers to the question: is radioactive contamination the culprit? A scientific research topic has been assigned to the scientific group of two research institutes, the Nuclear Science and Technology Institute and the Institute of Environmental Medicine and Hygiene, to coordinate in the implementation of 2006-2010.

Of course, not only residents of Thach Son village , but anyone, no matter where in the earth, are daily and lifelong in an environment containing radioactive substances. The problem is to survey, analyze to clarify the level of radioactive material, or the radioactive contamination in Thach Son area is too high compared to the permitted standard, and higher than the adjacent locations. but outside the scope of influence of factories such as Lam Thao phosphate superphosphate, Pin - Vinh Phu battery .

If the answer is negative, at least not discovering the significant difference in radioactive contamination between the two areas mentioned above, suspicion and control, it means the culprit causing the village event. Thach Son cancer 'is not radioactive.

Select the object

The radioactive environment in which people live together consists of two types: natural radiation and artificial radioactivity.

Artificial radioactivity was born in laboratories and especially by nuclear weapons tests many years ago. However, in the territory of Vietnam, according to the recent survey results of the research groups of the Nuclear Science and Technology Institute, the Phu Tho region is not an anomaly in artificial radioactivity, closed The contribution of artificial radioisotopes to environmental radioactivity contamination is not more than 1%. Thus, only access to natural radioactive substances.

Natural radioisotopes have existed on earth for billions of years, ever since its formation. These isotopes emit radiation rays of alpha, beta and gamma, which affect humans most significantly, rays. In addition, it is possible to view cosmic rays originating from our planet as natural radiation.

These radioactive rays create irradiated doses that are harmful to the human body. The level of harm to the body depends on the magnitude of the radiation dose measured in siver / hour (Sv / h). This projection dose, with the participation of different types of radiation, is shown in Figure 1.

On the 'cake' that divides radioactivity 1, two radioactive objects play the biggest role.

One is Radon radioactive gas . When people breathe into the lungs, radon radionuclides will emit alpha, beta and gamma radiation that bombard the cells from inside the body. This group of people has the greatest impact on human health and contributes up to half of the total projection dose.

Secondly, radioisotopes are located in the soil layer on the ground. Radionuclides on the face layer continuously emit distant radiation and affect the body from the outside and contribute up to 20% of the projection dose.

Internal dose: Radon toxic gas

In order to apply the comparative comparison method, the research team selected the following two types of enumeration areas, survey and data collection:

Suspected locations contain high levels of radioactive material, or high irradiation doses. That is the area of ​​Lam Thao phosphate superphosphates and Pin - factories located in Thach Son area . and the adjacent residential area of ​​Thach Son and Chu Hoa communes (in Lam Thao district, Phu Tho).

The control area is Luong Lo commune (in Thanh Ba district, Phu Tho), located more than 20 km away from the above factories, located on the other side of the Red River.

First of all, the comparison was made for radon radioactive gas. The most appropriate radiation measurement methods have been used. For example, the concentration of radon in the home has been measured by cumulative method with stain-points placed in a fixed position in the house for 3 to 6 months. Radon concentrations are determined from the number of traces left in the structure. Radon concentrations in outdoor air are measured by an alpha meter (called Alpha Guard).

The magnitude of the radon concentration is indicated by the Berquerel unit in a cubic meter, or Bq / m3. From the concentration can calculate the irradiation dose calculated in Silver units / time, such as Sv / year or microSv / hour etc. .

Surveying and surveying were conducted at 35 different locations in two areas: ' questionable ' areas, including the factory area (8 locations) and residential areas (19 locations) around; belong to Chu Hoa and Thach Son communes. Control area - Luong Lo commune.

The results are recorded in table 1 with the average value of Radon (Bq / m3) and the error (or STDV standard deviation) for each region.

Table 1- Radon concentration in air No. TT Survey area (number of locations) Rn / STDV concentration (Bq / m3) 'questionable' area - Factory areas (8)
- Chu Hoa commune: (9)
- Thach Son Commune: (10) 9.5 5.5
11.0 10.5
14.7 9.0 Control area - Commune Luong Lo: (8) 11.1 3.3

We can comment on the survey results given in the table as follows: Average Rn concentration in the areas of the two areas - 'questioning' and control - are close together, the difference is negligible in Round error of measurement.

With this survey result, the radioactive effect is caused by the internal radiation dose caused by radon in the 'cancer village', apparently, only similar Luong Luong control area is located far from chemical plants.

In addition, comparing with radiation safety standards, the measured radon concentrations in all surveyed areas are low. In all three survey areas (see Table 1) the measured radon concentrations are in two numbers, while according to the international radiation safety standards, only those with radon concentrations higher than 1000 Bq / m3 is recommended to pay attention to lower.

External projection dose: Gamma on the ground

Also in the two selected comparison areas, the gamma absorbed dose at a distance of 1 m from the ground was surveyed in 'suspect' areas and compared to Radon targets. The device used is the Serveymeter TCS 171 reliable dedicated portable dosimeter (ALOKA). The machine is calibrated by the secondary radiation standard room (SSDL) located at the Nuclear Science and Technology Institute.

The effective gamma absorbed dose was investigated at 244 points in 3 areas: * The area of ​​Lam Thao phosphate superphosphate factories, Pin - Antico… with 61 positions. (Residential area around factories with 61 measurement locations in Thach Son commune and 60 locations in Chu Hoa commune., Control area, Luong Lo commune with 62 measurement locations)

The collected data has been synthesized and presented in digital maps and diagrams. Effective absorbed dose rate measurements are shown on maps (Figure 2a and Figure 2b). The survey locations are round, light density on the figure showing low high dose rate.

Figure 2.1- Map of distribution rate of Thach Son commune - Chu Hoa commune.

Figure 2.2 - Map of distribution rate of Luong Lo commune.

From the results obtained can be evaluated: i / According to the density on the two maps, the dose rate is in the range of 0.05 to 0.156 micro Sv / h. ii / Also from the lightness, it can be seen that the dose rate in the two survey areas ('doubt' and control) has no significant difference, and is in the normal range as many radioactive environments. Other normal.

For a more quantitative assessment of the external gamma absorbed dose, the research team analyzed the diagram. The team calculated the average value of the gamma dose rate fluctuating around the value of 0.1 microSv / h, and the highest value did not exceed 0.16 microSv, even in the hypothetical plant area. is the place where toxic radioactive substances are dispersed to the residential areas of Thach Son cancer village. At the same time, calculate the annual gamma dose for each resident in Thach Son, Chu Hoa and Luong Lu areas. That is: 0.904 miliSv / year.

Comparing with international and Vietnamese safety standards, the value of gamma absorbed dose is low and equivalent to the average of many countries in the world. In other words, the radioactive environment in Thanh Son and Chu Hoa residential areas is really normal.

Conclusion: Numbers speak

Thus, the radioactive environment in the area of ​​factories and residents of " cancer village " Thach Son (area of ​​questioning) and remote areas (control areas), especially two typical measurements ( Radon concentrations causing internal dose and external gamma dose value), were investigated by advanced methods and equipment.

Two approaches, external projection and internal dose, give consistent and complementary results, proving that the radioactive environment is normal in the production area and the residential environment with Supe Phosphate factories. , Battery battery factory in Lam Thao district, Phu Tho.

With these results, it is clear that there is no scientific basis to determine radioactive factors as one of the causes of the phenomenon called ' Thach Son cancer village ', if that phenomenon actually exists. .