Studying the Possibility of using Paint to Reduce the Amount of Radon Gas Emitted from Cement

Abstract


Introduction
The principal source of radon-222 in the worldwide environment is radium-226 in the earth's crust [1,2]. Because Ra-226 is found everywhere Rn-222 is ubiquitous throughout the geosphere, biosphere, and atmosphere. The radionuclide is extremely mobile [3]. Ionizing radiation is the most common type of radiation found in the earth's crust. The human being is constantly exposed to thorium, uranium, and their progeny in the environment [4][5][6]. The human radiation exposure is natural, with radon-222 accounting for the majority of it [7]. Rn-222 is a radioactive gas where it is a chemical element with the atomic number 86. It's a radioactive substance that's colorless, 28odourless, and tasteless [8][9][10]. It is a noble gas that occurs naturally in soils as an indirect decay product of uranium or thorium [11]. Because Rn-222 emitted in the air from the earth's crust or building floors reaches the walls inside or outside the building, the exposure to Rn-222 gas is higher in indoor air, which is evident in substandard buildings [12]. As ventilation improves and Rn-222 concentration rises, researchers in various countries have been examining and monitoring the Rn-222 gas released by building materials in recent years [13]. The purpose of the current study is to measure and investigate the C Rn in cement samples before and after painting with enamel paint.

Experimental Work
Ten samples of building material (cement) were collected from various locations, see Fig. 1. Our current investigation is based on studying these samples from different sources available in the local market.
In the first stage of the work each sample was cut in size (40 × 40cm) and 29 placed inside a sealed glass box containing two ports for air entry and exits from inside the box through plastic conductive tubes; see Fig. 2(a). In this way, the concentration of radon gas emitted from the sample to the atmosphere can be measured by the RAD-7 detector for 24 hours and note the difference in humidity and temperature during the measurements.
In the second stage of the work the samples were painted with enamel paint, see Fig. 2(b), and measured after painting in the same way as in the first stage. The measurement results were compared for the two cases.  To start the measurement, the detector systems had to be tuned according to Table 1. The annual effective dose (AED) in terms of (mSv/y) units was obtained using the relation [14,15]: where C Rn is the indoor concentration of radon in Bq/m 3 ; F is the adjustment factor (0.4 for indoor measurements); H is the occupancy factor (0.8 for indoor measurements); T is the number of hours in a year (8760 hours); and D is the dose conversion factor for the whole-body dose calculation (0.9 nSv per Bq m −3 h −1 ) [16]. The lung cancer cases per year per million people (CPPP) were obtained using the relation [17,18]:

Results and Discussion
Building materials have been identified as a source of Rn-222 emissions and it is critical to know the Rn-222 gas exhalation rate for samples set of cement material. The current research is based on examining ten samples of cement available in the Iraqi markets and warehouses and the work was done within the Baghdad governorate.
The C Rn of selected building materials samples was measured in units (Bq/m 3 ) before and after painting with enamel paint to know the effect of painting on Rn-222 concentrations. The annual effective dose was measured in units (mSv/y) for each sample of building materials after painting.
From Table 2 and Fig. 3 it was observed that the lowest level of C Rn was found in the sample (CE8) after painting which was equal to (15.74 Bq/m 3 ) after it was (25.19 Bq/m 3 ) and the highest value was found in the sample (CE9) which was with a value of (58.27 Bq/m 3 ) after it was (124.18 Bq/m 3 ) before painting. The effect of painting with enamel paint on the concentration of Rn-222 emitted from cement samples was observed.
The general average of C Rn for the group of samples is (38.22 Bq/m 3 ) after painting. The present results showed that the C Rn in the measured building samples is below the lower range (200-300 Bq/m 3 ) [19]. So, the results showed that these samples are safe from radiological hazards with respect to C Rn .
Using Eq.(1), Table 2 shows the internal annual effective dose (AED) received by the population due to the use of cement in construction after painting the samples was obtained. The measured results were with an average value (0.977 mSv / year). It ranges between (0.396 mSv / year) in sample (CE8) to (1.468 mSv / year) in the sample (CE9). Fig. 4 shows that all samples of building materials studied in the current work have annual effective doses less than the minimum range allowance (3-10 mSv/year) [20]. Table 2 also shows the annual incidence of lung cancer per million people (CPPP) was obtained. It was found that the risks of developing lung cancer when exposed to C Rn by samples of cement used in construction after painting ranged from (7.12) in (CE8) sample to (26.42) in (CE9) sample with an average value of (17.59) per million persons. Fig. 5 shows that these values that appeared and for all samples are less than the minimum allowed (170-230) [20].

Conclusions
After knowing the highest C Rn rate of the samples after they were painted was (58.27 Bq/m 3 ) in a sample (Iranian origin) and it was found that the lowest C Rn rate was (15.74 Bq/m 3 ) in the white cement sample (Turkish origin).
The conclusion is coating cement with enamel paint reduces Rn-222 emissions into the air and that all samples of cement used in construction in this study were within international limits so they are safe for consumption and do not pose a radiological hazard to people's health.