|Year : 2015 | Volume
| Issue : 1 | Page : 35-38
Natural radioactivity concentrations in some medicinal plants and annual committed effective dose from their consumption
Shaban Ramadan Mohamed Harb
Department of Physics, Faculty of Science, South Valley University, 83523 Qena, Egypt
|Date of Web Publication||14-Aug-2015|
Shaban Ramadan Mohamed Harb
Department of Physics, Faculty of Science, South Valley University, 83523 Qena
Source of Support: Nil., Conflict of Interest: None
Natural radioactive substances may be present in the environmental substances that have uses in pharmacy and medicine as health supplements. This paper presents natural radioactivity levels in some of the medicinal plants available in Egypt. Natural radionuclides such as 226Ra, 228Ra, and 40K were measured in medicinal plants samples collected from the local market in Qena, Upper Egypt. All measurements were performed with a gamma spectrometry with high-purity germanium detector. The radioactivity concentration ranged from 0.4 ± 0.2 to 21.0 ± 1.2 Bq/kg for 226Ra, from <0.3 to 42.3 ± 5.9 Bq/kg for 228Ra, and from 140 ± 6 Bq/kg to 1538 ± 54 Bq/kg for 40K. The total annual committed effective doses ranged from 0.003 to 0.073 mSvy−1 with an average value of 0.02 mSva−1
Keywords: Medicinal plants, environmental radioactivity, high-purity germanium detector, committed effective dose
|How to cite this article:|
Harb SR. Natural radioactivity concentrations in some medicinal plants and annual committed effective dose from their consumption. Radiat Prot Environ 2015;38:35-8
|How to cite this URL:|
Harb SR. Natural radioactivity concentrations in some medicinal plants and annual committed effective dose from their consumption. Radiat Prot Environ [serial online] 2015 [cited 2019 Jun 20];38:35-8. Available from: http://www.rpe.org.in/text.asp?2015/38/1/35/162816
| Introduction|| |
From the dawn of human history, a lot of plants were used as nutrients and in medicine. The study of the radioactivity concentration in plants in the environment are of interest within ecological and plant evolution under certain conditions of geochemical point of view and adaptation, and it thus provide information in the monitoring of environmental radioactivity., Radionuclides and their decay products from 238U and 232Th series together with 40K are terrestrial primordial radionuclides, which originated from the earth's crust and are the sources of natural radioactivity in the environment.
The World Health Organization define traditional medicine as comprising therapeutic practices that have been in existence, often for hundreds of years, before the development and spread of modern medicine and are still in use today.
The aim of this work was to study the natural radioactivity concentration in selected medicinal plants used in Qena, Egypt. In fact, the presence of radionuclides in these constitutes a pathway of their migration to the human, via the food chain or drinking. There are several sources that contribute to plants contamination such as direct deposition on surface, deposition on soil, root uptake, and transfer to leaves, barks, seeds, flowers, fruits, and berries.
| Experimental Methods|| |
Sampling and processing
Medicinal plants used in this work were obtained from the local market at Qena, Upper Egypt, and are listed in [Table 1]. The medicinal plant samples were washed with normal water, as for human consumption, weighed, and divided into small parts, dried in a stove at a temperature of 80°C for 48 h, ground into powder, and then filled in 250 mL polypropylene bottles. They were sealed and left for at least 4 weeks before counting by gamma spectrometry in order to ensure that radioactive secular equilibrium.
|Table 1: Activity concentration of 226Ra, 228Ra, and 40K (in Bqkg−1) and annual committed effective dose (mSva−1) in the medicinal plant samples (dry weight)|
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Direct determination of radionuclides in medicinal plant samples without any chemical treatment was performed at the Institute for Radioecology and Radiation Protection, Hanover University, Germany, using a p-type high-purity germanium coaxial detector (GEM 50198-P) of 35% relative efficiency, with a resolution of 1.78 keV at 1.332 MeV. It is shielded with 10 cm lead and 2 mm copper, and coupled to an 8192-channel analyzer. The counting efficiencies of the γ-ray peaks were measured using QCY48 standard solutions (Physikalisch-Technische Bundesanstalt, Germany) and were determined using a certified standard solution containing57 Co,60 Co,85 Sr,88 Y, 109Cd, 113Sn, 139Ce, 137Cs, and 241Am. The geometry of the experimental samples was the same as that of the standard samples [Figure 1].
Measurements and calculation
Calculation of radionuclides and annual committed effective dose
Following the spectrum analysis, counting rates for each detected photo peak and activity per mass unit for each of the detected nuclides are calculated. The specific activity (in Bq/kg) is given by harb.
Aspecific = (N/t – N0/t0)/(Iγ e m) (1)
Where, N is the net counts of a given peak, t = 18 – 24 h is the counting time for the sample. N0 is the background of the given peak, t0= 72 h is the counting time for the background, and ε is the detection efficiency. Iγ is the number of gamma photons per disintegration and m is the mass in kg of the measured sample. If there is more than one peak in the energy analysis range for a nuclide, an average of the peak activities is made, and the result is then the weighted average nuclide activity. Based on the measured γ-ray peaks, emitted by daughter radionuclides in the 232Th and 238U decay series, and 40K, their concentrations were determined. Calculations relied on the establishment of secular equilibrium in the samples, due to the much smaller lifetime of daughter radionuclides in the decay series of 232Th and 238U. The γ-rays of 212Pb (238.63 keV), 208Tl (583.2 keV), and 228Ac (338.4, 911 and 969 keV) were used to determine the 228Ra concentration. The γ-rays of 214Bi (609.3, 1120.3, and 1764.5 keV) and 214Pb (295.2 and 351.9 keV), for 226Ra. The 1461 keV gamma of 40 k was used to determine the concentration of 40 k in different samples. The total uncertainty value is composed of the random and systematic errors in all the factors involved in producing the final nuclide concentration result listed in [Table 1].
Having obtained the values for the specific activity concentrations of the individual naturally occurring radionuclides in the medicinal plants, the average annual committed effective dose, Eave, for ingestion of naturally occurring radioactive materials (NORMs) in the medicinal plants were calculated using the expression (2) given by Lordford.
Eave = Ip. DCFing. Asp (2)
Where DCFing is the dose conversion factor for ingestion, for each radionuclide (i.e., 2.8 × 10−7 Sv/Bq, 6.7 × 10−7 Sv/Bq, and 6.2 × 10−9 Sv/Bq for 226Ra, 228Ra, and 40K, respectively, for an adult,, Ip is the consumption rate from intake of NORMs in medicinal plants, a consumption rate of 1.8 kg/year was assumed for all the medicinal plants used in this study, assuming that a patient needs 100 ml/day of the herbal preparation or product during the treatment period. Moreover, Asp is the activity concentration in the plant sample.
| Results and Discussions|| |
[Table 1], [Figure 2] and [Figure 3] show the activity concentrations (Bq/kg) of the natural radionuclides 226Ra, 228Ra, and 40K determined in the medicinal plant selected in this study. All natural radionuclides were determined in 18 medicinal plants samples; the data show its activity concentrations ranged between 0.4 ± 0.2 and 21.0 ± 1.2, <0.3 and 43 ± 6, 140 ± 6 and 1538 ± 54 Bq/kg for 226Ra, 228Ra, and 40K, respectively. All samples showed 226Ra, 228Ra, and 40K activity concentrations higher than the minimum detectable activity. The highest activity concentration was found in the results of nees, for 226Ra, sweet laurel for 226Ra, 228Ra, and 40K.
|Figure 2: The variation of the activity concentrations of 226Ra, and 228Ra, in the different kinds of medicinal plant|
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|Figure 3: The variation of the activity concentrations of 40K in the different kinds of medicinal plant average annual committed effective dose in the medicinal plants|
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The variations in the activity concentrations could be due to differences in the geological location of the plants and the radiochemical composition of the soils in which these medicinal plants are grown or cultivated since the levels of activity concentration of natural radionuclides are not normalized across the globe and the plants ability to absorb particular elements more than the others.
From [Table 1] and [Figure 4] we can see that the average annual committed effective doses due to the ingestion of 226Ra, 228Ra, and 40K in the medicinal plant. The total annual committed effective doses of 226Ra, 228Ra, and 40K varied from 0.003 to 0.07 mSvy−1 with an average value of 0.02 mSvy−1. The highest average was recorded for sweet laurel and tamarind has the lowest. [Figure 4] shows the average annual committed effective dose due to radionuclides in the medicinal plant samples. However, the calculated average annual effective dose to any individual in the population group due to the ingestion of natural radionuclides in the medicinal plants is far below the average radiation dose of 0.3 mSvy−1 received per person worldwide.
|Figure 4: The variation of the annual committed effective dose from natural radionuclides ( 226Ra, 228Ra, and 40K) in the medicinal plant samples|
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| Conclusions|| |
Natural radionuclides such as 226Ra, 228Ra, and 40K were measured in medicinal plants collected from the local markets in Qena, Upper Egypt. The radioactivity concentration ranged from 0.4 ± 0.2 to 21.0 ± 1.2 Bq/kg for 226Ra, from <0.3 to 42.3 ± 5.9 Bq/kg for 228Ra, and from 140 ± 6 Bq/kg to 1538 ± 54 Bq/kg for 40K. The total annual committed effective doses ranged from 0.003 to 0.073 mSvy−1 with an average value of 0.02 mSv.
| Acknowledgments|| |
The author thank Prof. C. Walther, Director of Institute for Radioecology and Radiation Protection (IRS), Hannover University, Germany, for his encouragement and support.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]