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Estimated the radiation hazard indices and ingestion effective dose in wheat flour samples of Iraq markets

Abstract

In this research, Uranium (238U), Thorium (232Th) and Potassium (40K) specific activity in (Bq/kg) were measured in (12) different types of wheat flours that are available in Iraqi markets. The gamma spectrometry method with a NaI(Tl) detector has been used for radiometric measurements. Also in this study we have calculated the radiation hazard indices (radium equivalent activity and internal hazard index) and Ingestion effective dose in all samples.

It is found that the specific activity in wheat flour samples were varied from (1.086 ± 0.0866) Bq/kg to (12.532 ± 2.026) Bq/kg, for238U, For 232Th From (0.126 ± 0.066) Bq/kg to (4.298 ± 0.388) Bq/kg and for 40K from (41.842 ± 5.875) Bq/kg to (264.729 ± 3.843) Bq/kg. Also, it is found that the of radium equivalent activity and internal hazard index in wheat flour samples ranged from (3.4031) Bq/kg to (35.1523) Bq/kg and from (0.0091) to (0.1219) respectively. But The range of summation of the Ingestion effective dose were varied from (0.0317) mSv/y to (0.5734) mSv/y. This study prove that the natural radioactivity, radiation hazard indices and Ingestion effective dose were lower than the safe.

Review

The world is naturally radioactive and approximately 82% of human-absorbed radiation doses, which are out of control, arise from natural sources such as cosmic, terrestrial, and exposure from inhalation or intake radiation sources. In recent years, several international studies have been carried out, which have reported different values regarding the effect of background radiation on human health.

Introduction

Natural radioactivity is caused by the presence of natural occurring radioactive matter (NORM) in the environment. Examples of natural radionuclides include isotopes of potassium (40K), uranium (238U and its decay series), and thorium (232Th and its decay series). In addition to being long-lived (in the order of 1010 years), these radionuclides are typically present in air, soil, and water in different amounts and levels of activity. Natural radionuclides are found in terrestrial and aquatic food chains, with subsequent transfer to humans through ingestion of food. As such, international efforts were brought together collaboratively to apply adequate procedures in investigating radionuclides in food (IAEA, International Atomic Energy Agency, Measurements of Radionuclides in Food and Environment [1989]), and to set essential guidelines to protect against high levels of internal exposure that may be caused by food consumption (ICRP [1996]; UNSCEAR [2000]).

Since wheat flour is one of the essential foods that is consumed in Iraqis daily lives, the desire to establish a national baseline of radioactivity exposure from different types of wheat flour samples that available in Iraq markets is very critical. Wheat flour is a powder made from the grinding of wheat used for human consumption. Wheat flour, the “Staff of Life”, has been an essential commodity to human existence through the centuries and is currently the most widely consumed staple food. Moreover, numerous studies were conducted worldwide to investigate natural radionuclides in food consumed in different parts of the world (Hosseini et al. [2006]; Jibiri & Okusanya [2008]; Ababneh et al. [2009]; Desimoni et al. [2009]). For a systematic treatment, a methodical approach is undertaken that focuses on a wheat flour type of food per study. Because wheat flour is popular among all ages, the current study focuses on investigating the natural radioactive content in all times of food.

Material and methods

Sample collection and preparation

Twelve samples of the most available types of flour were collected from the local markets in Iraq to measure natural activity. The types of samples are listed in Table 1. After collection, each flour sample was kept in a plastic bag and labeled according to its name. All of wheat flour samples were weighed and then dried in an oven at 105°C overnight and reweighed to find the water content. The samples were crushed and were made to pass through a 0.5-mm sieve. Sieved samples were weighed and a mass of 600 g of each sample was placed in a plastic container. The plastic containers were hermetically sealed with adhesive tape for 30 days for secular equilibrium to take place (Nasim et al. [2012]).

Table 1 Types and origin of wheat flour samples in this study

Measurement system

Natural radioactivity levels were measured using a gamma spectrometer which includes gamma multichannel analyzer equipped with NaI(Tl) detector of (3″ × 3″) crystal dimension as Figure 1. The gamma spectra were analyzed using the ORTEC Maestro-32 data acquisition and analysis system. An energy calibration for this detector is performed with a set of standard gamma ray 37000 Bq active 137Cs, 60Co,54Mn and 22Na sources from USNRC and State License Expert Quantities, “Gamma Source Set”, Model RSS- 8. The detector had coaxial closed-facing geometry with the following specifications: The calculated resolution is 7.9% for energy of 661.66 keV of 137Cs standard source. Relative efficiency at 1.33 MeV 60Co was 22% and at 1.274 MeV 22Na was 24%. The lowest limit of detection (LLD) for 238U, 232Th and 40K were 10.86 Bq/kg, 0.569 Bq/kg and 0.0261 Bq/kg respectively. The detector was shielded by a cylindrical lead shield in order to achieve the lowest background level. An energy calibration for this detector was performed with a set of standard γ-ray 37000 Bq active 137Cs, 60Co,54Mn, and 22Na sources. In this study, the activity concentration of 40K was determined directly from the peak areas at 1460 keV. The activity concentrations of 238U and 232Th were calculated assuming secular equilibrium with their decay products. The gamma transition lines of 214Bi (1765 keV) were used to calculate activity concentration of radioisotope in the 238U-series. The activity concentrations of radioisotope in the 232Th-series were determined using gamma transition lines of 208Tl (2614 keV). The counting time for each sample was at 18000 sec.

Figure 1
figure1

Block diagram of the equipment’s set up of NaI(Tl) detector.

Calculation of activity

Since the counting rate is proportional to the amount of the radioactivity in a sample, the Activity Concentration (Ac) which can be determined as a specific activity as the follows (Maduar & Junior [2007]):

A C = C B G ε o c M t I γ
(1)

Where Ac is the specific activity in (Bq/kg), C is the area under the photo peaks, ε% : Percentage of energy efficiency. Iɤ is the percentage of gamma-emission probability of the radionuclide under consideration, t is counting time in (Sec.), M is mass of sample in (kg) and BG is background.

Radium equivalent activity

Radium equivalent activity (Ra eq ) is used to assess the hazards associated with materials that contain 238U, 232Th and 40K in Bq/kg (Nasim et al. [2012]), which is, determined by assuming that 370 Bq/kg of 226Ra or 260 Bq/kg of 232Th or 4810 Bq/kg of 40K produce the same γ dose rate. The Ra eq of a sample in (Bq/kg) can be achieved using the following relation (Nasim et al. [2012]; Singh et al. [2005]; Yu et al. [1992]):

R a eq Bq / kg = A U + 1.43 x A T h + A k × 0.077
(2)

Internal hazard index

This hazard can be quantified by the internal hazard index (Hin) (Nasim et al. [2012]; El-Arabi [2007]; Quindos et al. [1987]). This is given by the following equation:

H in = A U / 185 + A T h / 259 + A K / 4810
(3)

The internal hazard index should also be less than one to provide safe levels of radon and its short-lived daughters for the respiratory organs of individuals living in the dwellings.

Ingestion effective dose

The Ingestion effective dose due to the intake of 238U, 233Th and 40K in foods can be evaluated using the following expression: (ICRP [1995]; Janet Ayobami [2014]).

H T , r = i U i * C i , r * g T , r
(4)

where, i denotes a food group, the coefficients Ui and C i,r denote the consumption rate (kg/y) and activity concentration of the radionuclide r of interest (Bq/kg), respectively, and g T,r is the dose conversion coefficient for ingestion of radionuclide r (Sv/Bq) in tissue T. For adult members of the public, the recommended dose conversion coefficient gT,r for 40K, 226Ra(238U), and 232Th, are 6.2 × 10−9, 2.8 × 10−7 and 2.2 × 10−7 Sv/Bq respectively (IAEA [1996]).

The average consumption rate of wheat flour according to report of ministry of trade in Iraq for adults is 110 Kg/y (Source : The Iraqi Ministry of Trade).

Results and discussion

The specific activity due to 238U, 232Th and 40K in different kinds of wheat flour samples has been measured as shown in Table 2. The specific activity of 238U was found in the range of (1.086 ± 0.0866) Bq/kg to (12.532 ± 2.026)Bq/kg with an average (6.603 ± 3.715) Bq/kg, 232Th from (0.126 ± 0.066)Bq/kg to (4.298 ± 0.388)Bq/kg with an average (1.9465 ± 1.331)Bq/kg and 40K from (41.842 ± 5.875) Bq/kg to (264.729 ± 3.843)Bq/kg with an average (133.097 ± 67.044) Bq/kg.

Table 2 Specific activity of 238 U, 232 Th and 40 K in wheat flour samples

There is a variation in the specific activity of radionuclides in different wheat flour samples, for example (F1) which is Turkish Farina has lowest 238U concentration, while (F11) which is Lebanese Good sentences has the maximum value, (F8) Turkish Super has the lowest 232Th concentration while the maximum is (F7) also Turkish Sankar , and the lowest 40K concentration is (F8) which is Turkish Super and the maximum is (F2) Saudi Arabia Fine semolina. The results obtained show that the specific activity of 238U, 232Th and 40K in all wheat flour samples appeared lower than recommended limit of UNSCEAR (United Nations Scientific Committee on Effects of Atomic Radiation (UNSCEAR) [2008]).

The radiation hazard indices (radium equivalent activity and internal hazard indices) were calculated for all samples in this study as shown in Table 3).The radium equivalent activity internal hazard indices were varied from (3.4031) to (35.1523) with an average (19.6347 ± 9.1680) and from (0.0091) to (0.1219) with an average (0.0708 ± 0.0341) respectively.

Table 3 Radium equivalent activity and internal hazard index in wheat flour samples

The values of all the radiation hazard indices in this study (radium equivalent activity and internal hazard indices are lowest value in sample (F8) Turkish Super and the highest value in sample (F2) Saudi Arabia Fine semolina. This indicates that the internal hazard index in wheat flour samples were lower than the permissible limits of 1 recommended by UNSCEAR (UNSCEAR [2000]), while the radium equivalent activity also were lower than the maximum permissible level of 370 Bq/kg recommended by UNSCEAR (UNSCEAR [2000]).

Table 4 shows the results of the Ingestion effective dose in (mSv/y) for adult due to specific activity of 238U, 232Th and 40K in wheat flour samples which it is calculated using Eq. (4). The range of summation of the Ingestion effective dose were varied from (0.0317) mSv/y (at sample F8) to (0.5734) mSv/y (at sample F11) with an average (0.3213 ± 0.1657) mSv/y, but Figure 2 shows the compare between average of the Ingestion effective dose for 238U, 232Th and 40K in wheat flour samples which obtain the average of Ingestion effective dose due to 238U was higher than due to 232Th and 40K because of the increased the dose conversion coefficient for ingestion of radionuclide. This indicates that the Ingestion effective dose in all wheat flour samples were lower than the permissible limits of 1 mSv/y recommended by ICRP (ICRP [1996]).

Table 4 Ingestion effective dose for adult in wheat flour samples
Figure 2
figure2

Ingestion effective dose in wheat flour samples.

Conclusion

The present study has presented the specific activity of radionuclides 238U, 232Th and 40K using gamma ray spectroscope in different type of wheat flour that are regularly consumed by adults age in Iraq. Specific activity concentrations of these radionuclides in samples were lower than as reported by UNSCEAR. Also the radium equivalent activity and internal hazard indices values obtained when compared with the world permissible values were found to be below the standards limit which due to be radiologically hazard safe. The high value of summation of Ingestion effective was less than 1 mSv/y, the limit recommended for the public (ICRP [1996]), hence wheat flour samples in Iraq markets products are safe to consumers.

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Acknowledgements

I would like to knowledge all those contributed in declaring this issue. Special thanks to the staff of the department of physics at Kufa University.

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Correspondence to Ali Abid Abojassim.

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The authors declare that they have no competing interests.

Authors’ contributions

AAA and HHA-G carried out the Nuclear radiation studies, participated in the sequence alignment and drafted the manuscript. SHK collected and arranged wheat flour samples, also contributed to the collection of references of scientific. All authors read and approved the final manuscript.

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Abojassim, A.A., Al-Gazaly, H.H. & Kadhim, S.H. Estimated the radiation hazard indices and ingestion effective dose in wheat flour samples of Iraq markets. FoodContamination 1, 6 (2014). https://doi.org/10.1186/s40550-014-0006-7

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Keywords

  • Wheat flour
  • Natural radioactivity
  • Iraq market and gamma spectroscopy