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TECHNICAL NOTE
Year : 2019  |  Volume : 42  |  Issue : 1  |  Page : 57-62  

Assessment of ambient gamma dose rate in different locations of Amritsar city, Punjab, India


1 Department of Applied Sciences, Swami Sarvanand Group of Institute, Dina Nagar, Punjab, India
2 Department of Physics, DAV College, Amritsar, Punjab, India

Date of Submission15-Feb-2019
Date of Decision07-Mar-2019
Date of Acceptance17-Mar-2019
Date of Web Publication3-Jun-2019

Correspondence Address:
Dr. Ajay Kumar
Department of Physics, DAV College, Amritsar - 143 001, Punjab
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/rpe.RPE_6_19

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  Abstract 


Preliminary results of ambient indoor and outdoor gamma dose rates estimated in 20 distinct areas of Amritsar city, Punjab, are exhibited by utilizing Dosimeter-Radiometer MKS-03 (SARAD). This study was planned in such a way to get a uniform and representative distribution of estimations. The indoor to outdoor dose rate ratio was ascertained which showed that the indoor gamma dose rate as contrasted with outdoor gamma dose rate has elevated levels of exposure due to confined space and poor ventilation. The indoor and outdoor annual effective dose rate was likewise estimated from the exposure point of view, and it varied from 0.35 to 1.61 mSv/y and from 0.11 to 0.44 mSv/y. The average values of outdoor and indoor effective dose rate levels in all of these locations were well below the world average value prescribed by the United Nations Scientific Committee on Effects of Atomic Radiations.

Keywords: Annual effective dose, gamma dose rate, indoor and outdoor ratio, radiation exposure


How to cite this article:
Sharma S, Kumar A. Assessment of ambient gamma dose rate in different locations of Amritsar city, Punjab, India. Radiat Prot Environ 2019;42:57-62

How to cite this URL:
Sharma S, Kumar A. Assessment of ambient gamma dose rate in different locations of Amritsar city, Punjab, India. Radiat Prot Environ [serial online] 2019 [cited 2019 Jun 25];42:57-62. Available from: http://www.rpe.org.in/text.asp?2019/42/1/57/259671




  Introduction Top


Human beings are inexorably exposed to natural background radiations from universe, earth stratum, sustenance, building materials, air, and even components that constitute their own particular body. The knowledge of dispersion of radioactive nuclides and radiation levels in nature is vital for surveying the impacts of radiation exposure because of both terrestrial and extraterrestrial sources. Radioisotopes' occurrence in soil influences terrestrial gamma radiation levels. The impact of inestimable beams (cosmic rays) and cosmogenic radioactive nuclides cannot be overlooked; the main exposure is imposed by naturally occurring radioactive nuclide materials, i.e., primordial radioactive nuclides.[1]

Naturally occurring radioactive materials (NORM) are found in varying concentrations of rocks and soils. The natural radioactivity levels depend on geological aspects of soil and rocks. The terrestrial radiations because of NORMs in the air (environment) may result in an external and internal exposure to the public through the ingestion or inhalation pathways.[2] The assessment of terrestrial radiations is essential since they may have a significant contribution to the aggregate dose (1–10 mSv) of the population.[3]

Most building materials of terrestrial origin contain small amounts of NORMs, mainly radionuclides from the 238U and 232Th decay chains and the radioactive isotope of potassium,40 K. The external radiation exposure is due to the gamma emitting radioactive nuclides, which in the uranium series currently belong to the decay chain section beginning with radium-226 (226Ra). The internal (inhalation) radiation exposure is because of radon-222 (222Rn), and barely to radon-220 (220Rn), and their short-lived decay products, exhaled out from construction materials into the room air.[2] However, the fast developing utilization of reused industrial byproducts containing Technologically Enhanced Natural Occurring Radioactive Materials (TENORM) in the construction industry may widely increase the levels of normal background radiation exposures in buildings.[4]Coal fired debris (ash), introduced as a waste in the burning of coal, is used as an additive to cement, in concrete, and in some countries, bricks are made from fly ash. Coal slag is utilized as a part of floor structures as insulating filling material. Phosphogypsum, a byproduct in the production of phosphorous fertilizers, is used as building material, and red mud, a loss from essential aluminum production, is utilized as a part of bricks, ceramics, and tiles.[5]

Naturally occurring radioactive materials (NORM) and rapid turn-over in TENORM is creating a major concern of elevated levels of public exposures not only in industrialized but also in developing countries. The challenge of general population exposure is even more prominent in developing countries on the ground that large portion of these countries do not have the adequate structure and guidelines for estimating the population exposure and evaluating the radioactive nuclides contained in the building materials.[6] This leads to the rapid utilization of these construction materials, hence making health risks to the overall populace.[7]

Radioactivity in building materials may possibly expose individuals to extensive quantities. This exposure rate could bring about generally some additional exposures contrasted with that because of the normal background of around 2 mSv/y.

This investigation was a part of our effort to set up standard information for natural environmental radiation levels in Amritsar city of Punjab state and helpful for evaluating the general population dose. In the underlying period of this investigation, radon concentration levels in water[8] and exhalation studies in soil samples[9] were estimated in various parts of the city.

The present study has been carried out to observe gamma dose rates in indoor and outdoor environments of Amritsar city, Punjab, India. This sort of work has not been completed up until this point, in this part of the country and subsequently happens to be the first of its kind. The primary objective of this investigation was to compute the annual effective dose (AED) received by the inhabitants of the study area. Results obtained from the present investigation have been contrasted with the national and worldwide information accessible from the literature and utilized as a standard in remedial activities against environmental contamination in the future.

Geology of the area

Amritsar district lies between 31°28'30” and 32°03'15” North latitude and 74°29'30” and 75°24'15” East longitude. Amritsar district falls in between Ravi river and Beas river. Ravi river flows in northwest of the locale and forms an international border with Pakistan [Figure 1]. Beas river flows in the eastern part of the district. There are three nalahs (an arrow steep-sided channel in the loose earth by running water) which drain Amritsar region from northeast to southwest. Kiran Saiki nalah flows in the northern part of the district. Hudiara nalah and Kasur nalah drain the central part of the district whereas Patti nalah drains southeastern part of the district. Upper Bari Doab canal is the main canal passing through the central part of the district. Lahore branch and Kasur branch lower are the major tributaries of the Upper Bari Doab canal.
Figure 1: Map of surveyed area during the present investigation of Amritsar city, Punjab

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The district forms part of Upper Bari Doab and is underlain by formations of Quaternary age comprising of alluvium deposits belonging to vast Indus alluvial plains. Subsurface geological formations comprise of fine to coarse-grained sand, silt, clay, and kankar. Gravel associated with sand beds occurs along the left bank of Ravi. The beds of thin clay exist alternating with thick sand beds and pinch out at short distances against sand beds.

Soils in the western part of the district are coarse-loamy, calcareous soils, whereas in the central part of the district soils are fine loamy, calcareous, and are well drained. The soils are Ustochrepts to Haplustaff type. Gravel associated with sand beds occurs along the left bank of Ravi. The beds of thin clay exist alternating with thick sand beds and pinch out at short distances against sand beds.


  Materials and Methods Top


The ambient indoor and outdoor gamma dose rates have been measured in randomly chosen locations of Amritsar, by using Dosimeter-Radiometer MKS-03D[10] gamma detector meter, at about one meter above the ground surface. It is a GM tube based survey meter with digital display. This gadget functions admirably at all altitudes with maximum relative humidity <95% and within the temperature range of −20°C to 50°C. The sensitive energy region of the device is 0.05–3.0 MeV, with a precision factor of ±15%. For calibration, a fixed source-to-detector distance variable-dose rate method was used. The survey meter is then exposed at computed distances, and actual exposure dose rate readings are recorded. From the readings taken, the calibration factor is computed. Acceptable limit ranges from 0.8 to 1.2. The exposure rate that can be estimated by this device ranged between 0.01 μSv/h and 0.1 Sv/h. Because of the random nature of the radioactive decays, the radiation exposure rate varies rapidly with respect to time. For each location, two readings (at different circumstances) were taken, each spanning overtime period of 2 min. Most of the locations in the present examination are in urban areas; so, cemented and marble type of houses have been selected for indoor measurements. Data presented in this article were the mean estimation of two measurements for each location. The exposure rate estimated in μRh−1 was converted into absorbed dosage rate μGy/y using the transformation factors[11]:



The results are presented in terms of both μR/h and μGy/y.

Annual effective dose (AED)

The AED resulting from the gamma-ray emission attributed to the radioactive nuclides (226Ra, 232Th, and 40 K) is obtained using the following formula[7],[12]:

AEDindoor(μSv/y) = indoor gamma dose rate (μSv/h) × Texposure× OFindoor

AEDoutdoor(μSv/y) = outdoor gamma dose rate (μSv/h) × Texposure× OFoutdoor

where Texposure is the exposure duration per year i.e., 8760 h/y, OFoutdoor and OFindoor are occupancy factor for outdoor (0.2) and indoor (0.8) effective dose for environmental exposures to gamma ray, respectively.


  Results and Discussion Top


The assessed ambient indoor and outdoor gamma dose rate in 20 different locations of Amritsar city, Punjab, India was organized in [Table 1]. Minimum annual indoor gamma dose rate value (626 ± 112 μGy/y) was recorded at two locations, i.e., Lawrence road and Nagar Nigam Avenue while maximum value (2878 ± 25 μGy/y) was estimated at Batala Nagar [Table 1]. On the other hand, minimum and maximum outdoor gamma dose rate (750 ± 12 μGy/y and 3128 ± 37 μGy/y) were seen in the house situated in Nagar Nigam and Batala Nagar, respectively. Average estimations of annual indoor and outdoor gamma dose rates were found as 1664 ± 585 and 1658 ± 353 μGy/y. The minimum indoor and outdoor gamma dose rate is accounted for in similar location (Nagar Nigam) which is exposed with sandstone and shale lithology while the maximum indoor and outdoor gamma dose rate was found at Batala Nagar. The variation of indoor and outdoor gamma dose rate is shown in [Figure 2].
Table 1: Indoor and outdoor gamma dose rate in Amritsar city

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Figure 2: Variation of annual indoor and outdoor gamma dose rate in Amritsar city

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The average indoor gamma dose rate was comparable to the outdoor gamma dose rate which might be due to poor ventilation rate and more accumulation of radioactive gases in the indoor environment. The value of outdoor gamma dose rate was higher than indoor gamma dose rate because construction materials have less radioactivity content than that of surrounding earth. The soils in the examination area has both sandstones and shales which contains 2.2 - 3 ppm of uranium.[13] The substance of 232Th concentration level in sandstones might be up to 10 mg/kg, and in typical shale and mudstone, its concentration run from 10 to 13 mg/kg. Monazite sands may likewise contain large fractions of 232Th and constitute one of the major ores of 232Th.[11]

The results of experimentally determined estimations of indoor and outdoor gamma dose rates, indoor and outdoor AED, and indoor to outdoor dose ratio observed in different locations are also outlined in [Table 1]. The averaged values of gamma dose rate have been differed from 0.05 μSv/h to 0.23 μSv/h, with the mean estimation of 0.13 μSv/h for indoor conditions and from 0.06 μSv/h to 0.25 μSv/h, with the mean estimation of 0.13 μSv/h for outdoors, respectively. The outcomes revealed that the estimations of indoor gamma dose rate were found equivalent to the outdoor gamma dose rate. The variation of indoor and outdoor gamma dose rate was also introduced in [Figure 3].
Figure 3: (a) Variation of indoor gamma dose rate with locations. (b) Variation of outdoor gamma dose rate with locations

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The linear relationship analysis between the indoor and outdoor gamma dose rate is shown in [Figure 4] with a slope of 0.48. The estimation of “r” called the linear correlation coefficient that measures the strength and direction of a linear relationship between indoor and outdoor gamma dose rates was found as 0.70. This value is close to “1” indicating a positive relationship among indoor and outdoor gamma dose rates. Many of the houses in this study are made of cement and marble. Since in the current investigation indoor gamma dose rate (1664 ±585 μGy/y) are observed to be comparable to the outdoor gamma dose rate (1658 ± 535 μGy/y) [Table 1], which suggests that construction material of the houses and surrounding radioactivity contributed equally to enhancing the indoor and outdoor gamma levels. The overall trend of data indicates that with increasing indoor gamma dose rates, outdoor gamma dose rate also increases and vice versa.
Figure 4: Linear correlation between indoor and outdoor gamma dose rate

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Gamma dose rates for the current survey have been compared with the results obtained for various studies conducted in different parts of the world and summarized in United Nations Scientific Committee on Effects of Atomic Radiation (UNSCEAR)[7] report [Figure 5]. Mean indoor and outdoor gamma dose rates measured for the current study were found as 1664 ± 585 and 1658 ± 535 μGy/y, respectively. As may be seen from [Figure 5] that indoor gamma dose rate measured for the current study is greater than those reported for various countries including United States (333 μGy/y), Japan (464 μGy/y), Denmark (473 μGy/y), Finland (639 μGy/y), Norway (692 μGy/y), France (657 μGy/y), Germany (613 μGy/y), United Kingdom (526 μGy/y), Poland (587 μGy/y), Greece (587 μGy/y), Slovenia (657 μGy/y), New Zealand (175 μGy/y), China (867 μGy/y), Hungary (832 μGy/y), and Portugal (885 μGy/y).[7]
Figure 5: Comparison of indoor gamma dose rate of Amritsar with different countries

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On the other hand, measured average values of gamma dose rate for Amritsar is comparable to the values reported for countries such as Iran (1,007 μGy/y), Italy (920 μGy/y), Spain (964 μGy/y), and Australia (902 μGy/y).[7]

The estimations of indoor and outdoor AED have varied from 350 to 1612 μSv/y with an average of 946 ± 605 μSv/y and from 105 μSv/y to 438 μSv/y, with an average of 226 ± 88 μSv/y, respectively [Table 1]. All the estimations of indoor and outdoor effective dose rate were found well below the ICRP prescribed level of (specifically set for releases from nuclear facilities) 1000 μSv/y.[14] [Figure 6] shows the comparison between the indoor and the outdoor AED. The indoor AED was observed to be higher than the outdoor AED may be expected to the indoor–outdoor pressure difference which is caused by temperature difference, wind, barometric pressure, and unbalanced mechanical ventilation. The outdoor radioactive nuclides concentration is far below compared to the indoor radionuclide concentration because the radiation exhaled from the ground is rapidly diffused over vast atmosphere, but buildings and structures may keep this dilution. This result in an accumulation of radionuclides inside the buildings, rising up out of the floor and wall materials, but also relies on house-to-house variability, even for areas with low exhalation rates from the ground.[15]
Figure 6: Comparison of annual indoor and outdoor effective dose (μSv/y)

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The variation of indoor to outdoor gamma dose ratio has likewise been obtained and presented in [Table 1]. The arithmetic mean of indoor to outdoor gamma dose rate has observed to be 1.02 ± 0.31 (range 0.45–1.62) obtained from gamma survey meter. In normal background areas of India, the proportion of indoor to outdoor gamma dose rate is observed to be around 1.2, especially in tiled/cemented floor and concrete walls and ceilings.[16] Chougaonkar et al., 2004 has reported the mean value of indoor to outdoor ratio for bricks, cemented and tiled houses.[17] The obtained average values of the ratio are almost the same as that of Chougaonkar et al.[17] because construction materials have less radioactivity content than that of the surrounding earth (mean value = 0.8). The higher values of the ratio than 1.2 attributes to mud types of houses (wall/floor of mud) and has the radioactivity content greater than that of surrounding soil.


  Conclusions Top


A preliminary study of ambient indoor/outdoor gamma dose rates measurement have been undertaken using gamma survey meter MKS-03D. Minimum and maximum annual outdoor gamma dose rate was found as 750 and 3128 μGy/y, respectively. Similarly, minimum and maximum annual indoor gamma dose rates were found as 626 and 2878 μGy/y, respectively. Measured average estimations of indoor and outdoor gamma dose rates are generally higher than the world average gamma dosage rate (57 nGy/h or ~499 μGy/y as reported in UNSCEAR (2000)). The reason for higher dosage rates might be attributed because of the particular geography of the area under study when contrasted with rest of the world. The indoor AED was observed to be higher than the outdoor AED which might be because of the indoor–outdoor pressure difference.

Acknowledgment

The author(s) are thankful to D. A. V. College, Amritsar for providing necessary facilities to carry out this research work.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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Gulam L, Bochicchio F, Carpentieri C, Milic G, Stajic J, Krstic D, et al. High annual radon concentration in dwellings and natural radioactivity content in nearby soil in some rural areas of Kosovo and Metohija (Balkan region). Nucl Tech Radiat 2013;28:60-7.  Back to cited text no. 15
    
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Chougaonkar MP, Eappen KP, Ramachandran TV, Shetty PG, Mayya YS, Sadasivan S, et al. Profiles of doses to the population living in the high background radiation areas in Kerala, India. J Environ Radioact 2004;71:27597.  Back to cited text no. 17
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
 
 
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