Radon (222Rn), an inert gas, is considered a silent killer due to its carcinogenic characteristics. Dhaka city is situated on the banks of the Buriganga River, which is regarded as the lifeline of Dhaka city because it serves as a significant source of the city’s water supply for domestic and industrial purposes. Thirty water samples (10 tap water from Dhaka city and 20 surface samples from the Buriganga River) were collected and analyzed using a RAD H2O accessory for 222Rn concentration. The average 222Rn concentration in tap and river water was 1.54 ± 0.38 Bq/L and 0.68 ± 0.29 Bq/L, respectively. All the values were found below the maximum contamination limit (MCL) of 11.1 Bq/L set by the USEPA, the WHO-recommended safe limit of 100 Bq/L, and the UNSCEAR suggested range of 4–40 Bq/L. The mean values of the total annual effective doses due to inhalation and ingestion were calculated to be 9.77 μSv/y and 4.29 μSv/y for tap water and river water, respectively. Although all these values were well below the permissible limit of 100 μSv/y proposed by WHO, they cannot be neglected because of the hazardous nature of 222Rn, especially considering their entry to the human body via inhalation and ingestion pathways. The obtained data may serve as a reference for future 222Rn-related works.

1. Introduction

Humans are continuously exposed to natural radiation, primarily from terrestrial and extra-terrestrial sources [1]. Among the existing sources of ionizing radiation in the environment, 222Rn alone is the major contributor (more than 50%) of the total radiation dose to humans [2]. 222Rn is the only gaseous element in the 238U decay series and possesses no color, odor, or taste. This (222Rn) short-lived (T1/2 = 3.82 days) radioactive nucleus is formed due to the alpha decay of 226Ra. Among the three naturally occurring radioisotopes, 222Rn is the most abundant in nature as Thoron (220Rn) and Actinon (219Rn) have relatively very short half-lives of 55s and 3.2s, respectively.

222Rn is present naturally in the earth’s strata. Its abundance in the earth’s crust fluctuates with the variation of geology and lithology of the area. Due to its high mobility, 222Rn gas can swiftly travel from soil and rocks to water and air. Albeit, the concentration of 222Rn in water depends on the temperature, lithology, geology, rainfall, and earthquake activities [3]. 222Rn is highly volatile, easily dissolved, and escapes from the water. A relatively higher concentration of 222Rn is found in groundwater than in surface water due to the aeration process [3]. Because of its gaseous nature, 222Rn is used as a tectonic tracer [4] to determine the tectonic fault lines and predict earthquakes.

222Rn is considered a hazardous gas due to its potential to affect human cells and tissues biologically. Ingestion through the gastrointestinal tract and inhalation via the respiratory tract are the two major pathways of entering 222Rn into the human body. Both paths are potentially risky, affecting the lung and the gastrointestinal system. In the case of inhalation, the short-lived metallic progeny of 222Rn (mostly 218Po and 214Po) are deposited in the lungs and damage the cells and the tissues of the respiratory system via high-energy alpha emission. That is why it is one of the main contributors to escalating lung cancer risks. The IARC (The International Agency for Research on Cancer), a part of WHO, classified 222Rn as a group 1 carcinogen [5, 6].

Water is vital for all life; human beings use water regularly for various purposes, including bathing, drinking, etc. However, water consumption is the primary cause of 222Rn exposure through the ingestion pathway, whereas the emanation of 222Rn from water causes exposure through the inhalation of air. As 222Rn is loosely soluble in water, it can easily emanate from water to air [7]. For that reason, 222Rn activity measurement in water is necessary to protect people from radiological hazards. Many international organizations propose a safe limit on 222Rn concentration in water, and almost all developed countries have their national guidelines for radiation safety. The World Health Organization recommended a safe limit of 100 Bq/L for 222Rn in the water [8], whereas the USEPA suggested the maximum contamination level (MCL) of 11.1 Bq/L [9]. The USEPA also proposes an alternative maximum contamination level (AMCL) of 148 Bq/L [9]. To apprehend the health hazard of 222Rn, measurement of the annual effective dose due to 222Rn ingestion and inhalation is essential. The WHO recommends that the total annual effective dose due to 222Rn in water should be < 100 μSv [10].

Numerous studies have been performed worldwide to measure the 222Rn level in various water resources such as tap water, river water, deep well water, bore well water, bottled water, etc. [1, 3, 7, 11, 12]. Several advanced countries have a national reference limit of radon in water and indoor air to ensure radiological safety for public health. Bangladesh has no such reference level for 222Rn in water. Millions of people living in the Dhaka megacity solely rely on tap water for their daily household purposes, such as washing, bathing, drinking, cooking, etc. The Buriganga river serves as one of the busiest major transportation routes/hubs, as well as many businesses and trade centers that are situated on the bank of this river. This indicates a greater possibility of 222Rn exposure to the general populace. So, it is necessary to measure the 222Rn level in the tap water and the Buriganga river water to find out if it is within the safe limit or not, which eventually will help to ensure the radiological safety of public health.

The purpose of this study is to (a) measure 222Rn concentration in the chemically and biologically polluted Buriganga river water and the tap water of the megacity Dhaka, b) calculate the associated radiological hazards, c) to contribute to the setting up of a factual baseline data which will assist the authority to structure a national reference level of 222Rn water.

2. Methodology

2.1 Study area

Dhaka, the capital city of Bangladesh, as well as one of the most densely populated megacities in the world, is the prime focus of this study. Dhaka is located between latitudes 23°42’ and 23°54’N and longitudes 90°20’ and 90°28’E. The geographical area of this city is 306.38 square kilometers, where more than 20 million people [13]. Several rivers, like Buriganga, Balu, Tongi Khal, and Turag, surround the city from the south, east, west, and north [14], respectively. However, the Buriganga river has a major share, and it forms the southern and western boundaries of Dhaka city. The length of this river flowing through Dhaka is 11 km, the depth is 10m, and the width is 400m. The latitude and the longitude of this river are 23° 37’ 59.99” N, 90° 25’ 59.99” E [15]. Because of the large-scale industrial activities on the bank of the Buriganga river, it has become the worst polluted river in the country.

2.2 Geology of Dhaka city and its periphery region

Dhaka, the megacity, is placed at the southern end of the Madhupur tract, 1.5–10 m (average 6 m) above the adjoining floodplains [16, 17]. The area is characterized by Quaternary alluvial sequences of the Madhupur Tract, known as Pleistocene terrace deposits that surround Holocene deposits of the peripheral rivers [18–20]. The geological map of the study area is illustrated in Fig 1(b), showing different geological units present in this area. The Pleistocene terrace deposits of varying thickness (an average of 10 m thick in Dhaka) are subdivided by Upper and Lower Madhupur Clay deposits. The Upper Madhupur Clay deposits are characterized by reddish brown to pale yellow sticky clay and silty clay, containing ferruginous nodules and dark spots of manganese, compacted highly weathered and oxidized residual deposits. On the other hand, the Lower Madhupur Clay deposits primarily contain pale yellowish to yellowish brown sandy clay to clayey sand and silty sand with similar nodules and spots but less weathered and oxidized than the upper [16, 17]. The Holocene deposits are further subdivided into alluvial floodplain deposits comprising natural levee deposits, bar deposits, point bar deposits, back swamp deposits, floodplain deposits, and valley fill deposits. Floodplain deposits mainly comprise grey to dark grey color sticky clay to clayey silt, with discontinuous sand, oxidized root, rootlets, and organic matter. Whereas the valley fill deposits consist of dark grey to yellowish to olive brown color silty clay, clay, marshy clay, and peat [21]. A sequence of fine to coarse-grained micaceous quartzofeldspathic sands containing Dupi Tila Formation of Pliocene age, hydro geologically known as the Dupi Tila aquifers, the primary aquifer of Dhaka city, underlies the Madhupur Clay and is not exposed anywhere in the city [17, 19, 20, 22]. A gravel bed lies at the bottom of the Dupi Tila Formation, which grades upward from coarse-grained sands to medium-grained sands to fine-grained sands at the top. The Dupi Tila Formation is divided by a discontinuous clay layer into two aquifers: an upper fine-grained aquifer (approximately 40–50 m thick) and a lower coarse-grained aquifer (approximately 80 m thick) [17]. A summary of the Pliocene to Recent lithological and aquifer characteristics of the study area has been given in Table 1. The geochemical study of the groundwater of the Dupi Tila aquifer shows that the Ca/Mg-HCO3 type and weathering of aluminusilicates control the distribution of major ions in the aquifers [23]. The Dupi Tila and Madhupur Formations are isolated by extensive incision of the land surface during the late Quaternary, and forming a number of faults at their boundaries which affect the aquifer river system and the groundwater flow of this area [19–21, 24, 25]. It is assumed that due to the elevation of the river bed with the top of the Dupi Tila sands has through connection between the and the rivers surrounding Dhaka (i.e. Buriganga, Balu and Turag River) and the aquifer is possible along certain reaches [17, 26, 27].

Fig 1.

(a) The study area map showing the sampling location of river water (RW) and tap water (TW). The map has been produced using ArcGIS 10.4.1 software. The sources of basemaps of administrative boundaries and inland water bodies: Esri, GADM, Garmin, DigitalGlobe, GeoEye, GEBCO, USGS, NOAA, National Geographic, EPA, Geonames.org, the GIS User Community and other contributors. (b) The geology of the study area (the sources of basemaps are similar to (a) and the geological units modified after [16, 28, 29]).


2.3 Sampling

Thirty water samples, including 20 river water and 10 tap water (Fig 1a), were collected in November 2021 using a 500 mL plastic bottle prior to the winter season. The river water samples were collected from the highly polluted Buriganga river by following the stratified sampling technique approved by IAEA [30]. The majority of the samples were collected from heavily populated riverbank areas such as Sadarghat, Showari Ghat, Mitford Ghat, Gabtoli, etc. The bottle was fully submerged directly into the water during the river water collection to prevent air bubbles in the bottle. The tap waters were collected from different localities of the megacity Dhaka using a systematic grid sampling technique approved by the IAEA [30]. Before sample collection, the tap was opened for several minutes, and the water was allowed to flow. Afterward, the bottle was filled and sealed tightly. Prevention of aeration during sampling was the prime concern to avoid the escape of dissolved 222Rn in the water. Each of the samples was labeled with a unique sample ID (RW for river water and TW for tap water), and the GPS of the collection points and the collection time were recorded. These water samples were taken immediately to the Laboratory of the Health Physics Division in the Atomic Energy Centre Dhaka of Bangladesh Atomic Energy Commission.

2.4 Experimental procedure

The 222Rn activity concentration in collected water samples was measured using RAD7, a portable electric 222Rn detector with RAD-H2O accessories (manufactured by Durridge Co. Ltd). The RAD H2O is an accessory of the RAD7 detector that allows measuring radon in water at concentrations above the minimum detectable activity (MDA). The MDA concentration of this instrument is 0.004 Bq/L [5, 31]. A schematic diagram of the experimental setup is illustrated in Fig 2. The inner cell of the RAD7 is a hemisphere coated with an electrical conductor where the energy of emitted alpha particles from 222Rn and its progeny are converted into electrical signals. Before analyzing the samples, the RAD7 detector needs to be 222Rn free and dry. Dry air was purged for 10 minutes, lowering the humidity below 10%. The collected water samples were transferred into a 250 mL glass vial and connected with the RAD7. The 222Rn emanation occurred by aerating the water via a glass frit in a closed-loop system. An internal air circulating pump recirculates the air through the closed-loop system to extract the 222Rn from the water until the equilibrium is reached. The wat-250 process was selected to measure 222Rn in water, where the extraction efficiency was 94%. The equilibrium state is reached within 5 minutes, and after this, no more 222Rn can be extracted from the water. The air is circulated by the pump aerating the water and supplying the 222Rn to the RAD7 detector. This process runs for 30 minutes in four cycles to measure the 222Rn in the samples. The RAD7 summarizes the average and corrected 222Rn concentration measurements obtained from each sample for four cycles at the end of the run in a printout. For a cycle when no counts were collected, the RAD7 displays an uncertainty value based on a two-sigma, 95% confidence interval that is equivalent to ± 4 counts [32].

2.5 Dosimetry calculation

Internal 222Rn exposure comes primarily from 222Rn inhalation and ingestion, which is harmful to the respiratory organs. When water is collected and used, 222Rn is inhaled, and 222Rn is ingested when 222Rn-contaminated water is consumed. Therefore, by using Eqs (1) and (2), the annual effective dose due to 222Rn inhalation and ingestion is calculated from the experimentally measured values of the 222Rn concentration [1, 2, 5, 7]. The total annual effective dose is calculated by using Eq (3).

  1. Dig and ∑Din represents effective doses due to ingestion and inhalation, respectively
  2. CRnW = 222Rn activity concentration in collected samples measured by RAD-H2O detector (Bq/L)
  3. CW (Daily water consumption) = 3 L/day [1, 10, 33]
  4. EDC (Effective Dose Coefficient) = 3.5 nSv/Bq for 222Rn ingestion [2]
  5. 10−3 is used for the conversion of nano-to-micro
  6. RAW (ratio of 222Rn in the air to water) = 10−4 [2]
  7. F (equilibrium factor between 222Rn and its progeny) = 0.4 [2]
  8. O (mean indoor occupancy factor) = 7000 h/y [2]
  9. DCF (dose conversion factor for 222Rn exposure) = 9 nSv(hBqm-3)-1 [2]

2.6 Ethics approval

This is an observational study. The Atomic Energy Centre Dhaka Research Ethics Committee has confirmed that no ethical approval is required.

3. Results and discussion

3.1 222Rn in river water

As demonstrated in Table 2, the measured 222Rn concentration in the collected twenty river water samples from the highly polluted Buriganga river varied from 0.35 ± 0.18 to 1.16 ± 0.61 Bq/L with an average of 0.68 ± 0.29Bq/L. The maximum 222Rn concentration (1.16 ± 0.61 Bq/L) was found in the sample collected from the Forashgonj Kheyaghat area (RW17). There is a direct swage-drain line (from the Dolai Khal) near the Forashgonj Kheyaghat, which may contaminate the area with technologically enhanced naturally occurring radioactive materials (TENORMs), consequently may increase the 222Rn level in that location. The sample collected from the Wais Ghat area (RW15) had the minimum 222Rn concentration (0.35 ± 0.18 Bq/L). The 222Rn level in these river water samples is relatively low as the aeration of surface water accelerates the emanation of 222Rn into the environment [5, 34]. No sample either contained a 222Rn concentration level more than the safe limit of 100 Bq/L recommended by the WHO or exceeded the maximum contamination limit (MCL) of 11.1 Bq/L set by USEPA [8, 9]. The obtained radon concentrations were also below the UNSCEAR suggested range of 4–40 Bq/L [35].

For each river water sample, the annual dose due to 222Rn inhalation and ingestion is listed in Table 2. The mean annual effective dose due to river water ingestion and inhalation were 2.59 μSv/y and 1.70 μSv/y, respectively. The total annual effective dose for river water ranged from 2.22 μSv/y to 7.38 μSv/y with an average of 4.29 μSv/y. All of these values were well below the maximum permissible limit of 100 μSv/y set by WHO [8].

In Table 3, the present study for river water is compared with the reported results worldwide. The 222Rn level was found very high in some river water, such as the 222Rn level (60 Bq/L) in the Rajouri of Pir Panjal, Kashmir was high due to the mountainous area where many minerals were found in the soil of that region [36]. The study at Ekiti, Nigeria, claimed that the high 222Rn level (42–88 Bq/L) was found in river water due to the local geology covered with migmatite, porphyritic granite, granite gneiss, and undifferentiated schist [3]. In another study, the authors claimed the Gold and Bismuth mining site near the study area in Edu LGA, Kwara State, Nigeria, was the main reason for the high 222Rn level (19.14 ± 3.98 Bq/L) [37]. Nevertheless, the geological map of the Buriganga shows that there are no mountains or volcanic areas around this river. Neither any mining site nor the study area was covered with minerals. The Buriganga riverbed is mainly clay instead of rocks [17, 26, 27]. These were the significant reasons for the low 222Rn level in this river water. Additionally, the result of this study is consistent with the previous research carried out in different regions of the world, such as in Karnataka, India (0.16–1.79 Bq/L) [38], Hemavathi River India (0.67 Bq/L) [39], Kirkuk, Iraq (0.359Bq/L) [40].

3.2 222Rn in tap water

As illustrated in Table 4, the 222Rn concentration in the ten tap water samples collected from Dhaka city varied from 0.56 ± 0.30 to 3.06 ± 0.60 Bq/L with an average of 1.54 ± 0.38 Bq/L. The lowest 222Rn concentration (0.56 ± 0.30 Bq/L) was found in the Bongshal area (TW10). The sample collected from the Mohammadpur area (TW04) contained the highest 222Rn concentration (3.06 ± 0.61 Bq/L). A thorough investigation found that deep tube well water was stored in a tank and then supplied to the tap in the house from where the TW04 was collected. The water was stored in a closed tank that prevented air contact with water. For this reason, the 222Rn gas hardly emanates from the water, so the 222Rn level was higher than the others. However, all the samples contained lower 222Rn levels than both the maximum contamination limit (MCL) of 11.1 Bq/L set by USEPA and the safe limit of 100 Bq/L recommended by the WHO [11, 42–44].

The annual effective dose due to 222Rn inhalation and ingestion for each tap water sample is listed in Table 3. The maximum and the minimum values of annual effective dose due to tap water ingestion were 11.73 μSv/y and 2.15 μSv/y, with an average of 5.89 μSv/y. For inhalation, it ranged from 1.41 μSv/y to 7.71μSv/y with a mean of 3.87 μSv/y. The total annual effective dose for tap water ranged from 3.56 μSv/y and 19.44 μSv/y with an average of 9.77 μSv/y. All of these values were way below the maximum permissible limit of 100 μSv/y set by WHO [8].

Table 5 compares the present study for tap water with the reported literature worldwide. According to the previous literature, a high 222Rn level in tap water was found in some countries. A study in the Sabzevaran fault, Iran, found the 222Rn level in tap water higher (17.12 Bq/L) than in the MCL. The authors concluded that a high 222Rn level was due to volcanic, metamorphic, and sedimentary rocks surrounding the study area [45]. A study in Kenya found the 222Rn level (37 Bq/L) much higher than the MCL in tap water samples; due to the studied area being located near a volcanic region and the maximum tap water of the area was collected from underground water sources, the local geology was the primary reason for the abnormally higher 222Rn level [12].

The tap water of Dhaka city is collected from surface water treatment plants as well as extracted underground water by using different pumps [54], which are then supplied all over the city through a piping system. However, the geology of the present study area neither consisted of any volcanic, granitic, or metamorphic rock nor any volcanic region nearby. Therefore, these may be the leading causes of the lower 222Rn level in the tap water of Dhaka city. Moreover, the result of this study is consistent with many studies conducted in China [11], Thailand [7], Palestine [43], Malaysia [46], and India [48].

The present study shows that the 222Rn level in river water is much lower than in tap water. River water is easily in contact with the open air, which accelerates the emanation of 222Rn, while tap water has less contact with the air. Tap water is supplied in a closed piping system from the storage tank to the tap, so the aeration is negligible compared to surface water. Additionally, a portion of the tap water of Dhaka city is supplied from a groundwater source which was the primary reason for the high 222Rn level in some samples like TW04.

3.3 Radiological risks based on geology of the study area

Radon emanates from soils, rocks, alluvial sediments, and/or aquifer matrices and enters the groundwater and air. Radon, the major contributor to natural background radiation exposure, and its progenies such as 218Po, 214Po, and 214Bi release energetic alpha particles (high linear energy transfer) after inhalation and/or ingestion, causing lining in the stomach and lung cancer in the human body. Therefore, considering the health effect of radon, it is important to identify the areas with high radon concentration, their source, and relation with local geology to prevent the adverse effects on human being and the environment [55]. Though radon (222Rn) and thoron (220Rn) occurs naturally in most soils, sediments, and rocks as a radioactive decay product of 238U of 232Th respectively, the amount differs with localities and geological materials. Radon potential depends on the concentration of naturally occurring radionuclides such as 238U or 226Ra and 232Th in the soils and types of bedrock present in the area [56]. Different geological factors such as lithology/rock type, porosity, permeability, compaction, emanation capacity of the ground, soil constituents, and tectonic features like faults, thrust, and joints, along with the geochemical and hydrogeological conditions of the area mainly control the source, distribution, transport and migration of radon in the soils, sediments, and rocks [57–59]. Certain rock types such as granites, metamorphosed granitic rocks, phosphate rocks with enriched uranium, coal deposits, black shale fractured/faulted rocks, and the subsequent soils resulting from these rocks are the most common sources of radon gas [56, 59, 60]. On the other hand, quartzose sandstone, non-organic shales, and siltstones are the least likely sources of radon [61], but under a favorable reducing environment, uranium mineralization may occur in alluvial-type sedimentary deposits which can then contain and emanate radon [59]. Based on the above facts and the geology of the study area, the radon potential and their associated health risks are evaluated in this study. Geologically, the study area mainly consists of Pleistocene terrace deposit (mixture of clay, silt and sand), alluvium silt, clay, mash clay, peat, valley fill deposits and bar sand (Fig 1b). A limited number of studies on distribution of NORMs in soils of Dhaka city and its surrounding areas and their radiological risks are available in the literature. Miah et al., 1998, studied on the distribution of radionuclides in soil samples in and around Dhaka city and found that the activity concentrations of 226Ra, 232Th and 40K varied as 21–43 Bq/kg, 9–22 Bq/kg, and 165–750 Bq/kg, respectively, and except 40K, the values of 226Ra and 232Th are below the world average [62]. On the other hand, the average background radiation dose level in and around Dhaka City shows 2.00 ± 0.47 mSv/y over a period of ten years, from 2006 to 2015, and demonstrates that no appreciable shift was seen even after the Fukusima Daiichi nuclear power plant disaster in Japan [63]. Therefore, due to the presence of low concentration of radioactive materials such as 226Ra and 232Th in the soils of Dhaka city and its periphery environs, mostly alluvial and clayey type sediments and/or soil, liberation of diffused radon in the atmosphere resulting a relatively lower concentration of radon in the associated river and tap water.

The Stochastic radiation model is based on the probabilistic nature of radiation-induced cancer and suggests that there is no threshold limit for radiation exposure below which the risk of cancer becomes zero. This means that even a single atom of 222Rn in water can potentially cause hazard to the body by ionizing molecules and damaging cellular structures. Therefore, it is important to closely monitor the levels of 222Rn in water, as even a low concentration can pose a risk to human health. Despite all measured values of 222Rn in the tap and river water of Dhaka city show below the limit set by the USEPA and WHO, continuous monitoring is essential to ensure that the levels remain within the safe limits. The USEPA limit for 222Rn in drinking water is 11.1 Bq/L, while the WHO guideline value is 100 Bq/L. In this study, the measured levels of 222Rn in tap water and river water ranged from 0.56 ± 0.30 to 3.06 ± 0.61 Bq/L and from 0.35 ± 0.18 to 1.16 ± 0.61 Bq/L, respectively. The corresponding effective doses were found to be below the limit of 0.1 mSv/y recommended by the WHO [8]. Nevertheless, given the potential health risks associated with even little concentration of 222Rn in water, continuous monitoring of its concentration is essential to ensure safety of public health.

Many advanced countries have established national reference limits for radon in water and indoor air in order to ensure radiological safety and protect public health. However, Bangladesh currently lacks such a reference level for 222Rn in water, despite millions of people in the Dhaka megacity relying solely on tap water for daily household activities, including washing, bathing, drinking, and cooking. Given that the Buriganga River serves as a major transportation hub and facilitates too many businesses and trade centers, there is a greater likelihood of 222Rn exposure for the general population. In terms of concentration, it has been observed in this study that the tap water have a higher concentration of 222Rn than the river water. This is because, radon in river water can be easily diluted due to greater surface and interactions. However, this can vary depending on factors such as the local geology and the treatment processes employed for tap water. When it comes to dose, the risk of exposure to 222Rn from tap water is greater than from river water, since people are likely consume more tap water than river water. However, exposure to 222Rn in river water can still occur through activities such as swimming, fishing, etc. Overall, from an environmental and scientific viewpoint, it is important to monitor the concentration of 222Rn in both tap water and river water to ensure that exposure levels do not exceed the safe limits. This can help to protect public health and ensure that the water that use for daily activities is safe and free from harmful contaminants. Therefore, this study measures the 222Rn levels in both tap water and Buriganga river water to determine if they fall within the safe limits and ultimately ensure the radiological safety of the public. This study on 222Rn levels in Dhaka city’s water may provide a valuable insight for future research on radiation exposure and human health.

4. Conclusion

In this study in Dhaka city, 222Rn level in river and tap water was measured using a RAD H2O accessory to ensure public health safety from radiological hazards due to radon. The ranges of measured 222Rn concentrations in the river water (0.35 ± 0.18 to 1.16 ± 0.61 Bq/L) and the tap water (0.56 ± 0.30 to 3.06 ± 0.61 Bq/L) showed lower than the limit set by the WHO and the USEPA [44]. Also, the total annual effective doses were within the safe limit set by the WHO [8]. Considering the carcinogenic characteristics of 222Rn, frequent monitoring of 222Rn in various dwelling media is essential to ensure public health safety. Further extensive research should be carried out for 222Rn mapping of the country.

A few recommendations are proposed for future 222Rn-related works,

  • Expansion of the study to other regions of Bangladesh is essential to obtain a better understanding on the distribution of 222Rn in different environmental media, including water, air, and soil.
  • It is necessary to investigate the potential impact of local geological factors, such as soil type and groundwater composition, on the levels of 222Rn in water resources.
  • Exploration of the relationship between 222Rn exposure and cancer incidence rates in the region is crucial to gain a better understanding on the implications of the public health.
  • A risk assessment study should be conducted to evaluate the potential health risks associated with the chronic exposure to low levels of 222Rn in water resources in Dhaka and other regions of Bangladesh.
  • A long-term monitoring program needs to be developed and implemented to track the changes of 222Rn levels over time and ensure that the safety of public health remain effective.


  1. 1.
    Rani S., Kansal S., Singla A. K., and Mehra R., “Radiological risk assessment to the public due to the presence of radon in water of Barnala district, Punjab, India,” Environ. Geochem. Health, vol. 43, no. 12, pp. 5011–5024, 2021. pmid:34173905
  2. 2.
    UNSCEAR, SOURCES AND EFFECTS OF IONIZING RADIATION United Nations Scientific Committee on the Effects of Atomic Radiation, vol. I, no. c. 2010.
  3. 3.
    Faweya E. B., Agbetuyi O. A., Talabi A. O., Adewumi T., and Faweya O., “Radiological Implication of 222Rn Concentrations in Waters from Quarries Environs, Correlation with 226Ra Concentrations and Rocks Geochemistry,” Arab. J. Geosci., vol. 14, no. 11, 2021.
  4. 4.
    Ahmad N., Rehman J., ur Rehman J., and Nasar G., “Assessments of 226Ra and 222Rn concentration in well and tap water from Sik, Malaysia, and consequent dose estimates,” Hum. Ecol. Risk Assess., vol. 25, no. 7, pp. 1697–1706, 2019.
  5. 5.
    Ismail N. F., Hashim S., Mohd Sanusi M. S., Abdul Rahman A. T., and Bradley D. A., “Radon levels of water sources in the southwest coastal region of Peninsular Malaysia,” Appl. Sci., vol. 11, no. 15, 2021.
  6. 6.
    WHO, “Who Handbook on Indoor Radon:A Public Health Perspective.” p. 4, 2009.
  7. 7.
    Thumvijit T. et al., “Identifying indoor radon sources in Pa Miang, Chiang Mai, Thailand,” Sci. Rep., vol. 10, no. 1, pp. 1–14, 2020. pmid:33082391
  8. 8.
    WHO, “Guidelines for drinking-water quality.” 2008.
  9. 9.
    USEPA, “Radon in Drinking Water Regulations,” 2012.
  10. 10.
    WHO, “Guidelines for drinking-water quality, 4th edition,” 2017.
  11. 11.
    Yong J., Liu Q., Wu B., Hu Y., and Feng G., “Assessment of radiation dose hazards caused by radon and its progenies in tap water by the human dosimetric model,” J. Water Health, vol. 19, no. 6, pp. 933–945, 2021. pmid:34874901
  12. 12.
    Mustapha A. O., Patel J. P., and Rathore I. V. S., “Preliminary report on radon concentration in drinking water and indoor air in Kenya,” Environ. Geochem. Health, vol. 24, no. 4, pp. 387–396, 2002.
  13. 13.
  14. 14.
    Asiatic Society of Bangladesh, “Dhaka, Geology—Banglapedia,” 2021. https://en.banglapedia.org/index.php/Dhaka,_Geology (accessed Dec. 24, 2022).
  15. 15.
    Asiatic Society of Bangladesh, “Buriganga River—Banglapedia,” 2021. https://en.banglapedia.org/index.php?title=Buriganga_River (accessed Dec. 24, 2022).
  16. 16.
    K. M. Ahmed, M. S. Islam, S. Sultana, S. Ahmed, and G. Rabbani, “Changes in the groundwater regime of Dhaka City: a historical perspective,” Environ. Cap. Dhaka-Plants Wildl. Gard. Park. Air Water Earthq., pp. 383–400, 2010.
  17. 17.
    Burgess W. G., Hasan M. K., Rihani E., Ahmed K. M., Hoque M. A., and Darling W. G., “Groundwater quality trends in the Dupi Tila aquifer of Dhaka, Bangladesh: sources of contamination evaluated using modelling and environmental isotopes,” Int. J. Urban Sustain. Dev., vol. 3, no. 1, pp. 56–76, 2011.
  18. 18.
    Hoque M. A., “Hydrostratigraphy and Aqnifer Piezornetry of Dhaka City,” Inst. Water Flood Manag., 2004, Accessed: Sep. 21, 2022. [Online]. Available: http://lib.buet.ac.bd:8080/xmlui/handle/123456789/1970.
  19. 19.
    Rahman M. A., Wiegand B. A., Badruzzaman A. B. M., and Ptak T., “Hydrogeological analysis of the upper Dupi Tila Aquifer, towards the implementation of a managed aquifer-recharge project in Dhaka City, Bangladesh,” Hydrogeol. J., vol. 21, no. 5, pp. 1071–1089, 2013, doi: Hydrogeological analysis of the upper Dupi Tila Aquifer, towards the implementation of a managed aquifer-recharge project in Dhaka City, Bangladesh.
  20. 20.
    Bodrud-Doza M., Islam S. M. D. U., Rume T., Quraishi S. B., Rahman M. S., and Bhuiyan M. A. H., “Groundwater quality and human health risk assessment for safe and sustainable water supply of Dhaka City dwellers in Bangladesh,” Groundw. Sustain. Dev., vol. 10, p. 100374, Apr. 2020.
  21. 21.
    M. H. Monsur, “Quaternary Geology of Bangladesh, 1st ed., Dhaka.,” 2020.
  22. 22.
    DWASA and IWM, “Resource assessment and monitoring of water supply sources for Dhaka city,” Final Rep. Resour. assessment, Part 2., 2008.
  23. 23.
    M. Islam et al., “Inferring major ion chemistry and quality of groundwater in Dupi Tila aquifer, Dhaka city, Bangladesh,” 2021.
  24. 24.
    Hasan M. K., Burgess W., and Dottridge J., “The vulnerability of the Dupi Tila aquifer of Dhaka, Bangladesh,” IAHS-AISH Publ., no. 259, pp. 91–98, 1999.
  25. 25.
    Hoque M. A., Hoque M. M., and Ahmed K. M., “Declining groundwater level and aquifer dewatering in Dhaka metropolitan area, Bangladesh: Causes and quantification,” Hydrogeol. J., vol. 15, no. 8, pp. 1523–1534, Dec. 2007.
  26. 26.
    M. K. Hasan, W. G. Burgess, and J. Dottridge, “Hydraulic and hydrochemical implications of river-aquifer interaction, Dhaka, Bangladesh,” Gambl. with Groundwater-Physical, Chem. Biol. Asp. aquifer-stream relations, pp. 413–418, 1998.
  27. 27.
    K. M. Ahmed and W. G. Burgess, “Surface water and groundwater interaction in Bangladesh hydrogeology,” Groundw. Resour. Dev. Bangladesh Backgr. to Arsen. Cris. Agric. potential Environ. Bangladesh Cent. Adv. Stud. Univ. Press Ltd., Dhaka, Bangladesh, 2003.
  28. 28.
    Khan R. et al., “Distribution, sources and ecological risk of trace elements and polycyclic aromatic hydrocarbons in sediments from a polluted urban river in central Bangladesh,” Environ. Nanotechnology, Monit. Manag., vol. 14, p. 100318, Dec. 2020.
  29. 29.
    Karim S., Khatun M., Ali R. M. E., and Munsura Akther K., “Geomorphology and Geology of the Dhaka City Corporation Area-an Approach of Remote Sensing and GIS Technique,” Int. J. Astron., vol. 6, no. 2, pp. 7–16, 2019, [Online]. http://www.openscienceonline.com/journal/aass.
  30. 30.
    International Atomic Energy Agency, “Guidelines on soil and vegetation sampling for radiological monitoring,” Tech. Reports Ser. No. 486, no. 486, 2019.
  31. 31.
    DURRIDGE Company Inc., RAD H20 User Manual, no. 978. 2011.
  32. 32.
    K. M. Opondo and K. Sims, Electronic Radon Detector User Manual. 2012.
  33. 33.
    Milton A. H., Rahman H., Smith W., Shrestha R., and Dear K., “Water consumption patterns in rural Bangladesh: Are we underestimating total arsenic load?,” J. Water Health, 2006. pmid:17176814
  34. 34.
    Orosun M. M., Ajibola T. B., Akinyose F. C., Osanyinlusi O., Afolayan O. D., and Mahmud M. O., “Assessment of ambient gamma radiation dose and annual effective dose associated with radon in drinking water from gold and lead mining area of Moro, North-Central Nigeria,” J. Radioanal. Nucl. Chem., vol. 328, no. 1, pp. 129–136, 2021.
  35. 35.
    UNSCEAR, “Sources and effects of ionizing radiation,” vol. 1, 2008.
  36. 36.
    Nazir S., Simnani S., Sahoo B. K., Mishra R., Sharma T., and Masood S., “Monitoring geothermal springs and groundwater of Pir Panjal, Jammu and Kashmir, for radon contamination,” J. Radioanal. Nucl. Chem., vol. 326, no. 3, pp. 1915–1923, 2020.
  37. 37.
    Lawal W., “Assessment of Annual Effective Dose Associated with Radon in Drinking Water from Gold and Bismuth Mining area of Edu, Kwara, North-central Nigeria,” Pollution, vol. 7, no. 1, pp. 231–240, 2021.
  38. 38.
    Rajashekara K. M., Narayana Y., and Siddappa K., “222Rn concentration in ground water and river water of coastal Karnataka,” Radiat. Meas., vol. 42, no. 3, pp. 472–478, 2007.
  39. 39.
    Shivanandappa K. C. and Yerol N., “Radon concentration in water, soil and sediment of Hemavathi River environments,” Indoor Built Environ., vol. 27, no. 5, pp. 587–596, 2018.
  40. 40.
    Kareem D. O., Ibrahim A. A., and Ibrahiem O. S., “Heavy metal and radon gas concentration levels in Khasa River in Kirkuk City (NE Iraq) and the associated health effects,” Arab. J. Geosci., vol. 13, no. 19, 2020.
  41. 41.
    Nita D. C., Moldovan M., Sferle T., Ona V. D., and Burghele B. D., “Radon concentrations in water and indoor air in North—West regions of Romania,” Rom. Reports Phys., vol. 58, no. SUPPL., pp. 2016–2020, 2013.
  42. 42.
    Şahin Bal S., Tanrıverdi E., Yalçın S., Doğru M., and Özbey F., “The radon concentrations of some waters in Bitlis (Turkey) and their dose estimates,” Environ. Dev. Sustain., vol. 23, no. 12, pp. 17650–17667, 2021.
  43. 43.
    Al Zabadi H., Musmar S., Issa S., Dwaikat N., and Saffarini G., “Exposure assessment of radon in the drinking water supplies: A descriptive study in Palestine,” BMC Res. Notes, vol. 5, 2012. pmid:22243625
  44. 44.
    USEPA, “RADON IN DRINKING WATER,” Environ. Prot., no. 4607, pp. 1–4, 1999.
  45. 45.
    Shamsaddini M., Negarestani A., Malakootian M., and Javid N., “Study of radon concentration of drinking water sources in adjacent areas of Sabzevaran fault,” J. Radioanal. Nucl. Chem., vol. 326, no. 2, pp. 1437–1446, 2020.
  46. 46.
    Salih N. F., “Determine the Contaminations of Radon in the Drinking Water Using NTDs (CR-39) and RAD7 Detectors,” Arab. J. Sci. Eng., vol. 46, no. 6, pp. 6061–6074, 2021.
  47. 47.
    Darabi Fard Z., Rahimi M., Malakootian M., and Javid N., “Studying radon concentration in drinking water resources in Zarand city (Iran) and its villages,” J. Radioanal. Nucl. Chem., vol. 326, pp. 33–39, 2020.
  48. 48.
    Yashaswini T., Ningappa C., Niranjan R. S., and Sannappa J., “Radon Concentration Level in Ground and Drinking Water around Kabini River Basin, Karnataka,” J. Geol. Soc. India, vol. 95, no. 3, pp. 273–278, 2020.
  49. 49.
    Öge Ö. and Gökçe H., “Author ‘ s Accepted Manuscript,” Appl. Radiat. Isot., 2018.
  50. 50.
    Mittal S., Rani A., and Mehra R., “Radon levels in drinking water and soil samples of Jodhpur and Nagaur districts of Rajasthan, India,” Appl. Radiat. Isot., vol. 113, pp. 53–59, 2016. pmid:27135605
  51. 51.
    Ahmad N., Jaafar M. S., and Alsaffar M. S., “Study of radon concentration and toxic elements indrinking and irrigated water and its implications in Sungai Petani, Kedah, Malaysia,” J. Radiat. Res. Appl. Sci., vol. 8, no. 3, pp. 294–299, 2015.
  52. 52.
    Moldovan M., Niţǎ D. C., Cucos-dinu A., Dicu T., Bican-brişan N., and Cosma C., “Radon concentration in drinking water and supplementary exposure in Bǎiţa-ŞTei Mining area, Bihor county (Romania),” Radiat. Prot. Dosimetry, vol. 158, no. 4, pp. 447–452, 2014. pmid:24153421
  53. 53.
    Akar Tarim U. et al., “Evaluation of radon concentration in well and tap waters in Bursa, Turkey,” Radiat. Prot. Dosimetry, vol. 150, no. 2, pp. 207–212, 2011. pmid:21990391
  54. 54.
    The Nature Conservancy, “Urban Water Blueprint—Dhaka,” 2022. http://water.nature.org/waterblueprint/city/dhaka/#/c=8:24.25758:90.26042 (accessed Jan. 08, 2022).
  55. 55.
    Mostečak A., Perković D., Kapor F., and Veinović Ž., “Radon mapping in croatia and its relation to geology,” Rudarsko Geolosko Naftni Zbornik, vol. 33, no. 3. University of Zagreb, Faculty of Political Sciences, pp. 1–11, Jul. 1, 2018.
  56. 56.
    Khan M. A. et al., “Health risks associated with radon concentrations in carbonate and evaporite sequences of the uranium-rich district Karak, Pakistan,” Front. Environ. Sci., vol. 10, p. 1814, Sep. 2022.
  57. 57.
    Choubey V. M., Sharma K. K., and Ramola R. C., “Geology of radon occurrence around Jari in Parvati Valley, Himachal Pradesh, India,” J. Environ. Radioact., vol. 34, no. 2, pp. 139–147, Jan. 1997.
  58. 58.
    Alonso H., Rubiano J. G., Guerra J. G., Arnedo M. A., Tejera A., and Martel P., “Assessment of radon risk areas in the Eastern Canary Islands using soil radon gas concentration and gas permeability of soils,” Sci. Total Environ., vol. 664, pp. 449–460, May 2019. pmid:30759409
  59. 59.
    Majumder R. K. et al., “Measurement of radon concentrations and their annual effective doses in soils and rocks of Jaintiapur and its adjacent areas, Sylhet, North-east Bangladesh,” J. Radioanal. Nucl. Chem., vol. 329, no. 1, pp. 265–277, Jul. 2021.
  60. 60.
    Appleton J. D. and Miles J. C. H., “A statistical evaluation of the geogenic controls on indoor radon concentrations and radon risk,” J. Environ. Radioact., vol. 101, no. 10, pp. 799–803, Oct. 2010. pmid:19577346
  61. 61.
    Gundersen L. C. S., “‘Radon in sheared metamorphic and igneous rocks,’ in Geologic and geochemical field studies of radon in rocks, soils, and water.,” U.S. Geol. Surv. Bull., pp. 38–49, 1991.
  62. 62.
    UNSCEAR, “Sources and Effects of Ionizing Radiation, United Nations Scientific Committee on the Effects of Atomic Radiation, Annex B,” 2000.
  63. 63.
    Begum M. et al., “Assessment of Background Radiation Level in Different Locations of Bangladesh,” Nucl. Sci. Appl., vol. 27, no. 1, pp. 33–36, 2018, [Online]. https://www.researchgate.net/publication/336686432_Assessment_of_Background_Radiation_Level_in_Different_Locations_of_Bangladesh.

Leave a Reply

Your email address will not be published. Required fields are marked *