Age-dependent dose assessment of uranium exposure in groundwater of Ganderbal and Budgam districts in Jammu and Kashmir Open Access

When present in extremely high concentrations, uranium and its decay products are considered hazardous and may pose major health hazards due to their radioactive nature. The heavy wastewater pollutants, e.g., brine discharged into the groundwater resources degrade the water quality. This makes the water unsuitable for drinking and industrial applications directly (desalination). Humans interact with naturally occurring uranium because, from rocks and soil, uranium comes in water, food, and air also and these are the main sources through which uranium enters human bodies. Therefore, exact knowledge of uranium is very useful in dose estimation due to its progeny. Naturally, uranium exists in three isotopic mixtures, i.e. ²³⁸U (99.27%), ²³⁵U (0.72%), and ²³⁴U (0.0054%). This abundance is as per mass, not by activity because as per activity, ²³⁵U is important and not ²³⁸U. The oxidation states of uranium are +3, + 4, + 5, and +6 in aqueous solutions. Only uranium in the +6-valence state is soluble in water. The +4-valance state is virtually insoluble (Singh et al. 2013; Mehra et al. 2017; Ali et al. 2019; Aközcan et al. 2021). Thus, apart from inhalation, ingestion, and terrestrial exposure, skin chemisorption and also food from plants are the common paths through which radionuclides enter human bodies. Uranium is a common and ancient radionuclide that can be found in distinct chemical forms in all kinds of rocks, soil, groundwater, and food. Uranium has a density of 18.9 g cm⁻³, which is 65% greater than lead. Uranium is classified as toxic because it has no recognized metabolic role in the human body. It is considered a non-essential metal for all species which occurs frequently in the environment. Uranium also reacts with oxygen easily and forms +4 (UO₂ and U⁴⁺) to +6 (UO₃ and ⁠) compounds. It is quickly leached, and copious of the significant ore deposits of uranium are generated by ground water at a typical pH (Babu et al. 2008; Birke et al. 2010; Alaboodi et al. 2020). Uranium can be migrated and fetched by environmental processes like transfiguration and oxidation/reduction techniques (Ajay et al. 2016; Nazir et al. 2021). Among the various sources, drinking water is considered as a major source through which uranium enters the human body as almost 85% of uranium is considered to come from drinking water and 15% from ingested food. An impermanent chemical change can occur by about 0.1 mg/kg of body weight from natural uranium (van Gerwen et al. 2020; Pintilie-Nicolov et al. 2021). Uranium is considered a health threat owing to its radioactive nature and also because it is a heavy metal that can cause chemical toxicity which is carcinogenic in nature. In addition to this, uranium can cause severe DNA destruction due to alpha emission. Kidney, liver, and bones are the main uranium-accumulation locations in the human body. Uranium also gets eliminated from the body at a higher scale through urine, blood, and, to a lesser extent; organ accumulation (Li et al. 2009; Sahoo et al. 2009; Yellowhair et al. 2018). Accumulation on bone surfaces can be considered to be in proportion to the age-specific rate of calcium deposition for different age groups. The rate of uranium sacking from distinguishable bone volume is thought to be commensurate with the bone's age-dependent desorption scale. The rapid loss of uranium from the interchangeable bone volume and surface is thought to be age-insensitive. The contemporary era is characterized by a ‘compartmental model of uranium in human hair’ (Leggett 1994). It is a recycling model and very similar to the ICRP's uranium bio-kinetic model (Karpas et al. 2005). Uranium is mostly found in blood in a compound form with bicarbonates, proteins, and red blood cells (RBCs). Chemical toxicity, metabolic toxicity, and physiologically dynamic toxicity are all known health effects of uranium consumption. Furthermore, new research shows serious injury to the brain, reproduction, and inappropriate behavior as well as gene expression. Uranium poses serious harmful chemical toxicity to kidneys (Lestaevel et al. 2005; Kathren & Burklin 2008; Kaur & Mehra 2019; Kwon et al. 2021). An elevated level of uranium in drinking water can cause acute renal failure and death. Due to its heavy metal and highly ionizing nature, the chemical toxicity effect on human health is greater than radio toxicity. The new bio-kinetic model of iodine recommended by ICRP has been modified by Koreans that provides a way to calculate the dose estimation of radioiodine which is also a fission product of uranium. This study shows that the accumulation of uranium in the thyroid gland is also a serious threat to human health as the secretion gland of the thyroid is not able to differentiate between the radioiodine and stable iodine (Mudd 2008; Leggett 2010; Shin et al. 2016).

In the last few decades, the study of uranium has shown great interest as the level is frequently found to increase above the World Health Organization (WHO) and United States Environmental Protection Agency (USEPA) limit (30 μgl⁻¹) in drinking water. Literature validates that the uranium level has increased in various countries such as Finland (Frengstad et al. 2000), Norway (Singh et al. 2014), and Switzerland (Stalder et al. 2012). It is also observed that Punjab is one of the states that shows a higher rise in cancer patients due to the elevated level of uranium concentration in the groundwater. The main reason behind this is the excessive use of chemical fertilizers and the Industrial Revolution (Liesch et al. 2015; Saini et al. 2016; Bjørklund et al. 2020; Sharma et al. 2021). According to UNSCEAR, 2.4 mSvY⁻¹ is the population's effective dose due to natural sources. Food and water consumption is responsible for 0.29 mSv. Radioactive elements generated by nuclear power plants or transferred from nuclear bomb fallout have a radiological ecological impact. It has been observed that long-lived radionuclides ¹³⁴CS (half-life: 2.1 y) and ¹³⁷CS (half-life: 30.1 y) contribute to the progressive internal effective dose which further helps to know the cancer-prone sites. This study is very useful for the general public, as they are occupationally or environmentally exposed to this artificially produced radio-cesium (Harrison & Streffer 2007; Paquet 2019; Prasad et al. 2019). The International Commission for Radiological Protection has recently released a set of standards for internal effective dose estimation as well as the ability to estimate committed effective dose directly (Committee 1995; Eckerman et al. 2012; Bhat & Shyju 2014).

In the present study, an attempt has been made to summarize the radiological toxicity of uranium as it will remain in the human body for a longer period of time due to the very long biological half-life of uranium and becomes more noxious. Age-effective as well as organ-effective doses are calculated as per the ICRP'S dose conversion factors. Literature shows that there is very little study of uranium in Kashmir Valley particularly in the Ganderbal and Budgam districts. Therefore, in this study, an analysis has been made to assess the age-specific doses to various organs of the human body received from uranium in groundwater. The present study is the first time an attempt has been made to analyze the doses to various organs due to the retention of uranium in the human body.

The Budgam district is considered the youngest district in the Kashmir valley. This district lies between 33°48ʹ 42.79ʺ – 34° 52ʹ 2.56ʺ N latitudes and 74°24ʹ 2.69ʺ –74° 55ʹ 20.25ʺ E longitudes with an average altitude of 1,684 m. This district is one of the closest districts to Srinagar which is the summer capital of Jammu and Kashmir. It shares borders with Baramulla and Srinagar in the north, Pulwama in the southeast and Shopian in the south. This district has plains as well as mountainous regions. It has sharp features due to its elevation from sea level and is famous for its various tourist destinations like Nilnag, Yusmarg, Sange-Safed, and the Tomb of Sheikh Nor-ud–din Nooranietc. The main rocks found in the district are shale, quartzite, limestone, and conglomerates.

The effluent seepage from various rivers, streams, and lakes, as well as upland inflow and irrigated fields, are the major sources of groundwater in the Ganderbal and Budgam regions, apart from precipitation in snow and rain form. Two aquifer formations are formed in the Budgam region; one is a hard aquifer (Panjal traps), and the other is a soft aquifer (Alluvium and Karewas). The aquifer system in the Ganderbal region consists of varying thicknesses of alluvium composed of sand, silt, gravel, pebbles, sandy silt, and boulders, and the mixed assembly of these sediments confirms the most potent groundwater reservoir consists of multilayer coarse granular material.

The water samples are collected from different locations in 100-mL polypropylene bottles. The polypropylene bottles were acid-leached for uranium analysis. The samples are taken from tube wells and taps. The tube wells and taps, being at different depths, were first opened for 3–5 min. The water samples are then filtered using filter paper of 0.45 μm pore-size so that the impurities are removed from the water before analysis.

The light-emitting diode (LED) fluorimeter method is considered the most reliable method for analyzing the uranium in groundwater. The accuracy of measuring uranium concentration is in the range of 0.5–1,000 μg/L and has a precision of 5%. The fluorescence of the uranyl complex is the basic principle of the LED fluorimeter, which is formed by fluren (buffered complex of sodium pyrophosphate and ortho-phosphoric acid). The reason for adding buffer is to maintain PH at its optimum level, as fluorescence is PH-dependent. The fluorescence is measured using a sensitive photomultiplier tube (PMT). The various other possible fluorescence due to the impurities in the water is blocked by using an optical long-pass filter. The intensity as well as wavelength distribution of the emission spectrum can be measured using this technique.

There are various pathways through which uranium enters the human body. Drinking water is observed as the main pathway through which it enters the human body. The radiation dose for various age groups due to drinking water can be measured using a dose conversion factor prescribed for various age groups according to the water intake capability (Rani et al. 2013; Jakhu et al. 2016). Therefore, the ingestion dose can be calculated using the following relation (1):

The reason for the low uranium concentration in Ganderbal district can be considered due to the geology in the region. The lofty mountains and glaciers are the source of the Sindh River, which is the main water resource in the Ganderbal district. While the lower concentration of uranium in Budgam than in Ganderbal can be considered mainly due to the hydrogeology of that region. The sediments, which consist of sand, cobbles, pebbles, boulders, and gravel, are interlayered with thick clay beds that form the aquifer system of the region. Thus, the sedimentary deposits form the multilayered major aquifer for the whole region. From this analysis, we can conclude that the two districts, viz Ganderbal and Budgam are among the least contaminated regions in India as per the literature.

The prescribed level of annual ingestion dose for humans from drinking water consumption is 100 μSvY⁻¹ (WHO 2003). This prescribed level of annual ingestion dose represents approximately 4.2% of AED from natural background radiation (WHO 2003). The mean average ingestion dose received by the 0–6-month-old group is lower than that of the 7–12-month-old group, due to the lower intake of water (256 L) as compared to (7–12) month-old group (292 L). It is observed that the annual ingestion dose for infants is comparatively higher than that of adults even though adults drink more water than infants. The main reason behind the variation in ingestion doses is due to the metabolism of infants and smaller organ weights, resulting in infants being more radiosensitive than adults. Females also receive higher doses during pregnancy and lactation due to increased water consumption during this period. The observed annual ingestion dose due to the different water intake capacities of various groups is presented in Table 2. From Table 2, it is clear that the annual ingestion dose varies in the range of 0.21–3.4 μSvY⁻¹ for the Ganderbal region and from 0.01 to 4.2 μSvY⁻¹ for the Budgam Region.

The elements such as Ni, Cu, As, and Pb have pernicious effects on the human body. The same effects of uranium can be seen, as it is a heavy metal. Uranium is an element that has a very long biological half-life and therefore becomes malignant at very low doses. It is perceived from various studies that uranium has more chemical toxicity effects than radiological effects. However, its radiological effect dominates when retained in the body for a longer period. It has very dangerous effects on some internal body organs, like the kidney, which is more susceptible than other organs. The doses to various organs are calculated using ICRP's dose conversion factors (ICRP 1995) and presented in Table 3.

It is observed that the doses to the bones are much higher as compared to any other organ. The radiological effect on bone cells is cancerous, but bones show a less perceptive nature than any other organs of the human body. The dose varies from a maximum of 1.1 μSv to a minimum of 0.02 μSv due to the radiosensitive cells present in the bone surfaces, with an average value of 0.463 μSv (Table 3).

The red bone marrow is also one of the organs that receive high doses. Irradiation to the bone marrow can directly cause leukemia. The dose received by red bone marrow varies from a maximum of 0.14 to a minimum of 0.001 μSv with an average value of 0.55 μSv reported in Table 3.

As the thyroid gland is very sensitive to irradiation so, radiological effects dominate and may cause cancer. It was also found that the thyroid gland is incapable of differentiating between radioiodine and iodine. Thus, it is more prone to cancer. The doses received by the thyroid gland are in the range of 0.2–10 nSv as shown in Table 3.

The breast is one of the most radiosensitive organs in the human body. But in the case of ingested uranium, the thyroid gland and the breast have equal sensitivity. Doses received by breast are found in the range of 0.2–10.0 nSv, as reported in Table 3.

Gonads are highly sensitive to ionizing radiation, both in males and females. There are three effects of radiation on gonads. The main effect is the introduction of hereditary insufficiencies. The doses received from the present study for male and female gonads are in the range of 0.3–12.2 nSv and 0.3–10 nSv (Table 3), respectively.

Skin is also observed to be sensitive to the radiation. The oxygenated and proliferating cells present in the skin make it sensitive to irradiation. Usually, reddening is seen in the skin when humans are exposed to the radiation. In the present study, it is observed that the general public is receiving an average dose of 4.2 nSv (Table 3).

The upper part of the alimentary tract is called the esophagus. The main function of the esophagus is to carry food and water from the mouth to the stomach. The dose received by the public from the study area was in the range of 0.2–10.0 nSv (Table 3).

The two important parts of the gastrointestinal (GI) tract are the stomach wall and the colon. The outer mucosa and inner submucosa, muscularis, externa, and serosa are parts of the stomach wall. The average dose received by the stomach wall and colon is 4.2 and 6.1 nSv, respectively, as shown in Table 3.

The largest part of the human body is the liver. The liver shows slow turnover because of the hepatocyte cells present in the liver. The liver also receives high doses. Therefore, the liver receives a much higher dose value than any other internal human body tissue. The dose received by the liver is in the maximum range of 0.19 to a minimum of 0.001 μSv (Table 3).

The bladder wall receives the urine excreted from the kidneys. The four layers that form the bladder wall are the outer layer the serosa, the muscular layer, the submucosa, and the mucosa. The bladder wall has also detrusor muscle fibers. Therefore, the dose received by the public during the study is in the range of 0.3–10.0 nSv as presented in Table 3.

This work explores the distribution of uranium in groundwater samples from the two districts of Kashmir Valley namely Ganderbal and Budgam, emphasizing doses that vary with age and their effects on different organ systems. The results show that the concentration of uranium in both districts is below the allowable level established by the USEPA, suggesting that these areas are among the least affected in India. Due to the region's unique geology, where the Sindh River, a significant water supply, originates from high mountains and glaciers, Ganderbal has been found to have a low uranium concentration. On the other hand, hydrogeological factors – more precisely, sedimentary deposits that create a multilayered aquifer system – are responsible for Budgam's lower concentration. The age-dependent dose analysis shows how ingestion doses vary across life stages, with babies requiring relatively higher doses because of their increased sensitivity and smaller organ weights. Because they drink more water, women also experience higher dosages, especially during pregnancy and lactation.

The distribution of doses to different organs emphasizes the possible health hazards related to exposure to uranium. The thyroid gland, red bone marrow, and bones are exposed to comparatively larger dosages, highlighting the importance of considering these organs when evaluating their effects on health. The study sheds light on potential health dangers for inhabitants relying on groundwater in these districts and offers insightful information about the consequences of uranium's radioactivity and chemical toxicity. The uranium concentration in the present study shows consistency with the study of uranium and radon concentrations in Srinagar city (Nazir et al. 2021). In Srinagar city, the uranium is below the prescribed limits of various regulatory organizations, but the radon concentration is high at certain places. The overall dose evaluation of the study area can be measured in future for the health implications for the general public

This study has limitations even though it provides important new information about the distribution of uranium in the districts of Ganderbal and Budgam. The first drawback is that the sampling locations were limited to these particular areas. Subsequent research endeavors ought to expand the geographic scope, incorporating a variety of places in order to furnish a more exhaustive comprehension of uranium dispersion in groundwater throughout unique topographies. The study's second restriction concerns the sample size. While the data gathered is valuable, a larger sample size could improve the study's statistical robustness and wider application. Furthermore, possible fluctuations in uranium content over time may not be fully captured by the temporal snapshot used in the study. A longitudinal method could be useful in future studies to take temporal and seasonal changes into account. Addressing these limitations will pave the way for a more nuanced and thorough understanding of the complex interplay between uranium distribution, health risks, and environmental factors. The present study forms the baseline for the future prevention and safety measures taken for better quality drinking water. Further, radon mapping can be done in future so that the exact radiation doses can be determined. In the present study, only uranium concentration has been calculated from which the exact doses for the general public cannot be accessed. Also, for the age-dependent doses, survey of water intake for different age groups can be made for the proper dosage evaluation.

The present study was carried out for the analysis of uranium in groundwater by using LED fluorimeter. The analysis reveals that all the samples fall under the permissible limits prescribed by USEPA and the World Health Organization which is 30 μgl⁻¹. Therefore, the groundwater of the study area is safe for drinking purposes. The uranium concentration obtained by the depth shows that water content is readily available in the Ganderbal and Budgam regions of Kashmir. A statistical analysis of the uranium concentration for the Ganderbal and Budgam shows that the uranium concentration is below the permissible limits prescribed by USEPA. The study also discloses that infants are more sensitive to radiation as compared to other age groups or adults. Thus, infants are at more risk due to ingested uranium through groundwater. Further, the doses to various organs are calculated, which shows that the bones, red bone marrow, thyroid gland, and skin are the various organs of the human body that receive the majority of the dose from ingested uranium through groundwater. As the uranium concentration is very low in the study area, it is mainly considered due to the presence of mountains and glaciers in the area. Therefore, the study area shows a uniform distribution of uranium.

The authors thank the Department of Physics, NIT Jalandhar, Punjab for providing the laboratory facilities.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.