Exploring carcinogenic and non-carcinogenic health risks across age-groups from geogenic and anthropogenic contamination in groundwater of semi-arid region, Northwest India.

Groundwater resources are crucial for maintaining a healthy ecosystem and ensuring environmental stability in geographically diverse areas (Li et al., 2018). However, the challenges related to water scarcity and continuous water quality deterioration caused by geogenic and anthropogenic contaminants are diminishing the clean and potable water supply. These challenges are exacerbated by a changing climate, unplanned development, population growth, extensive use of chemical fertilizers, and expanding anthropogenic activities (He and Wu, 2019). The excessive reliance on groundwater for irrigation, industrial, and domestic purposes is placing alarming pressure on this vital resource, especially in developing countries (Rao et al., 2024).

In recent decades, regions like the northwest of the Indian subcontinent have experienced a consistent decline in groundwater level and quality (Joshi et al., 2021). Contaminants’ accumulation in prevailing aquifers across northwest India, driven by irrigation practices, evaporation, groundwater abstraction, mineralization, and leachates, is regarded as a more significant threat to groundwater quality than groundwater depletion, resulting in health risks. Earlier, Lapworth et al. (2017) revealed that Alluvium aquifers in some parts of Northwest India are severely impacted by excessive Fluoride (F^–), Uranium (U), and Nitrate (NO₃^–) contents. However, health risks from the consumption of F^–, U, and NO₃^– contaminated groundwater through multiple pathways have been rarely studied in the region, which significantly affects the life span of an individual.

F^– is released in groundwater from the dissolution of minerals such as Fluorite, Fluorapatite, Villiaumite, Hornblende, Muscovite, and Biotite (Reddy et al., 2010). F^– concentrations ranging from 0.5 to 1.5 mg/l are crucial for promoting teeth and bone development. However, exceeding the concentration of more than >1.5 mg/l (WHO, 2017) can lead to pitting and mottling of teeth, skeletal and dental fluorosis, as well as chronic kidney diseases (Li et al., 2019). Moreover, F^– is capable of replacing the hydroxide ion present in hydroxyapatite in bones, which causes bone damage (Montazeri et al., 2011).

Similarly, U enters the groundwater through the dissolution of minerals like Uraninite, Pitchblende, Rutherfordine, Gummite, Schoepite, Coffinite, and Uranophane (Devaraj et al., 2021). U can also contaminate groundwater through anthropogenic sources, including phosphate fertilizers, mining activities, and radioactive waste disposal. The intake of high concentrations of U via oral and dermal routes with >30 ug/l is considered unsafe for health (Ramadan et al., 2022), and its impacts are often found to be connected with bone-health-related issues and chronic nephrotoxicity (Kumar et al., 2020). Depleted U can enter the human body as uranyl oxides. The primary uranyl oxides (U₃O₈, UO₂, and UO₃) exhibit varying solubility in body fluids, with UO₃ dissolving within weeks, while U₃O₈ and UO₂ take years to dissolve. Uranium-hexafluoride (UF₆) is a readily soluble U compound than uranyl oxides [UO₃, U₃O₈ and UO₂]. In body fluids, U dissolves as the uranyl ion (UO₂²⁺), which can interact with biological molecules. Once absorbed into the bloodstream, U is transported and retained in body tissues and organs, forming soluble complexes with bicarbonate, citrate, or proteins (Bleise et al., 2003). U is also capable of binding with Ca²⁺, which ultimately modifies the crystal structure of minerals present in bone (Kurttio et al., 2005).

The excessive concentrations of NO₃^– (>50 mg/L) in shallow aquifers act as an indicator of anthropogenic contamination, as it primarily enters the aquifer through leaching from nitrogenous fertilizers, herbicides, pesticides, agricultural activities, untreated industrial waste products, and leachate from landfills, septic systems, and farms (Reddy et al., 2009). These anthropogenic sources could add NO₃^– to the aquifer system, resulting from nitrification. The consumption of NO₃^– contaminated groundwater can cause hypertension and reduce blood cells’ oxygen-carrying capacity, ultimately leading to methemoglobinemia (blue baby syndrome) in newborn babies (Zhang et al., 2018). However, NO₃^– is not carcinogenic; it becomes so after binding with secondary and tertiary amines in the gastrointestinal tract (Dan-Hassan et al., 2012).

Regarding arid and semi-arid climatic regions such as Rajasthan, Coyte et al. (2019) highlighted elevated concentrations of these contaminants amid prevailing adverse climatic conditions and water scarcity resulting from over-extraction. This study mainly focused on the occurrence, hydrogeochemistry, geogenic and anthropogenic contaminants and associated health risks. However, studies published by Mittal et al. (2017), Pandit et al. (2022), Rani et al. (2023), and Menaria et al. (2023) have emphasized health risks associated with U in various parts of Rajasthan. Still, the status of the synergistic health impact of tri-contaminants on the different age-groups persists as a gap and remains unclear. The lack of such studies encourages further research on groundwater contamination and its carcinogenic and non-carcinogenic effects, as well as radio-sensitive threats to various age-groups in groundwater-vulnerable regions. The current study focuses on F^–, U, and NO₃^– as key contaminants due to their co-occurrence in similar hydrogeological conditions, such as alkaline and oxidizing groundwater, through processes like rock-water interaction, leaching, and evaporation (Post et al., 2017). Moreover, drinking water guidelines overlook their combined risks, focusing on individual contaminants despite evidence of increased toxicity from co-occurring contaminants.

Therefore, the current study uses an integrated approach to investigate F^–, U, and NO₃^– status in groundwater, controlling processes, and associated health risks in different age-groups using the Monte Carlo simulation. An extensive health survey was also conducted to understand health impacts. Hence, this study provides valuable insights into the occurrence of contaminants, their geochemical controls, and potential health impacts. The current study stands out for its distinctive focus on a diverse population residing in both underdeveloped rural areas and well-developed urban regions, encompassing various economic backgrounds. The population’s active involvement in groundwater-dependent activities, such as extensive irrigation and industrial work, adds a unique dimension to the research. Moreover, the Central Ground Water Board in India (CGWB, 2023) classifies this region as critical for groundwater extraction, highlighting an urgent need for innovative studies. By employing a novel approach, this research aims to assess the contamination and potential impacts on the population within the context of their prevailing environmental conditions, offering fresh insights into risk assessment.