Extreme exposure of fluoride and arsenic contamination in shallow coastal aquifers of the Ganges delta, transboundary of the Indo-Bangladesh region.

3.6. Health risk assessment (HRA)

GW quality analysis and corresponding health risk assessment become a very significant concern in recent times due to the increasing nature of pollutant day by day. Therefore, our study is notably based on these emerging issues and also gets remarkable results regarding adults and child health who have significant contact with contaminated GW through ingestion and dermal contact, which puts them in severe non-carcinogenic disease. Our study shows how a large number of people, irrespective of adults and children, experienced several health issues due to the input of arsenic and fluoride through different pathways. The derived result in Fig. 9A interprets, the adults of a large part of the middle area along with eastern portion of our considered study region are experiencing very high non-cancer-causing wellbeing issues by reason of As consumption along with cutaneous exposure; high degree of health issues also found in the entire eastern region in a scattered way. Whereas children are less affected compared to adults, a spatially central region of this study area falls under very high non-carcinogenic disease-affected areas (Fig. 9B); a significant portion of the western parts for both adults and child falls under the low and very low affected areas. In the case of fluoride-related disease, the people of the eastern and north-eastern regions, both adults and children (Fig. 9C and 9D) are experiencing significant health issues due to fluoride ingestion and contact by dermal pathways; the rest of the study area experienced very low and low non-carcinogenic health issues whereas, some part of central region (Fig. 9C) and extensive part of southern region (Fig. 9D) is witnessed with moderate health problems.

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Fig. 9. Health risk map of study region: (A) As affected areas for adults, (B) As affected areas for children, (C) F^– affected areas for adults, (D) F^– affected areas for children.

4. Discussion

The pollution of the GW aquifer is rapidly increasing in recent years due to man-induced activities along with different geogenic reasons across the world (Rao et al., 2017). Developing countries like India and Bangladesh are exceptionally struck by extreme F^– and As GW pollution, which badly impacts the quality of GW, GW ecosystem, physical wellbeing of humans, and development status of humans (Rezaei et al., 2019, Akhter et al., 2023, Patel et al., 2023). The deltaic and coastal GW aquifers throughout the world are contaminated with different trace elements by anthropogenic activities, which has caused various chronic waterborne diseases (Wei et al., 2022). Higher concentration and accumulation of unwanted trace elements in excessive quantities diluted the GW aquifers and made them harmful for consumption. Thus, the availability of fresh drinking water areas has declined at an alarming rate throughout the world in the last few decades. The high growth of population coupled with decreasing potential good quality of GW sources put tremendous pressure on GW aquifers at a global level. Intake of polluted GW in daily basis caused different carcinogenic and non-carcinogenic prolonged diseases in the GW vulnerable regions. GW played a crucial role in fulfilling the demand for potable drinking water in most countries worldwide. Every shallow as well as deep GW aquifers have to be monitored at global scale regularly for maintaining the GW quality. The physical condition of the common people and environmental sustainability could be maintained through the application of regular monitoring of GW wells and implementation of various management measures (Karunanidhi et al., 2022, Zhang et al., 2022a). Several conventional methods along with geospatial tools, machine learning methods and statistical approaches employed in the field of GW quality measurement in different coastal belts across the world (Emenike et al., 2018, Narsimha and Rajitha, 2018, Wagh et al., 2020).In this study, we have evaluated the GW quality and overall health status of the Indo-Bangladesh delta region’s residents by adopting EWQI and HRA. The findings of the previous research articles (Ahmad and Khan, 2015, Murshed and Kaluarachchi, 2018, Everard et al., 2019, Mandal et al., 2019, Sharma et al., 2019, Hermans et al., 2022) successfully assessed the condition of GW and possible health risk in this region. The vulnerability of F^– and As exposure was identified through some related GW pollutants collected from the Indo-Bangladesh delta region. It is crystal clear from the WQI map that the eastern, southern, middle and south eastern part of the Indo-Bangladesh delta region suffers from poor GW quality issues, which severely impacted different human body organs. Besides adults in this region, children are brutally attacked by various sorts of non-carcinogenic life-threatening disorders each year due to consuming extremely poor GW. The maximum part of the study region experienced very poor GW quality and high to very high-risk zone for human health in both dry and wet periods. Almost 55% of the Indo-Bangladesh delta region GW is unsuitable for cultivation and consumption.The current research work focused on prediction of possible health risk status of the people as a result of consuming polluted GW in the Indo-Bangladesh delta region. In this purpose, we have considered 16 GW contaminants for analysing the GW quality and its possible impact on human body. Apart from these conditioning factors, several other components have greatly influenced the GW quality of any region of the world, namely – geological structure, lithological formation, pattern of land use and land cover, amount of acid rainfall, leaching and percolation rate, runoff, nature of parent rock etc. which were not considered for this study. Although the collection of water samples is a challenging task for the researchers thus, the number of samples is small compared to the vast extent of the entire study area; in our study, we have predominantly focused on drinking water quality and its related health issues but not focused on surface water quality. Those could be a limitation of the study to evaluate the GW quality and forecast the human’s physical condition in the Indo-Bangladesh delta region. This region is significantly contaminated in both GW and surface water; therefore, future researchers can conduct intensive research on surface water vulnerability by developing new methods and approaches and health impacts by correlating both water sources. Despite these drawbacks, the current research work efficiently measured and evaluated the GW quality condition along with possible human health issues in the Indo-Bangladesh delta region as a result of elevated exposure to toxic F^– and As contamination and also demonstrated that a significant area of the IBDR has been significantly facing extremely poor GW quality, environmental concerns, and several health-related issues in both the dry and wet seasons, respectively, for As and F^– exposure. Policymakers will benefit from knowing this information when making agricultural decisions in the future.