Fluoride contamination and water quality fluctuations in Mianwali District Pakistan and its implications for human health and sustainable agriculture

Abstract

This study offers a thorough evaluation of groundwater quality in the Mianwali region of Pakistan. A total 510 groundwater samples were collected from 176 government water supply facilities spread over three tehsils of the district. After that, the samples were examined for several Physio-chemical, and microbiological characteristics. The WHO standard level was surpassed by 35% of the samples collected for concentration of fluoride. According to the Fluoride Pollution Index (FPI) data, 68% of samples were classified as having moderate contamination, indicating a moderate presence of fluoride, while around 22% of samples fell into the low contamination group, signifying the fluoride concentration is within safe levels. It is noteworthy that 9% of the samples that were gathered had significant levels of fluoride contamination that were above the allowable limits for fluoride. The Gibbs plot analysis indicated that the overall control on groundwater chemistry in the study area is of rock types and evaporation. About 58% of the samples are affected by rock types and included significant contributions from minerals breakdown, chemical weathering of fluoride-rich rocks, showing high levels of fluoride. On the other hand, the remaining 41% of samples show the influence of evaporation: increased salinity and sodium levels are evident. The elevated fluoride concentrations in the groundwater sources pose health risks through dental and skeletal fluorosis to consumers consuming raw water. Moderate contamination, obtained for most samples, can also affect agricultural productivity by slowing down soil quality and crop uptake, hence entering the food chain. These results show clearly the importance of introducing effective and rational management of groundwater from the Mianwali region to protect human well-being and ensure sustainable water use.

Supplementary Information

The online version contains supplementary material available at 10.1038/s41598-025-89321-5.

Introduction

Fluoride contamination of groundwater has become one of most severe global public health and environmental concerns. Groundwater serves as the primary source of drinking water and irrigation in many regions, including Pakistan, where surface water resources are often scarce¹. In Pakistan, the agricultural sector is the engine of the economy and caters to a substantial working rural population. Groundwater is vital to support agricultural activity, especially in arid and semi-arid areas with low rainfall². Nevertheless, high levels of fluoride in groundwater lead to serious risks to human health, resulting in dental and skeletal fluorosis and other diseases³. The geochemical behavior of fluoride in groundwater is a critical factor in designing effective water management and response measures.

Fluoride concentrations in groundwater are influenced by a variety of factors, including mineral dissolution, evaporation, and anthropogenic activities⁴. The quality and quantity of groundwater are also shaped by geological, climatic, and human interactions, making it a dynamic and complex resource⁵. For instance, Devic⁶ emphasized that sustainable groundwater management requires a thorough understanding of these variables, as they directly affect both current and future generations’ access to safe water. Worldwide, groundwater constitutes about 99.97% of available fresh water, which is therefore a significant water supply for human use and agriculture, especially in developing countries⁷.

Groundwater is a life line for more than 50% of people in developing world regions, by means of shallow boreholes, wells and springs⁸. Carrard⁹ commented that in South America (around 150 million people) and Asia (1 billion) the majority depend significantly on groundwater, notably in areas where surface water is unreliabile, or even absent. Arid and semi-arid areas, e.g., Pakistan, are confronted with the problems of limited rainfall, high evaporation rates and increased water scarcity. As a result, excessive use has resulted in aquifer draw-down, saltiness, and contamination, thereby aggravating the water resource management of these regions¹⁰.

Pakistan is among the countries most vulnerable to water scarcity, with projections indicating that it may face severe droughts and a looming water crisis in the near future¹¹. The Mianwali district, in the arid and semi-arid region of Pakistan, represents phenomena of these types. Water shortages due to the scarcity of the surface water resources¹² make this area very dependent on groundwater for both domestic and crop production. Excessive groundwater extraction in the region has caused reduced water tables, aquifer depletion and strengthened contaminant susceptibility.

Under these conditions, it becomes very necessary to evaluate the groundwater quality in Mianwali district for a number of reasons. Specifically, the use of groundwater for drinking and irrigation requires an unambiguous assessment of its usability for these purposes. Second, groundwater contamination brings serious health threat, as it can cause transmission of waterborne diseases and ecological damage in a long term. Lately, over-pumping of groundwater carries out serious consequences such as land subsidence, and depletion of the groundwater aquifer with negative effects on crops yields and damage to ecosystem stability¹³. This study aims to address these critical issues by evaluating the geochemical behavior of fluoride in groundwater, identifying contamination hotspots, and providing recommendations for sustainable water resource management in the region.

Research question:

What are the levels and distribution of fluoride contamination in Mianwali district groundwater and their implications for the quality of drinking water, irrigation supply, and human health?

Reason for research:

Fluoride contamination, its possible impacts human and agriculture health has not been studied for whole Mianwali district, This study, therefore, arises from the fact that research in this area was minimum.

Aims and Objective of the Study:

1. To map the fluoride contamination in groundwater.

2. To evaluate the quality of groundwater for drinking and for agricultural use.

3. To evaluate health risk associated with fluoridated drinking water.

Materials and methods

Study area, hydrogeology, and sample collection

Mianwali district, which encompasses the three tehsils of Mianwali, Isa Khel, and Piplan, is situated in Pakistan’s Punjab province (Fig. 1). Geographically, Mianwali district is a bounded geographical area part of the Punjab province of Pakistan. The study area falls approximately between 32.573° to 33.520° latitude and 70.546° to 71.918° longitude. In this range, the coverage includes varied terrain as well as hydrogeological features that will be observed to influence the groundwater quality and availability across the district. The Salt Range is located to the north of this area, while the Indus River runs to the east. The Government of Pakistan’s Bureau of Statistics reports that its total area is 5,840 square kilometers, with1.057 million inhabitants (GOP, 2024). The regional Geological map is presented in Fig. 2. The study area mostly comprised of quaternary alluvium deposits (Farid et al., 2018).

Fig. 1.

Study Area and Sample Colleton sites.

Fig. 2.

Regional Geological Map with study area in red circle¹².

According to the Mianwali district profile of the government of Punjab, the study region’s climate is severe, having long, heated summers which typically runs from May to September, with an average temperature of 42° Celsius. June is the warmest month during the summer. The months from November to February are mild to cool in the region. December and January being the coolest months with temperature swings around 3 to 4 °C.

Hydrogeology of Mianwali district is marked by the presence of alluvial deposits¹¹. These accumulations are mostly made up of clay, silt, and sand. The main aquifer system in the district of Mianwali is an unconfined alluvial aquifer. Such an aquifer feeds mainly through various sources, which include precipitation mainly in the form of rain, and collection of surface water from rivers and streams and runoff from practices related to irrigation for agriculture. (Fig. 3).

Fig. 3.

Land Use and Land Cover Map of Study Area.

Water quality analysis was performed on samples following the PCRWR laboratory’s procedures and adhering to standard analytical procedures. For this purpose, 510 samples were collected from 176 water systems in October and November (2022/23) ( including Government water supply schemes, boreholes for drinking water, hand pumps) present in three tehsils: Mianwali, Isa Khel, and Piplan. Each sampling location is determined by GPS shown in Fig. 1a. A total of 510 water samples was collected solely from groundwater sources, such as 176 different water supply schemes, boreholes, and hand pumps intended for drinking. Samples were collected systematically from the source of origin (borehole, hand pump, etc.) down to the ultimate consumer for possible variations in chemistry along the distribution system. No significant changes of water chemistry in the supply chain were found, thus allowing the mean values from each source to be used for analysis purposes.

Boreholes and hand pumps selected for sampling have depths of generally varying between 50 and 300 m, depicting the groundwater extraction practices in the district of Mianwali. Surface water sources like rivers, streams, or dug wells were excluded from this study to narrow down the analyses to the quality of water. In alignment with Cutter et al., (2017) on Sampling and Sample-handling methods. The containers were treated 10% solution of nitric acid and cleaned with distilled water. The samples were collected after a ten minutes pumping duration and placed in high-quality polyethylene containers of 1000 ml capacity. All samples were transported directly to the lab for analysis. The study used the combination of standard methods and sophisticated instruments to analyze groundwater samples with regard to various key parameters critical for understanding water quality. Electrical conductivity, pH, and total dissolved solids were measured carefully using a portable digital conductivity meter and a precision pH meter. Atomic absorption spectrophotometry was used to test the existence of critical cations, including potassium, sodium, and iron. The method is highly accurate for analyzing trace metals, where even trace amounts can be estimated with absolute precision. Samples from all the groundwater collected during the testing process were preserved in cool temperature at 4 °C so that no shifts in their chemical composition occurred during the process of analysis. In addition to cations, the anions like fluoride, phosphate, sulfate, nitrate, bicarbonate and chloride concentration was determined by using microtitre plates with the aim of further enhancing the speed and precision of the tests carried out. All tests were carried out in Pakistan Council of Research in Water Resources (PCRWR) Laboratories. The laboratory of the Pakistan Council of Research in Water Resources, PCRWR conducted the testing of water samples. PCRWR uses analytical techniques that are in line with international practices and relies more frequently on methods established by the American Public Health Association, APHA as outlined in the “Standard Methods for the Examination of Water and Wastewater.” In comparison to APHA standards, PCRWR laboratory standard procedures are mainly near the best practices around the country, whereby ensuring accuracy and reliability in the analysis procedures. The procedures are aimed at making data scientifically sound and comparable with international studies.

Geostatistical analysis

The groundwater lab results were analyzed for the Mianwali region using Microsoft Excel to measure ion proportions and compare results to World Health Organization standards¹². The Gibbs and Piper diagrams were utilized to study ion distribution and categorize samples into five groups based on geochemical processes. The Gibbs diagram explains the effects of varied processes on water chemistry between rocks and water. The Piper trilinear diagram has a diamond shape at its center; along with its two sides, there are two triangles whose ends represent cations and anions. Key factors affecting water chemistry include evaporation and climate variations.

Water quality index

Water quality index WQI was first suggested by Horton¹³, is an effective and efficient method for determining and forecasting the overall quality of water bodies, particularly groundwater, intended for human use to ascertain its safety¹⁴. Water quality of drinking water was subsequently determined as compared to drinking quality standards set by WHO¹⁵. WQI refers to the permissible limits of the water quality parameters as specified by the World Health Organization (WHO) in its 2017 Guidelines for Drinking-water Quality. These are essentially international standards, widely accepted and recognized for evaluation of drinking-water suitability^16,17.

The Water quality index was calculated in Table 1, and the information was determined according to Eq. 1.

1

Table 1.

Illustrating the District Mianwali groundwater’s water quality index (WQI).

S. No	WQI	No of Samples	% of Samples	Property
1	0–25	86	17	Excellent
2	26–50	330	65	Good
3	51–75	58	11	Poor
4	76–100	16	3	Very Poor
5	> 100	20	4	Worse

The “n” shows the number of variables or parameters. Every one of the ‘n’ water high-quality parameters had been given the sub-index or first-rate ranking as ‘Qn’ while “Wn” represents it as a unit of the burden of the “n” parameter. For this reason, the unit weight of each water high-quality parameter “Wn” is inversely connected with the designated widespread for every parameter.

2

Where, the unit weight given to the “n” parameter *is represented *by “Wn” *and the adopted values of the “n” parameter follow on “S”. The “n” unit of measure is also the proportionality constant; in this case, the value is 1.

3

The values assigned to each variable Snandthe minimum concentration threshold of ground water to drinking limits ‘Cn’ as illustrated bythe world health organization were, then used to evaluate Qn.

4

Lastly, as demonstrated by the studies of Khan and Jhariya¹⁸, Rabeiy¹⁹ and Boateng²⁰, the water quality index was determined utilizing “Qn” along with “Wn” following Eq. 1.

5

Assessment for irrigation purpose

To determine whether water is suitable for irrigation, its chemical composition must be considered as it affects the soil and vegetation. The number of ions present in water can be determined through five measurements: electrical conductivity (EC), soluble sodium percentage (SSP); permeability index; magnesium hazard (MH); and Kelly’s Ratio. The total salt concentration is also estimated by these measurement indicators. In the case of Na ⁺, although the solution is a basic, it is possible to suppose that considerable proportions of Ca and Mg also contribute. The sodium adsorption ratio measures whether Ca^{2 +} and Mg^{2 +} would help to make the soil, and often the irrigated areas of fields, virtually free of Na⁺²¹. This ratio is calculated using formula 6.

6

Kelly’s relatively simple algorithm for determining salinity levels in groundwater is based upon correlation of sodium content with the percentages of magnesium and calcium²². Through chemical reactions with calcium and magnesium, excess sodium produces harmful chemicals that affect the growth of plants and the quality of water²³. Equation 7 is used to determine KR.

7

Salinity can be determined as the ratio of potassium and sodium to calcium along with magnesium. High sodium as well as potassium concentrations cause calcium along with magnesium ions to be displaced, which hinders the flow of water²⁴. Equation 8 is used to measure the sodium percentage.

8

By comparing calcium and magnesium contents, the Magnesium Hazard establishes salinity levels. Water with high magnesium-to-calcium ratios may have a higher pH²⁵. Equation 9 is used to compute the Magnesium Hazard.

9

The sodium soluble percentage (SSP) evaluates salinity levels through a comparison of the concentrations of sodium, calcium, and magnesium²⁶. According to Wali²³, plants tissue and leaves may burn as a result of contagiousness caused by excessive sodium levels relative to calcium and magnesium.

10

Elsayed²⁷ states that PI is necessary to assess irrigation water quality in terms of soil permeability and that is affected by Na⁺, Ca²⁺, Mg²⁺, and HCO₃⁻ concentrations. Equation 11 is used to estimate the water circulation in the soil.

11

Health risk assessment

The study investigated potential health risks to humans linked to drinking water contaminated with fluoride. Its goal is to detect non-harmful health hazards induced by high concentration of fluoride in water for consumption^28–30. Taking into consideration the fluoride excretion from water consumption, the average daily consumption of fluoride from drinking water was measured in milligrams per day (mg/kg/day). Equation 12 is used in the computation to get the average daily dosage (ADD).

12

In this case, the parameters are as follows: The variables that determine the fluoride concentration in a sample are C (milligrams/liter), EF (exposure frequency), ED (exposure duration) (30 years for adults, 12 years for children), BW (average body weight; 70 kg for adults, 15 kg for children), and AT (average exposure time). Equation 13 was then used to determine the risk quotient (HQ):

13

The recommended daily intake of fluoride in water for consumption is known as RFD (0.06 mg/kg). Samples with HQ less than one (HQ < 1) are safe to drink. Water samples with HQ more than one (HQ > 1) are potentially harmful to health and have too much fluoride in them for safe consumption.

Fluoride pollution index (FPI)

Fluoride pollution of ground water is a serious threat in many parts of the world one such region is Mianwali¹¹. To construct the Fluoride Pollution Index (FPI), Eq. 14 adds together groundwater proportions of bicarbonate, pH, sodium/calcium ratio and fluoride, each of which is weighted accordingly according to Haji et al., (2021). The Fluoride Pollution Index (FPI) ranges from 1 to 2, indicating minimal pollution³¹. A value of 3 or more, on the other hand, indicates that levels are at least ‘medium’ polluted. Equation 14 serves as an instrument to create the Fluoride Pollution Index (FPI)³².

14

The fluoride can ideally be expressed as “W_F”, or the weight concentration. WHCO₃₋represents the concentration of bicarbonate by weight. As the ratio of sodium to calcium is expressed through symbols in Section 25 of Chinese Electrochemical Standards, W Na⁺/Ca²⁺.The pH scale is demonstrated through symbol WpH, where the sign N denotes the overall quantity of parameters (4 in this example). The FPI values that were obtained offer a numerical evaluation of the level of fluoride contamination in the groundwater of District Mianwali.

Results and discussion

According to a thorough examination of the samples collected in study area, in collected groundwater samples, the average pH was 7.94., and the majority of them fell between 7.7 and 9.05, which are acceptable ranges. Out of the 510 water samples, 474 samples (92.9%) were below the recommended range, and 36 samples (7.1%) exceeded the WHO guideline limit. TDS levels varied greatly, between 3 and 12,224 mg/L, with an average of 983.03.of these cases, 41.2% (210 samples) were over the WHO standard level, whereas 58.8% (300 samples) fell within acceptable bounds. Notably, 41.17% of the Mianwali district’s water tests were determined to be brackish, while 58.83% of the samples were allocated as fresh water. Groundwater fluoride concentrations ranged between 0.02 and 5.35 mg/L, with 35.1% (179 samples) exceeding WHO recommended limit of 1.5 mg/L while 64.9% (331 samples) being below the permissible range. Out of 236 samples, 58.5% (138 samples) in Isakhail tehsil had fluoride, whereas 16% (41 samples) of 255 samples in Mianwali exhibited concentrations of fluoride above the 1.5 mg/L WHO recommended limit for water consumption. Significant elements that are closely related to water hardness can be found in groundwater, including high quantities of calcium and magnesium. Calcium levels ranged from 4 to 400 mg/L; 98.1% (500 samples) fell within the permissible range, while 10 samples, or 1.9%, were beyond the 300 mg/L WHO recommended limit.Magnesium concentrations ranged from 5 to 403 mg/L, with 7.1% (36 samples) above the 150 mg/L WHO recommendation limit and 92.9% (474 samples) below it.

The range of sodium (Na⁺) values was 2 to 1050 mg/L; of these, 69.4% (354 samples) were within the permissible range, while 30.6% (156 samples) exceeded the 200 mg/L WHO guideline limit. Potassium (K⁺) values ranged from 0.6 to 112 mg/L; 444 samples (87.1%) fell within the permissible range, while 66 samples (12.9%) surpassed the WHO guideline limit of 10 mg/L. Concentrations of bicarbonate (HCO₃⁻) varied from 20 to 760 mg/L; of these, 85.3% (435 samples) were within the permissible range while 14.7% (75 samples) exceeded the 350 mg/L WHO standard limit. The amounts of chloride (Cl⁻) varied from 7 to 2616 mg/L; 91.9% (469 samples) fell below the permissible range, while 8.1% (41 samples) exceeded the 250 mg/L WHO guideline limit. The samples exhibited sulphate values varying from 8 to 2735 mg/L, of which 67.8% (346 samples) were within the permissible range and 32.2% (164 samples) exceeded the 400 mg/L WHO standard limit. The values of NO₃⁻ and CO₃ are 100% within the WHO’s recommended limits. TDS levels in groundwater are greatly impacted by sulphate content. Isa Khel has the highest sulphate concentration 50.4% (119 samples) out of 236 samples, while in Mianwali 17.6% (45 samples) out of 255 samples exceeds the WHO standard limit. Arsenic is commonly found in ferrous coal, shale, and clay, as well as in geothermal areas.

Its concentration in 14 samples from Isa Khel and 24 samples from Mianwali ranged from 0 to 25 µg/l. Of these samples, 39 samples (or 7.6%) surpass the recommended limit of 10 µg/l by WHO, while 92.4% (471 samples) fall below the permissible range. The range of phosphate values is 0 to 1.13 mg/l, with 99.6% at the recommended limit and 0.4% over the 0.3 mg/l WHO guideline limit. Phosphate produced by the decomposition of phosphate rocks is usually poorly soluble and binds to soil particles.

Water quality index (WQI) analysis

There are five ranges for the Water Quality Index (WQI) values: 0–25, 26–50, 51–75, 76–100, and more than 100. The following categories are represented by: Very Poor, Excellent, Good, Poor, and Worse. The Table 1 also shows the percentage of samples that fall into each WQI category. According to WQI, 17% of samples are of excellent standard (0–25), while 65% of samples are classified as good (26–50). Additionally, 11% of the samples were categorized as poor (51–75), and just 3% as extremely poor (76–100). Lastly, 4% of samples (> 100) show even worse quality.

Groundwater hydrochemical facies

Determining the flow patterns and chemical sources of groundwater requires understanding its geochemical makeup. One of the most critical techniques is hydrochemical facies analysis, which explains the sources and classifications of water types. In this study area a Piper three-line diagram was used to establish the hydrochemical facies, which classifies and distinguishing between diverse types of water. The Piper diagram comprises two triangles denoting the concentration of anions and cations. A middle diamond indicates a summary of groundwater features. Based on the Piper plot, the predominant water samples display the mixed types Ca²⁺-Mg²⁺-Cl⁻, Na⁺-Cl⁻-SO₄²⁻, and Ca²⁺-HCO₃⁻, as well as the mixed types Ca²⁺-Na⁺-HCO₃⁻ and Ca²⁺-Cl⁻.

The Cation triangle analysis shows that the majority of the samples fall into areas B, which represents the no dominant species, D representing sodium forms. There are few samples in regions A representing calcium forms and C representing magnesium forms. The anion triangle analysis indicates that most samples are found in section F, representing sulphate type, B, representing non-dominant type. Additionally, a few samples can be found in region G representing chloride type, and approximately few can be found in region E showing bicarbonate type. In the Piper diagram, the interaction between cations and anions shows this region to have high sodium and sulphate concentrations. The deviation may be linked to several factors including weathering, evaporation, silicate breakdown in rocks or soils, and human activity (Fig. 4).

Fig. 4.

Piper diagram representing groundwater of District Mianwali.

Groundwater chemistry mechanisms

To base adequacy of such resources for irrigation and domestic use, an investigator first needs to understand their chemical composition. Using Gibbs diagram proposed by Gibbs, the main variables influencing groundwater chemistry can be identified. For this purpose, one should use the Gibbs diagram, which is a plot of the ratios of some anions and cations as vs. total dissolved solids (TDS) respectively. As observed in Fig. 5, Gibbs diagrams of the research area reveal that a significant proportion of groundwater samples exhibit predominant lithology and evaporation features. Specifically, 58.8% of analyzed samples were attributed to the predominant lithological category. This shows that there is continuous mineral dissolution and chemical weathering occurring in the rock requite. According to Kaur³³ fluoride toxicity in groundwater is likely sourced from interaction of water with closely associated fluoride-containing minerals in local aquifers. Conversely, evaporation, which is mostly due to sodium, was predominant in roughly 41.2% of the samples and leading to increase salinity levels through the accumulation of dissolved solids. The lithological and evaporative characteristics of groundwater samples are influenced by anthropogenic activities and urbanization, which also lead to high dissolved solids concentrations.

Fig. 5.

illustrating the Gibbs Diagram. (a) Cations, (b) Anions.

Water quality indices analysis

Assessment of groundwater quality indices for irrigation

Plant development depends on the minerals soil as well as the soil’s capacity for drainage, which are connected to irrigation water appropriateness. Poorly drained regions may result in poor water quality, although well-drained soil can sustain plant development even in the presence of salt water. Parameters like EC, SAR, PI, KR, SSP, and MH, together with their categorization, serve to emphasize the evaluation (Table 2). According to Richard’s (1954) classification of sodium adsorption ratio values, 97.65% of the collected samples are excellent and remaining samples are good, meaning that there is no risk of alkaloid exposure to crops (Figure S1; Supplementary Material). Kelly’s ratio values vary from 0.08 to 12.98 meq/L, and the categorization indicates that 67.65% of the collected samples are suitable for irrigation (Figure S2; Supplementary Material). Elevated sodium levels harm plant development and soil salinity. When assessed solely based on sodium content, 45 samples were excellent, 359 samples were satisfactory or acceptable, and 106 samples were questionable or insufficient (Figure S3; Supplementary Material). The magnesium hazard values, with an average of 56.31, show that 71.17% of the collected samples are not suitable for irrigation. Based on sodium soluble percentage, 10.9% of the samples meet outstanding criteria, 30% meet good standards, 55.2% meet acceptable standards, and 3.9% are unsuitable for irrigation. Permeability index typically indicates that the ground water of district Mianwali are appropriate for irrigation (Figure S4; Supplementary Material).

Table 2.

Water quality assessment for Irrigation.

S. No	Sodium Adsorption Ratio	Water Quality	Total samples	%age
1	< 10	Excellent	498	97.65
2	10–18	Good	12	2.35
3	18–26	Doubtful	Nil	Nil
S No	Kelly’s Ratio
1	< 1	Suitable	345	67.65
2	> 1	Unsuitable	165	32.35
S No	Sodium Percentage (Na%)
1	< 20	Excellent	45	8.83
2	20–40	Good	147	28.83
3	40–60	Permissible	212	41.57
4	60–80	Doubtful	85	16.67
5	> 80	Unstable	21	4.1
S No	Magnesium Hazards
1	< 50	Suitable	147	28.83
2	> 50	Harmful	363	71.17
S No	Sodium Soluble Percentage
1	< 20	Excellent	55	10.9
2	20–40	Good	153	30
3	40–80	Fair	282	55.2
4	> 80	Poor	20	3.9
S No	Permeability Index
1	> 75%	Suitable	115	22.55
2	25 – 75%	Good	382	74.90
3	< 25%	Unsuitable	13	2.55
S No	Electrical Conductivity
1	< 250	Excellent	11	2.16
2	250–750	Good	70	13.73
3	750–2250	Permissible	351	68.83
4	2250–6000	Very high	75	14.70
5	6000-10,000	Extremely high	3	0.58

Fluoride concentration in the Mianwali district:

Concentration of fluoride in the Mianwali district have a standard deviation of 1.29 mg/L and vary between 0.02 and 5.35 mg/L (Table 3).The WHO recommended level of 1.5 mg/L is exceeded by 35.1% of the samples (179 samples), whereas 64.9% (331 samples) are within the acceptable range. Separately, 236 samples were obtained in Isa Khel, of which 58.5% (138 samples) had fluoride; similarly, 255 samples were collected in Mianwali, of which 16% (41 samples) contained fluoride, exceeding the WHO recommended limit. Most groundwater samples from the research region were dangerous due to their increased fluoride concentrations. The level of fluoride pollution observed in this study greater than that reported in Zaid²⁸.

Table 3.

The concentration of fluoride in groundwater of District Mianwali and its impact on human health⁴⁰.

Classes	Fluoride concentration mg/L	Samples	%age	Effects on human health
C 1	< 0.5	126	24.71	Resistive to cavities in the teeth
C2	0.5–1.5	205	40.19	Stimulates the growth of healthy teeth and bones
C 3	1.5–2.5	115	22.55	Fosters kids’ dental fluorosis
C 4	2.5-4.0	62	12.15	Fosters youngsters’ fluorosis of the teeth
C 5	0.4-5.0	-	-	Increased skeletal and tooth fluorosis
C 6	5.0–10	2	0.4	Fosters the severe skeletal fluorosis
C 7	> 10	-	-	Severe fluorosis of the skeleton and even cancer
HQ	Range	Class	Percentage
	< 1	Safe	80.57%
	> 1	Unsafe	19.43%

Salinity hazards (EC)

The Wilcox plot (Fig. 6) and USSL plot (Fig. 7), generated using Python, shows the relationship between sodium content and EC, indicating moderate suitability for plant growth. Most samples are in the good or acceptable range, while others are rated as excellent, good, questionable, or inadequate.

Fig. 6.

Groundwater classification, based on EC and Sodium percentage³⁸.

Fig. 7.

Groundwater sample classification based on sodium and salinity hazards³⁹.

Health risk evaluation for children and adults concerning fluoride exposure.

Reducing the risk of dental decay can be achieved by limiting fluoride consumption, which is crucial for tooth protection³⁴. According to Dehghani³⁵, adults require fluoride to prevent tooth decay, whereas children require it to safeguard their developing teeth. Nonetheless, human teeth and bones might be harmed by consuming high amounts of fluoride-contaminated water (> 1.5 mg/L). Long-term consumption of fluoridated water can lead to neurotoxicity, skeletal toxicity, joint discomfort, and an increased risk of bone fractures³⁶. Dissanayake³⁷ divided water into various groups based on the amount of fluoride present and how it affected dental and skeletal fluorosis. As indicated in Table 3, water samples gathered from the research region are divided into seven groups based on the effects of fluoride and its concentration. All collected samples were distributed into seven classes for Health Risk Assessment (Fig. 8a). The hazard quotient values for all samples were determined; those exhibiting an HQ > 1 are deemed potentially hazardous to the health of the local population (Fig. 8b).

Fig. 8.

Spatial Distribution Maps for Health Risk Assessment in District Mianwali. (a) Fluoride Concentration Map (b) HQ Map.

Fluoride pollution index analysis

The study area’s groundwater quality can be determined primarily by analyzing the Fluoride Pollution Index (FPI). A total of 510 samples were collected; of these, 115 samples (22.55%) fall into the low contamination category, indicating that the proportion of fluoride is within permissible limits. Of the 348 samples, the majority (68.24%) had moderate contamination, meaning that there was moderate fluoride present (Fig. 9). It is worth noting that 46 samples (9.02%) showed a high level of contamination exceeding the permissible limits for fluoride (Table 4). The spatial distribution map shows the pollution index, with light blue areas indicating low fluoride concentrations within acceptable limits, and blue color areas indicating medium fluoride concentrations while light green areas show high fluoride contamination above acceptable limits. Based on these findings, specific treatments and regulatory actions are desperately needed to lower concentration of fluoride in district Mianwali while preserving environmental as well as public health (Fig. 10).

Fig. 9.

Fluoride Concentration of studied samples in District Mianwali with maximum allowed concentration.

Table 4.

Groundwater classification referring to the Fluoride Pollution Index (FPI) and fluoride risk index (FRI).

Fluoride Pollution Index (FPI)
FPI Scales (mg/L)	Category	No of Samples	Percentage of Samples
1–2	Low	115	22.55
2–3	Medium	348	68.24
3–4	High	46	9.02
Fluoride Risk Index
Fluoride Concentration (mg/L)	Risk Category	No of Samples	% of Samples
≤ 0.49	Very Low	126	24.71
0.50–0.99	Low	117	22.94
1.00-1.49	Moderate	87	17.06
1.50–1.99	High	70	13.73
2.00-2.49	Very High	44	8.63
> 2.49	Extremely High	66	12.94

Fig. 10.

Fluoride Pollution Index (FPI) map of District Mianwali.

The spatial distribution map of fluoride concentration, Fig. 8a, and the Fluoride Pollution Index, FPI, map, Fig. 10, are different since these two represent various aspects of the impact of fluoride in the study area. Fluoride concentration map, Fig. 8a, shows the measured concentration values of fluoride in the groundwater direct across the region. On this map, a picture of where concentrations are high, medium, or low is presented based on mere data observed. On the other hand, the FPI map (Fig. 10) is a composite index integrating not only fluoride concentration but also parameters influencing the behavior of fluoride, including groundwater chemistry, TDS, and potential health risks. Calculated in a form of integrated indices, the FPI reflects overall risks in pollution associated with fluoride, which may include moderate concentrations in certain areas but has significant cumulative effects from other factors.

Therefore, this discrepancy appears only because the FPI is a far broader indicator of the environmental and health impacts of fluoride than mere concentration. The manuscript could then clarify its explanation to the reader about these two maps and their different purposes.

Discussion

According to the digital elevation model (Fig. 11), it found significant concentrations of fluoride in groundwater samples around the elevations, probably due to geological processes and hydrological dynamics. Higher elevations act as recharge zones because water from higher elevations displaces groundwater. As the water flows downward, it combines with fluoride-rich minerals, releasing fluoride ions into the groundwater. Slowed water circulation at high altitudes prolongs this process, allowing more fluoride to be produced.

Fig. 11.

Show Digital Elevation Model and Fluoride Concentration Map of Mianwali.

To address the health implications of fluoride exposure, it is crucial to distinguish the exposure effect on adults and children since there exist physiological responses and vulnerability differences between them. Children are more vulnerable to fluoride exposure because their body weights are minimal, their water intake compared to their body weight is high, and their skeletal and dental parts are still developing. Chronic exposure in children may result in dental and skeletal fluorosis, depending on the concentration and duration of the fluoride content.

Adults are less susceptible to developmental effects but have long-term consequences through skeletal fluorosis and pain because of stiffness, due to high levels of fluoride exposure. Calculations of ADD and HQ show that children have a usually greater quotient due to higher intake in comparison to body weight.

High fluoride contamination in water can significantly impair agriculture by impacting the health of the soil and crop productivity. Excess fluoride in irrigation water can accumulate in soil, thereby changing its chemical compositions leading to toxicities that affect plant growth. Fluoride ions can trigger interference with the normal intake of necessary nutrients such as calcium, magnesium, and phosphorus, reducing yields and quality in crops.

Some plants are more sensitive to fluoride, and high concentrations are known to cause symptoms such as chlorosis and necrosis of the leaves and stunted growth. In addition, improper use of water contaminated with fluoride can lead to soil accumulation of high toxic levels that may not only threaten the crop existing in the soil but also reduce the quality of the soil for future farming practices. Addressing this problem requires a search for alternative water sources, changes in soil management practices, and possibly employing water treatment solutions to reduce fluoride levels before irrigation.

Conclusion

Overview of Groundwater Quality: A comprehensive appraisal of the groundwater quality for Mianwali district, Punjab, has been carried out focusing on the fluoride concentration and its associated potential impact on both health and agriculture.

Fluoride Contamination: In this study, 35.1% of the groundwater samples exceeded the WHO-recommended fluoride limit of 1.5 mg/L, implying that the presence of fluoride contamination in the studied region is a serious matter as it poses a potential risk to health.

The other critical water quality parameters evaluated, besides fluoride, were TDS, calcium, magnesium, sodium, and bicarbonate. Most samples were within permissible limits, but certain parameters, such as TDS and sodium, were above the recommended limit for a significant proportion of samples.

Health Effects: High fluoride concentrations may cause dental and skeletal fluorosis, although this will heavily impact children since they consume more water per body weight compared to adults. Adults may suffer from some joint and skeletal disorders after long-term exposure.

Agricultural Concerns: Excessive levels of fluoride in water will again negatively affect agricultural productivity and soil health. Fluorides in soil can retard nutrient uptake in plants, thereby affecting crop yield and quality.

Recommendations: Based on the findings, it is crucial to implement measures to reduce fluoride contamination, such as alternative water sources, water treatment technologies, and awareness programs. Further studies should also assess the health impacts of fluoride exposure in the region.

Limitations and Future Research: The study was more water quality-focused with no inclusion of direct health impacts on the population. Future research should include epidemiological studies in testing health effects from exposure to fluoride and working towards mitigation interventions for such affected communities.

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Electronic supplementary material

Below is the link to the electronic supplementary material.

Author contributions

Faisal Rehman (First Author), Zahid Ullah (second Author) and Tahir Azeem (Third Author) did conceptualization, methodology, and writing original draft. Jamil Siddique (Fourth Author), Omar Riaz (Fifth Author), Rahima Ali Hashmi (Sixth Author) did analysis and editing for manuscript. Faisal Rehman (Seventh / Corresponding Author) and Shaheed Ahmad (Last Author) did technical revisions for write up of draft manuscript and finalized it. All authors reviewed the manuscript.

Data availability

All data generated or analyzed during this study are included in this published article [and its supplementary information files Table S 1 and Table S 2].

Declarations

Competing interests

The authors declare no competing interests.