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. 2025 Jul 1;15:22036. doi: 10.1038/s41598-025-04761-3

Evaluation of drinking water quality and health risk assessment in rural primary schools along the Thai Myanmar border

Kezang Choda 1, Sirirat Sangkarak 1, Pannamas Maneekan 2, Pattaneeya Prangthip 3, Suda Ittisupornrat 4, Numfon Eaktasang 5, Suthirat Kittipongvises 6, Jenyuk Lohwacharin 7, Athit Phetrak 1,✉
PMCID: PMC12214613  PMID: 40594224

Abstract

Safe drinking water in schools is important for students’ health. Despite the presence of water treatment systems in rural schools, systematic monitoring and evaluation of drinking water quality are often insufficiently integrated into risk assessment frameworks, potentially compromising student health. In this study, a cross-sectional survey was conducted using drinking water samples from rural primary schools along the Thai–Myanmar border in Kanchanaburi, Thailand, aiming to evaluate the quality of drinking water in terms of physicochemical and bacteriological parameters and assess the health risks to students. A total of 52 drinking water samples were collected for water quality analysis. Among these, approximately 42% (n = 22) of these collected samples did not comply with Thailand’s recommended limits of drinking water quality. Among the noncompliant samples, total coliform bacteria were detected in 59% (n = 13), fluoride concentrations exceeded the permissible limit of 0.70 mg/L in 18% (n = 4), and arsenic levels surpassed the recommended limit of 10 µg/L in 9% (n = 2). These contaminants may pose a potential health risk to students. Health risk assessments indicated that, although the majority of hazard index (HI) and cancer risk (CR) values were within acceptable limits (HI < 1; CR between 1 × 10⁻6 and 1 × 10⁻4), the 95th percentile values exceeded these thresholds, suggesting potential health risks for students consuming the contaminated water. To mitigate health risks associated with contaminated drinking water in rural primary schools, the implementation of effective water treatment systems, coupled with routine monitoring of drinking water quality and proper maintenance, is recommended. However, this study has some limitations, including a restricted geographic coverage and reliance on generalized exposure parameters, which constrain causal inferences between contaminant exposure and health outcomes. Future research should expand the study area and incorporate region-specific behavioral data to more comprehensively assess chronic exposure risks and the effectiveness of intervention strategies.

Supplementary Information

The online version contains supplementary material available at 10.1038/s41598-025-04761-3.

Keywords: Arsenic, Drinking water, Fluoride, School health, Thai–Myanmar border

Subject terms: Environmental sciences, Risk factors

Introduction

Access to safe drinking water is essential for protecting public health and promoting overall wellbeing1. However, biological and chemical contaminants can enter water sources through various activities, leading to the deterioration of water quality2. Biological hazards include pathogenic microorganisms such as Escherichia coli, which can contaminate water supplies via sewage leaks, agricultural runoff, and inadequate sanitation, resulting in gastrointestinal illnesses3. Chemical hazards, such as arsenic, lead, and fluoride, are often introduced through natural deposits and industrial processes4. The presence of these substances in water poses serious health risks, particularly for children5.

Children generally require higher-quality drinking water than adults because their developing organ systems and weaker physiological defenses make them more vulnerable to harmful substances6. Considering that children consume a considerable part of their daily water intake in school, where they spend a substantial portion of the day7, providing safe drinking water in schools can lead to increased water consumption among students8, thereby supporting the enhancement of short-term memory9, improving visual attention10, and reducing diarrhea and student absenteeism11. In contrast, students may be exposed to harmful microorganisms from unsafe drinking water, potentially leading to outbreaks of waterborne diseases12,13. Therefore, ensuring a good drinking water quality in schools through a comprehensive monitoring, including the evaluation of trace compounds and their physicochemical and biological properties, is essential for sustaining students’ health and improving their academic performance.

In low- and middle-income countries, primary school children often lack access to water and sanitation facilities that meet basic safety standards, frequently resulting in a high incidence of gastrointestinal illnesses, which affect negatively their academic performance11,14. In Thailand, the rapid economic growth and urbanization have contributed to an increasingly severe environmental degradation, posing health risks to children15. For instance, fluoride concentrations as high as 0.92 mg/L have been reported in community water sources in Kanchanaburi Province16. Given the potential benefits of water consumption on health and cognitive outcomes, ensuring the availability of safe drinking water in schools has become a pressing concern among both the private and public sectors17. Over the past decade, awareness of safe drinking water has grown, particularly in rural areas along the Thai–Myanmar border18. Therefore, many primary schools in these areas have gradually implemented drinking water treatment systems. To protect public health, Thailand has established recommended drinking water quality limits through the Department of Health, Ministry of Public health19, which align with the World Health Organization’s (WHO) guideline20. It delineates maximum permissible concentrations for various contaminants to ensure the safety of drinking water. Notably, Thailand has set the fluoride limit at 0.7 mg/L, a threshold more stringent than the WHO’s guideline of 1.5 mg/L. This conservative limit is particularly pertinent in tropical climates like Thailand, where higher water consumption rates can increase fluoride intake, thereby elevating the risk of dental fluorosis among children.

Drinking water treatment systems in school settings typically consist of three main phases, i.e., pretreatment, main treatment, and post-treatment. In the pretreatment phase, turbidity from water is removed using filtration system. The main treatment phase involves advanced purification systems such as activated carbon adsorption and membrane filtration techniques including microfiltration, ultrafiltration, nanofiltration, and reverse osmosis (RO), which help eliminate organic substances and residual chlorine, improving water taste and removing some pathogenic microorganisms. Finally, the main goal of the post-treatment phase is disinfection to further eliminate pathogenic microorganisms, often using ultraviolet light6,21. However, many drinking water treatment systems in schools fail to deliver the expected quality or quantity of drinking water22–24, mainly due to the installation of unsuitable treatment systems, the limited understanding of the basic treatment principles by plant operators, poor equipment maintenance, and financial limitations. For example, the presence of pathogenic microorganisms, such as Blastocystis and elevated fluoride concentrations (1.147 mg/L) in drinking water have been reported in rural Thai schools25,26. Similarly, E. coli contamination was detected in 7.8% of school water samples in Hanoi, Vietnam27, reflecting broader regional challenges. As results, inadequate water treatment systems put schools at potential risk of waterborne diseases, including gastrointestinal infections, dental fluorosis, and other health concerns. These findings suggest that water treatment failures remain a persistent and widespread issue in many developing countries. In contrast, such failures are relatively rare in developed nations24. Implementing comprehensive health risk assessments is therefore critical to evaluate the potential health risks to schoolchildren from the ingestion of contaminated drinking water28.

Ensuring access to safe and affordable drinking water remains a global priority, as emphasized by the United Nations Sustainable Development Goal 6 (SDG 6), which advocates for universal access to clean water and sanitation to support health, equity, and sustainable development29. Although many water treatment systems in rural schools along the Thai–Myanmar border are currently operated and primarily managed by teachers and janitors, the safety of drinking water and related risk parameters have not been thoroughly explored, representing a significant knowledge gap. Addressing this gap is crucial to ensure the effectiveness of existing treatment systems and to protect the health of schoolchildren in this area.

Therefore, this study aimed to evaluate the drinking water quality and conduct a health risk assessment in primary schools along the Thai–Myanmar border in Thailand. This region is characterized by a lack of systematic water quality monitoring, making the study particularly valuable in addressing an underexplored area of public health concern. The novelty of this study lies in that it provides for the first-time essential water quality data to support ongoing efforts toward improving the safety of drinking water in these rural school areas in Thailand. The findings will help strengthen public trust in the quality of rural schools’ water supplies.

Materials and methods

Study area

Kanchanaburi, the third largest province of Thailand, is located in the western part of the country and shares a border with Myanmar (Fig. 1(a-b). This area is in the tropical monsoon and characterized by distinctive landscapes, such as plains, mountains, and rivers, which may influence water quality dynamics30. From 2020 to 2022, the total rainfall precipitation ranged from 1,144 to 1,553 mm, with the highest precipitation occurring in October (Figs. 1(c–e)). The average monthly minimum and maximum temperatures ranged between 18.2 °C and 38.7 °C (Figs. 1(f–h)), with the hottest period spanning from March to April31. In this study, drinking water samples were collected from rural primary schools along the Thai–Myanmar border, which encompasses three major districts, namely, Sai Yok (SY), Thongphaphum (TPP), and Sangkhaburi (SKB), crossing the border in Kanchanaburi. These rural primary schools were selected based on their proximity to the Myanmar border, where communities face challenges in accessing safe drinking water and adequate sanitation. Additionally, the region has raised environmental health concerns, particularly regarding water contamination. These primary schools rely on various water sources, including groundwater, surface water, rain water, bottle water and village water supply, as drinking water sources for students, with the number of children ranging from 34 to 1,581. In addition, various purification systems are adopted for drinking water production, such as multimedia filtration, softening, RO and ultraviolet. Further details are provided in Table S1.

Fig. 1.

Fig. 1

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(a-b) Map of study areas locating in Sai Yok (SY), Thongphaphum (TPP) and Sangkhaburi (SKB), Kanchanaburi, Thailand, (c-e) monthly rainfall precipitation and (f-h) average monthly minimum and maximum temperatures in Kanchanaburi between 2020 and 2022.

Sample collection and water quality analysis

We collected a total of 52 drinking water samples from 49 primary schools, including three branch campuses, across the SY (n = 24), TPP (n = 15), and SKB (n = 13) districts. These samples represent 87% of the 60 targeted school settings and were collected in March 2023. The purposive sampling was conducted at the point of consumption, specifically from drinking water station within the school, to ensure the assessment of water quality as directly consumed by students. (Details on sampling techniques and inclusion and exclusion criteria is shown in supplementary information of Text-S1). Prior to collecting each sample, we disinfected the faucet’s exterior and allow the water run for about 3 min to remove any standing water. For the analysis of microbial parameters, such as total coliform and E. coli, a sterile glass container was used to collect the water sample, in which collected water was kept at 4 °C in an icebox and then analyzed within 12 h. To quantify total coliform and E. coli in water sample, aliquot of 1 mL of water sample was then spread on Petrifilm (3 M, USA) and incubated at 35 ± 1 °C for 24 h for total coliform and for 48 h for E. coli. For physicochemical water qualities analysis, another set of pre-cleaned polyethylene bottle of 1 L was used to collect water samples. All water samples were analyzed using the standard method for testing water and wastewater32. The pH, total dissolved solids (TDS) and turbidity of unfiltered samples were assessed on-site using a portable multi-probe meter (HACH, HQ40d, USA) and turbidity meter (HACH, 2100Q, USA), respectively. For each sample, a portion volume was filtered via 0.45 μm nylon membrane filter prior to fluoride (Ion chromatography, Methorm), dissolved organic carbon (DOC) (Multi N/C 2100, Analytik Jena, Germany) and UV254 (U2700, Shimadzu, Japan) analyses. Additionally, a portion of each filtered sample (50 mL) was acidified by nitric acid (65% v/v) to suppress pH below 2 for heavy metals analysis (inductively coupled plasma spectrometry-mass spectrometry (ICP-MS) (Nexion 2000, PerkinElmer, USA)). This process was carried out to ensure the complete dissolution of all heavy metals within the sample33. Additionally, the concentration of total mercury (Hg) was separately measured in accordance with US EPA Method 245.1 using discrete direct purge reducing vaporization cold vapor atomic absorption spectrophotometry (Mercury Analyzer, RA-7000 A; Nippon Instruments Corporation, Tokyo, Japan). During the course of analysis, average value of duplicate measurements was reported to verify the precision of the procedure. The limits of detection (LOD) and quantification (LOQ) for analyzing heavy metals in water samples were determined by performing ten repeated measurements of a blank sample, following the methodology described by Tanvir et al., (2020)34 as shown in Table S2.

Health risk assessment

Health risk assessment is a systematic approach employed to estimate the potential adverse health effects resulting from exposure to toxic contaminants35. The approach includes four steps namely, hazard identification, dose-response assessment, exposure assessment and risk characterization, which may be expressed in term of either carcinogenic or noncarcinogenic health risks1. In this study, drinking water intake pathway for primary school students was primarily considered as exposure scenario with potential toxic compounds. The chronic daily intake (CDI) per unit weight via oral exposure (mg/(kg-day)) can be determined using Eq. (1):

graphic file with name d33e527.gif 1

where C represents the concentration of contaminants in water (mg/L), IR denotes the water ingestion rate (L/day, IR = 1.18 L/day for children33), EF is the exposure frequency (days/year, EF = 200 days/year), ED stands for the exposure duration (years, ED = 6 years for students in primary school33), BW indicates the average body weight (kg, BW = 20 kg for female students and BW = 24.68 kg for male students)28), and AT represents the average exposure time (days, AT = 1,200 days for schoolchildren).

Risk characterization was performed at the final phase of the health risk assessment. The primary factors that need to be considered in toxicity risk evaluation are the reference dose (RfD) for characterizing noncarcinogenic risks and the slope factor (SF) for characterizing carcinogenic risks, as shown in Table S3. The schoolchildren’s health risks associated with drinking water consumption were evaluated regarding both chronic (noncarcinogenic) and carcinogenic effects, utilizing the estimated CDI values and established toxicity thresholds for each potentially hazardous compound. The noncarcinogenic risk was determined by calculating the hazard quotient (HQ) according to Eq. (2):

graphic file with name d33e555.gif 2

where a HQ value exceeding 1 denotes an unacceptable risk of adverse noncarcinogenic health effects and an HQ value below 1 implies a tolerable level of risk33. When evaluating the risk related to multiple toxic substances, the individual HQ values were combined into the Hazard Index (HI) as shown in Eq. (3). This equation is the summation of each HQ value and the last step from four of the health risk assessment.

graphic file with name d33e570.gif 3

where: k is differnt contaminants. A HI greater than 1 indicates an unacceptable risk of noncarcinogenic health effects, whereas an HI below 1 suggests an acceptable level of risk36.

For carcinogenic health risk, the cancer risk (CR) can be estimated by multiplying the CDI (mg/kg-day) with the SF (mg/kg-day) as shown in Eq. (4).

graphic file with name d33e590.gif 4

A CR value between 1 × 10−6 and 1 × 10−4 can be considered as an acceptable threshold for the carcinogenic risk37. A CR value below 1 × 10−6 is considered negligible, requiring no further concern. However, a CR value exceeding 1 × 10−4 indicates a significant carcinogenic threat36,38.

Statistical analysis

The drinking water quality was statistically analyzed using SPSS statistic 18.0. The normality of the data sets was assessed by performing a Shapiro–Wilk test. To identify significant differences in water quality parameters among the study areas, one-way analysis of variance (ANOVA) followed by a post-hoc LSD test was performed to normalized the data, and nonparametric Kruskal–Wallis ANOVA on ranks was used for non-normal distributions. The association between types of water treatment and compliant statuses of drinking water was assessed using the Pearson Chi-square test. A significance level of p < 0.05 was applied throughout the study.

Results and discussion

Water quality in terms of physicochemical and bacteriological parameters

The water quality characteristics of the primary schools in the three study sites were assessed and compared, as illustrated in Fig. 2. The average pH levels across all study locations (TPP 6.95 < SY 7.04 < SKB 7.14) fell within the acceptable range for drinking water (pH 6.5–8.5) (Fig. 2(a)). However, four out of 52 water samples (8%) failed to meet the minimum drinking water quality for pH (pH < 6.5). Although the pH of drinking water does not directly affect human health, low pH values can exert an indirect influence on health by changing other water quality factors such as metal solubility27. The mean turbidity values (Fig. 2(b)) reported for these areas (SY 0.37 < TPP 0.38 < SKB 1.97) were significantly below the maximum allowable level (MAL) for drinking water, i.e., 5 nephelometric turbidity unit (NTU), except for one sample from SKB, which exhibited a value of 20.9 NTU, which was above the MAL. This raises concerns because elevated turbidity levels are generally associated with the presence of pathogenic microorganisms and can reduce the efficacy of bactericidal agents such as chlorine and UV radiation39.

Fig. 2.

Fig. 2

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Boxplot analysis of physicochemical parameters of drinking water in SY, TPP and SKB; (a) pH, (b) turbidity, (c) TDS, (d) total hardness. The dashed line in (a)-(d) represents the maximum allowable concentrations of Thailand’s recommended limits of drinking water quality.

Generally, TDS value is a measure of the level of mineralization in water40. All treated water samples obtained from these areas were considerably below the MAL of the drinking water quality for TDS of 500 mg/L19 (Figure (2(c)). Additionally, the levels of total hardness on average (Figure (2(d)) (SKB 76 < TPP < 98 < SY108) were relatively below the Thailand’s recommended limit of drinking water quality of 300 mg/L as calcium carbonate (CaCO3)19. However, a small portion of the treated water samples (4%) had a high level of total hardness above the recommended limit. According to Rahman et al. (2021)28, the mean total hardness of drinking water in the southwestern coastal region of Bangladesh was 560.57 mg/L as CaCO3, which exceeded the average levels found in our study. This elevated hardness in the coastal regions is likely due to seawater intrusion into groundwater resulting in a high mineral content41, in contrast to the conditions observed in our study. However, to improve the hardness reduction, additional treatment options including nanofiltration should be considered, providing safe drinking water42.

The bacteriological characteristics of drinking water are an important parameter for evaluating its quality. In particular, the presence of total coliform and E. coli as potential pathogens in drinking water43 indicates that harmful fecal pathogens that can cause acute gastrointestinal illness44 have been potentially introduced at the water source or during transportation and distribution45. In this study, total coliform was detected in 13 water samples (1–100 colony-forming unit (CFU)/mL), whereas only one sample had a positive result for E. coli (1–10 CFU/mL) (Fig. 3). The recommended limits of drinking water quality in Thailand and WHO guideline recommend that both total coliform and E. coli should be absent in drinking water19,20; however, they were present in the treated water samples. Although most water treatment systems installed in the study areas, combined with disinfection systems, could efficiently improve the drinking water quality in terms of total coliform and E. coli, the relatively high presence of these bacteria in the drinking water collected in these schools suggests the occurrence of bacterial cross-contamination caused by unhygienic environments and practices. An unhygienic surrounding environment could reintroduce contaminants into treated water46. According to the findings reported by Vannavong et al. (2018), storing water even for a short period of time can also result in bacterial contamination of drinking water due to unhygienic practices47. Therefore, promoting health education, focusing on safe water storage and hygiene practices (e.g., hand washing), coupled with improved sanitation in schools, are recommended due to its proven potential to substantially lower the incidence of school-related waterborne diseases associated to bacterial contamination48,49.

Fig. 3.

Fig. 3

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Bacteriological parameters of drinking water (a) total coliform, (b) E. coli.

Water quality in terms of dissolved organic matter (DOM)

The presence of DOM in treated drinking water has a profound impact on water quality parameters such as taste and odor, affecting consumer acceptance50. DOM can also serve as a substrate for microbial growth in treated water and distribution systems. Therefore, minimizing DOM levels is important for ensuring a safe drinking water supply51,52.

DOM is commonly quantified using dissolved organic carbon (DOC) and ultraviolet (UV) absorbance at 254 nm (UV254)52,53. The ratio between UV254 and DOC as specific UV absorbance at 254 nm (SUVA254) is a valuable indicator for the water quality in terms of DOM and also indicates the DOM characteristics in water samples, such as aromaticity53. Water samples with a SUVA254 value above 3 L/mg⋅m typically contains DOM with hydrophobic properties and high-molecular-weight fractions, such as humic compounds54. These properties can reduce the effectiveness of chlorine as a disinfectant and cause the formation of disinfection byproducts such as trihalomethanes in water54. Conversely, a SUVA254 value below 3 L/mg⋅m suggests that DOM primarily comprises hydrophilic fractions54, which is the most conducive type of DOM to bacterial growth51.

Figure 4(a) shows the DOC concentration in the drinking water collected from the three study locations. The average DOC concentration was relatively low (TPP 0.89 < SKB 1.11 < SY 1.78), ranging between 0.04 and 7.64 mg/L. The average SUVA254 of the finished water from SY (1.33) was considerably lower than those from TPP (3.07) (p-value = 0.017) and SKB (3.86) (p-value = 0.033) (Fig. 4(b)). This indicates the presence of DOM with mainly hydrophilic characteristics in the finished water from SY, whereas the predominant DOM in TPP and SKB exhibited hydrophobic properties.

Fig. 4.

Fig. 4

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Boxplot analysis of (a) DOC concentration and (b) SUVA254of drinking water in different school areas of SY, TPP and SKB. The dash line in (a) refers maximum allowable DOC concentration regulated by in water quality standards specified in Japan’s water supply act (Sakai et al., 2013)55.

Although neither the drinking water guidelines from Thailand nor those from the WHO recommend a MAL for DOM, such as DOC, in drinking water, Japan has adopted 3 mg/L of DOC as MAL in the finished water as a drinking water standard55. Thus, the DOC concentration limit of 3 mg/L could be employed as a drinking water quality standard with respect to organic carbon55. Our results revealed that six water samples (11.5% of all samples) had a DOC level exceeding 3 mg/L. Interestingly, 29 out of the 52 samples (56% of all samples) had a DOC concentration greater than that in the feed water (Figure S1). This could be due to the release of a substantial amount of organic carbon into the water when passing through the treatment systems during the initial phase of operation56. Other contributing factors include the release of trapped particles from filtration media or storage tanks over time and the leaching of organic compounds from high-density polyethylene (HDPE)-treated water tanks and/or pipe materials57. These could be potential factors for enhancing the DOC levels in treated water. However, further monitoring of DOC concentrations at different stages of the treatment processes should be conducted.

Heavy metal and fluoride content in drinking water samples

The presence of heavy metals and fluoride in drinking water poses serious risks to human health36,58. Figure 5 shows the concentrations of heavy metals and fluoride in the drinking water collected from the three study areas. The total Hg concentration reported from these areas (Fig. 5(a)) varied from 0.04 to 2.23 ng/L (average concentration: SKB 0.35 < TPP 0.48 < SY 1.07), which was significantly lower than the permissible Hg limit for drinking water (1000 ng/L)19. Additionally, the concentrations of Mn, Fe, and Cu detected in water samples were significantly below the recommended limits of 300, 300, and 1000 µg/L, respectively19 (Figs. 5(b–d)). The Pb and total Cr concentrations were also below the drinking water limits of 10 and 50 µg/L, respectively (Figs. 5(e–f)). Additionally, the Ni concentration was significantly lower than the Thailand’s recommended limits for drinking water quality of 70 µg/L in all samples (Figs. 5(g)). Meanwhile, the Cd concentrations were undetectable because they were below the detection limit of 0.107 µg/L.

Fig. 5.

Fig. 5

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Boxplot analysis of heavy metals (a) total Hg, (b) Mn, (c) Fe, (d) Cu, (e) Pb, (f) total Cr, (g) Ni, (h) total As, and (i) fluoride in drinking water in different school areas of SY, TPP and SKB. The dashed and solid lines in Fig. 5(a)-(i) represent the maximum allowable concentrations of Thailand’s recommended limits of drinking water quality and the World Health Organization, respectively.

The average As concentrations were below the MAL (10 µg/L) for drinking water (Fig. 5(h)), as previously reported by Hung et al. (2020)27, who found low As levels (4 µg/L) in school drinking water in Hanoi, Vietnam. However, 2 out of the 52 samples (4%) analyzed in the present study (SY: 10.8 µg/L and TPP: 15.8 µg/L) exceeded this limit. Similar results for As levels in drinking water (9.2–12.8 µg/L) in Vehari District, Punjab Pakistan were reported by Murtaza et al. (2020)33. Additionally, Rahman et al. (2021)28 reported a higher As level of 35 µg/L in the southwest coastal area of Bangladesh. Thus, to preserve children’s health and prevent long-term health complications, it must be ensured that the As level in drinking water remains below 10 µg/L.

The high prevalence of dental fluorosis among children aged between 6 and 12 years has been attributed to excessive fluoride exposure from drinking water59. In this study, all water samples had average fluoride concentrations (Fig. 5(i)) (SKB 0.06 < SY 0.20 < TPP 0.26) that fell within the range for tap water (0.07–0.17 mg/L) reported by Mandinic et al. (2010)60 and were below the mean fluoride levels reported in other studies57,61. Nevertheless, 8% and 4% of the water samples exceeded the Thailand’s recommended limits for drinking water quality (0.7 mg/L)19 and the WHO (1.5 mg/L)20, respectively (Fig. 5(i)). It is noteworthy that the fluoride concentration was the highest among the measured substances, while the concentrations of heavy metals followed the order Cu > Fe > As/Pb > Ni/Mn > Cr > > Hg. These results are consistent with the findings of Mohammadpour et al. (2023), who reported that the concentration of potentially toxic elements in the drinking water of Shiraz, Iran, followed the sequence Fe > Mn > Pb > Hg36. Therefore, school authorities should ensure that schoolchildren and staff have access to safe drinking water.

Noncompliance of the treated water samples with drinking water standards

Figure 6(a) illustrates the percentage of treated water samples that did not meet the Thailand’s recommended limits for drinking water quality. It should be noted that a maximum DOC level of 3 mg/L was used as a benchmark for acceptable water quality in this study55. Of the 52 samples, 22 (42%) did not comply with the Thailand’s recommended limits of drinking water quality. The highest noncompliance rate was observed in TPP (53%), followed by SY (50%), with the lowest in SKB (15%).

Fig. 6.

Fig. 6

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(a) Contribution of noncompliant drinking water sample and (b) noncompliant water variable with national drinking water standard.

Among the noncompliant samples, total coliform was the most frequently observed variable (59%), followed by DOC (27%), fluoride and pH (18%), As and total hardness (9%), and E. coli and turbidity (5%), as illustrated in Fig. 6(b). The predominant detection of total coliform in drinking water suggests the occurrence of cross-contamination likely due to unhygienic practices and environments, which aligns with the findings of Khanal et al. (2023)62. Additionally, malfunctioning or inadequate maintenance of the UV equipment might be responsible for the high levels of total coliforms in the treated water.

Among the noncompliant parameters, DOC, fluoride, and As were detected at moderate levels, indicating the incomplete removal of these pollutants during the water treatment process. Meanwhile, noncompliance with the pH standard could be related to a decrease in pH caused by the reverse osmosis system, as noted by Khanal et al. (2023)62. According to the results of this study, noncompliance with the recommend limits in terms of total coliform, DOC, fluoride, and As levels can lead to public health concerns including gastrointestinal illnesses and other chronic health issues33,61,63.

The water treatment systems implemented across the surveyed primary schools were classified into three main categories: (i) systems incorporating reverse osmosis (RO) (n = 22), (ii) softener-based systems (n = 19), and (iii) other systems, such as those utilizing ultrafiltration membranes (n = 11) (Table S4). Implementing of RO and softener systems were mostly contributed to 42% and 37% of all types water treatment. However, total coliforms were the most frequently detected non-compliant parameter (Fig. 6). Furthermore, statistical analysis revealed no significant association between the type of water treatment system and compliance with Thailand’s recommended limits (p = 0.393) (Table S4). These findings suggest that the type of water treatment system alone may not be a determining factor in achieving compliance with Thailand’s recommended limits of drinking water quality. This underscores the critical importance of regular maintenance and proper operation of water treatment systems, as inadequate upkeep can lead to increased bacterial contamination, aligning with findings by Gad et al. (2024)64.

Health risk assessment of primary school students exposed to Hg, Mn, Cu, Pb, total Cr, Ni, As, and fluoride in drinking water

The total concentration of the analyzed substances in the drinking water samples was used to calculate the average CDI (Fig. 7(a)). On the basis of the available RfD values, seven metals, i.e., Hg, Mn, Cu, Pb, Cr, Ni, and As, as well as fluoride were selected to estimate the HQ (Fig. 7(b)) as a measure of the noncarcinogenic risk to schoolchildren from drinking water ingestion (Fig. 7(c)). Exposure to these toxic elements in drinking water is directly related to body weight, which can be demonstrated by the CDI value65. Owing to their small body size, children are considered a vulnerable group as they accumulate higher levels of contaminants from drinking water66. The variation in the CDI values for the schoolchildren in the study area is shown in Fig. 7(a). The highest mean CDI value was found upon exposure to fluoride (1.1 × 10−2 mg/kg-day), followed by Cu (6.0 × 10−4 mg/kg-day), As (4.9 × 10−5 mg/kg-day), Pb (4.4 × 10−5 mg/kg-day), Mn (3.0 × 10−5 mg/kg-day), Ni (2.9 × 10−5 mg/kg-day), Cr (1.1 × 10−5 g/kg-day), and Hg (4.1 × 10−8 mg/kg-day).

Fig. 7.

Fig. 7

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Boxplot analysis of (a) CDI values, (b) HQ value for female and male students, (c) HI value and (d) CR value of As exposure for male and female students in three study areas.

To assess the human health risks associated with these metals and fluoride in drinking water, both HQ and HI values were calculated based on oral consumption. As shown in Figs. 7(b-c), although most of the average HQ values were below 1, the HQ at the 95th percentile of As and fluoride was close to 1 (Fig. 7(b)). This suggests that approximately 5% of the HQ values may exceed the acceptable noncarcinogenic harmful health risk according to the health risk estimation for As and fluoride.

Figure 7(c) illustrates the estimated HI values for female and male students among the different school locations. HI values above 1.0 are indicative of potential adverse health effects of exposure to toxic substances1,38. In this study, the calculated average cumulative HI values were below 1 (Fig. 7(c)), but the 95th percentile HI values were above 1 (1.82 for female students and 1.47 for male students). Considering the study sites, the average HI values for all locations were below 1. However, the 95th percentile for HI values for SY and TPP exceeded 1. These findings indicate that some children in the study areas may be at risk of non-cancer health issues due to exposure to trace metals and fluoride in drinking water.

Long-term exposure to low concentrations of hazardous metals may cause various cancers58,67. Cancer risk is generally defined as the likelihood of an individual to develop cancer over their lifetime due to exposure to a potential carcinogen68. The calculated cancer risk values for As in all drinking water samples for female and male students are shown in Fig. 7(d). Most of the values ranged between the threshold acceptable level of 1 × 10−6 and 1 × 10−4, whereas CR values at the 95th percentile exceeded 1 × 10−4, representing high carcinogenic risk, especially in the SY and TPP areas. These findings indicate that additional treatment of drinking water is required in the study area owing to the high carcinogenic risk due to As exposure, which poses a serious threat to the health of schoolchildren.

Strengths and limitations

To our best knowledge, this study addresses a critical public health concern, especially in rural primary schools where the need for safe drinking water for schoolchildren is often neglected. This study focuses on evaluating drinking water quality and conducting a health risk assessment in rural primary schools along the Thai-Myanmar border. Monitoring school drinking water quality can yield valuable insights into key water parameters relative to drinking water standard/guideline, while health risk assessment (both non-cancer and cancer) can support the effective risk management and help establish optimal pollutant limits. Our findings provide significant scientific insights for assessing the disease burden with hazardous substances in drinking water in the rural primary schools along this border region.

However, we acknowledge that there are several limitations to this study. First, our study lacked the statistical power to comprehensively assess all drinking water samples from primary schools along the Thai–Myanmar border in Kanchanaburi. We focused on collecting drinking water samples from the main stations representing rural primary schools located in three major areas, namely SY, TPP, and SKB, with the aim of providing a more targeted, yet representative understanding of the drinking water quality and potential effects of contaminant exposure on schoolchildren. Nonetheless, future research should involve expanding the sample size and geographic coverage to provide a more holistic view of water contamination in the region. Second, although oral ingestion remains the primary route of exposure to contaminants in drinking water, other pathways of exposure, such as dermal absorption and inhalation, should be considered for a comprehensive health risk assessment. These additional exposure routes may contribute to the overall exposure of students to certain contaminants, particularly those that are volatile or water-soluble. Thus, evaluating all potential exposure routes in future studies would allow for a more complete health risk assessment. Finally, the health risk assessment in this study was based on the available literature and general population data for factors like BW, IR, and ED, which despite providing useful insights may not fully represent the specific behaviors and characteristics of the schoolchildren in the study region. Future studies should prioritize collecting region-specific data and real measurements to precisely identify local behavior, such as drinking water consumption rates and exposure durations, to enhance the accuracy of the health risk assessment.

Conclusion

This study highlights the significant concerns regarding the safety of drinking water in rural primary schools along the Thai–Myanmar border. Notably, 42% of water samples exceeded recommendation limits of drinking water quality in Thailand, with total coliforms identified as the most prevalent contaminant. Elevated concentrations of fluoride and arsenic were also detected, surpassing Thailand’s recommended limits of 0.7 mg/L for fluoride and 10 µg/L for arsenic, respectively, posing potential health risks to schoolchildren. Health risk assessments revealed that while the majority of hazard index (HI) and cancer risk (CR) values remained within acceptable limits (HI < 1; CR between 1 × 10⁻⁶ and 1 × 10⁻⁴), the 95th percentile values exceeded these thresholds, indicating potential non-carcinogenic and carcinogenic health risks for children consuming the contaminated water. These findings highlight the pressing need for implementing effective water treatment systems with proper maintenance, coupled with regular monitoring of drinking water quality in rural school settings, to mitigate associated health risks. Future studies should prioritize the collection of region-specific data and expand geographic coverage to facilitate comprehensive health risk assessments for schoolchildren and evaluate the effectiveness of intervention strategies.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Supplementary Material 1 (43.6KB, docx)

Acknowledgements

This study was financially supported by the Master of Science Program in School Health (International Program), Faculty of Tropical Medicine at Mahidol University, and The Office of Her Royal Highness Princess Maha Chakri Sirindhorn’s Projects (OPSP). We extend our gratitude to the OPSP staff for their invaluable support. Special thanks to Dr. Tippayarat Yoonuan from the Department of Helminthology for their essential support in fieldwork for this research. We also appreciate the laboratory assistance from Analytik Jena Fareast Thailand Ltd. and Miss Tiyanun Jurkvon at MU-FRF for DOC and heavy metal measurements, respectively.

Author contributions

Kezang Choda: Data curation, Formal analysis, Investigation, Methodology, Writing–original draft, Writing–review & editing, Sirirat Sangkarak: Formal analysis, Investigation, Methodology, Writing–review & editing, Pannamas Maneekan: Data curation, Investigation, Formal analysis, Writing–review & editing, Pattaneeya Prangthip: Writing–review & editing, Investigation, Suda Ittisupornrat: Writing–review & editing, Numfon Eaktasang: Writing–review & editing, Suthirat Kittipongvises: Writing–review & editing, Jenyuk Lohwacharin: Writing–review & editing, Athit Phetrak: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Resources, Supervision, Validation, Visualization, Writing–original draft, Writing–review & editing.

Data availability

The data analyzed in this study are available within the published article and its supplementary information file.

Declarations

Competing interests

The authors declare no competing interests.

Footnotes

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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Supplementary Material 1 (43.6KB, docx)

Data Availability Statement

The data analyzed in this study are available within the published article and its supplementary information file.

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