Water quality health challenges in Iran's UNESCO Heritage arid regions: Focus on nitrate and fluoride Open Access

Aqueducts play an essential role in transporting groundwater and supporting civilizations. However, the ancient structures might contain contaminants and pathogens that could pose risks to human health (De Feo et al. 2013). Therefore, it is crucial to identify pollution sources, understand how contaminants reach people, and assess potential health risks to ensure groundwater safety for consumption (Morales et al. 2023). The water quality index (WQI) method offers a means to evaluate the overall water quality in urban water sources by analyzing various physical and chemical parameters (Şener et al. 2017). It was demonstrated that high levels of nitrate and fluoride in groundwater can lead to various health risks over time. In this regard, high nitrate concentrations can cause methemoglobinemia, also known as ‘blue baby syndrome,’ as well as gastrointestinal issues and other health problems in adults (Duncan et al. 1997; Kom et al. 2022). Additionally, excessive fluoride intake from drinking water can result in dental fluorosis and skeletal fluorosis (Moeini & Azhdarpoor 2021). Numerous studies have investigated groundwater chemistry across various climates, landscapes, rock types, and water flow patterns, consistently identifying elevated levels of chemical components that can lead to diverse outcomes. For instance, a study examining ancient Roman waterways in Italy detected heavy metals that could potentially pose health hazards. These metals were attributed to the degradation of waterway materials and external sources of pollution (Delile et al. 2017; Sammartino et al. 2023). Similarly, research conducted in Greece and Turkey revealed the presence of pathogens such as coliform bacteria and parasites in historical water systems, thereby endangering the health of individuals dependent on these water sources (Gerasimidis et al. 2009). The primary concern regarding contaminated groundwater extends beyond its impact on water availability to encompass the potential long-term health risks for consumers of drinking water. In the Loess Plateau region of China, studies have shown that 43% of infants, 22% of children, 8% of teenagers, and 4% of adults face increased health risks due to the consumption of contaminated groundwater (Wang et al. 2022). For instance, a study conducted by Rao et al. (2021) in the Nalgonda district of India revealed that 95.5% of the groundwater in the region posed a significant risk for non-carcinogenic health effects due to exposure to nitrate and fluoride through oral intake (Rao et al. 2021). The findings underscore the importance of risk assessment in different regions concerning ancient groundwater sources. While previous research has extensively examined chemical and microbial factors in various water sources globally (Mohebbi et al. 2013; Kalankesh & Zazouli 2019; Kalankesh et al. 2019; Islam et al. 2021; Li et al. 2022; Jing et al. 2023), limited studies have focused on the risk assessment of aqueducts as ancient groundwater resources, particularly in Gonabad city in Eastern Iran. The unique geology and hydrological characteristics of arid regions heavily depend on aqueduct systems. Consequently, it is essential to evaluate the occurrence and levels of chemical contaminants and organic substances in the water. This research aims to fill this research gap by conducting a thorough analysis of the chemical and microbial constituents, along with the related risk factors, in Ganat, cisterns, and water distribution networks that are situated in the eastern part of Iran.

The study was conducted in Gonabad city, which is located in the southern part of the Razavi Khorasan Province, Iran (34°21′10″ N, 58°41′01″ E), with 36,367 populations and falls under the arid and semi-arid climate region. According to the latest available data, the practice of excavating Ganats dates back over 3,000 years and there are a total of 26 Ganats that range in discharge from 10 to 120 L/s. Significantly, some of them are the most prominent Ganats in history and are popular with customers in the region (Golkarian & Rahmati 2018).

Additionally, pH was measured by a pH meter (Metrohm instrument model 827). EC was determined by a conductivity meter (Trans). For TDS, the sample was evaporated in a pre-weighed vessel and dried to constant weight at 180 ± 2°C. The concentration of Cl⁻, F⁻, NO₃, SO₄, and Na⁺ was determined by Dionex ICS-1000 from the USA.

THI < 1 shows no health risk to humans, while THI > 1 indicates a higher level of hazard (Peirovi-Minaee et al. 2024).

SPSS 26 software was used to analyze data. Additionally, the acceptable range of chemical parameters is compared with national and international standards guidelines (Table 1) (WHO, 2011).

All physicochemical parameters of water samples in different resources are presented in Table 2.

In the physicochemical analysis of water resources in Gonabad city, significant variations were found in key chemical and microbial characteristics. The water quality generally met WHO guidelines (Organization 2004) and Iranian standards (ISIRI 2010). However, some samples had high conductivity and TDS values, suggesting the presence of dissolved minerals that may require additional treatment for standard water quality. Additionally, high chloride concentrations pose risks for consumption (Hosseininia & Hassanzadeh 2023). The presence of total coliforms in certain samples indicates microbial contamination. Data on the WQI showed different water quality classes at various sampling sites. Site 2 had good water quality in its distribution and cisterns, while site 3 had poor quality. Poor quality at some sites may be due to runoff from farmlands, industrial areas, or sewage systems, leading to contamination with chemicals, pesticides, or pathogens. Inadequate harvesting methods could also cause contamination by dust, debris, or animal waste. Insufficient filtration or treatment could leave harmful substances in the water. The aqueducts in site 2 and cisterns in site 1 were in very poor condition due to leakage, infiltration, ageing infrastructure, and lack of maintenance. Cracks or breaks in aqueducts could compromise water quality by allowing contaminated water to enter. Corrosion in older aqueduct pipes could introduce harmful substances. These water quality variations are influenced by pollution sources, natural processes, infrastructure issues, land use practices, and climate change. Both microbial and chemical contaminants can affect water quality and public health (Balasooriya et al. 2023). Interventions to address these issues can improve water quality and community well-being. Collaboration is crucial for sustainable water resource management. A study on nitrate and fluoride levels in water sources showed compliance with WHO standards (Figure 2). However, nitrate and fluoride levels exceeded WHO guidelines for children at S5, indicating a higher risk of exposure for children at this location (Figure 3). Nitrate can cause methemoglobinaemia or ‘blue baby syndrome’ in infants by affecting oxygen transport in blood cells. Excessive fluoride intake can lead to dental and skeletal fluorosis, affecting bone and teeth health (Jamshidi et al. 2021). The study emphasizes the importance of monitoring non-carcinogenic contaminants in drinking water to safeguard public health, especially for vulnerable groups like children. Children face a higher risk of non-carcinogenic health effects from nitrate and fluoride than adults. The research indicates a significant health risk for children exposed to these contaminants in water, with children showing a higher THI and experiencing a greater cumulative health impact (Cao et al. 2016). By identifying age-related vulnerabilities in health risk assessments for environmental contaminants, further research and monitoring are necessary to comprehend the variations in THI levels between adults and children. This will aid in creating evidence-based strategies to safeguard public health, particularly for children who might be more vulnerable to health impacts from environmental exposures.

The physio-chemical analysis of water sources in Gonabad city revealed variations in key parameters such as pH, conductivity, TDS, chloride, sulphate, and microbial contamination. While pH levels were acceptable, fluctuations in conductivity and TDS indicated potential contamination sources requiring investigation. Elevated chloride and sulphate levels pose health risks necessitating treatment, while microbial contamination raises serious public health concerns. The WQI variations are linked to pollution sources and infrastructure deficiencies needing targeted interventions. Nitrate and fluoride compliance was observed, but health risks, especially for children, remain. The THI highlights different risks for adults and children. Collaborative water resource management is crucial for public health protection, addressing pollution sources, seasonal changes, and emerging contaminants for community well-being. Ongoing monitoring and research aim to reduce risks and safeguard public health from nitrate and fluoride exposure.

The authors wish to express their appreciation to the Social Determinants of Health Research Center at Gonabad University of Medical Sciences, Gonabad, Iran.

This work is funded by the Social Determinants of Health Research Center Gonabad University of Medical Sciences, Gonabad, Iran [Code number: IR.GMU.REC.1402.131] and Student Research Committee, Gonabad University of Medical Sciences, Gonabad, Iran [Code number: IR.GMU.REC.1403.0.31].

All authors critically reviewed and approved the final manuscript.

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

The authors declare that there is no conflict.