Desalination and Water Treatment 170 (2019) 176–186 www.deswater.com December doi: 10.5004/dwt.2019.24691 Spatial distribution of fluoride and nitrate in groundwater and its associated human health risk assessment in residents living in Western Khorasan Razavi, Iran Mehdi Qasemia, Mojtaba Afsharniaa,*, Mansoureh Farhanga, Mansour Ghaderpoorib, Abdolreza Karimic, Hassan Abbasid,e, Ahmad Zareia,* aDepartment of Environmental Health Engineering, School of Health, Social Determinants of Health Research Center, Gonabad University of Medical Sciences, Gonabad, Iran, Tel. +98 5157223514; emails: [email protected] (M. Afsharnia), [email protected] (A. Zarei), [email protected] (M. Qasemi), [email protected] (M. Farhang) bDepartment of Environmental Health Engineering, School of Health, Lorestan University of Medical Sciences, Khorramabad, Iran, Tel. +98 8432227134; email: [email protected] cDepartment of Civil Engineering, Faculty of Engineering, Qom University of Technology (QUT), Qom, Iran, Tel. +98 2536641601; email: [email protected] dStudent Research Commitee, Gonabad University of Medical Sciences, Iran, Tel. +98 5155424047; email: [email protected] eHealth & Treatment Center of Bardaskan, Iran Received 8 March 2019; Accepted 9 July 2019 abstract Fluoride and nitrate are the important factors that influence the drinking water quality. A health risk assessment was performed for exposure to fluoride and nitrate via drinking water ingestion pathway for the inhabitants living in Bardaskan County, Iran. In the present work, totally 30 drinking water samples were collected from private wells, monitoring wells, and boreholes during June 2018, from different previously unexplored rural and urban areas. The concentration of fluoride and nitrate varied from 0.55 to 1.75 mg/L (mean 0.873 mg/L) and from 5.7 to 25.4 mg/L (mean 12.58 mg/L), respectively. None of the 30 studied areas had fluoride, except one place, and nitrate concentrations above WHO guidelines. Hazard index (HI) values for adults, children and infants varied from 0.4160 to 1.1886 (mean 0.6405), from 1.0921 to 3.1203 (mean 1.6813) and from 1.165 to 3.3283 (mean 1.7934), respectively. HI estimated for groundwater in 3.3%, 100%, and 100% cases were found to be above the safety limit of 1 for adults, children, and infants, respectively. This research provides evidence that local residents in Bardaskan County may be at a high risk of health problems caused from fluoride and nitrate in drinking water. It is, therefore, important to take some remedial measures to prevent any health problem in this county. Keywords: Fluoride; Nitrate; Human health; Risk assessment; Bardaskan 1. Introduction drinking water among freshwater resources in many regions of the world [4,5] and Iran because it is available in all Safe water is a key resource necessary for the life of seasons and is less polluted than surface water and its need all organisms on the globe [1,2]. It is argued that 80% of is increasing due to fast growth of population, urbanization, the diseases in the world come through the poor quality industrialization, which has exacerbated the water quality in of drinking water [3]. Groundwater is the main source of the recent years [6]. Groundwater is the water beneath the earth’s surface that moves freely through pores and cracks * Corresponding authors. in rocks, sediments, and soils [7]. However, there are many 1944-3994/1944-3986 © 2019 Desalination Publications. All rights reserved. M. Qasemi et al. / Desalination and Water Treatment 170 (2019) 176–186 177 concerns about the quality of drinking water due to both methaemoglobinaemia or ‘blue baby syndrome’ in infants natural processes (physical and chemical weathering and under 6 months of age [35–37]. In methaemoglobinaemia, erosion of rocks, ore, and volcanic deposits) and human the oxygen-carrying capability of haemoglobin is remark- activities (agriculture and industries) [8]. ably decreased due to its conversion to methaemoglobin. Fluoride and nitrate are the critical ions that influence Nitrate itself is not carcinogenic but when transformed into the groundwater quality and have gained considerable nitrite in the gastrointestinal tract, it combines with sec- attention in recent decades owing to their high concentra- ondary and tertiary amines to generate nitrosamines which tions currently detected in drinking water and as such their have been considered as a potent human carcinogen [38]. deleterious impacts on human health [9–12]. Due to natural Literature reviews have shown that infants are exposed processes as well as human activities, the concentrations of to high concentrations of nitrate in drinking water when fluoride in water resources may exceed the recommended it is used to mix formula milk or other baby foods [38,39]. levels [13]. Fluoride in water naturally arises from weather- Elevated concentrations of nitrate in surface water bodies ing and dissociation of fluoride containing rocks and sedi- may lead to various ecological and environmental issues, ments including fluorite (CaF2), fluorapatite (Ca5(PO4)3F), including eutrophication and seasonal hypoxia [40]. WHO and cryolite (Na3AlF6) [14]. Generally there exist about has established the maximum permissible limit of 50 mg/L 85 million tons of fluoride deposits in the earth crust uni- as nitrate in drinking water to prevent methaemoglobinae- versally. Weathering of fluoride containing rocks and long- mia in infants. Therefore, it is necessary to understand com- term rock–water reactions increase fluoride concentration in pletely the contaminants and the associated health risks, groundwater. Fluoride is a natural element present in varied in order to better evaluate the potential health risk of toxic concentrations globally in water bodies [15]. Fluoride con- chemicals to consumers. tamination has been a universal environmental problem for Risk assessment proposed by U.S. Environmental years predominantly in mid-latitude regions of the world Protection Agency (USEPA) has proven to be a helpful and and has caused great concerns mainly due to its omnipresent frequently applied methodology for groundwater manage- nature and risk to human health [1,16,17]. 65% of endemic ment, environmental planning, and decision making in many fluorosis in many regions in the world is due to the consump- studies [41–43]. The aims of this research were to evaluate tion of excessive fluoride content in drinking water [18,19]. the fluoride and nitrate contamination in drinking water in Worldwide, natural fluoride level in groundwater is found as Bardaskan County and to assess the associated health risk high as 30 mg/L in more than 30 countries including Mexico, through consumption in adults, children, and infants using India, China, India, Pakistan, Iran, West Africa, Thailand, model proposed by the USEPA. The findings of the present China, Sri Lanka, Southern Africa, etc. [9]. work would be useful to health professional and decision Generally, fluoride has both beneficial and harmful makers for protecting the groundwater quality and govern- impacts on human health [20,21]. Fluoride does not exhibit ment in working out strategies for clean drinking water sup- any colour, taste or smell when dissolved in water and hence, plies and risk management. its concentration in range of 0.4–1.0 mg/L has a positive effect on human health, as it protects us from tooth cavity by help- ing calcification process of dental enamel [22]. However, flu- 2. Materials and methods oride level above 1.5 mg/L is detrimental and causes various 2.1. Study area description health problems including dental and skeletal fluorosis, oste- oporosis, arthritis, brittle bones, certain types of cancer, infer- This study was performed in Bardaskan County. tility, Alzheimer, brain damage, and thyroid disorder [23]. Bardaskan is located in Razavi Khorasan Province in East Based on World Health Organization (WHO), the optimum of Iran covering an area of 8,535 km2. At the 2017 census, range of fluoride in drinking water is set to be 0.5–1.5 mg/L its population was 68,392. The county has three districts [24]. Some researchers noticed that the water having high pH including Central District (Bardaskan), Anabad District, and values can increase the fluoride dissolution processes and Shahrabad District. This county has three cities including ion-exchange between fluoride ion and hydroxyl. Elevated Bardaskan, Anabad, and Shahrabad. The population has bicarbonate and sodium may also increase the fluoride level considerably dispersed in villages where accessibility of in groundwater [25,26]. infrastructure for the proper treatment and transportation of Another chemical of concern in water is nitrate. Nitrogen surface water are not always possible. The county is located is the main constituent of the air, comprising about 80% in the north of the Great Salt Desert (Dasht-e Kavir). The of the air we inhale. Many human activities can increase climate of Bardaskan County falls under arid climatic zone the nitrate concentrations to problematic concentrations. with extreme temperatures (hot summer and dryness in the Nitrate can originate from farming activities by application non-rainy seasons), relatively low precipitation and high of inorganic fertilizers, or manure from livestock, leaking evapotranspiration. The northern area of Bardaskan is cold from the sewage network and septic tanks. Nitrate is one in winter and in the south and central areas changes from of the important water contaminants in the