Environmental Science and Pollution Research https://doi.org/10.1007/s11356-020-08451-7 RESEARCH ARTICLE Spatial distribution of endemic fluorosis caused by drinking water in a high-fluorine area in Ningxia, China Mingji Li1 & Xiangning Qu2 & Hong Miao1 & Shengjin Wen1 & Zhaoyang Hua1 & Zhenghu Ma2 & Zhirun He2 Received: 29 November 2019 /Accepted: 16 March 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract Endemic fluorosis is widespread in China, especially in the arid and semi-arid areas of northwest China, where endemic fluorosis caused by consumption of drinking water high in fluorine content is very common. We analyzed data on endemic fluorosis collected in Ningxia, a typical high-fluorine area in the north of China. Fluorosis cases were identified in 539 villages in 1981, in 4449 villages in 2010, and in 3269 villages in 2017. These were located in 19 administrative counties. In 2017, a total of 1.07 million individuals suffered from fluorosis in Ningxia, with more children suffering from dental fluorosis and skeletal fluorosis. Among Qingshuihe River basin disease areas, the high incidence of endemic fluorosis is in Yuanzhou District and Xiji County of Guyuan City. The paper holds that the genesis of the high incidence of endemic fluorosis in Qingshui River basin is mainly caused by chemical weathering, evaporation and concentration, and dissolution of fluorine-containing rocks around the basin, which is also closely related to the semi-arid geographical region background, basin structure, groundwater chemical character- istics, and climatic conditions of the basin. The process of mutual recharge and transformation between Qingshui River and shallow groundwater in the basin is intense. There is a close coupling relationship between the power of central and southern Ningxia disease areas and Qingshui River watershed of excess fluorine water. Because the traditional drinking water source of the residents in the basin is shallow groundwater, the underground water is the main cause of the high incidence of endemic fluorosis. The results show that Xiji County and Yuanzhou District were the areas of high incidence of endemic fluorosis which gradually decreased to the middle and lower reaches of Qingshui River. In space, distribution characteristics are Qingshui River source area > Qingshui River valley basin area, tributary area > trunk stream area, upstream area > middle reaches area> downstream area of Qingshui River. This is relatively consistent with the spatial distribution of fluoride ion content in Qingshui River groundwater. Keywords Endemic fluorosis . Arid area . High-fluorine water . Spatial distribution Introduction is estimated that there are currently over 21 million patients with dental fluorosis and over 10 million patients with skeletal Fluorosis is a widespread endemic disease in China. As early fluorosis in China (DDCMH, China). The cause of these con- as 1980, a general survey identified cases of fluorosis in more ditions is in most cases excessive uptake of fluorine via drink- than 7100 villages, distributed over 1000 counties in China. It ing water. Low but regular uptake of fluorine is beneficial for dental health, but when present concentrations are above Responsible editor: Philippe Garrigues 1 mg/L in drinking water, it can lead to dental fluorosis, and at concentrations beyond 3 mg/L, the incidence of dental fluo- * Mingji Li rosis will reach 100% for exposed individuals. The World [email protected] Health Organization (WHO) advises a maximum allowable * Hong Miao fluorine concentration of 1.5 mg/L in drinking water (Fawell [email protected] 2006). The occurrence of dental fluorosis is further related to local 1 Resource and Environment Department, Ningxia University, temperatures (related to increased water consumption in Yinchun 750021, China warmer climates), intake of calcium and phosphorus, and in- 2 Western Ecology Research Center, Ningxia University, dividual differences. An imbalance of vitamins A and D, and Yinchun 750021, China Ca and P uptake can increase the dental damage associated Environ Sci Pollut Res with fluorine (Li 2004). Drinking water guidelines set by the while the collective influence of river water, groundwater, and Chinese government require the fluorine concentration in mu- rainfall in China remains to be assessed. This is particularly nicipal drinking water to remain within the range of 0.5– important in the high-fluorine region in northwestern China, 1.0 mg/L. In recent years, efforts have been made to mitigate where a loess plateau is rich in carbonate with an alkaline pH adverse effects of endemic fluorosis in high-fluorine areas, (Liu et al. 1966), and fluorine-bearing minerals such as mica, through improving water quality and, when needed, by amphiboles, tourmaline, and apatite are abundant. Through relocating communities through the project of eco-migration rainfall, groundwater leaching, circulation, and exchange be- conducted by the government; from the 1980s to the end of tween groundwater and surface water, fluorine can be released 2016, the ecological migration project in Ningxia, led by the from these minerals to be introduced into surface water includ- local government, has relocated more than 1 million people ing river water. from the contiguous poverty-stricken areas of the Liupanshan Our research studies the coupling relationship between the Mountains to the areas along the Yellow River. The Ningxia fluorine content and the incidence of endemic fluorosis in the ecological migration project is a process of population spatial Qingshui river basin. And we aim to investigate groundwater reconstruction under the response of ecological pressure in the and surface water are the main reasons that affecting the health ecologically fragile area and the extremely poor area of of residents in the basin, and encourge the local government of Liupanshan Mountains. Ningxia to carry out water reform projects and migration Owing to the relatively high prevalence of endemic fluoro- projects. sis in China, the fluorine distribution, origin, and other factors responsible for the disease have frequently been investigated. Liu and colleagues demonstrated in 1980 that endemic fluo- rosis was mainly concentrated in 3 regions within China: an Material and methods east-to-west belt in the northern deserts, a region along the northern coast, and a region in the south, with a number of Study area localized smaller areas elsewhere. Groundwater with a high fluorine content was correlating with geological conditions, Ningxia is a land-locked province in the north of China soil lithology, and hydrochemical characteristics in Northern (Fig. 1, right). The Qingshui River flows through Ningxia China (Liu et al. 1980), while in Inner Mongolia it was mainly and its basin (shaded gray in the figure) covers 4 counties detected in the alluvial-pluvial plain at the mountain front (Xiji, Tongxin, Haiyuan, and part of Zhongning County) and (Feng et al. 2015), suggesting an origin from fluorine- 3 districts (Yuanzhou, Hongsibu, and Shapotou Districts)that containing minerals and rocks in the surrounding mountains. together account for 49.98% of the land surface of Ningxia. A correlation with soils and groundwater rich in sodium car- Among them, Xiji, Tongxin, and Haiyuan Counties and bonate was identified (He et al. 2010). Low Ca2+ concentra- Yuanzhou District are part of a poverty-stricken area of the tions further favor the formation of high-fluorine groundwater, Liupanshan Mountains designated by the Chinese govern- as is a slight alkalinity (Mao et al. 2016). This was demon- ment to receive special attention to mitigate poverty-related strated in the plain and mountain front of Inner Mongolia, problems including improvement of drinking water quality. − 18 where pH and concentrations of HCO3 , δ O, δD, and total The eastern and south-central parts of Ningxia see a high dissolved solids (TDS) were all higher in high-fluorine incidence of endemic fluorosis and goiter. The local climate groundwater collected in the plain than those in the mountain is arid with little rainfall and water supply is limited. In the front (Li et al. 2018). Similar findings were reported from south-central area, the annual rainfall is about 300 mm, mostly inland river basins in Yanchi, Ningxia (Wu et al. 2018). occurring during the wet season from July to October, whereas Piper trilinear diagrams were used to indicate the groundwater annual evaporation exceeds 2300 mm. Local populations of- facies are basically identical in different seasons, and ten use untreated spring and well water as sources for drinking hydrochemical facies are of the Na-Cl type and Na-SO4-Cl water despite its poor quality. The Qingshui River system is type, while Gibbs diagrams illustrated that groundwaters re- the only first tributary of the Yellow River in central and side in evaporation-dominant areas, highlighting the crucial southern Ningxia. Qingshui River basin is the main area role of evaporation in the chemistry of groundwater (Wu where the Qingshui River and the shallow groundwater in et al. 2018). the basin resupply and transform each other. Current investigations of high-fluorine water and its con- The local geography surrounding the river basin is charac- sequences to human health mainly focus on (a) the occur- terized by mountains with thick strata deposited during the rence, classification, and pathogenesis of endemic fluorosis; Jurassic, Cretaceous, and Tertiary Periods. These strata are (b) sources,