Using Shungite in Water Defluoridation by Galvanocoagulation

Objective To detect the levels of oxidative stress in brain and serum of rats with chronic fluorosis and the antagonistic effects of vitamin E (VitE), and to reveal the role of oxidative stress in brain injury. Methods Thirty healthy SD rats were divided into three groups based on body weight by means of a random number table (10 rats in each group, half male and half female). In the control group, the rats were fed with drinking water containing less than 0.5 mg/L fluoride; in the fluoride group, the rats were fed with high doses of sodium fluoride in drinking water (50.0 mg/L) and the VitE antagonistic group were fed with the same content of fluoride in drinking water as the fluoride group, but adding VitE (50.0 mg/kg) by intragastric administration once a day. All rats were fed with normal diet (6.2 mg/kg). After exposure to fluoride for 10 months, all rats were put to death, dental fluorosis of the rats was examined and the fluoride content in bone was determined by fluoride-ion selective electrode; the activity of superoxide dismutase (SOD) was determined by the xanthine oxidase method and glutathione peroxidase (GSH-Px) by the colorimetric method, the level of malonaldehyde (MDA) by the glucosinolates barbituric acid fluorescence method and the levels of OH-, H2O2 and in rat serum and/or brain were detected by the colorimetric method. Results In the rats of the fluoride group, fluoride content in bone was higher as compared to control [bone fluoride: (211.07 ± 48.52) vs. (33.40 ± 9.26) mg/kg,P < 0.01]. The activities of SOD and GSH-Px in rat brains of the fluoride group [(20.10 ± 1.98) kU/g, (28.70 ± 19.35) kU/L] were significantly lower than those of controls [(37.05 ± 3.13) kU/g, (59.63 ± 12.83) kU/L, all P < 0.01], the activity of SOD in VitE antagonistic group [(26.27 ± 1.74) kU/g] was higher than the fluoride group (P < 0.01); the activities of SOD and GSH-Px in rat serum of the fluoride group were significantly decreased [(11.55 ± 1.75) kU/L, (79.50 ± 19.18) U/L] than those of controls [(20.79 ± 2.43) kU/L, (170.00 ± 14.68) U/L, all P < 0.01], the activity of SOD in VitE antagonistic group[(17.23 ± 0.68) kU/L] was higher than the fluoride group (P < 0.01). The levels of MDA in rat brain and serum of the fluoride group [(8.84 ± 0.69) μmol/L, (1.46 ± 0.11) nmol/L] were significantly higher than those of controls [(1.27 ± 0.74) μmol/L, (0.83 ± 0.10) nmol/L, all P < 0.01], VitE antagonistic groups [(4.51 ± 1.13) μmol/L, (1.29 ± 0.02) nmol/L] were lower than the fluoride groups (all P < 0.01). The levels of OH-, H2O2 and in rat brains of the fluoride group [(24.24 ± 1.80) kU/g, (15.28 ± 2.97) mmol/L, (6.53 ± 0.96) U/g] were significantly higher than those of controls [(11.44 ± 1.63)kU/g, (5.28 ± 1.20) mmol/L, (2.93 ± 0.42) U/g, all P < 0.01], VitE antagonistic groups [(14.43 ± 0.76) kU/g, (8.09 ± 0.55) mmol/L, (4.41 ± 0.49) U/g] were lower than the fluoride groups (all P< 0.01). Conclusions Elevated levels of oxidative stress are found in brain and serum of the rats with chronic fluorosis, which may be a main mechanism of brain injury. VitE may play an important antagonistic role in oxidative damage induced by fluoride toxicity. Key words: Fluorosis; Oxidative stress; Brain; Serum; Vitamin E

Objective To observe the expression of interleukin-6 (IL-6), glycoprotein 130 (gp130), phosphatidylinositol 3-kinase (PI3K) and protein kinase B (Akt) in bone tissue of fluorosis mice and explore the mechanisms of IL-6/gp130 signaling pathway in the pathogenesis of bone injury caused by fluoride. Methods Sixty-four male Balb/c mice were divided into 4 groups based on body weight by random number table method and 16 mice were in each group. The mice in control group were fed with distilled water, experimental animals in low, middle and high dose groups were fed with distilled water containing NaF 25, 50 and 100 mg/L, respectively. The mice were fed for three months to establish a drinking water fluorosis model. Mice dental fluorosis was observed and the fluoride contents in spine were detected by fluorine-ion selective electrode method. The changes of morphology and cell ultra structure in fluorosis bone tissue were observed by optical and electronic microscope. The activities of serum alkaline phosphatase (ALP) and acid phosphatase (ACP) were detected by micro enzyme labeled method. The levels of serum IL-6 were detected by enzyme-linked immunosorbent assay. The mRNA expression levels of IL-6, gp130, PI3K and Akt in long bone tissue were detected by real-time fluorescence quantitative PCR (real-time PCR). The protein expression levels and activity of gp130, PI3K and Akt were detected by Western blotting. Results The rates of dental fluorosis in low fluoride group, middle fluoride group and high fluoride group were 62.5% (10/16), 100.0% (15/15) and 100.0% (16/16), respectively, and all the fluoride groups were higher than control group (0, 0/15, all P < 0.05). Fluoride contents of bone were significantly increased with increase of fluoride doses (F= 309.716, P < 0.05). The bone trabecular thickness and density in fluorosis mice were remarkably increased and disorder, and bone sclerosis was observed under optical microscope. The percentage of trabecular bone area was significantly increased with increase of fluoride doses(F= 25.161, P < 0.05). Ultra structurally, swelling of cells, dilation of endoplasmic reticulum, chromatin margination in osteoblasts and osteoclasts of high fluoride group were observed which indicated that cells ultra structure was apparently damaged. The activities of serum ALP and ACP were significantly increased with increase of fluoride doses (F= 19.586, 13.329, all P < 0.05), and both high fluoride group [(8.05 ± 1.10), (10.95 ± 1.85) King unit] and middle fluoride group [(6.48 ± 0.92), (9.18 ± 0.76) King unit] were significantly higher than control group [(5.15 ± 0.73), (7.49 ± 0.66) King unit, all P < 0.05]. The levels of serum IL-6 in control group, low fluoride group, middle fluoride group and high fluoride group were (5.98 ± 1.43), (7.54 ± 2.16), (5.25 ± 1.97), (6.31 ± 1.36) ng/L, respectively, the differences were statistically significant (F= 3.840, P < 0.05), and low fluoride group was significantly higher than control group (P < 0.05), and middle fluoride group was significantly lower than low fluoride group (P < 0.05). The differences of mRNA expression levels of IL-6, gp130, PI3K and Akt in long bone tissue between groups were statistically significant (F= 9.952, 8.954, 6.997, 21.504, all P < 0.05), and high fluoride group (0.59 ± 0.42, 0.46 ± 0.22, 0.55 ± 0.30, 0.61 ± 0.10) was lower than control group (1.10 ± 0.54, 1.16 ± 0.67, 1.20 ± 0.84, 1.06 ± 0.37) and low fluoride group (1.86 ± 0.63, 1.61 ± 0.64, 1.74 ± 0.65, 1.70 ± 0.58, all P < 0.05), and all mRNA expression except gp130 of low fluoride group was higher than that of control group (all P < 0.05). The differences of protein expression levels and activities of gp130, PI3K and Akt in long bone tissue between groups were statistically significant (F= 4.777, 7.479, 3.535, all P < 0.05), and low fluoride group (0.66 ± 0.10, 0.69 ± 0.12, 0.92 ± 0.09) was significantly higher than control group (0.51 ± 0.11, 0.47 ± 0.06, 0.66 ± 0.14, all P < 0.05), and high fluoride group (0.42 ± 0.11, 0.38 ± 0.06, 0.67 ± 0.14) was lower than low fluoride group (all P < 0.05). Conclusion The mRNA and protein expression levels of IL-6, gp130, PI3K and Akt in bone tissue of fluorosis mice have changed, which indicates that IL-6/gp130 signaling pathway may be involved in the pathogenesis of bone injury caused by fluoride. Key words: Fluorine; Mice; Interleukin-6; Glycoproteins; Bone and Bones

Objective To investigate the current status of coal-burning endemic fluorosis and the fluoride content in foods and drinking water in Hongya County,Sichuan Province.Methods Dental fluorosis and urinary fluoride were suveyed in children of 8～12 years old in two schools which repectively located in Gaomiao and Wawushan Town.The adults above 20 years old underwent clinical examination.At the same time,fifty adults above 20 years old in Garden Village were chosen to take forearm and calf X-ray films to find out the evidence of skeletal fluorosis.The content of fluoride in food such as bacon,corn,dry capsicum in Sanxing Village in Gaomiao Town and Futian Village in Wawushan Town as well as drinking water in five families in Sanxing Village were determined.Results The dental fluorosis rate of children was 40.76%(161/395),the dental fluorosis index was 0.86 in Gaomiao Town.The dental fluorosis rate of children was 14.36%(82/571),the dental fluorosis index was 0.31 in Wawushan Town.The medium value of the urine fluoride was 0.81 mg/L.ranged 0.16～3.89 mg/L.The positive rate oi the clinical examination of skeletal fluorosis was 5.27%(27/512),the X-rays detective rate was 4.00%(2/50).The medium value in bacon,corn,dry capsicum were 6.00,0.64,1.49 mg/kg.The averaged content of the fluoride in drinking water(0.14±0.06)mg/L of local household was within the eligible limitation.Conclusions It is currently a mild endemic disease in Hongya Country,its incidence is reduced apparently,pathogenetic environmental fluoride content is reduced.The main source of fluoride is from the preserved ham contaminated with fluoride,which is epidemiologically significant in endemic area of Hongya County.Defluoriding countermeasures should be taken in the endemic areas. Key words: Fluoride poisoning; Fluorosis,dental; X-rays; Environmental pollution

Objective To investigate and master the outcome of endemic fluorosis surveillance, the use and management situation of the facilities for decreasing fluorine in water-related endemic fluorosis in Fengshun County, Guangdong Province. Methods The surveillance was carried out according to The National Surveillance Scheme of Endemic Fluorosis in 1991 - 2007. Dazhai, Hupo and Anquan Villages in Fengshun County of Guangdong Province were selected as monitoring spots. The dental fluorosis of 8 - 12 years old children was examined with Dean index, the fluoride contents in urine and drinking water were determined with fluoride selective ion electrode method. Clinical and X-ray skeletal fluorosis of adults over 16 years of age were examined every 3 to 5 years. Results The fluoride contents in water almost reached the hygienic requirements (1.0 mg/L) in Dazhai (0.83 mg/L in 2007) and Anquan Villages(0.27 mg/L in 2007) after improving water and decreasing fluorine. The prevalence rate of dental fluorosis of students aged 8 - 12 years old fluctuated and decreased gradually, especially prevalence rate of mederate and severe fluorosis decreased obviously and reached the hygienic requirements (30%) after altering water source(20.8% in Dazhai, 3.8% in Anquan in 2007). But the fluoride contents in water were in relatively high level (1.01～2.30 mg/L), and the prevalence rate of dental fluorosis of students aged 8-12 years old(44.3% in 2007) was above the hygienic requirements in Hupo Village after improving water and decreasing fluorine. The dental fluorosis index in Daizai, Hupo and Anquan Villages dropped from 1.5, 3.0 and 1.3 in 1991 to 0.30, 0.80 and 0.10 in 2007, respectively. Epidemic strength reached respectively the criteria in mild and non-endemic areas. Fluoride contents in urine of children aged 8-12 years old in the three villages all were under the limit of 1.50 mg/L after 2002. The prevalence rate of adult clinical fluorosis [31.8% (84/264), 34.4% (131/381), 44.1% (89/202) in 1991; 11.0% (43/388), 12.9% (61/473), 9.6% (27/280) in 2005] and positive detection rate of skeletal fluorosis examined by X-ray [70.0% (35/50), 86.0% (43/50), 46.0% (23/50) in 1991 ; 20.0% (10/50), 16.0% (8/50),10.0% (5/50) in 2005] decreased gradually in Dazahai, Hupo and Anquan Villages. Conclusions The fluoride contents in the Dazhai Village and Anquan Village have met the national hygienic standard, with water fluoride content and the rate of dental fluorosis of 8 - 12 years children nearly matching to that of non-disease area. The prevalence of endemic fluorosis in the surveillance villages has been under control. Key words: Fluoride poisoning; Fluorosis; dental; Surveillance

A 2-year comparison of three topical fluoride agents

Objective To investigate the running condition of defluoridation projects and fluoride concentration in drinking-water in Anyang City of Henan Province.Methods Cluster sampfing of Anyang,Hua, Neihuang,Tangyin Counties emdimic fluomsis poining of Anyang City was conducted places of different orientation, about 1/3 towns in the selected examination towns had their defluoridation project investigated.Results Among 472 pwjects investigated,427 were running normally,accounting for 90.47%(427/472),only 9.53%(45/472)of the projects were out of service.68.62%(293/427)of the pwjects had normal fluoride concentration in drinking water, 31.38%(134/427)of the projects failed to do 80.In Hua County,41.00%(41/100)of the projects were out of service. In Neihuang County.70.39%(107/152)of the projects had abnormally high fluoride concentration in drinking water. Conclusions Defluoriding projects are out of service and fluoride concentration in drinking water exceeds the standard in Hua,Neihuang Counties of Anyang City.We must analyse the cause of it seriously,work out measures, promote a healthy and sustainable development of defluondation projects Key words: Fluorine; Drinking water; Data collection

In some parts of Tanzania, fluoride ion concentrations in potable water are higher than recommended by WHO. Consequently, searches for economically and technically viable strategies are required to address this problem. This work aims to determine the potential of phosphate rock mined from Minjingu area in Northern Tanzania as water de-fluoridatant. The results obtained are reported herein. The rock particles were chemically activated and then characterised by XRF, XRD and nitrogen physisorption. Results showed that the main component of chemically activated rock particles was calcium hydroxyapatite with Ca/P ratio of 1.55 whereas the main component of non-activated particles was calcium fluoroapatite (Ca/P ratio of 1.66). The results also indicated that activated rock material was mesoporous with a BET surface area of 57.4 m2/g. Results for water defluoridation showed that the material had a fluoride ion percentage removal of about 90%, when the adsorbent dose was 8 g, contact time of 30 minutes, initial fluoride ion concentration 5 mg/L, pH values of 6.0 to 7.2 and batch volume of 50 mL. The material could be regenerated using 1% NaOH and reused in the water defluoridation process. Therefore, Minjingu Phosphate Rock (MPR) is potential water de-fluoridatant.

The paper presents the results of the study on the impact of the initial concentration of urea nitrate and fluoride ion in the leaching solution on the weight decrease of granite mined at Prydniprovsk Specialized Quarry and the change in the fluoride ion concentration in the solution during intermittent and continuous agitation. During the experiments, we used urea nitrate with weight fraction of nitrate acid 41.5%, urea - 44.3%, water - 14.2%, and ammonium fluoride-bifluoride (fluorine content was 61.2%). Fluoride ion concentration was measured using a fluoride-selective electrode relatively a saturated silver chloride half-cell while the acidity of solutions was measured by titrimetry. Weight decrease was studied for a granite sample, grain fraction -2.0 + 1.0 mm, during intermittent stirring depending on the initial concentration of urea nitrate 0.25 g/dm3, 0.5 g/dm3, and 1.0 g/dm3 and fluoride ion 2.81×10-2 g/dm3 to 3.20×10-1 g/dm3 with intermittent stirring at a temperature of 20±2 °C for 7 days. The data on the change in sample weight depending on the initial concentration of fluoride ion and addition of urea nitrate were received. It was revealed that the decrease in the fluoride ion concentration ambiguously depended on the initial concentration of both urea nitrate and fluoride ion. In our opinion, the fluoride ion concentration decrease occurred with adding urea nitrate due to the fact that nitric acid urea could form adducts with both sulfuric and fluoric acids resulting in the decrease of their reactivity. We have studied the decrease of the granite sample weight and the change in the fluoride ion concentration under continuous stirring and at a temperature of 30±2 °C for 4 days. It was found that the change in the sample weight and concentration of fluoride ion during continuous stirring differed from the similar data obtained during intermittent stirring due to more intensive formation of urea nitrate adducts with sulfuric and fluoride acids. The initial dissolution rate was calculated for a granite sample, its value was 2.384×10-7 s-1 after adding urea nitrate and 2.299×10-7 s-1 without its addition.

Objective To investigate the effects of fluoride on trabecular bone of the tibia and lumbar in BALB/c mice. Methods Totally 64 four-week-old BALB/c mice were randomly divided into 4 groups by weight, 16 per group: control group (treated with distilled water) and 3 sodium fluoride (NaF) exposure groups (treated with NaF at 25, 50 and 100 mg/L F-), respectively. At 12 weeks, mice were killed and blood, two hind limbs and lumbar were collected. Bone fluoride content and incidence rates of dental fluorosis were determined. Serum content of alkaline phosphatase (AKP) and acid phosphatase (ACP) were detected by micro enzyme labeled method. The ultrastructure of osteoblasts and osteoclasts in lumbar were observed via transmission electron microscope. The pathological changes of the trabecular bone of the tibia and the lumbar were observed under optical microscope, the percentage of trabecular area (%Tb.Ar) was measured with Image-Pro Plus (IPP) software. Results Bone fluoride contents of low, middle and high fluoride groups [(1 828.62 ± 102.93), (3 308.27 ± 185.63), (4 933.36 ± 301.16) mg/kg] were higher than that of the control group [(775.23 ± 92.56) mg/kg, all P < 0.05]. The incidences of dental fluorosis in the 4 groups were 0 (0/16) , 47% (7/15) , 93% (14/15) and 100% (16/16) , respectively; the difference was statistically significant (χ2= 27.23, P < 0.05). In middle and high fluoride groups, serum AKP [(18.30 ± 1.99), (24.50 ± 3.14) king unit/100 ml] and ACP [(11.97 ± 1.73), (11.31 ± 1.46) king unit/100 ml] were significantly higher than those of control [(14.63 ± 1.21), (9.07 ± 1.47) king unit/100 ml, respectively, all P < 0.05]. Under the electron microscope, osteoblast had developed organelles in each fluoride group, rough endoplasmic reticulum, Golgi body, and mitochondria were abundant, and nucleolus was obvious in the osteoblast. Osteoclast was rich in mitochondria, ruffled border clear and distributed phagocytic vacuoles in low fluoride group and middle fluoride group. Compared with the control group (17.03 ± 3.73), HE staining of tibia % Tb.Ar in high fluoride group (28.79 ± 8.26) was significantly increased (P < 0.05). The lumbar spine %Tb.Ar in low, middle and high fluoride groups (15.87 ± 2.59, 18.28 ± 0.89, 21.99 ± 1.81) were higher than that of the control group (12.06 ± 1.76, all P < 0.05]. Conclusions BALB/c mice could be used as a model of skeletal fluorosis. Osteoblast and osteoclast are activated in BALB/c mice with skeletal fluorosis. Bone formation is more obvious than bone resorption and bone mass is increased. What is more, bone mass has increased more significantly in the lumbar spine of mice. Key words: Fluorides; Bone and bone tissue; Osteoblast; Osteoclast

Objective To find out the status of drinking-water-borne endemic fluorosis and the effect of preventive measures in Hebei Province,so as to provide a basis to prevent and cure fluorosis.Methods One affected county (city,district) with drinking-water-borne endemic fluorosis was sampled in every city and 10 water improvement projects were investigated in that county.Three villages were taken out in every county.The operating state of the projects,the water fluoride content,and the dental fluorosis of children aged 8-12 and skeletal fluorosis of adults were investigated in these villages.Results A total of 93 projects were investigated,among which 94.6％(88/93) were operating properly and the qualified rate(fluoride content ≤ 1.2 mg/L) of the projects was 54.84％(51/93).Among the 9 large projects,the water fluoride content of 7 projects exceeded 1.2 mg/L.A total of 23 villages with water improvement projects were investigated and only 43.4％ (10/23) of them water fluoride content were lower than 1.2 mg/L.The dental fluorosis rate,the dental fluorosis index and the rate of skeletal fluorosis were 33.2％ (532/1601),0.74 and 5.7％ (66/1155),respectively.In the 7 villages without water improvement projects,2 of them exceeded 2.0 mg/L,but lower than and equal to 4.0 mg/L of water fluorosis and 5 of them were normal(＜ 1.2 mg/L).The dental fluorosis rate,the dental fluorosis index and the rate of skeletal fluorosis were 33.4％ (111/332),0.72 and 2.9％ (10/350),respectively.Conclutions The qualified rate of water improvement projects of fluoride content ≤ 1.2 mg/L is low and the endemic fluorosis is still comparatively serious in Hebei Province.The progress of water improvement projects in the areas with endemic fluorosis should be accelerated and the quality of water improvement projects should be increased. Key words: Drinking water; Fluorosis, dental; Skeletal fluorosis; Data collection

目的 研究骨质改变在饮不同水氟水平人群中的分布规律.方法在无工业氟污染,主要品种的粮菜和空气氟水平无明显差异的农村,选择9个等级饮水氟水平(0.24～10.81mg/L)的村,对居民按年龄和性别采用分层随机抽样,进行骨X线照像,观察骨质改变.结果饮水氟水平与各度骨质硬化率呈正相关关系,与骨质硬化指数也呈正相关关系(极轻度除外).骨质疏松分布在饮水氟水平5.6mg/L以下地区的55岁以上人群,饮水氟水平与骨质疏松率呈负相关关系.骨质软化分布在饮水氟水平5.6mg/L及以上地区.混合型改变无明显规律性.结论各种类型和各种程度的骨质改变的出现与饮水氟水平密切相关.在调查的人群中有与氟骨症有关的轻度(早期)骨质改变.在饮水氟0.24～1.0mg/L水平已有一定数量的氟骨症存在。

The high prevalence of dental fluorosis and bone mineralization deficiency as a result of exposure to fluorides has increased in Kenya over the years due to consumption of water with elevated levels of fluoride. The World Health Organization (WHO) provides a guideline of 1.5 mg/L level of fluoride in drinking water. However, majority of studies carried out in Kenya over the last 40 plus years have indicated very high levels of fluoride in drinking water in various regions, with a prevalence in dental fluorosis observed in children and adults living in Rift valley and central regions due to basaltic and volcanic rocks. Unfortunately, this trend of fluoride-induced enamel changes has been observed in other regions such as Nairobi and Machakos which were originally presumed to contain low fluoride levels. This study sought to analyse the applicability of Maerua subcordata root powder (MSRP) in the removal of fluorides in borehole drinking water. Fresh Maerua subcordata roots were peeled to obtain the white flesh, chopped into small pieces, dried and ground into powder. The process parameters varied were; fluoride ion concentration [F−] (0–12 mg/L), adsorbent dosage (0–200 g/L) and equilibration time (30–240 min) [F−] were hence analysed before and after treatment using ion selective electrode (ISE) fluoride meter. Results indicated that MSRP is a viable plant in fluoride treatment with approximately 68% fluoride ion removal efficiency. An MSRP dosage of 200 g/L was found optimal in [F−] reduction while a 2 mg/L [F−] concentration recorded the highest reduction of [F−]. The optimal equilibration time was found to be 30 min. The results can be used to develop a low-cost column for treatment of high fluoride waters in rural areas using MSRP. Borehole samples were treated with MSRP using the optimized conditions; however their reduction levels were lower than the [F−] standards used. It is envisaged that with further modification and/or doping with zero-valent iron nanoparticles, it’s efficiency will be improved.

Chronic Kidney Disease of uncertain etiology (CKDu) is a fatal disease which causes death from kidney failure due to the unknown risk factors and has already affected more than 400,000 people in rural agricultural landscape (dry zone) of Sri Lanka. This has become a major health hazard in Sri Lanka. The drinking water is supplied using bowsers and several reverse osmosis (RO) plants have been installed in some areas of Sri Lanka and they are not viable solutions. Therefore, rainwater comes up as an alternative for drinking water. The primary objective of this study is to determine whether rainwater can be used as an alternative safe drinking water source in Girandurukotte area in terms of water quality. The physical, chemical and biological analysis were performed to compare the water quality parameters of 3 water sources (groundwater, surface water and rainwater) in the Girandurukotte area. The sample size of each source is 20 (n=20) and rainwater collected in pre-monsoon and post-monsoon periods. The most common storage tanks (polyethylene (PE) and ferrocement (FC) were subjected to this study to compare the water quality depending on the material of the rainwater tank. The results show that there is a significant difference in rainwater in terms of water quality compared to groundwater and surface water. There is a significant difference (p<0.05) in parameters such as, colour, turbidity, pH, Cd, As, Zn, Pb, Na, K, Mg, free ammonia, fluoride, total hardness, total alkalinity, nitrate and nitrite. In the comparison of storage material, rainwater in FC tank was high in pH while rainwater in PE tank was lower in pH and have a significant difference (p<0.05) for some water quality parameters such as pH, total alkalinity and total dissolved solids. Still water quality of rainwater collected in both tanks (PE and FC) was within portable drinking water standards (Sri Lanka Standards; 614, 2013) and there is no likelihood of Cd, Pb and As contamination in rainwater and fluoride content, hardness is well below safe limits. Keywords: CKDu, Rainwater harvesting, Groundwater, Ferrocement, Polyethylene

Fluoride is a common constituent in most of the rocks and the release of fluoride into groundwater is the major problem in several parts of the world. The present study was carried out with the objective of identifying sources and mechanism of release of fluoride from the rocks and its impact on human health in Vaniyar river basin, Dharmapuri district, Tamil Nadu. Groundwater samples were collected from 44 wells once in 2 months from June 2011 to August 2014 and analyzed for major cations and anions using an ion chromatograph. The possible reasons for the increased concentration of fluoride in groundwater of the area were investigated by taking into account of the agricultural practises and the major rock types in the area. The observed order of the dominance of cations in groundwater in the study area is Na+ > Ca2+ > Mg2+ > K+ and that of anions is Cl− > HCO3− > SO42− > CO3− > F−. The fluoride concentration in groundwater of this region ranges from 0.15 to 6.14 mg/l. Out of 569 samples analysed, fluoride concentration exceeded the maximum permissible limit of the drinking water standards of BIS 1.5 mg/l in 396 samples. Many people living in this area are suffering from dental and skeletal fluorosis due to prolonged use of fluoride-rich groundwater for drinking. Concentration of fluoride in groundwater is relatively low in wells located in charnockite region, whereas the concentration of fluoride in groundwater is high in the deep wells in regions comprising of epidote hornblende biotite gneiss. The major source of fluoride in groundwater in the area is due to leaching of fluoride-bearing minerals. Fluoride ions from biotite and hornblende minerals leach into the groundwater and contribute high fluoride concentration in this region. The concentration of fluoride in groundwater increases when the water level is deep indicating higher release of fluoride from greater depth. The geochemical reactions that control the release of fluoride from fluoride-bearing minerals such as biotite and hornblende into groundwater were identified. Removal of high concentration of fluoride from drinking water is necessary in this region and measures should be taken to supply water after removal of fluoride for the betterment of the livelihood in the area.

Non-ideality and ion-pairing in saturated aqueous solution of sodium fluoride at 25 °C