Distribution Of Fluoride In Groundwater Research Articles

Occurrence and Distribution of Fluoride in Groundwater and Drinking Water Vulnerability of a Tropical Dry Region of Andhra Pradesh, India

There has been a growing concern over the occurrence of fluoride (F−) in groundwater and the impact of F− exposure on human health issues over the past decades. So, this study conducted a regional–scale assessment of the occurrence and trend of groundwater F− distribution [2014–2018] integrated with locally field–based investigations on F− exposure to a few selected families (10 households and 35 respondents) and reason behind their consumption of F− containing water (n = 18). In the local study, water samples were collected from multiple sources around the selected households by dividing them into consumptive and non–consumptive use. Results revealed that across the state of Andhra Pradesh, the occurrence of F− is more than the permissible limit in groundwater, and it has been increasing over the years (2014–2018) (average SD is 0.55), and the local study showed that the groundwater had an average of 1.5 mg/L F−, while other sourced water had an average of <1 mg/L F−. Most interestingly, nine families are consuming non–F− containing water (<0.52 mg F−/day) which is commercially available, while only one family is consuming F− containing groundwater and being exposed to >3 mg F−/day. This disparity in fluoride exposure is dependent on economic stability and health exposure policies.

Investigating spatial distribution of fluoride in groundwater with respect to hydro-geochemical characteristics and associated probabilistic health risk in Baruipur block of West Bengal, India

Fluoride (F−) enrichment in groundwater of the lower Gangetic plain in West Bengal, India is a major concern. Fluoride contamination and its toxicity were reported earlier in this region; however, limited evidence was available on the precise site of contamination, hydro-geochemical attributions of F− mobilization and probabilistic health risk caused by fluoridated groundwater. The present study addresses the research gap by exploring the spatial distribution and physico-chemical parameters of fluoridated groundwater along with the depth-wise sedimental distribution of F−. Approximately, 10 % of the groundwater samples (n = 824) exhibited high F− ≥ 1.5 mg/l from 5, out of 19 gram-panchayats and Baruipur municipality area and the maximum F− was observed in Dhapdhapi-II gram-panchayat with 43.7 % of samples showed ≥1.5 mg/l (n = 167). The distribution patterns of cations and anions in fluoridated groundwater were Na+ > Ca2+ > Mg2+ > Fe > K+ and Cl− > HCO3− > SO42− > CO32− > NO3− > F−. Different statistical models like Piper and Gibbs diagram, Chloro Alkaline plot, Saturation index were applied to better understand the hydro-geochemical characteristics for F− leaching in groundwater. Fluoridated groundwater is of Na-Cl type which implies strong saline character. The intermediate zone between evaporation and rock dominance area controls F− mobilization along with ion-exchange process occurring between groundwater and host silicate mineral. Furthermore, saturation index proves geogenic activities related to groundwater F− mobilization. All cations present in sediment samples are closely interlinked with F− in the depth range of 0–18.3 m. Mineralogical analyses revealed that muscovite is the most responsible mineral for F− mobilization. The probabilistic health risk assessment disclosed severe health hazard in the order of infants > adults > children > teenagers through F− tainted groundwater. At P95 percentile dose, all the studied age groups showed THQ >1 from Dhapdhapi-II gram-panchayat. Supply of F− safe drinking water is required through reliable water supply strategies in the studied area.

Potential health risk assessment and distribution of fluoride in groundwater of Munger, Bihar India: a case study

High fluoride intake via groundwater is a very serious problem for human health, especially in children. The present study focused on the health risk in children between 5–15 years due to higher consumption of fluoride in water used for potable purposes. A total of 195 samples of groundwater were analyzed for water parameters like pH, EC, TDS, fluoride, etc. On the basis of the primary data on the quality of drinking water, non-carcinogenic health risks of excessive fluoride intake in children were evaluated. Findings showed that the concentration of fluoride in Munger lies from 0.029 to 12 (mg/l) and 13.8% of total samples contain fluoride exceeding the allowable limit (1.5 mg/l). Hazard quotient value through ingestion of drinking water with high-level fluoride content varies from 0.625 to 8.571 whereas via dermal exposure hazard, quotient value lies in between 0.001 to 0.012. Therefore, the total hazard quotient obtained in Munger varied from 0.626 to 8.58. This indicates that children in Munger are highly vulnerable to non-carcinogenic health risks via prolonged fluoride intake mainly through the drinking water pathway. The outcome of the sensitivity analysis revealed that the concentration of fluoride is the most influential parameter in non-carcinogenic health risk.

Spatial Distribution of Fluoride in Groundwater of Narasinghpur Block, Cuttack, Odisha, India

Aims: Fluoride-rich groundwater is common in granite aquifers throughout India and the world. The fluoride concentration of tube well water was investigated in this study. Also discussion was made on fluorides and their correlation with other water-quality indicators.
 Place and Duration of Study: The research area i.e. Narasinghpur block fall in the western half of the Cuttack district of Odisha under lateritic uplands and hilly tract. Before the rainy season (January, 2020), fifty two groundwater samples from different places in Narasinghpur were collected.
 Methodology: Standard procedures were used for collecting, preserving, analysing, and interpreting several parameters viz., pH, EC, Ca2+, Mg2+, Na+, HCO3-, CO32-, F- etc. of water samples.
 Results: The content of fluoride ranged from 0.58 to 4.95 mg L-1. Fluoride containing minerals released into groundwater due to the alkaline pH and high bicarbonate levels. The arid environment of the region, the predominance of granitic, khondalitic, and charnockitic rocks, the longer contact time with fluoride-bearing minerals, and the minimal freshwater exchange are responsible for the high concentration of fluorides in the groundwater. Positive correlations were found between F- and pH (r= 0.681**), Na+ (r= 0.690**), and HCO3- (r= 0.719**), and negative correlations with Ca2+ (r= -0.565**) and Mg2+ (r= -0.597**).
 Conclusion: Majority of the groundwater samples collected from gram panchayats falling under the block contained fluoride level higher than that set by BIS/WHO standard, posing a hazard to various ecosystems. The people dependent on these groundwater resources are prone to several health hazards.

Fluoride in Groundwater, Its Variation with Seasons and Relationship with Other Water Quality Parameters in Rangareddy District of Telangana, India

Fluorine, which occurs naturally as fluoride in the earth’s crust in small amounts, is essential to humans and animals and is known to stimulate plant growth when present in small concentrations. However, higher concentrations of fluoride in drinking water cause dental and skeletal fluorosis in animals and humans and when present in high concentrations in groundwater used for irrigation, it accumulates in the plants and the soil and causes undesirable effects. A study was carried out during kharif, 2015 and rabi season of 2015-16 in Talakondapalle Mandal of Rangareddy District, Telangana state, India, to measure and map the distribution of fluoride in groundwater in borewells used for irrigation, to observe seasonal variation in fluoride content and to examine the relationship of fluoride with other water quality parameters such as pH, EC, Cl-1, CO3-, HCO3-, SO4-2, Ca+2, Mg+2, Na+, K+, RSC and SAR. Fluoride in groundwater ranged between 0.72 to 4.50 ppm with a mean of 2.84 ppm and standard deviation of 1.30 ppm in kharif season and from 1.32 to 4.92 ppm with a mean of 3.29 ppm and standard deviation of 0.24 ppm in rabi season. Except for two borewells in kharif, fluoride concentration was higher than the permissible limit of 1 ppm. Groundwater fluoride map of the study area was generated using kriging technique. Fluoride concentration was higher in all the borewells in rabi over kharif with mean fluoride concentration being 15.8% higher in rabi season. Fluoride concentration was significantly positively correlated with pH, HCO3-, Na+, SAR and RSC of ground water and significantly negatively correlated with Ca+2.

Spatial variability of the sources and distribution of fluoride in groundwater of the Sanya alluvial plain aquifers in northern Tanzania

Groundwater contamination from geogenic sources poses challenges to many countries, especially in the developing world. In Tanzania, the elevated fluoride (F−) concentration and related chronic fluorosis associated with drinking F− rich water are common in the East African Rift Valley regions. In these regions, F− concentration is space dependence which poses much uncertainty when targeting safe source for drinking water. To account for the spatial effects, integrated exploratory spatial data analysis, regression analysis, and geographical information systems tools were used to associate the distribution of F− in groundwater with spatial variability in terrain slopes, volcanic deposits, recharge water/vadose materials contact time, groundwater resource development for irrigated agriculture in the Sanya alluvial plain (SAP) of northern Tanzania. The F− concentration increased with distance from steep slopes where the high scale of variation was recorded in the gentle sloping and flat grounds within the SAP. The areas covered with debris avalanche deposits in the gentle sloping and flat grounds correlated with the high spatial variability in F− concentration. Furthermore, the high spatial variability in F− correlated positively with depth to groundwater in the Sanya flood plain. In contrast, a negative correlation between F− and borehole depth was observed. The current irrigation practices in the Sanya alluvial plain contribute to the high spatial variability in F− concentration, particularly within the perched shallow aquifers in the volcanic river valleys. The findings of this study are important to the overall chain of safe water supply process in historically fluorotic regions. They provide new insights into the well-known F− contamination through the use of modern geospatial methods and technologies. In Tanzania's context, the findings can improve the current process of drilling permits issuance by the authority and guide the local borehole drillers to be precise in siting safe source for drinking water.

Distribution of fluoride in groundwater around Chagan Lake and its risk assessment under the influence of human activities

Abstract Chagan Lake is located in the area of Western Jilin for which waterways have high fluorine content. Because of the construction of water conservancy projects and agricultural irrigation areas, the groundwater replenishment and drainage conditions there have changed. Groundwater test data were used to analyze the status of groundwater fluoride with this changing hydrodynamic gradient. The paper established a health risk assessment model based on triangular fuzzy number. The results show that the samples of phreatic water and confined water with excessive fluoride content accounted for 68.74% and 29.4%, respectively. Samples that exceeded standards of fluoride content were mainly distributed in the northwest and southwest. The chemistry of phreatic water is more complicated than that of confined water. The water quality categories are mainly poor and very poor. The formation of major anions and cations was mainly controlled by evaporation and rock weathering. It was also found that non-carcinogenic risks of fluoride in phreatic water are greater than those in confined water. The risk indices for children and adults were [1.1, 1.6] and [0.6, 0.9], respectively (α = 0.8). The non-carcinogenic risk assessment model based on triangular fuzzy numbers has a higher reference value than that of traditional models.

Occurrence and distribution of fluoride in groundwater of chad formation aquifers in Borno state, Nigeria

Borno State is largely underlain by the Chad Formation which is the youngest stratigraphic sequence in the Chad Basin and most prolific in terms of groundwater resources The Formation consists of the three prominent water bearing zones known as the Upper Middle and Lower zone aquifers The Middle and the Lower zone aquifers are confined while the Upper zone aquifer is unconfined semi confined and confined in some places A total of water samples were collected from boreholes and hand dug wells tapping these aquifers The samples were collected using plastic bottles and at each sampling point pH temperature and electrical conductivity were measured using portable pH EC meter In the laboratory samples were analysed for fluoride concentration using Spectrophotometer with detection limit of mg l The Upper zone aquifer has fluoride concentration within the WHO acceptable limit of less than mg l except for a sample in Magumeri which has concentration of mg l The Middle and Lower zone aquifers have relatively higher concentrations with the highest of mg l in Gubio and mg l in New Marte respectively The relatively higher concentrations above the WHO limit of mg l in these aquifers might be because of leaching from the confining clay layers enhanced by long residence time and high temperature The alkaline nature of water in these aquifers and their moderate electrical conductivity favour dissolution of fluoride In the study area cases of mild to severe dental fluorosis have been observed in areas with high fluoride concentration ndash above the WHO limit In New Marte for instance where the highest fluoride concentrations was recorded cases of skeletal fluorosis have been noticed

Mechanism of fluoride enrichment in groundwater of hard rock aquifers in Medak, Telangana State, South India

A total of 194 groundwater samples were collected from wells in hard rock aquifers of the Medak district, South India, to assess the distribution of fluoride in groundwater and to determine whether this chemical constituent was likely to be causing adverse health effects on groundwater user in the region. The study revealed that the fluoride concentration in groundwater ranged between 0.2 and 7.4 mg/L with an average concentration of 2.7 mg/L. About 57% of groundwater tested has fluoride concentrations more than the maximum permissible limit of 1.5 mg/L. The highest concentrations of fluoride were measured in groundwater in the north-eastern part of the Medak region especially in the Siddipeta, Chinnakodur, Nanganoor and Dubhaka regions. The areas are underlain by granites which contain fluoride-bearing minerals like apatite and biotite. Due to water–rock interactions, the fluoride has become enriched in groundwater due to the weathering and leaching of fluoride-bearing minerals. The pH and bicarbonate concentrations of the groundwater are varied from 6.6 to 8.8 and 18 to 527 mg/L, respectively. High fluoride concentration in the groundwater of the study area is observed when pH and the bicarbonate concentration are high. Data plotted in Gibbs diagram show that all groundwater samples fall under rock weathering dominance group with a trend towards the evaporation dominance category. An assessment of the chemical composition of groundwater reveals that most of the groundwater samples have compositions of Ca2+–Mg2+–Cl− > Ca2+–Na+–HCO3 − > Ca2+–HCO3 − > Na+–HCO3 −. This suggests that the characteristics of the groundwater flow regime, long residence time and the extent of groundwater interaction with rocks are the major factors that influence the concentration of fluoride. It is advised not to utilize the groundwater for drinking purpose in the areas delineated, and they should depend on alternate safe source.

Fluoride distribution in groundwater, soil and some crops grown in fluoride endemic area

ABSTRACT : Fluoride content of ground water, soils and some cereal and vegetable crops were estimated in 26 villages in Aatmakoor mandal of Nalgonda district, Telangana, India. The results indicated that, accumulation of fluoride (F) was observed in different plant parts of crops irrigated with F contaminated ground water (0.73 to 3.25 and 1.12 to 4.67 mg L-1 during Kharif and Rabi seasons, respectively) grown in soil containing 0.41 to 2.32 and 0.68 to 2.63 mg kg-1 available fluoride during Kharif and Rabi seasons, respectively. All the values obtained were well below the toxic limit of 2.57 to 6.44 mg kg-1 in soil and maximum contaminant level of 4.0 mg kg-1 in crops and vegetable stipulated by EPA, FAO, and WHO Joint standard limit for fluoride. The implication of the results is that the use of the ground water for irrigation and the contribution of fluoride to the soil and absorption by the crops, has no deleterious effect on the soil and some crops cultivated with ground water. Maximum accumulation of F (mg kg-1 dry wt.) occurred in the roots followed by shoot and economic part. The mean F levels in the economic part of the crops analyzed are follows the order, paddy > sorghum > red gram in Kharif and groundnut > paddy > sorghum in Rabi.

High fluoride in groundwater of an industrialized area of Eastern India (Odisha): inferences from geochemical and isotopic investigation

An assessment of fluoride distribution in groundwater of an industrialized area (Talchir), Odisha, India, was carried out to understand the potential sources and processes. This study is significant as the water resources are being endangered by the mining and other industrial activities in this region. High concentration of fluoride (4.4 mg/L) was observed in groundwater of this area, which was attributed mainly to mining activities. Additional source for high fluoride is the basement granitic rock containing fluoride bearing minerals like amphibole, biotite and fluorite. The dominant chemical types are found to be Na–Ca–HCO3, Na–Mg–HCO3, Ca–Mg–HCO3 and Ca–Na–HCO3. The groundwater facies variation was found in accordance with the local lithology. There was no marked difference in the fluoride concentration of groundwaters between near and far off mining zone. Geochemical modeling indicated precipitation of calcite and dolomite as the driving force for the release of fluoride from the formation. In addition to the precipitation of calcite and dolomite, evapotranspiration also contributes to high fluoride in groundwater. Environmental stable isotopes inferred that there was no clear isotopic distinction between high and low fluoride groundwater and the groundwater was found to be evaporated. Environmental tritium data suggested that the groundwater was modern and fluoride enrichment was facilitated by long residence time of groundwater. Statistical methods also corroborate the geochemical and isotopic inferences. The study highlights that natural geogenic source is the main cause for high fluoride in groundwater refuting earlier theories that attribute mining activities as the only source for high fluoride in this region.

Fluoride content of minerals in gneissic rocks at an area of endemic dental fluorosis in Sri Lanka: estimates from combined petrographic and electron microprobe analysis

A mass balance of the mineralogical sources of fluoride in charnockitic gneiss bedrock and regolith (weathered rock) in Sri Lanka has been undertaken, using optical petrography and Scanning Electron Microscopy (SEM) with energy dispersive X-ray spectrometry (EDX) to support development of a conceptual model of fluoride release to groundwater. Bedrock and regolith samples were collected in Polonnaruwa where there is a widespread occurrence of dental fluorosis attributed to excessive fluoride (up 5.25mg/L) in groundwater, while primary minerals of the gneissic bedrock are identified as the ultimate source of fluoride. Fluoride leaching related to long-term weathering of the bedrock and development of the regolith, control the occurrence of F in the groundwater system which is yet unresolved. In the study area, the charnockitic gneiss bedrock is mantled by a few meters thick regolith within which the groundwater table fluctuates seasonally. Mineral abundance and mineral fluoride content were estimated using petrographic and SEM analysis. Plagioclase, hornblende, pyroxene, K-feldspar, quartz, biotite and titanite (sphene) were the major minerals of the rock though the mineral proportions vary widely over the area. Apatite and magnetite were present as accessory minerals. Fluoride concentrations obtained from SEM-EDX analysis were combined with the volume percentage of minerals from petrography to estimate the total rock fluoride concentration. The order of fluoride abundance was apatite (highest), biotite, titanite, and hornblende. Plagioclase, K feldspar, pyroxene and magnetite did not have any noticeable fluoride concentrations. Loss of fluoride from the rock mass upon weathering was clearly evident and hornblende appeared to be the most significant fluoride releasing agent through weathering. Apatite, though present in accessory amounts, is distributed evenly in the rock and hence may be considered as a steady fluoride donor causing elevated and uniform fluoride distribution in groundwater. On the other hand, hornblende and biotite though of irregular occurrence (area wise), may cause high fluoride anomalies in groundwater in areas of high abundance.

Re-examining the Spatial Distribution of Fluoride in Groundwater of Sri Lanka: A Field Study at Nochchiyagama, Anuradhapura

Fluoride is well known for both beneficial and detrimental effects on human health. Fluoride improves the dental health by preventing cavities. However, excessive amounts of fluoride lead to the development of dental and skeletal fluorosis. There is a narrow range between fluoride intake which is advantageous and those which begin to be damaging. Dental fluorosis caused by fluoride rich drinking water is a common health issue in the dry climate zone of Sri Lanka. The spatial distribution of fluoride in groundwater in Sri Lanka has been extensively studied and several fluoride distribution maps have been published to date. However, careful analysis of these maps reveal that the fluoride distribution presented in some geographical regions does not agree with each other. This study focused on examining the fluoride distribution in Nochchiyagama, Anuradhapura to re-evaluate its fluoride distribution. During the study, approximately 200 water samples were collected from dug and tube wells, water reservoirs and canals. Fluoride concentration of the samples was determined by the fluoride selective electrode method. Other physico-chemical properties of water such as pH, conductivity, hardness etc. were determined by internationally accepted standard methods. The average fluoride concentration in Nochchiyagama was 1.1±0.8 mg/l (n=202) in the range 0.29 to 5.52 mg/l; however, many of the published maps state the fluoride distribution in the Nochchiyagamaarea as 0.5 to 1.0 mg/l. A careful examination of the fluoride data reveals two distinct fluoride distribution patterns. The geographical area between the Puttlam-Anuradhapura highway (A12) and the Wilpaththu National Park generally has a higher fluoride content with an average 1.2±1.0 mg/l (n=103) in the range 0.31 to 5.52 mg/l. The area between Puttlam-Anuradhapura highway (A12) and Thabuththegama-Anuradhapura highway (A28) has an average fluoride concentration of 0.9±0.5 mg/l (n=99) in the range 0.29 to 2.53 mg/l. The first geographical area had about eight fluoride hot spots (<2.5 mg/l) while other region had only two. One of the most visible hydrological differences in these two regions is that the first region solely depends on rainwater for water requirements while the other one has a complex network of irrigational canals distributing water from the Kala Oya irrigational scheme.

Spatial distribution of fluoride in groundwater of Sri Lanka

Fluoride ions in drinking water is well known for both beneficial and detrimental effects on health. Millions of inhabitants in the Dry Zone of Sri Lanka are vulnerable to fluorosis due to consumption of high fluoride groundwater. The objective of this study is to upgrade the spatial distribution map of groundwater fluoride levels in Sri Lanka. The map was prepared using nearly 14000 groundwater fluoride data that were collected from primary and secondary sources. The fluoride map of Sri Lanka indicates that the climate and hydrological conditions appear to play a major role in the geochemical distribution of fluoride in groundwater. In some cases, over 25 % of wells have more than 2 mg/L of fluoride, which is much higher than the recommended level for tropical countries. As shown in the map, even within the Dry Zone region, some low fluoride regions can be observed. This may probably be due to the effect of surface water, which contains fairly low levels of fluoride. In general, from among the chemical parameters in groundwater, fluoride stands out as an ion that appears to seriously affect the water quality of the Dry Zone. Doi: http://dx.doi.org/10.4038/jnsfsr.v40i4.5044 J.Natn.Sci.Foundation Sri Lanka 2012 40 (4):303-309

A study on the status of fluoride ion in groundwater of coastal hard rock aquifers of south India

India has an increasing incidence of fluorosis, dental and skeletal, with nearly about 62 million people at risk. High fluoride groundwaters are present especially in the hard rock areas of the country. This paper analyzes the most extensive database on fluoride and other chemical constituent distribution in the coastal hard rock aquifers of Thoothukudi district. A total of 135 samples were collected and analyzed for major cations and anions to assess the geochemical process. The fluoride concentration in drinking waters varied from BDL to 3.2 mg l−1 in the study area. Majority of the samples do not comply with WHO standards for most of the water quality parameters. The saturation index of fluorite saturation index was used to correlate with F− to identify their relationship to increase of fluoride levels. The correlation between the F− concentration and the water type was also attempted. Spatial distribution of fluoride in groundwater was studied to understand the influencing factors. The relationship of F− with HCO− 3, Na+ and pH concentrations were studied and found that HCO− 3, has good correlation with F− than the other parameters.

Geochemical provenance and spatial distribution of fluoride in groundwater of Taiyuan basin, China

Hydrogeochemistry data were utilized to understand origin, distribution, and geochemical evolution of the high-fluoride groundwater in Taiyuan basin, China. In the study area, the spatial distribution of the high-fluoride groundwater are strictly controlled by the host rock and geomorphic conditions. Three types of groundwater with the F− concentration of 2 mg/L are located in the areas bordering the limestone zones, in the areas bordering the sandstone of Permian and Carboniferous, and in the depressions of the central parts of the basin, respectively. The high-fluoride groundwater mostly have the high values of TDS, and its values of pH range from 7.2 to 8.8. The most common water types of the high-fluoride groundwater are Na·Ca–HCO3 and Na·Mg–HCO3. The geochemical mode reveals that the dissolution of the fluorine-containing minerals and the evaporation effect of the shallow groundwater control the evolution of high F− concentration in Taiyuan basin.

Geochemical provenance and spatial distribution of fluoride in groundwater of Mayo Tsanaga River Basin, Far North Region, Cameroon: implications for incidence of fluorosis and optimal consumption dose

The 500,000 inhabitants of Mayo Tsanaga River Basin are vulnerable to a "silent" fluorosis from groundwater consumption. For the first time, the groundwater is investigated for the purpose of identifying the provenance of fluoride and estimating an optimal dose of fluoride in the study area. Based on the fluoride content of groundwater, fluorine and major oxides abundances in rocks from the study area, mean annual atmospheric temperature, and on-site diagnosis of fluorosis in children, the following results and conclusions are obtained: Fluoride concentration in groundwater ranges from 0.19 to 15.2 mg/l. Samples with fluoride content of <1.5 mg/l show Ca-HCO(3) signatures, while those with fluoride >1.5 mg/l show a tendency towards Na-HCO(3) type. Fluor-apatite and micas in the granites were identified as the main provenance of fluoride in the groundwater through water-rock interactions in an alkaline medium. The optimal fluoride dose in drinking water of the study area should be 0.7 mg/l, and could be adjusted downward to a level of 0.6 mg/l due to the high consumption rate of groundwater, especially during drier periods.

Fluoride distribution in groundwater and survey of dental fluorosis among school children in the villages of the Jhajjar District of Haryana, India

Fluoride concentration of groundwater reserves occurs in many places in the world. A critical area for such contamination in India is alluvial soil of the plain region, consisting of five blocks (Jhajjar, Bahadurgarh, Beri, Matanhail, and Sahalawas) of the Jhajjar District adjacent to the National Capital Territory of India, New Delhi. The purpose of this study was to assess the association between water fluoride levels and prevalence of dental fluorosis among school children of the Jhajjar District of Haryana, India. The fluoride content in underground drinking water sources was found to vary in villages. Hence, the villages were categorized as high-fluoride villages (1.52-4.0 mg F/l) and low/normal-fluoride villages (0.30-1.0 mg F/l). The source of dental fluorosis data was school-going children (7-15 years) showing different stages and types of fluorosis who were permanent resident of these villages. The fraction of dental fluorosis-affected children varied from 30% to 94.85% in the high-fluoride villages and from 8.80% to 28.20% in the low/normal-fluoride villages. The results of the present study revealed that there existed a significant positive correlation between fluoride concentration in drinking water and dental fluorosis in high-fluoride villages (r = 0.508; p < 0.001) and insignificant correlation in low-fluoride villages.

Distribution of fluoride in groundwater of Maku area, northwest of Iran

High fluoride groundwater occurs in Maku area, in the north of West Azarbaijan province, northwest of Iran. Groundwater is the main source of drinking water for the area residents. Groundwater samples were collected from 72 selected points including 40 basaltic and 32 nonbasaltic springs and wells, in two stages, during June and August 2006. The areas with high fluoride concentrations have been identified, and the possible causes for its variation have been investigated. Regional hydrogeochemical investigation indicates that water-rock interaction is probably the main reason for the high concentration of ions in groundwater. The concentration of F− in groundwater is positively correlated with that of HCO3 − and Na+, indicating that groundwater with high HCO3 − and Na+ concentrations help to dissolve some fluoride-rich minerals. All of the water samples, collected from the basaltic areas do not meet the water quality standards for fluoride concentration and some other parameters. Hence, it is not suitable for consumption without any prior treatment. Inhabitants of the area that obtain their drinking water supplies from basaltic springs and wells are suffering from dental fluorosis. The population of the study area is at a high risk due to excessive fluoride intake especially when they are unaware of the amount of fluoride being ingested due to lack of awareness.

Fluoride distribution in the environment along the gradient of a phosphate-fertilizer production emission (southern Brazil)

Airborne fluoride was determined in the rainwater, surface soil and groundwater along a gradient of emission of a phosphate fertilizer factory in Rio Grande, southern Brazil. Concentrations of fluoride in rainwater and groundwater achieved 3 mg l(-1) and 5 mg l(-1), respectively, and were dependent on pH. The fluoride deposited from emissions accumulated in a superficial horizon of soil in quantities comparable to those in the manufactured end-products--up to 23,000 mg kg(-1). Fluoride distribution in the environment is controlled by physical-chemical parameters of emission, rain intensity and soil properties. The highest fluoride concentrations were registered at a close distance of up to 2 km from the factory. The distribution of fluoride in groundwater resembled the same distribution in rainwater due to the high permeability of the local soils. Fluoride penetration to the groundwater also depended on the type of vegetation cover. The groundwater in woodland areas was less affected by contamination of fluoride than in the grassland areas, most probably because of the influence of eucalyptus throughfall, which increases the pH of wet precipitates.