Spatial distribution and seasonal variation in fluoride enrichment in groundwater and its associated human health risk assessment in Telangana State, South India

Abstract

Groundwater is a vital source of drinking water in Siddipet rural and urban regions of Central Telangana, South India and it is a major cause of fluoride toxicity in humans. The intake of elevated fluoride has a significant impact on human health, especially immediate problems that are seen in children's teeth. The primary aim of the study was to identify the seasonal variation in fluoride concentration and associated health risks in the residents of the study region. To assess the fluoride contamination in groundwater, a total of 158 samples were analyzed in two seasons. The mean concentrations of fluoride 1.26 mg/L and 2.21 mg/L were 1.46 and 2.8 times higher than the acceptable limit of 1.5 mg/L, before and after monsoon respectively. To estimate the human health risks due to the ingestion of elevated fluoride through drinking water, hazard quotient fluoride (HQFluoride) was calculated using the United States Environmental Protection Agency method. HQFluoride values were 0.44–2.44 and 0.89–4.67 for children, 0.36–2.00 and 0.73–3.82 for females, and 0.41–2.26 and 0.82–4.31 for males in pre- and post-monsoon seasons respectively, suggesting emphatically greater risk than the acceptable limits (HQFluoride > 1), which generates health risks.

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Spatial distribution and seasonal variation in
fluoride enrichment in groundwater and its
associated human health risk assessment in
Telangana State, South India
Adimalla Narsimha & Sanda Rajitha
To cite this article: Adimalla Narsimha & Sanda Rajitha (2018) Spatial distribution and seasonal
variation in fluoride enrichment in groundwater and its associated human health risk assessment in
Telangana State, South India, Human and Ecological Risk Assessment: An International Journal,
24:8, 2119-2132, DOI: 10.1080/10807039.2018.1438176
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Spatial distribution and seasonal variation in fluoride
enrichment in groundwater and its associated human health
risk assessment in Telangana State, South India
Adimalla Narsimha
a
,
b
and Sanda Rajitha
c
a
School of Environmental Science and Engineering, Chang’an University, Xi’an, China;
b
Key Laboratory of
Subsurface Hydrology and Ecological Effects in Arid Region of the Ministry of Education, Chang’an University,
Xi’an, Shaanxi, China;
c
Department of Applied Geochemistry, Osmania University, Hyderabad, Telangana, India
ARTICLE HISTORY
Received 27 January 2018
Revised manuscript
accepted 5 February 2018
ABSTRACT
Groundwater is a vital source of drinking water in Siddipet rural and
urban regions of Central Telangana, South India and it is a major cause
of fluoride toxicity in humans. The intake of elevated fluoride has a
significant impact on human health, especially immediate problems that
are seen in children’s teeth. The primary aim of the study was to identify
the seasonal variation in fluoride concentration and associated health
risks in the residents of the study region. To assess the fluoride
contamination in groundwater, a total of 158 samples were analyzed in
two seasons. The mean concentrations of fluoride 1.26 mg/L and
2.21 mg/L were 1.46 and 2.8 times higher than the acceptable limit of
1.5 mg/L, before and after monsoon respectively. To estimate the
human health risks due to the ingestion of elevated fluoride through
drinking water, hazard quotient fluoride (HQ
Fluoride
) was calculated using
the United States Environmental Protection Agency method. HQ
Fluoride
values were 0.44–2.44 and 0.89–4.67 for children, 0.36–2.00 and 0.73–
3.82 for females, and 0.41–2.26 and 0.82–4.31 for males in pre- and post-
monsoon seasons respectively, suggesting emphatically greater risk
than the acceptable limits (HQ
Fluoride
>1), which generates health risks.
KEYWORDS
fluoride contamination;
groundwater; human health
risk assessment; Siddipet
region; South India
Introduction
To supply safe drinking water is a critical issue in most parts of the rural regions in the world,
due to natural, anthropogenic, and man-made contaminants that have emerged in recent
years. It is reported that 80% of the diseases in the world come through the poor quality of
drinking water and 65% of endemic fluorosis in arid and semi-arid regions in the world is due
to the intake of elevated fluoride content in drinking water (Narsimha and Sudarshan 2017a,
2017b; Felsenfeld and Robert 1991). Therefore, the occurrence and distribution of fluoride in
groundwater/drinking water have gained worldwide attention, because it shows a remarkable
CONTACT Adimalla Narsimha adimallanarsimha@gmail.com; adimallanarsimha@163.com School of Environmental
Science and Engineering, Chang’an University, No. 126 Yanta Road, Xi’an 710054, China; Key Laboratory of Subsurface Hydrol-
ogy and Ecological Effects in Arid Region of the Ministry of Education, Chang’an University, No. 126 Yanta Road, Xi’an 710054,
Shaanxi, China.
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/bher.
© 2018 Taylor & Francis Group, LLC
HUMAN AND ECOLOGICAL RISK ASSESSMENT
2018, VOL. 24, NO. 8, 2119–2132
https://doi.org/10.1080/10807039.2018.1438176

impact on human health. The World Health Organization has designed a guideline of values
for drinking water for fluoride content in between 0.5 and 1.5 mg/L (WHO 2011). Intake of
fluoride water below 0.5 mg/L and above 1.5 mg/L can result in a number of health risks. Ele-
vated fluoride >1.5 mg/L of groundwater, which is used as drinking water, can cause severe
dental and skeletal fluorosis, renal, and neuronal disorders along with myopathy (Ayoob and
Gupta 2006; Adimalla and Venkatayogi 2017; Narsimha 2018; Narsimha and Sudarshan
2013). More than 200 million people suffer from the deadly disease called fluorosis in twenty
nations all over the world: Tanzania, Argentina, USA, Morocco, Algeria, Mexico, Syria, Jordan,
Egypt, Libya, Algeria, Sudan, Kenya, Turkey, Iraq, Iran, Afghanistan, New Zealand, Japan,
Thailand, Sri Lanka, Syria, Canada, Saudi Arabia, India, northern Thailand, and China (Ahada
and Suthar 2017; Adimalla and Venkatayogi 2017; Narsimha and Sudarshan 2017a;Ayoob
and Gupta 2006; Carrillo-Rivera et al. 2002; Naseem et al. 2010). This fluorosis has shown
adverse effects in developing countries like India and China, where approximately 66 million
and 45 million people are affected by this disease, respectively (Adimalla and Venkatayogi
2017;Liet al. 2015;2016). Recent investigations suggested that 20 states in India are consid-
ered as endemic regions of fluorosis, and all the districts in Telangana state, where groundwa-
ter is the primary source of drinking water, are also at risk of dental and skeletal fluorosis
(Adimalla and Venkatayogi 2017). High accumulation of fluorides in groundwater is common
in Telangana state, where greater geological part is covered by granitic materials that contain
fluoride-bearing minerals: fluorite (CaF
2
), fluorapatite [Ca
5
(PO
4
)
3
(Cl,F,OH)], cryolite
(Na
3
AlF
6
), villiaumite (NaF), lepidolite KLi(Fe,Mg)Al(AlSi
4
O
10
)(F,OH), hornblende
NaCa
2
(Mg,Fe,Al)
5
(Si,Al)
8
O
22
(OH,F)
2
, herderite Ca(BePO
4
)(F,OH), holmquistite Li
2
(Mg,
Fe
2C
)
3
(Al,Fe
3C
)
2
(Si
2
O
22
)(OH,F)
2,
topaz (Al
2
(F,OH)SiO
4
), wohlerite NaCa
2
(Zr,Nb)O(Si
2
,O
7
)F,
topaz Al
2
SiO
4
(OH,F)
2,
arfvedsonite (Na
3
Fe
42C
Fe
3C
(Si
4
O
11
)
2
(OH,F)
2
, tainiolite (KLiMg
2
(-
Si
4
O
10
)F
2
, polylithionite (KLi
2
Al(Si
4
O
10
)(F,OH)
2
, muscovite (KAl
2
(AlSi
3
O
10
)(OH,F)
2
,micro-
lite (Ca,Na)
2
Ta
2
O
6
(O,OH,F), pyrochlore (NaCaNb
2
O
5
F), bastnasite (CeCO
3
F), gagrinite
(NaCaYF
6
), fluocerite (CeF
3
), synchisite CeCa(CO
3
)
2
F, parisite (Ce
2
Ca(CO
3
)
3
F
2
etc., (Handa
1975;Bailey1977; Adimalla and Venkatayogi 2017;Apambireet al. 1997;Ozsvath2009).
Therefore, fluoride can be released into groundwater above fluoride-bearing minerals through
rock–water interaction and weathering processes. A number of researchers noticed that the
alkaline nature of water can accelerate the fluoride dissolution processes and ion-exchange
between F
¡
and OH
¡
. High bicarbonate and sodium can also help to enhance the fluoride
concentration in groundwater. Moreover, Na
C
-HCO
3
¡
type of water may also elevate the fluo-
ride content in the groundwater (Adimalla and Venkatayogi 2017; Narsimha and Sudarshan
2017a,2017b; Saxena and Ahmed 2003; Raju 2017;Ozsvath2009).
However, the majority of the populace suffers from various health problems, fluorosis being a
prominent one among them in the Telangana region of South India. Human health risk assess-
ment is the most important tool introduced by the United States Environmental Protection
Agency (USEPA, 1980)andisdefined as the process to assess the nature and possibility of
adverse health effects in humans who consume highly contaminated water. The level of fluoride
ion above the acceptable limits in groundwater can surely harm plants, animals, and cause severe
health problems in humans (Mahato et al. 2016;Nazet al. 2016;Liet al. 2016; USEPA 1999). A
vast number of researchers studied human health risk assessment in different regions; for exam-
ple, Ahada and Suthar (2017) conducted a study in the southern districts of Punjab, India with
emphasis on human health risks associated with high groundwater fluoride intake and found
that children are more vulnerable to fluorosis. In Odisha, health risk assessment in drinking
2120 A. NARSIMHA AND S. RAJITHA

water was conducted by Naz et al. (2016). The assessment of health risks caused by nitrate and
fluoride contaminants in drinking water was conducted in different parts of China (Chen et al.
2017;WuandSun2015;Liet al. 2016). However, chronic daily intake (CDI), hazard quotient of
fluoride (HQ
Fluoride
), fluoride concentrations (F
c
)
,
daily ingestion dose (DID), reference dose for
chronicoralexposureoffluoride (RfD), total exposure frequencies (TEF), exposure duration
(ED), average body weight (ABW), and average exposure time (AET) are very essential to esti-
mate the human health risks and detailed description is presented in the “material and methods”
section under the subheading “Human exposure health risk assessment”. The populace of the
region, which is being presently studied, relies on groundwater for drinking purposes, without
any prior examination. They are more prone to health risks when it comes to endemic fluorosis.
Hence, the aim of the study was to evaluate the fluoride content in groundwater, its seasonal var-
iation, and possible health hazards to the local residents of Siddipet district of central Telangana,
South India. Moreover, the assessment of the health risks in adults (males and females) and chil-
dren caused by the ingestion of fluoride-rich water, which was proposed by the United States
Environmental Protection Agency (USEPA), was also employed in this study region.
Methods and materials
Study area
The study region is bounded by east longitude 78.76942–78.90232 and north latitude
18.06768–18.24402 and Siddipet is a city in Siddipet district, located in central part of Telan-
gana State, South India (Figure 1). The area under investigation falls under semi-arid zone,
with a hot, humid climate, and is predominantly occupied by granite/gneiss of Archean age.
The area experiences a semi-arid climate with an annual mean temperature of 30 C. How-
ever, the months from April to June are the hottest with the temperature going up to 35–
40 C. The mean annual rainfall is recorded as 745 mm, occurring mostly during the south-
west monsoon period (June–September).
Groundwater samples collection and analysis
A total of 158 groundwater samples were collected in two seasons, 104 in the pre-mon-
soon season in the months of May and June, and 54 samples in the post-monsoon sea-
son in the month of December 2016 (Figure 1). Groundwater samples were collected in
pre-cleaned 500-ml polyethylene bottles, following the standard guidelines (APHA
1999). Hydrogen ion concentration (pH), electrical conductivity (EC), and total dis-
solved solids (TDS) were measured in the field immediately after the collection of the
samples by using pH/EC/TDS meter (Hanna HI 9811–5). Anions (carbonate CO
32¡
,
bicarbonate HCO
3
¡
, chloride Cl
¡
, sulphate SO
42¡
,nitrateNO
3
¡
,andfluoride F
¡
), cati-
ons (calcium Ca
2C
,MagnesiumMg
2C
,sodiumNa
C
, and potassium K
C
), and total hard-
ness (TH) were analyzed in the wet chemical laboratory, department of Applied
Geochemistry, Osmania University. The fluoride concentration in groundwater was
determined electrochemically, using fluoride ion-selective electrode (APHA 1999). The
electrode used was an Orion fluoride electrode, coupled to an Orion electrometer. Stan-
dard fluoride solutions (0.1–10 mg/L) were prepared from a stock solution (100 mg/L)
of sodium fluoride. As per experimental requirement, 2 ml of total ionic strength
HUMAN AND ECOLOGICAL RISK ASSESSMENT 2121

adjusting buffer grade III (TISAB III) was added to 20 ml of sample. The ion meter
was calibrated for a slope of ¡59.2 §2, and detailed procedure is presented in Table 1.
The ion-balance error (e) computation, taking the total cations Pgc(calciumCa
2C
,
Mg
2C
,Na
C
,andK
C
), and total anions Pga(HCO
3
¡
,Cl
¡
,SO
42¡
,NO
3
¡
,andF
¡
)for
each sample and computed using the equation e D[Pgc¡Pga]/[PgcCPga] £
100, is observed within the acceptable limit of §5 (Domenic and Schwartz 1990).
Human exposure health risk assessment
Eighty percent of the diseases in the world occur through the intake of poor-quality
drinking water, and 90% of endemic fluorosis in India is caused by the ingestion of
highly fluoride-contaminated drinking water for a long period of time (Narsimha and
Sudarahan 2017b; Felsenfeld and Robert 1991). Hence, it is very essential to know the
health risk assessment of the daily intake of excess dose of fluoride through drinking
water. The US Environmental Protection Agency USEPA (1993) prescribed a standard
procedure for the estimation of human health risk due to the consumption of elevated
fluoride content in drinking water. In view of this concern, the Chronic Daily Intake
Figure 1. Location of groundwater samples and study region.
2122 A. NARSIMHA AND S. RAJITHA

Table 1. Instrumental, titrimetric, and calculation methods were used for chemical analysis of groundwater samples from Siddipet region of Central Telangana,
South India.
Parameters Characteristics Analytical method Reagents Unit Reference
General pH pH/EC/TDS meter pH 4, 7, and 9.2 —APHA 1999
Electrical Conductivity pH/EC/TDS meter Potassium chloride mS/cm APHA 1999
Total dissolved solids (TDS) Calculation EC X (0.55 to 0.75) mg/L Hem 1991
Total hardness (as CaCO
3
) EDTA titrimetric EDTA, ammonia buffer, and Eriochrome Black-T
(EBT) indicator
mg/L APHA 1999
Major cations Calcium (as Ca
2C
) EDTA titrimetric EDTA, sodium hydroxide, and murexide mg/L APHA 1999
Magnesium (as Mg
2C
) Calculation MgH DTH-CaH; Mg DMgH X Eq.Wt of Mg X
Normality of EDTA
mg/L APHA 1999
Sodium (as Na
C
) Flame photometric Sodium chloride (NaCl) and KCl mg/L APHA 1999
Potassium (as K
C
) Flame photometric NaCl and KCl mg/L APHA 1999
Major anions Bicarbonates (HCO
3
¡
) Titrimetric Hydrosulfuric acid (H
2
SO
4
), phenolphthalein, and
methyl orange
mg/L APHA 1999
Chloride (Cl
¡
) Titrimetric Silver nitrate (AgNO
3
), potassium chromate mg/L APHA 1999
Sulphates (SO
42¡
) UV visible spectrophotometer HCl, ethyl alcohol, NaCl, barium chloride, sodium
sulphate
mg/L APHA 1999
Nitrate (NO
3
¡
) UV visible spectrophotometer Potassium nitrate (KNO3), Phenol disulfonic acid,
ammonia
mg/L APHA 1999
Fluoride (F
¡
) ISE (Ion selective electrode; Thermo Orion) TISAB III and NaF mg/L APHA 1999
HUMAN AND ECOLOGICAL RISK ASSESSMENT 2123

(CDI) fluoride in an individual drinking water sample was computed by Eq. (1).
Chronic Daily Intake CDIðÞD½Fc£DID £TEF £ED6½ABW £AET(1)
where CDI is expressed in mg/kg/d, F
c
: Fluoride concentration of the estimated groundwa-
tersamples(mg/L);DID:DailyIngestionDose of drinking water L/d; TEF: Total Exposure
of drinking water; ED: Exposure Duration assumed to be 64 years for males, 67 years for
females, and 12 years for children; ABW: Average Body weight taken as 65 kg for males,
55 kg for females, and 15 kg for children; and AET: Average Exposure Time is calculated
as the product of the number of years and number of days; the number of days for males,
females, and children are assumed to be 23360, 24455, and 4380 respectively, which is the
average statistical data of the adults (males and females) and children living in India
(Table 2). This study, mainly focused on fluoride contamination and its human health risk
assessment, comes under the non-carcinogenic risk, reflected by the HQ
Fluoride
(Hazard
Quotient of fluoride). HQ
Fluoride
is estimated by using Eq. (2).
HQFluoride DCDI6RfD (2)
where RfD is represented as a reference dose for chronic oral exposure of fluoride i.e.,
taken as 6E-2 mg/kg/da according to US Environmental Protection Agency (1993). The
obtained HQ
Fluoride
value, if >1, indicates potential for severe effect on human health,
whereas <1 is the acceptable limit for non-carcinogenic risk of HQ
Fluoride
(USEPA 1993).
Results and discussions
The hydrogeochemical data like the minimum, maximum, mean, median, and standard
deviation obtained from the results of groundwater samples before and after monsoon are
summarized in Table 3. The studied groundwater is alkaline in nature with the hydrogen
ion concentration ranging from 6.8 to 8.9 before monsoon, and 6.82 to 8.78 during the post-
monsoon seasons (Table 3). The means of EC, TDS, and TH before monsoon are
950.67 mS/cm, 1222.65 mg/L, and 207.77 mg/L, whereas after monsoon, the means are
1910.38 mS/cm, 480.43 mg/L, and 245.37 mg/L respectively (Table 3). The concentrations of
Ca
2C
,Mg
2C
,Na
C
,K
C
,NO
3
¡
,SO
42¡
, and Cl
¡
vary from 10 to 186 mg/L, 6 to 113 mg/L, 17
to 134 mg/L, 1 to 25 mg/L, 8.8 to 361 mg/L, 21 to 156 mg/L, 25 to 973 mg/L before monsoon,
Table 2. Human health risk parameters and their values.
Parameter Physical significance Values Units Reference
F
c
Fluoride concentrations 0.2–2.2 mg/L Pre-monsoon
0.8–4.8 Post-monsoon
DID Daily ingestion dose Males: 4 Females: 3 Children: 1 L/d Naz et al. 2016
TEF Total exposure frequencies 365 D/years Ahada and Suthar 2017;
USEPA 1999
ED Exposure duration Males: 64 Females: 67 Children:
12
Years WHO 2013
ABW Average body weight Males: 65 Females: 55 Children:
15
Kg ICMR 2009
AET Average exposure time Males: 23,360 Females: 24,455
Children: 4380
D WHO 2013
2124 A. NARSIMHA AND S. RAJITHA

whereas after monsoon the concentrations vary from 16 to 100 mg/L, 2 to 103 mg/L, 38 to
440 mg/L, 1 to 24 mg/L, 7 to 280 mg/L, 96 to 278 mg/L, 43 to 756 mg/L respectively
(Table 3). The mean dominance of cations is Na
C
>Ca
2C
>Mg
2C
>K
C
before and after
monsoon, whereas that of anions is Cl
¡
>HCO
3
¡
>NO
3
¡
>SO
42¡
>F
¡
before monsoon
and HCO
3¡
>Cl
¡
>SO
42¡
>NO
3¡
>F
¡
after monsoon.
Seasonal variation of fluoride contamination
The collected groundwater samples from the study region had high concentration of fluoride
after monsoon, the highest value being 4.2 mg/L, whereas before monsoon it was 2.2 mg/L.
The pre-monsoon fluoride concentration ranges from 0.4 to 2.2 mg/L, with a mean of
1.26 mg/L, and between 0.8 to 4.2 mg/L with a mean of 2.21 mg/L in post-monsoon seasons
in the studied groundwater (Table 3), shows values 1.46 and 2.8 times higher than the
WHO’s maximum acceptable limit of 1.5 mg/L (WHO 2011). Low fluoride concentrations
are observed in the northern part of the study region in pre- and post-monsoon seasons,
and spatial distribution of elevated fluoride concentration is seen in the southern region
(Figures 2a and b). Overall the fluoride variation and distribution pattern in pre- and post-
monsoon seasons are wide and uneven in the study region. Reddy and Rao (2006) noticed
that the uneven distribution of fluoride in Wailpalli Watershed in Nalgonda District is
mainly due to weathering mineral dissolution and the divergent fracture system is chiefly
associated with hydrochemical processes. Dissimilar distribution of fluoride concentration
in the study region could be due to the relative abundance of fluoride-bearing minerals.
However, high fluoride concentrations in groundwater have been noticed in the villages of
Narsapur (4.2 mg/L), Bakri Cheppal (3.7 mg/L), Lingareddipalli (3.7 mg/L), Tudkapalli
(3.2 mg/L), and Ponnala (3.3 mg/L), Mittapalli (2.9 mg/L), Ellupalli (2.8 mg/L), Siddipet
(2.9 mg/L), Gundavalli (2.5 mg/L), Rarukula (2.4 mg/L), Boggulonibanda (2.3 mg/L)m Tud-
kapalli (2.3 mg/L), Ganpur ((2.2 mg/L), mattubandalu (2.6 mg/L), and Gadicharalapalli
(2.2 mg/L) in the study region. Moreover, 31% and 80% of the groundwater samples had ele-
vated fluoride concentrations in between 1.5 and 4 mg/L in pre- and post-monsoon seasons
Table 3. Season-wise combined chemical composition of groundwater samples collected from the study
area.
Pre-monsoon Post-monsoon
Parameters Minimum Maximum Mean Median
Standard
deviation Minimum Maximum Mean Median
Standard
deviation
pH 6.8 8.9 7.59 7.5 0.52 6.82 8.78 7.56 7.53 0.42
EC 990 2535 950.67 706.81 559.15 1010 3850 1910.38 5830 647.5
TDS 646.4 2464 1222.65 1171.2 414.4 108 983 480.43 452.36 165.86
TH 50 565 207.77 195 90.68 125 575 245.37 227.5 97.06
HCO
3
¡
37 200 111.71 110 43.37 100 390 236.14 242 62.6
Cl
¡
25 973 230.96 192 180.11 43 756 230.82 181.05 164.88
SO
42¡
21 156 65.67 61 27.23 96 278 167.72 159.78 41.22
NO
3
¡
8.8 361 109.33 88 78.93 7 280 81.93 66 61.19
F
¡
0.4 2.2 1.26 1.2 0.5 0.8 4.2 2.21 2.05 0.72
Ca
2C
10 186 56.25 52.104 29.56 16 100 59.79 60.12 20.61
Mg
2C
6 113 34.1 31.59 17.92 2 103 23.9 18.83 20.23
Na
C
17 134 65.13 65 24.68 38 440 182.14 160.6 113.96
K
C
1 85 6.77 4 11.95 1 24 3.74 2 4.47
HUMAN AND ECOLOGICAL RISK ASSESSMENT 2125

respectively. The people in the region are severely affected by dental fluorosis and the health
risks associated with the ingestion of fluoride in groundwater are depicted in Figure 3.
The fluoride shows a significant correlation with pH, HCO
3
¡
, and Na
C
which specifies
that the alkaline nature of water with high HCO
3
¡
and Na
C
can accelerate the solubility of
fluorite in the groundwater of the studied region (Figures 4a–c). High sodium, bicarbonate,
and an alkaline pH increase the release of fluoride or ion exchange of fluoride by hydroxyl
ions (OH
¡
) (Narsimha and Sudarshan 2017a,2017b; Adimalla and Venkatayogi 2017; Nar-
simha 2018). Brouwer et al. (1988) noticed that high electro-negativity of fluoride is always
attracted by Ca
2C
ions, in teeth and bones and therefore excessive intake of fluoride may
cause pathological changes in teeth and bones and it may lead to further skeletal fluorosis.
Moreover, fluoride also exhibits a statistically significant negative correlation with NO
3
¡
(Figure 4e) and Ca
2C
(Figure 4d), which indicates that there is no substantial contribution of
fluoride in increasing its concentration by a significant amount from the anthropogenic
sources to the groundwater of the study region. In other words the reason for high fluoride
in the studied groundwater is geogenic sources, i.e., the dissolution of fluoride-bearing min-
erals can enhance the fluoride in the groundwater. The study region is occupied by the gra-
nitic rocks, which have abundance of fluoride-bearing minerals (Adimalla and Venkatayogi
2017). The main fluoride-bearing minerals are fluorite, apatite, muscovite, biotite, horn-
blende, villianmite, tremolite, cryolite, villiaumite, mica, etc. and they are well documented
in Telangana, India (Narsimha and Sudarshan 2018,2017a,2017b; Adimalla and Venka-
tayogi 2017). Therefore, weathering of fluoride-bearing minerals, through dissolution pro-
cess can cause the enhancement of fluoride in the study region’s groundwater.
Figure 2. (Continued).
2126 A. NARSIMHA AND S. RAJITHA

Assessment of health risk of high fluoride ingestion
Groundwater is adversely contaminated by F
¡
in arid and semi-arid regions in India, making it
unfit for drinking purposes, which causes high health risks to humans (Adimalla and Venka-
tayogi 2017). Elevated fluoride concentration is considered as a non-carcinogenic pollutant to
Figure 2. Spatial distribution of fluoride (a) before monsoon and (b) after monsoon in the study region.
Figure 3. Health risk effects associated with F
¡
ingestion in individuals.
HUMAN AND ECOLOGICAL RISK ASSESSMENT 2127

human health and performed in this study. Ahada and Suthar (2017) performed an assessment
of human health risk with high fluoride groundwater intake in Punjab, India and also found that
non-carcinogenic values of fluoride were 0.29–2.41 (adults) and 0.67–5.63 (children). Children
are vulnerable to the health risks caused by the intake of elevated fluoride groundwater in Pun-
jab, India. Chen et al. (2017)assessedfluoride contaminants in drinking water in semi-arid
region of China and found that 60% may pose adverse threats to infants and children, due to
higher fluoride water intake. In fact, fluoride is essential for human health in optimum quantities
Figure 4. Correlation between (a) F
¡
with pH, (b) F
¡
with HCO
3¡
, (c) F
¡
with Na
C
, (d) F
¡
with Ca
2C
, and
(d) F
¡
with NO
3
¡
.
Figure 5. Hazard Quotient of fluoride (HQ
Fluoride
) values with comparison with children and adults (males
and females): (a) before monsoon and (b) after monsoon in the study region.
2128 A. NARSIMHA AND S. RAJITHA

(0.5 to 1.5 mg/L), but excess fluoride intake is considered as hazardous to human health. In view
of human health concern, World Health Organization (WHO) has set the minimum and maxi-
mum limits of fluoride content for drinking water purposes as 0.5 and 1.5 mg/L respectively
(WHO 2011), which is the optimum range of dental health. Intake of high-fluoride drinking
water can cause mottling of teeth, calcification of ligaments, and crippling of bones (WHO
2011). The study region’sgroundwaterfluoride health risk assessment, which is classified into
five classes, is summarized in Table 4. About, 68% and 19% of the groundwater occurred in
class-II, and 31% and 80% are under class-III before and after monsoon respectively (Table 4).
In addition, in the study region, most of the people are vulnerable to dental and skeletal fluorosis,
due to the intake of high fluoride content in drinking water. Since drinking water is considered
as the primary route of fluoride exposure in the region’s population, constant exposure to ele-
vated fluoride water can lead to various fluorosis health hazards and children in particular are
quickly affected by the fluorosis problem and it is mainly observed in them in the study region.
Thus, knowing the assessment of health risks of high fluoride intake is very vital to live a better
and healthy life on earth. Hazard Quotient of fluoride (HQ
Fluoride
) in pre- and post-monsoon
seasons were 0.44–2.44 and 0.89–4.67 for children, 0.36–2.00 and 0.73–3.82 for adult females,
and 0.41–2.26 and 0.82–4.31 for adult males respectively. The high HQ
Fluoride
values were
noticed in the post-monsoon season with 4.67, 4.31, and 3.82 for children, males and females
respectively. Therefore, the increase of mineral dissolution in the post-monsoon season is one of
the reasons for elevated fluoride concentration in the groundwater of the study region. Ingestion
of elevated fluoride through drinking water can cause fluorosis health risk in children and adults.
Figures 5a and bshow the high health-risk vulnerability dominance order as males >females >
children. Therefore, this study indicates that children have more fluorosis health risks than
adults. In the study region groundwater samples contain higher fluoride in both seasons, which
is the principal reason for dental fluorosis in children and adults. Chen et al. (2017)foundthat
there is an interrelation between body size/weight and concentration of fluoride in drinking
water. Ravindra and Garg (2007)identified that the ingestion of excess fluoride during tooth
development, particularly in the teens, may also result in dental fluorosis. It is because children
have more sensitive bodies and less weight than adults that they are more vulnerable to health
risks through the ingestion of water having elevated fluoride content. Overall, ingestion of drink-
ing water in both seasons in the study region suggests that the majority of samples may induce
non-carcinogenic risk (in terms of HQ
Fluoride
), especially to children and adults. Residents living
inthestudyregionrelyonthesinglesourceofgroundwater,whichhaselevatedfluoride content,
for drinking purposes. Therefore, non-carcinogenic health hazard is the main problem facing the
people living in the study region. Consequently, the people of the study region are at high risk of
dental fluorosis, and if the people do not consume clean drinking water this problem may tre-
mendously increase in the future.
Table 4. Health risk effects associated with F
¡
ingestion in individuals.
Percentage of samples
Classes F (mg/L) Effect on human health (WHO 1996; Dissanayake 1991) Pre-monsoon Post-monsoon
Class-I <0.5 Conducive to dental caries 1 0
Class-II 0.5 to 1.5 Promotes development of strong bones and teeth 68 19
Class-III 1.5 to 4 Dental fluorosis (mottling of teeth) 31 80
Class-IV 4 to 10 Dental and skeletal fluorosis (pain in the back and neck bones) 0 1
Class-V >10 Crippling fluorosis 0 0
HUMAN AND ECOLOGICAL RISK ASSESSMENT 2129

Conclusions
Groundwater is the principal source of drinking water in the study region. The fluoride in
groundwater was higher than the recommended limit of 1.5 mg/L set by the WHO. The mean
concentrations of fluoride were 1.26 and 2.21 in pre- and post-monsoon seasons respectively.
About 31% in pre-monsoon and 80% in post-monsoon groundwater sampling location
showed 1.5 to 4 mg/L fluoride content in groundwater. A considerable amount of fluoride
enters into the human body through drinking water. So, HQ
Fluoride
was calculated as an indica-
tor of non-carcinogenic health risk hazard and higher values were obtained in the post-mon-
soon season. The range of HQ
Fluoride
was 0.44–2.44 and 0.89–4.67 for children, 0.36–2.00 and
0.73–3.82 for adult females, and 0.41–2.26 and 0.82–4.31 for adult males respectively. The
study reveals that children are highly prone to the health risks caused by dental fluorosis
through the intake of elevated fluoride water. Therefore, the study indicates that the frequent
monitoring of groundwater is a vital step to avoid human health risks and that groundwater
must be tested prior to consumption to avoid health risks, especially in children.
Acknowledgments
The authors would like to express their gratitude to the anonymous reviewers for their kind comments
which helped to increase the quality of the present work.
Funding
The funding for this research was provided by the Department of Science and Technology (DST),
Govt. of India, New Delhi under the Fast Track Young Scientist Scheme (No. SR/FTP/ES-13/2013) to
the first author (Adimalla Narsimha), who would like to express his sincere gratitude and appreciation
for the financial support.
ORCID
Adimalla Narsimha http://orcid.org/0000-0002-6182-8317
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