Total Water Quality And Total Human Health Hazard Indices Approach For Health Risk Evaluation With Oral Intake Pathway of Groundwater of Nitrate And Fluoride From A Rural Region of South India

15 Evaluation of chemical quality of groundwater and associated health hazards is a prerequisite 16 for taking remedial measures elsewhere. A rural region of South India was, thus, chosen for 17 the present study to assess the total quality of groundwater and also to decipher the human 18 health risk zones with respect to adults and children due to the groundwater pollution with 19 nitrate (NO  3 ) and fluoride (F  ) ions. Groundwater samples collected from the study region 20 were determined for various chemical parameters. According to the total water quality index, 21 groundwater quality is suitable for drinking purposes. However, the NO  3 (0.4 to 585.20 22 mg/L) and F  (0.22 to 5.41 mg/L) ions exceed the drinking water quality limits of 45 mg/L 23 and 1.5 mg/L in 34% and 25% of the groundwater samples, respectively. Nitrate fertilizers 24 appeared as the chief source of NO  3 , and the fluoride minerals as the main source of F  in 25 the groundwater body, which are further supported by principal component analysis. Total 26 human health hazard index (THHHI) was observed to be higher than its tolerable limit of 1.0 27 in 63% and 73% of the groundwater samples in respect of NO  3 and F  of adults and 28 children, respectively.


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Because of the rapid climatic changes, groundwater is an essential source globally, especially  The prominent rock exposures in the study region are basalts and granites (Fig. 1).

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Laterite patches also occur. The basalts are fine-grained and dark-colored volcanic rocks, 108 which are composed of calcic plagioclase feldspars and clinopyroxene with olivine, quartz, 109 The pH and electrical conductivity (EC) were measured in the field, using their 127 meters ( and NO  3 ), and ion-131 selective electrode (F  ), and following the standard water quality methods (APHA 2012).
Comprehensive tool for utilization of groundwater quality for drinking 136 137 The total water quality index (TWQI) is a comprehensive technique to express the overall 138 drinking water quality in a single term (Subba Rao et al. 2020;Wu et al. 2020a

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(1) When the TWQI is less than 50, it indicates an excellent quality of quality; when it is from 50 149 to 100, it shows a good quality of water; when it is between 100 and 200, it specifies a poor 150 quality of water; when it is from 200 and 300, it represents a very poor quality of water; when 151 it is more than 300, it suggests an unsuitable quality of water for drinking purpose. The NO  3 and F  ions were chosen for the human health risk assessment. The oral intake 156 procedure was selected for the computation of total human health hazard index (THHHI) with respect to adults and children (Li et al. 2019a, b;Wu et al. 2020). The THHHI was 158 calculated as shown in Eqs. 4 to 6 (USEPA 1991(USEPA , 2006. THHHI is the total human health hazard index (non-carcinogenic hazard).

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The tolerable limit of THHHI is 1.0 (USEPA 2014). If it is above than 1.0, the non-173 carcinogenic risk of the pollutant is greater than the tolerable level. If it is below 1.0, the non-174 carcinogenic risk is at acceptable limit. The pH in the groundwater ranged from 6.30 to 8.90 with a mean of 7.14 ( The Ca 2+ content was from 8.02 to 152.30 mg/L being a mean of 49.60 mg/L (Table 1).

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Fourteen percent of the groundwater sample showed a non-acceptable limit (75 mg/L) of  The HCO 3  was from 146.40 to 2,538 mg/L, with a mean of 1,014.31 mg/L (Table 1)   The higher alkalinity (pH and HCO 3  ) with Na + activates the leaching of fluoride 278 minerals occurring in the basement rocks and thus increases the higher F  content in the study region showed that the F  level less than 0.6 mg/L was observed mainly from the 283 northern part and also as very limited isolated patches in the southern part, which covers an 284 area of 20.36% of the total study region (Fig. 2b). A safe limit of F  (0.6 to 1.5 mg/L) was 285 found in the study region (58.47%). The next higher F  content (> For the identification of intensity of human health risk zones, the spatial distribution 334 of THHHI for adults and children was demonstrated in Fig. 3. The zones with less than 1.0 335 and more than 1.0 of THHHI were covered by 33.27% and 66.73% for adults and 28.25% 336 and 71.75% for children of the total study region, respectively. The first zone was in safe 337 limit (average THHHI: 0.54 for adults and 0.66 for children) with respect to non-cancer 338 health risk, while another one was in the unsafe limit (average THHHI: 4.15 for adults and 5.69 for children) of non-cancer health problem (Table 3). Thus, the intensity of human 340 health risk zone appears to be 1.37 times higher in children than in adults. These two zones 341 have obviously divided the region into the northern safe health zone and the southern unsafe 342 health zone, respectively, depending upon the intensity of the agricultural activities. Northwest China. Exposure and Health,9,[183][184][185][186][187][188][189][190][191][192][193][194][195] , 8, 9 to 11, 13, 14, 16, 18, 20, 22, 24, 25, 30, 33, 41 to 44, 46, 47, 49, 51