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

Evaluation of the chemical quality of groundwater and associated health hazards is a 37 prerequisite for taking remedial measures elsewhere. The rural region of South India was, thus, chosen for the present study to assess the total quality of groundwater and also to decipher the human health risk zones with respect to adults and children due to groundwater pollution with nitrate (NO  3 ) and fluoride (F  ) ions. Groundwater samples collected from the study region were determined for various chemical parameters. According to the total water quality index, groundwater quality is suitable for drinking purposes. However, the NO  3 (0.4 43 to 585.20 mg/L) and F  (0.22 to 5.41 mg/L) ions exceed the drinking water quality limits of 44 45 mg/L and 1.5 mg/L in 34% and 25% of the groundwater samples, respectively. Nitrate 45 fertilizers appeared as the chief source of NO  3 , and fluoride minerals as the main source of 46 F  in the groundwater body, which is further supported by principal component analysis. The 47 total human health hazard index (THHHI) was observed to be higher than its tolerable limit 48 of 1.0 in 63% and 73% of the groundwater samples in respect of NO  3 and F  of adults and 49 children, respectively. The intensity of human health risk zones of THHHI (>1.0) was 1.37 50 times higher in children (5.69) than in children (4.15), which cover an area of 71.75% and 51 66.73%, respectively. Thus, effective strategic measures were recommended for the 52 protection of groundwater resources from pollution and also for improving human health 53 conditions.

quality index, groundwater quality is suitable for drinking purposes. However, the NO  3 (0.4 43 to 585.20 mg/L) and F  (0.22 to 5.41 mg/L) ions exceed the drinking water quality limits of 44 45 mg/L and 1.5 mg/L in 34% and 25% of the groundwater samples, respectively. Nitrate 45 fertilizers appeared as the chief source of NO  3 , and fluoride minerals as the main source of 46 F  in the groundwater body, which is further supported by principal component analysis. The

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total human health hazard index (THHHI) was observed to be higher than its tolerable limit  It is a well-known fact that the consumption of contaminated groundwater by NO  3 92 more than 45 mg/L would cause methemoglobinemia (blue baby syndrome), where red blood 93 cells reduce their ability to carry oxygen, which leads to shortness of breath, heart attack, and 94 even death, especially in children. Sometimes, it leads to cancer also (WHO 2012 A hundred bore wells were observed in the study region during May 2015 (Fig. 1). The 144 groundwater samples were collected from them in one-liter capacity polythene bottles, which 145 were cleaned with 1:1 dilute hydrochloric acid and washed away with distilled water three 146 times before collecting the water samples, following the standard procedure (APHA 2012).

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The pH and electrical conductivity (EC) were measured in the field, using meters 149 ( The total water quality index (TWQI) is a comprehensive technique to express the overall 161 drinking water quality in a single term (Subba Rao et al. 2020;Wu et al. 2020a). The first 162 step in this index is the calculation of relative weight (Wi), after assigning the unit weight 163 (wi), for each chemical parameter on the basis of its relative significance to human health (Eq.

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(1) When the TWQI is less than 50, it indicates an excellent quality of quality; when it is from 50 172 to 100, it shows a good quality of water; when it is between 100 and 200, it specifies a poor 173 quality of water; when it is from 200 and 300, it represents a very poor quality of water; when 174 it is more than 300, it suggests an unsuitable quality of water for drinking purposes.   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 1.0, the non-196 carcinogenic risk of the pollutant is greater than the tolerable level. If it is below 1.0, the non-197 carcinogenic risk is at an acceptable limit. The pH in the groundwater ranged from 6.30 to 8.90 with a mean of 7.14 ( Table 1), which 204 indicates that it is slightly acidic to highly alkaline in nature. Three groundwater samples are  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 total water quality index (TWQI) is a scale to measure the overall drinking water quality  The higher alkalinity (pH and HCO 3  ) with Na + activates the leaching of fluoride 296 minerals occurring in the basement rocks and thus increases the higher F  content in the 297 groundwater system (Subba Rao et al. 2016, 2020a. Apart from this, the usage of phosphate 298 fertilizers may also lead to an increase in the concentration of F  in the groundwater (Subba 299 Rao et al. 2021a). The spatial distribution of concentration of F  ion in the groundwater of the 300 present study region showed that the F  level of less than 0.6 mg/L was observed mainly in 301 the northern part and also in very limited isolated patches in the southern part, which covers 302 an area of 20.36% of the total study region (Fig. 2b). A safe limit of F  (0.6 to 1.5 mg/L) was 303 found in the study region (58.47%). The next higher F  content (> 1.5 mg/L was found as   (Table 3). Thus, the intensity of 359 the human health risk zone appears to be 1.37 times higher in children than in adults. These The human health risk zone of the southern part appears to be caused by the 367 influence of the unlimited application of nitrogen fertilizers compared to that of fluoride 368 minerals and phosphate compost. This fact is established by observing the spatial distribution 369 of NO  3 and F  contents (Fig. 2), where the F  ion shows mostly the safe health zone The following conclusions were summarized, after observing the chemical quality of 394 groundwater and associated health problems in respect of NO  3 and F  ions in age groups of 395 adults and children, using the total water quality index (TWQI) and total human health hazard      , 8, 9 to 11, 13, 14, 16, 18, 20, 22, 24, 25, 30, 33, 41 to 44, 46, 47, 49, 51 , 7, 19 to 25, 28, 34, 36, 38, 39, 40, 42, 43, 50, 56, 59, 61, 64, and