Assessment of groundwater quality with special reference to fluoride and its impact on IQ of schoolchildren in six villages of the Mundra Region, Kachchh, Gujarat, India.

Abstract

Sixty groundwater (GW) samples from bore and dug wells averaging 560 feet deep were collected from the six villages of Baroi, Chhasara, Gundala, Mundra, Pragpar, and Zarpara in the semi-arid Mundra region of Kachchh, Gujarat, India. The mean temperature of the GW collection samples was 32.11oC, and the average slightly alkaline pH was 8.2, which is characteristic of GW in this semi-arid region. Average turbidity was 7.7 NTU, and the total dissolved solids (TDS) average was 1141.19 mg/L. Zarpara had the highest total alkalinity level of 620.84 mg/L, whereas the average was 392.01 mg/L. The average total water hardness level was 267.71 mg/ L, which falls under a normal range. The average biological oxygen demand (BOD) was less than 6 mg/L, and the dissolved oxygen (DO) was 7.6 mg/L. The average levels of calcium, magnesium, and chloride were within permissible limits. Fluoride (F) concentrations were higher in Chhasara, Gundala, and Mundra villages with values of 3.42, 1.8, and 1.9 mg/L (ppm), respectively. The socio-economic scale of the area was essentially low and equal, i.e., category E in a scale of A–E. Urine samples of 34 schoolchildren from high F and 50 from low F villages were collected and analyzed for F: 2.25 ppm in urine samples from villages having higher F levels in the GW, which was highly significant (p?0.01) as compared to 0.42 ppm F in the low F villages. The average IQ level of schoolchildren (N = 50) from the low F villages was 97.17, which is significantly higher (p?0.001) than 92.53 of schoolchildren (N = 34) from the high F villages.

EXCERPTS:

Table 1 … the average F concentration in the GW [groundwater] of the Chhasra, Mundra, and Gundala village areas exceeded the permissible limit of 1.5 mg/L as well as the desirable limit of 1.0 mg/L.23-24 On the other hand, the F concentration in the village areas of Baroi, Zarpara, and Pragpar fell below 1.0 mg/L.

Table 2 …compares the mean F levels in the GW drinking water and urine samples of the 84 schoolchildren who were tested. Results reveal a significantly higher F level (p?0.05) in drinking water correlated with higher F levels in the urine and vice versa for the lower F drinking water and urine samples.

Table 3 … shows that the concentration of F in urine of the 84 schoolchildren and distribution of their IQ scores were inversely related. The average IQ score of the 34 students drinking the high F water was significantly lower (p?0.05) than among the 50 students drinking the low F water.

Table 4 …shows the distribution of IQ scores of the schoolchildren according the high and low F villages.

DISCUSSION

Overall physico-chemical parameters of GW from six villages of Mundra are pristine for consumption except in three villages where fluoride concentration is higher than permissible limit.23-24 Intensive and long-term irrigation in the district is probably one of the factors that causes weathering and leaching of fluoride from the soils/weathered rocks, contributing F to the surface water and GW.25-26 Moreover, Kachchh has unique geological features, mainly made up of alkali, silicate, igneous, and sedimentary rocks, so that weathering contributes a major portion of fluorides to GW.

As the kidney is the principal organ for the excretion of F, the rate or degree of exposure to F was checked by analyzing the urinary F level.27 For the IQ testing, the majority of the students scored less than 109 which represents normal or below normal score of IQ. Further, the overall difference in the mean IQ was 4.64%, which is statistically significant. This difference is mainly due to 4% superior students (IQ Score > 119) in low F villages whereas no students represent the superior class in high fluoride villages (Table 4), which is in accordance to our previous study. It thus appears that elevated F exposure reduced higher levels of intelligence even more than it affects normal and below normal intelligence of the children.10 Our study results are also in agreement with those of Poureslami et al.16 for 180 school children in Iran, which revealed that the percentage of students ranked in the ranges of average, above average and excellent were higher in low F Baft than the percentage of students in the same ranks in high F Koohbanan. Likewise, the percentage of the students ranked in the ranges of below average and borderline were higher in Koohbanan than in Baft.

It is now clear from many reported studies that excessive intake of F can produce harmful effects on the developing brain,12 the detailed mechanism by which F influences IQ is not clear. However, there is evidence that F may involve in alteration of membrane lipid and reduction in cholinesterase activity in the brain. Guan et al.28 demonstrated that the contents of phospholipids and ubiquinone are altered in the brain of rats affected by chronic fluorosis, and therefore changes in membrane lipids could be involved in the pathogenesis of this disorder. A few studies on effect of NaF on neurotransmitter and neurochemical levels revealed alterations in dopamine, serotonin, 5-hydroxyindoleacetic acid, homovanillic acid, norepinephrine, acetylcholine esterase, and epinephrine in the hippocampus and neocortex regions of the rat and mice brain.29-30 Earlier, Yu et al.31 also demonstrated changes in neurotransmitters and their receptors in human fetal brain
from an endemic fluorosis area. Moreover, it is well established that F can pass through the placenta to the fetus, and with subsequent continuous exposure to F during childhood, it may have adverse effects on the developing brain, thereby causing decreased IQ in children.32-34

Therefore, the present investigation concludes that the three villages of Chhasara, Gundala, and Mundra, are F-contaminated villages. Because of high F concentrations in the GW, children in these villages have greater exposure to F that may lead in to low IQ as compared to the nearby villages of Baroi, Zarpara, and Pragpar, which have low F in their GW.

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