Fluoride occurrence and assessment of exposure dose of fluoride in shallow aquifers of Makur, Unnao district Uttar Pradesh, India

Abstract

The water samples from the shallow aquifers of Makur, Unnao district, Uttar Pradesh, was analyzed for fluoride content (F⁻) and other water quality parameters such as pH, EC, CO₃ ²⁻, HCO₃ ⁻, Cl⁻, Na⁺, Ca^2 +, Mg^2 + and RSC. It was found that the F⁻ concentration of water varied between 1.05 to 13.9 mgl^− 1 which exceeded the maximum desirable limits of 1.0 mgl^− 1 of F⁻ as laid down by BIS and 68% of water exceeded maximum permissible limits of 1.5 mgl^− 1 as prescribed by WHO. The correlation study of fluoride indicated that F⁻ has a significant (p < 0.05) positive relationship with pH (r = +0.59) and RSC (r = 0.54), while a significant negative correlation with Ca+Mg (r = −0.53) and Mg (r = −0.49). The exposure doses of fluoride in infants was found between 0.35 to 3.26 mg kg^− 1day^− 1 (if dug well water was used) whereas 0.36 to 4.63 mg kg^− 1day^− 1 (when shallow hand pumps) The exposure doses of water in case of children (20 kg body weight) varied between 0.157 to 1.47 mg kg^− 1day^− 1 (for dugwell) and 0.162 to 2.08 mg kg^− 1day^− 1 (for shallow hand pumps) whereas in case of adults (70 kg body weight), it varied between 0.09 to 0.839 mg kg^− 1day^− 1 (for dugwell) and 0.092 to 1.19 mg kg^− 1day^− 1 (shallow hand pumps) which is quite high against the standard value of 0.05 mg/kg/day which is the minimum risk level (MRL) calculated by the Agency for Toxic Substances and Disease Registry (ATSDR). The maximum exposure dose to fluoride for adults in the study area found to be 23.8 times higher than the ATSDR’s MRL.