The aim of this study was to assess the effect of fluoride on human health, focusing on the incidence of fluorosis, urinary fluoride concentration and fluoride level in drinking water in three fluoride-affected villages of Birbhum district, West Bengal, India. In one village urinary fluoride concentration was very high along with the occurrence of severe dental and skeletal fluorosis, though fluoride level in drinking water was within the permissible limit. The present study suggests that fluoride intake through other sources is also an important contributing factor in fluorosis, corroborating previous reports on high fluoride contents in crops and vegetables grown in fluoride-affected areas.
Though the concentration of fluoride in drinking water in Noapara was much higher than that in Kamdebpur, Chalk Atla and Junidpur, the urinary fluoride concentration in subjects of Noapara did not differ much. The predominance of severe skeletal and dental fluorosis in subjects of Noapara can probably be linked to high fluoride exposure but relatively less excretion (as evident from urinary fluoride levels). Interestingly, despite low fluoride (within the permissible limit) levels in drinking water, the urinary fluoride concentration of individuals residing in Kamdebpur village was found to be very high (highest 7.3 ppm). Again, 69.22% of the people surveyed from Kamdebpur were found to suffer from different forms of dental and skeletal fluorosis (Figure 1c, d and g). Thus, the evidence of fluorosis and elevated urinary fluoride concentration was not positively correlated with drinking water fluoride level in this sample population. In Junidpur, fluoride concentration in both drinking water and urine was low, but 30% of the population suffered from mild to moderate dental fluorosis. Data from the present study could not establish a direct correlation between drinking water fluoride level, urinary fluoride concentration and evidence of fluorosis among subjects inhabiting these four fluoride-endemic villages. Therefore, it led us to hypothesize that drinking water may not always be the major source for causing fluorosis. Anasuya and Paranjape26 and Tegegne et al.27 reported that processing parboiled rice and cooking rice with high fluoride-containing water can increase the level of fluoride significantly. Arora and Bhateja28 estimated mean fluoride concentration in the soil, wheat, rice and potato in and around Mathura city to be 1.41, 0.39, 0.42 and 1.01 ppm respectively. They observed a significant relation between mean fluoride concentration of the soil and mean fluoride concentration of rice and wheat. They concluded that the soil and crops, namely wheat, rice and potato can be an additional dietary source of fluoride. The present study indirectly corroborates these reports showing that not only drinking water, but fluoride intake through food, especially rice, pulses and vegetables might also significantly contribute to the development of fluorosis.