Although a strong connection between the environmental fluoride contamination and the fluorosis disease is nowadays worldwide well documented, the knowledge on the fluoride contamination levels of cultivated crops at the basis of the human food-chain is limited and fragmented. Adopting a systematic approach, this study reviews the available literature concerning the impacts of soil and water fluoride pollution on the safety and productivity of food and feed crops at a global scale, with the aim to provide a comprehensive overview of the current state of the art. The analyses of literature highlighted that food and feed crops exposed to soil and water fluoride pollution may reach concentrations of fluoride potentially harmful to human health. Nevertheless, despite the efforts already made to assess the crop fluoride accumulation in contaminated areas of India and China, the present study brings to light the lack of knowledge still existing on this issue for some regions strongly affected by environmental fluoride contamination such as the East African Rift Valley. Concerning the impacts of fluoride on cultivated crops, many authors observed that fluoride can produce toxic effects on plants leading to oxidative stress, reduction in chlorophyll content, alterations in the levels of proline, betaine, soluble sugars, nitrogen and macro and micronutrients. However, the appearance of symptoms such as visible injuries, reduced root and shoot length and yield decline was not always observed, also at high levels of fluoride exposure, and in some cases, the biomass production was even stimulated by increasing fluoride doses.

An investigation was carried out in Bankey Bazar block of Gaya and Rajauli block of Nawada districts in Bihar to assess the fluoride-contamination magnitude in groundwater and cultivated crops. The toxicological risk of fluoride exposure on three different age groups of the local populations has been measured. The groundwater was highly contaminated with fluoride (mean: 2.64 ± 1.8 mg/l) and alkaline in character (mean pH: 7.8 ± 0.38). About, 48.1 and 91% of the groundwater samples from Bankey Bazar (mean: 2.15 ± 1.78 mg/l) and Rajauli (mean: 3.2 ± 1.64 mg/l), respectively, cross the permissible limit of fluoride in drinking water. The major presence of fluoride in Bankey Bazar and Rajauli was confined at a depth range of 12.2–18.3 m (<0.5->8.0 mg/l) and 33.5–35.1 m (>1.5–8.0 mg/l), respectively and expected to be the hotspot territory in the regions. Mean fluoride concentrations in locally grown rice and wheat grain were found as 1.15 ± 0.81, 1.374 ± 0.667 mg/kg and 0.855 ± 0.226, 0.84 ± 0.186 mg/kg, respectively. Mean urinary fluoride concentrations of the studied populations were 10.4 ± 4.72 and 3.004 ± 1.97 mg/l, respectively. The cumulative EDI value for CTE and RME of the studied children was higher as compared to teenagers and adults. The hazard index (HI) for all the age groups residing in Bhaktuari of Bankey Bazar and Bhaunr, Phulwariya and Kachhariadih of Rajauli block was found much higher than the permissible limit (HI < 1). A good number of populations were suffering from dental and skeletal fluorosis. The life time non-cancerous risk (HILTNR) and probabilistic risk assessment based on fluoride exposure showed the potential threat among the residing populations.