Uranium and Fluoride Accumulation in Vegetable and Cereal Crops: A Review on Current Status and Crop-Wise Differences

Abstract

Uranium (U) and fluoride (F−) contamination in agricultural products, especially vegetable and cereal crops, has raised serious concerns about food safety and human health on a global scale. To date, numerous studies have reported U and F− contamination in vegetable and cereal crops at local scales, but the available information is dispersed, and crop-wise differences are lacking. This paper reviews the current status of knowledge on this subject by compiling relevant published literatures between 1983 and 2023 using databases such as Scopus, PubMed, Medline, ScienceDirect, and Google Scholar. Based on the median values, F− levels ranged from 0.5 to 177 mg/kg, with higher concentrations in non-leafy vegetables, such as Indian squash “Praecitrullus fistulosus” (177 mg/kg) and cucumber “Cucumis sativus” (96.25 mg/kg). For leafy vegetables, the maximum levels were recorded in bathua “Chenopodium album” (72.01 mg/kg) and mint “Mentha arvensis” (44.34 mg/kg), where more than 50% of the vegetable varieties had concentrations of >4 mg/kg. The concentration of U ranged from 0.01 to 17.28 mg/kg; tubers and peels of non-leafy vegetables, particularly radishes “Raphanus sativus” (1.15 mg/kg) and cucumber “Cucumis sativus” (0.42 mg/kg), contained higher levels. These crops have the potential to form organometallic complexes with U, resulting in more severe threats to human health. For cereal crops (based on median values), the maximum F− level was found in bajra “Pennisetum glaucum” (15.18 mg/kg), followed by chana “Cicer arietinum” (7.8 mg/kg) and split green gram “Vigna mungo” (4.14 mg/kg), while the maximum accumulation of U was recorded for barley “Hordeum vulgare” (2.89 mg/kg), followed by split green gram “Vigna mungo” (0.45 mg/kg). There are significant differences in U and F− concentrations in either crop type based on individual studies or countries. These differences can be explained mainly due to changes in geogenic and anthropogenic factors, thereby making policy decisions related to health and intake difficult at even small spatial scales. Methodologies for comprehensive regional—or larger—policy scales will require further research and should include strategies to restrict crop intake in specified “hot spots”.