Assessment of Arsenic and Cadmium Levels in Soils from Rice Farms in Hadejia, Jigawa State: Implications for Dietary Exposure

Abstract

Heavy metals are of significant toxicological concern to both humans and other organisms within the ecosystem. When present in the human body above certain threshold concentrations, these metals can lead to serious health complications. Arsenic (As) and Cadmium (Cd), in particular, are recognized for their carcinogenic potential at elevated exposure levels. Soil serves as the primary reservoir for these toxic elements, from which they can transfer to other environmental media such as water, air, and plants, eventually entering the human food chain. Existing literature has documented the high uptake rates of As and Cd by rice plants. Given that rice is a staple food in Nigeria, there is a critical need for routine surveillance of rice farms to monitor contamination levels. In this study, soil samples were collected from rice farms in Hadejia, Jigawa State -a region noted for intensive rice cultivation in Northern Nigeria. The samples were analysed using Microwave Plasma Atomic Emission Spectrometry (MP-AES) and validated with Atomic Absorption Spectrometry (AAS). The findings revealed that arsenic concentrations exceeded the Maximum Allowable Concentration (MAC) in soil by 77.5% and surpassed the recommended weekly tolerable intake level in rice by four orders of magnitude, indicating a significant public health risk. Pollution indices also indicated elevated contamination levels from both As and Cd. These results highlight the urgent need for comprehensive geochemical mapping to identify the sources of contamination and promote the use of rice cultivars with low arsenic uptake, thereby reducing dietary exposure and enhancing food safety.