Metal and Pesticide Assessments of Imported and Locally Cultivated Rice (<i>Oryza sativa</i>) in Senegal

Abstract

Identifying heavy metal and pesticide contaminants is an essential step in assessing the health indicators of rice cultivation and consumption in Africa. Information on the contaminant levels of the imported and cultivated rice consumed in Senegal seems lacking. In this study, we assessed heavy metals, pesticides, ash, and protein in rice using rice samples from India, Thailand, South America, Vietnam, and China. Arsenic, Pb, Cd, Ni, Cu, Mo, Co, Cr, and Al are usually found in the soils used for rice cultivation in northern Senegal. While the heavy metal levels measured in soils were above the threshold limit, only Pb, Cd, and Al were found in cultivated rice. In all the analyzed rice samples from each country, there were certain amounts of Pb, As Al, and Cd. The concentration ranges in the six countries were as follows: 0.635–1.165 mg kg−1 for Pb, 0.047–0.438 mg kg−1 for As, 2.22–95.54 mg kg−1 for Al, and 0.002–0.082 mg kg−1 for Cd. The protein content in cultivated rice in Senegal was 7.31 mg kg−1, while the average from the imported rice ranged between 6.42% and 7.32%. The humidity levels in imported rice ranged between 11.12% and 12.95%. The fat content for the rice from six countries ranged between 0.22% and 0.67%, and the ash content ranged between 0.23% and 0.48%. These results allowed for the determination of the carbohydrate concentration, which varied between 79.18% and 80.82%. Indeed, freshly harvested rice grains typically contain around 80% carbohydrates. We noticed the presence of pesticides in all rice samples. The levels of three pesticides (total Pyrethrin, Bensulfuron-methyl, Propanyl, and 2,4D) were found to be beyond their maximum residue limits (MRLs) from the Codex Alimentarius, whereas deltamethrin was found to be below its MRL. This study indicates the presence of heavy metals carcinogenic to humans (Al, As, Cd, and Pb). Additionally, this study reveals the presence of deltamethrin, which is classified as probably carcinogenic to humans (Group 1), and 2,4-dichlorophenoxyacetic acid, which is classified as possibly carcinogenic to humans (Group 2B).

Keywords

• toxic metals
• white rice
• pesticides
• macronutrients