Metal concentrations in cereals are not related to the Chronic Kidney Disease of unknown cause (CKDu) in Sri Lanka

Abstract

BACKGROUND AND AIM: Exposure to nephrotoxic metals (As, Pb, and Cd), as well as Se deficiency has been hypothesized as a possible cause of Chronic Kidney Disease of unknown cause (CKDu) in Sri Lanka; however, evidence is inconclusive. Here, we determined the concentrations of these elements in rice and other grains consumed in endemic and non-endemic regions of CKDu. METHODS: Dried and fine ground cereals were digested completely with trace metal grade nitric and hydrochloric acids and hydrogen peroxide. The clear completely digested solutions were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). RESULTS:Our results showed comparable mean concentrations (in µg/kg) of 23±17, 7.4±6.7, and 15.1±15.2 for As, Pb, and Cd, respectively, in rice from endemic regions, and 26±14, 10.5±6.3, and 12.3±15 in rice from non-endemic regions. Selenium concentrations (in mg/kg) were 0.05±0.02 and 0.04±0.02 in rice cultivated in endemic and non-endemic regions, respectively. Arsenic and Cd concentrations were significantly higher in rice compared to other grains, which themselves had higher Se than rice. All samples were below the Codex standards established for Cd (400 µg/kg for rice; 100 µg/kg for cereal grains), Pb (200 µg/kg), and total As (300 µg/kg). Our findings show that dietary exposure to low levels of As, Pb, Cd, and inadequate Se in staple grains cannot be linked to CKDu, suggesting that the disease could be multifactorial. Our previous water quality evaluation in the study area similarly does not appear to be implicated, which further highlights the lack of strong evidence on nephrotoxic metals exposure from food and water in the study area. CONCLUSIONS:More research is needed to understand the contribution of additional food materials among other risk factors to identify preventive strategies and minimize CKDu health cases in Sri Lanka and affected regions globally. KEYWORDS: CKDu, Nephrotoxic metals, Selenium deficiency, CKDu endemic and non-endemic regions, Sri Lanka.