Mapping of the Cadmium Lead and Mercury in Rice of Paddy Fields Within a CKDu Hotspot in Sri Lanka

Abstract

Purpose : Evidence of substantial levels of chronic exposure to heavy metals from food has emerged in a number of studies carried out in the recent past. The contamination of rice, the main dietary staple, is attributed in the main source to this chronic toxicity. Determining of source and magnitude of such contamination will assist to propose suitable public health interventions. Research Method : The area with the second highest prevalence of Chronic Kidney Disease of uncertain aetiology (CKDu) in Sri Lanka; Padaviya Divisional Secretariat area paddy fields were selected for the study. Paddy samples were collected from cross-section of locations with GPS locations, intended to represent the entire field. Paddy was processed for rice by routine methods. The fields were rain fed or irrigation fed, this being duly noted. Findings : Analytical results were expressed on a wet matter basis. Mercury was not detected in any of the 196 samples. Out of 196 rice samples, 21 (11%) had no detectable levels of lead or cadmium. Seventeen (9%) samples contained cadmium exceeding 50 μg/kg and lead exceeding 100 μg/kg. The minimum, maximum and mean lead levels in rice were 50, 790, 118 μg/kg respectively. Minimum, maximum and mean cadmium levels in rice were 30, 280, 33 μg/kg respectively. Lead contamination appeared to be an equally widespread issue in the tested irrigation water fed paddy fields. However, determined lead concentrations are significantly lower in rain-fed fields. Cadmium contamination seems to be significantly greater in the rain-fed fields than in irrigation-fed fields. Originality / Value : The magnitude of contamination of potential nephrotoxic heavy metals and its geospatial distribution in rice which is the main staple diet of people living around the studied paddy field where second highest CKDu prevalence were reported, and have been revealed. The information generated can be utilized to reduce the contaminant levels by agronomic practices and diet based public health intervention to reduce the human exposure.