Rice Cd Levels in Cambodia Ranged 3 Orders of Magnitude due to Season and Soil Cd Levels

Abstract

Cadmium (Cd) is a toxic trace element that can be transported from soil into rice grain, posing health threats to rice consumers. Among the global studies on rice grain Cd, only one market survey reported grain Cd levels from Cambodia, an important rice-growing country in Southeast Asia. Here, we collected paired rice and soil samples in the wet and dry seasons from major rice-growing regions across five provinces in Cambodia and report the relationships between plant Cd and soil Cd parameters. Both DTPA-extractable and nitric acid digestible soil Cd are significant predictors for Cd levels in rice straw and grain. Rice grain Cd concentrations ranged 3 orders of magnitude from 0.002 to 1.066 mg kg-1 with the median and mean concentrations of 0.024 and 0.091 mg kg-1, respectively; these values have an upper range that is higher than previously reported. The highest grain Cd levels were found in rice grown in the dry season from two provinces located southeast of Phnom Penh along the Lower Mekong River, and their corresponding soil Cd levels were relatively higher than those collected during the wet season and around the Tonle Sap. While the source of higher Cd may be geogenic or due to anthropogenic activities, our data demonstrate that geographical and perhaps seasonal differences in grain Cd exist even within a small country that might not be reflected in market surveys.