Cadmium and lead contents in rice available in various areas of Asia

Rice samples, 207 in total, were collected from 15 (Australia has been included in Asia) areas of Asia (192 samples) and in four areas in other parts of the world (15 samples). The samples were wet-ashed and analysed for cadmium (Cd-R) and lead (Pb-R) by flameless atomic absorption spectrophotometry. Both Cd-R and Pb-R in the 207 samples distributed log-normally, with a geometric mean (GM) [geometric standard deviation (GSD)] of 20.0 ng g-1 (3.176) and 15.7 ng g-1 (3.498), respectively. No significant difference was observed in Cd-R and Pb-R between common rice (188 samples) and glutinous rice (19 samples), whereas effects of polishing were absent on Cd-R and inconclusive on Pb-R. Among the 11 areas in which more than 10 samples were collected, the GM of Cd-R varied by less than 10 ng g-1 (i.e., Australia and India) to greater than 50 ng g-1 (Japan and Taiwan), and the GSD was also as large as three in many areas. A similar analysis for Pb-R showed an even wider variation in GM from the lowest of 5 ng g-1 (Japan) to the highest of 90 ng g-1 (India). Geometric standard deviations were also two or greater in most areas. Among the three areas (China, Korea and Japan) where Cd-R, cadmium in blood (Cd-B), Pb-R and lead in blood (Pb-B) values were all available, both Cd-R and Cd-B were high in Japan, medium in Korea and low in China, whereas Pb-R and Pb-B were low in Japan, and high in China and Korea. Possible causes of variation in Cd-R and Pb-R are discussed.