Cadmium content in rice and rice field soil in China, Indonesia and Japan, with special reference to soil type and daily intake from rice.

Abstract

The present study was carried out to: 1) assess cadmium content in both rice and soil of China, Indonesia and Japan, 2) determine the relation of cadmium content in rice and soil to soil type and country, and 3) estimate the average daily cadmium intake from rice from the results of cadmium analysis and rice consumption data of FAO. Much data on cadmium content in rice and soil of Japan have been reported (Iimura 1981; Masironi et al., 1977; Morishita 1981; Moritsugu et al., 1964; Nakatsuka et al., 1988; Yanagisawa 1984), but those for Indonesia are limited (Suzuki et al., 1988; Rivai et al., 1990). Moreover, the only data on cadmium content in rice of China have been reported by Rivai et al.(1990), none are available on the cadmium content in soil of China. Rice is a major source of cadmium intake for man in rice eating countries such as China, Indonesia and Japan. Thus, rice may be the best indicator to monitor cadmium exposure. Iimura (1981) reported the mean cadmium content in brown rice and paddy soil of Japan to be 90 and 450 ppb, respectively. Yanagisawa et al. (1984) found this parameter in brown rice and paddy soil from polluted area of Japan to be 0.37 and 1.35 ppm, respectively. Hutton et al. (1987) found the major sources of cadmium pollution to the agriculture land in England to be sewage disposal, manufacture manufacture and phosphate fertilizer. Morishita (1981) and Asami (1981) reported that rice grown in polluted soil contains more cadmium than that of non polluted soil. However, there are no data on relationship between cadmium content in rice and soil to the soil type. Assessment of the accumulation of cadmium content in rice and soil by soil type may also facilitate environmental monitoring. Daily cadmium intake from rice may be estimated from cadmium content in rice multiplied by daily rice consumption. Ohmomo (1981) reported the daily cadmium intake from rice of Japan to be 26 μg/person. Though the biological role of cadmium is not known for plants, under certain conditions it may accumulate in some plants to levels hazardous for animals and finally for man at the end of the food chain. This element, after entering into the soil would not be leached out and thus accumulate. Some of it is absorbed by plants that are a part of the ecological cycle. The hydrochloric acid extraction method can be used to detect the soluble fraction of the element absorbable from the roots of rice plants (Nihon Dojo Hiryo Gakkai 1986).