Dietary cadmium intake in polluted and non-polluted areas in Japan in the past and in the present
The purpose of this data compilation is to overview past and current dietary exposure (primarily via rice) of general populations to cadmium (Cd) in environmentally polluted and non-polluted areas in Japan, and to compare the levels with counterpart levels in other areas in Asia.
A literature survey was conducted for publications on this subject, in either Japanese or international languages, since the early 1970s. Most of the studies identified employed the food-duplicate method in combination with atomic absorption spectrometry for Cd determination, although a few studies utilized other methods, such as the market basket method and dithizon-colorimetry.
The highest estimate of dietary Cd intake (Cd-D), 600 μg Cd/day, was reported in the late 1960s for the local population in the Jinzu river basin, where Itai-itai disease had been endemic, and the Cd-D levels were 300 μg/day or higher in other polluted areas. Cd-D dropped to well below 100 μg/day when the polluted soil was replaced in the late 1970s and thereafter. In non-polluted areas, the Cd-D was reported to be approximately 100 μg/day in 1969, followed by a gradual decrease to approximately 40 μg/day in the late 1970s, to reach the current level of less than 30 μg/day. There is a trend of gradual reduction at the rate of 0.3 to 0.6 μg/day per year. Cd from rice accounted for 30 to 40% of the Cd-D in non-polluted areas, but a higher contribution was observed in some polluted areas. Nevertheless, the current Cd-D is still higher than the levels in other rice-dependent populations in east and south-east Asia.
The Cd-D levels reported for polluted areas were in excess of 300 μg Cd/day. Substantial reduction in Cd-D to the level below 100 μg/day was observed after remediation, such as replacement of polluted paddy soil. In non-polluted areas, there has been a gradual decrease in Cd-D in the past 25 years. Nevertheless, the levels in the current intake of the general population in Japan (25 to 30 μg/day, or <1/10 of the levels in polluted areas in the past) is still higher than the levels in other rice-dependent areas in Asia.