A 30-year follow-up study in a former cadmium-polluted area of Japan: the relationship between cadmium exposure and β 2 -microglobulin in the urine of Japanese people

Cadmium (Cd) is an environmental pollutant. Long-term exposure to Cd may lead to adverse health effects in humans. Our epidemiological studies showed that urinary Cd (U-Cd) concentrations increased from 2008 through 2014, although they decreased from 1986 through 2008. The aim of this study was to elucidate the long-term effects of the changing trend of cadmium exposure levels (U-Cd) on residents' renal function within 30 years after Cd exposure ceased. In 2016, urine samples were collected from each subject by visiting 20 elderly Japanese people (9 females and 11 males) living in the Kakehashi River basin, a previously Cd-polluted area in Ishikawa, Japan. The geometric means of the β -microglobulin (β -MG) and urinary Cd (U-Cd) continued to increase from 2014 until 2016. Furthermore, Cd concentration and β -MG in urine were still higher than those in the non-polluted areas in Japan. Multivariate linear regression was performed to associate β -MG (dependent variable) and U-Cd with sex and age (independent variables). Significant correlations were found among age, U-Cd, and β -MG, and these were clearer in females than in males. In summary, we propose that three decades after Cd exposure ceased, age is associated with β -MG more strongly than Cd for bodily impact. Moreover, renal tubular dysfunction is irreversible and worsens after exposure to Cd, with females being more sensitive to exposure.