A comparison between fecal cadmium and urinary β2-microglobulin, total protein, and cadmium among Japanese farmers : An epidemiological study in cooperation between Japan and Sweden

Abstract

A study was made of 156 farmers living in a cadmium-exposed area and 93 farmers in a reference area. All were between 50 and 69 years of age. Cadmium intake from food was estimated from daily fecal cadmium content, body burden from urinary cadmium concentration, and cadmium-induced renal effects from urinary β 2-microglobulin ( β 2-m) and total protein concentration. Average cadmium intake in the reference area was about 40 μg/day and in the exposed area about 150 μg/day. Average urinary cadmium excretion in the reference group was 2 μg/liter and in the exposed group 7.5 μg/liter. Average urinary β 2-m concentration in the reference group was 86 μg/liter and we defined tubular proteinuria as a β 2-m concentration higher than the average plus two standard deviations. With this definition the prevalence rate of tubular proteinuria was 3% in the reference group and 14% in the exposed group. Tubular proteinuria increased with age and with exposure duration. Increased total proteinuria was also more common in the exposed group but the prevalence rate ratio was 2.4 as compared to 4.4 for tubular proteinuria.