Abstract

To assess the health significance of the early renal changes after chronic exposure to cadmium, 23 workers removed from exposure because of the discovery of an increased urinary excretion of beta 2-microglobulin or retinol binding protein, or both, have been examined once a year for five years. Eight of these workers had also an increased albuminuria. These workers had been exposed to cadmium for six to 41.7 years (mean 25 years) and their first follow up examination took place when they had been removed from exposure for six years on average. At that time, their mean age was 58.6 years (range: 45.5-68.1). It has been confirmed that the proteinuria induced by cadmium is irreversible. The most important finding, however, is a significant increase of creatinine and beta 2-microglobulin concentrations in serum with time, indicating a progressive reduction of the glomerular filtration rate despite removal from exposure. It is estimated that on average this rate has decreased by 31 ml/min/1.73 m2 during the five year follow up study. This decrease is significantly greater (about five times) than that accounted for by aging and is not more pronounced in workers with impaired renal function at the start of the study than in those presenting only with subclinical signs of renal damage. Serum alkaline phosphatase activity also increases significantly with time. In conclusion, the present study indicates that the early renal changes induced by cadmium should be regarded as adverse effects; they are predictive of an exacerbation of the age related decline of the glomerular filtration rate.