Early indicators of renal dysfunction in silicotic workers.

Abstract

The aim of this study was to determine whether silicosis is associated with renal alterations detectable in urinary or blood-borne indicators of nephrotoxicity. The study used a cross-sectional design. The subjects comprised 116 male workers who had been exposed to silica for at least two years and had been diagnosed as having silicosis and 61 age-matched referents. The considered outcome measures were the concentrations of beta, -microglobulin and creatine in serum and the urinary excretion of albumin, retinol-binding protein, and beta-N-acetyl-D-glucosaminidase. Compared with the referents, the silicotic subjects excreted, on the average, slightly higher amounts of albumin, retinol-binding protein, and beta-N-acetyl-D-glucosaminidase. This increase did not correlate with the duration of exposure or the stage of silicosis and was not associated with an elevation in serum creatinine. The concentration of beta2-microglobulin in the serum of silicotic subjects showed a tendency to rise that became significant in the subgroup with pseudotumoral opacities. This effect, which did not correlate with markers of nephrotoxicity, is however more likely the consequence of silicosis-associated inflammatory reactions than of decreased renal filtration. The present study confirms that silicosis is associated with some infraclinical renal alterations. However, in the absence of a relationship with length of exposure or severity of silicosis, the implication of silica in their causation needs to be examined further.