Further evidence of human silica nephrotoxicity in occupationally exposed workers.

It has previously been shown that granite workers with heavy exposure to silica had glomerular and proximal tubular dysfunction evidenced by increased urinary excretions of albumin, alpha-1-microglobulin (AMG), and beta-N-acetyl-glucosaminidase (NAG). The investigation was replicated in another group of granite workers to further elucidate the exposure effect relation. The urinary excretion of albumin, alpha-1-microglobulin (AMG), beta-2-microglobulin (BMG), and beta-N-acetyl-glucosaminidase (NAG) was determined in two groups of granite workers with low and high exposure to silica. Low molecular weight proteinuria and enzymuria were significantly correlated with duration of exposure in the high but not the low exposure group. These increases were most pronounced in those with 10 or more years of heavy exposure, and in those with radiological evidence of pulmonary fibrosis, particularly those with rounded small opacities denoting classical silicosis. These results provide further evidence that prolonged and heavy exposure to silica is associated with nephrotoxic effects in granite workers.