RESUMO
Occupational exposure to silica dust could lead to renal alterations in the glomeruli and proximal tubules. In the present study, occupational exposure to silica dust has been examined as a possible risk factor with respect to subclinical signs of kidney dysfunction. One-hundred forty eight exposed workers from a ceramic factory versus 121 controls of matched age, socioeconomic status and smoking habits were included. Data was collected through a questionnaire and clinical examination. There was a high prevalence of renal complaints in the ceramic workers specially the loin pain, dysuria. Crystalluria was significantly higher in the exposed group (12.2%) than the controls (5%). Renal urinary biomarkers including the high-molecular-weight protein albumin (U.Malb); the low-molecular-weight protein α1-microglobulin (α(1)M); the lysosomal enzyme N-acetyl-ß-D-glucosaminidase (NAG) urinary excretion of copper (U.Cu) and zinc (U.Zn) have been investigated. Urinary levels of silica and creatinine (U.cr) were estimated. Data from the present study showed a high significant increase in the urinary excretion of all measured urinary parameters in the group of ceramic workers compared with control subjects. There were no significant differences in the means of U.Zn/U.cr, U.Malb/U.cr, and α(1)M/U.cr among the four investigated departments of ceramic factory. The significant difference was present mainly between the individual departments and the controls, while, there was significant differences in the means of U.Cu/U.cr, U.NAG/U.cr, and U.silica/U.cr among the four departments and the controls. Among the exposed workers, significant correlation was apparent between work duration and only U.Zn/U.cr (r=0.17, p<0.05), and U.Cu/U.cr (r=0.19, p<0.05), while all measured urinary parameters were significantly correlated with each other. On conclusion silica exposure leads to renal alterations which parallel the change in proteinuria and enzymuria, as well as the increased loss in urine of each of Zn and Cu. Measurement of the levels of urinary zinc and copper may serve as a sensitive indicator of the impaired renal function caused by silica exposure. The corresponding analytes could have potential value as indicators of renal function before the kidney is irreversibly injured and, thus could be suitable as monitoring tools for at-risk persons exposed to silica. Researches should assess whether the current occupational standards for silica adequately protect workers from renal disease or this established standard needs to be revised.