Demonstration of Subclinical Early Nephrotoxicity Induced by Occupational Exposure to Silica among Workers in Pottery Industry

Background: For many years, several studies drew attention to the possible nephrotoxic effects of silica and distinct renal dysfunction involving glomerular and renal tubules in workers exposed to silica. Objective: To determine the early signs of subclinical nephrotoxic effects among some Egyptian workers exposed to silica in the pottery industry. Methods: This study was carried out in El-Fawakhir handicraft pottery area, in Greater Cairo, Egypt. The studied population included 29 non-smoking male workers occupationally exposed to silica in addition to 35 non-smoking administrative male subjects who represented the comparison group in the study. Measured urinary parameters were concentrations of total protein (TP), microalbumin (Malb), activities of alkaline phosphatase (ALP), γ-glutamyl transferase (γ-GT), lactate dehydrogenase (LDH), kidney injury molecule-1 (KIM-1), and silicon (Si). Results: Silica-exposed workers showed significantly (p<0.05) increased levels of urinary TP, Malb, ALP, γ-GT, LDH, and KIM-1 compared with the comparison group. Among the silicaexposed group, increased urinary Si levels were positively and significantly correlated (Spearman's ρ>0.60, p<0.001 for all variables) with the elevated urinary proteins (including KIM-1) and enzymes levels. All measured urinary parameters were positively and significantly correlated (ρ>0.75, p<0.001 for all variables) with the duration of work among exposed subjects. No significant correlation was observed between the measured variables and the age of workers. Conclusion: There is associated subclinical glomerular and tubular affection among silica-exposed workers, which is related to the duration and intensity of exposure.