Effects of smoking and lead exposure on proximal tubular integrity among Egyptian industrial workers

Background. The hazards of occupational lead exposure are well documented. Tissue damage produced by lead is slow and progressive. The renal system is one of the systems primarily affected by lead. The present study aimed to evaluate renal proximal tubular functional and structural integrity among lead-exposed and cigarette-smoking male Egyptian workers. This study was extended to investigate the effect of lead exposure and cigarette smoking on urinary excretion of copper (Cu) and zinc (Zn). Methods. Participants included in the present study were 156 male workers grouped as follows: i) 75 lead non-exposed workers subgrouped into G(1) that consisted of 36 nonsmokers (age, 39.08 +/- 6.65 years) and G(2), which included 39 smokers (age, 43.87 +/- 9.93 years); ii) 45 lead-exposed workers (work duration <20 years) subgrouped into G(3) that consisted of 25 non-smokers (age, 37.40 +/- 3.76 years) and G(4), which included 20 smokers (age, 38.40 +/- 4.95 years), and iii) 36 lead-exposed workers (work duration <20 years) subgrouped into G(5) that consisted of 16 non-smokers (age, 45.94 +/- 4.19 years) and G(6), which included 20 smokers (age, 45.70 +/- 2.25 years). Functional integrity of proximal tubules was studied by determining urinary level of low-molecular-weight protein alpha(1)-microglobulin ((alpha(1)M), and structural integrity was investigated by measuring urinary activities of the lysosomal enzyme N-acetyl-beta-D-glucosaminidase (NAG) and the cytoplasmic enzyme glutathione S-transferase (GST). Urinary concentrations of Pb, Cu, Zn, and creatinine were also determined. Results. Data of the present investigation showed increased urinary excretion of all measured urinary parameters among lead-exposed workers in comparison with non-exposed workers whether they were non-smokers or smokers (G(3) ns. G(1), G(5) vs. G(1), G(4) vs. G(2), and G(6) vs. G(2)), with greater elevation among lead-exposed smokers than among lead-exposed non-smokers (G(4) vs. G(3), G(6) vs. G(5)). In addition, there was a greater increase in levels of all urinary parameters among workers with work duration greater than or equal to20 years than in those with <20 years' work duration (G(6) vs. G(4), G(5) vs. G(3)). Conclusions. Lead exposure in Egyptian workers causes damage to renal proximal tubules and results in its dysfunction. Cigarette smoking has a nephrotoxic effect and also is synergistic to lead nephrotoxicity on urinary excretion of GST and NAG, as well as Pb. (C) 2004 IMSS. Published by Elsevier Inc.