Pilot Study of Chromium Exposures in the Mongolian Leather Tanning Industry

Abstract

MAB3-PD-01 Session Title: Occupational Health (II) Introduction: Livestock-based industries are key economic drivers in Mongolia. Mongolian leather tanneries process 30,000 hides per day. Although regulatory standards exist for this industry, rapid growth in production has fueled concerns about its impact on worker and community health. In 2005, we conducted a pilot investigation of chromium levels among tannery workers and environmental samples from an urban area with high tannery density. Methods: Urine samples were collected from: 51 tannery workers (42 line workers, 9 managers), 32 workers from the industrial pre-treatment plant and the central sewage treatment plant (WWTP workers), and 28 control workers (garment factory, office workers). Samples were collected in acid-cleaned polyethylene bottles, microwave digested, and analyzed for total chromium by AAS (Zeeman 4100ZL, Perkin Elmer, Norwalk, CT). Environmental samples included 11 water and 3 sediment samples from a major river receiving tannery and sewage plant effluent, and 17 wastewater and 6 sludge samples from the 2 WWTPs. Samples were collected in acid-cleaned bottles, microwave digested, and analyzed for total chromium by ICP-AES (Perkin Elmer Optima 3000). Quality control samples included field and laboratory blanks. Statistical analyses were conducted in SAS 9.1 (SAS Institute, Cary, NC). Results: Mean chromium in the field blanks (n = 3) was 6 μg/L; results were blank corrected. Urinary chromium differed significantly among tannery, WWTP, and control workers (Kruskal Wallis P = 0.0004), with 95th percentile concentrations of 18.4 μg/L (tannery), 6.9 μg/L (WWTP), and 10.5 μg/L (control). Among tannery workers, urinary chromium did not differ significantly by job description (Wilcoxon Rank Sum P = 0.1816). Blank correction and method of handling below LOD values did not change test outcomes. Mean chromium was 6208 mg/kg in central WWTP sludge and 5430 mg/kg in pre-treatment plant sludge. Mean levels in wastewater sampled August 2005 from the pre-treatment plant were 1184 mg/L before and 29 mg/L after treatment (removal efficiency ∼97.5%). Removal efficiency dropped to 58% during peak tannery production (November to March). Pre-treatment plant effluent exceeded the Mongolian national standard (5 mg/L) regardless of season. Chromium was not detected in river water samples, and ranged from 15 to 64 mg/kg in sediment samples downstream from the central WWTP outfall. Conclusion: This is the first study to collect data on chromium exposures in the Mongolian leather tanning industry. Biologic sampling showed tannery workers have higher chromium exposures than other workers. High levels of urinary chromium among control workers was surprising; follow-up studies are currently underway.