Use of Inhalable Cr⁺⁶ Exposures to Characterize Urinary Chromium Concentrations in Plating Industry Workers

Abstract

In this study, both personal sampling and biological monitoring were conducted on 27 and 30 workers selected from decorative plating and hard-surface plating operation, respectively. For personal sampling, the inhalable aerosol sampling technique was adopted in order to measure worker’s soluble Cr⁺⁶ exposure level (C_INH) on the last day of the workweek. For biological monitoring, a urine specimen was collected at the end of the shift on the last day of the work week in order to determine a worker’s urinary chromium concentration (C_URINE). Results show that hard-surface plating workers had higher C_INH (arithmetic mean ≈ 25.2 μg/m³) than decorative plating workers (arithmetic mean ≈ 1.91 μg/m³). The above results could be due to the longer plating time involved in the former plating operation than in the latter. The relationship between C_INH and C_URINE was found as C_URINE=1.86 C_INH-0.21(R²=0.87, n=57), which suggests that the inhalable aerosol sampling results were able to explain the variation in workers’ urinary chromium concentrations up to 87%. Assuming the level of C_INH was equivalent to the current TLV-TWA of 50 μg/m³, the above regression model yielded a level of C_URINE as approximately 93 μg/g·creatinine. The above value is clearly different from the current present biological exposure index BEI of 30 μg/g·creatinine which is known to be applicable only to welding workers. The above discrepancy could be due to the intrinsic difference in particle size distribution between the Cr⁺⁶ droplets generated during the plating process and Cr⁺⁶ fumes generated during the welding process. Considering that no BEI has been suggested for chromium plating industries, the result obtained in this study will be helpful in introducing a new BEI in the future.