URINE VANADIUM CONCENTRATIONS IN WORKERS OVERHAULING AN OIL-FIRED BOILER

Since fuel oil ash contains vanadium (V), the measurement of urinary l evels of V may provide a biological marker in workers exposed to fuel oil ash. The usefulness of urine V samples as a biological monitoring tool ultimately depends on determining the appropriate time of samplin g relative to when exposure occurs. Twenty boilermakers were studied d uring the overhaul of a large oil-fired boiler. A total of 117 urine s amples were collected, 65 start-of-shift (S-O-S) and 52 end-of-shift ( E-O-S) samples. Air V exposures were estimated with personal sampling devices and work history diaries. Air V concentrations ranged from 0.3 6 to 32.19 mu g V/m(3), with a mean +/- SD of 19.1 +/- 10.7, and a med ian of 18.5. On the first day of work on the overhaul, the V urine lev els at the E-O-S (mean +/- SD were 1.53 +/- 0.53, median was 1.52 mg V /g creatinine) were significantly higher than those at the S-O-S (0.87 +/- 0.32, median was 0.83), P = 0.004. However, the V concentrations of the S-O-S urine samples on the last Monday of the study were not si gnificantly different from the S-O-S urine levels on the previous Satu rday, a time interval of about 38 hr between the end of exposure and s ample collection. The Spearman correlation coefficient (r) between the S-O-S urine V and the workplace concentration of V dust during the pr evious day was r = 0.35. In summary, the results suggest a rapid initi al clearance of V (elevating the E-O-S V concentration on the first da y of work relative to the S-O-S concentration), followed by a slow cle arance that is not complete 38 hr after the end of exposure, as eviden ced by the Monday morning urine V concentrations. The Spearman correla tions suggest that the S-O-S urine is preferred to the E-O-S urine for across-shift biological monitoring of V exposure. (C) 1998 Wiley-Liss , Inc.