Determination of germanium in urine and its usefulness for biomonitoring of inhalation exposure to inorganic germanium in the occupational setting

The present study aimed to assess whether urinary germanium concentration c an be used as a biomarker of inhalation exposure to airborne dust from meta llic germanium (Ge) or GeO2 in the occupational setting. A novel hydride ge neration-based method coupled with flow-injection graphite furnace atomic a bsorption spectrometry (HG/FI-GFAAS) was developed for the determination of urinary germanium. Tt was found that urinary germanium concentration could be reliably determined by a standard additions method after thorough diges tion of the urine and careful pH adjustment of the digest. The limit of det ection (LOD) in urine for the HG/FI-GFAAS method was 0.25 mug Ge L-1. In Be lgian control male subjects, the urinary germanium concentration was below this LOD. In 75 workers currently exposed to inorganic germanium compounds, respirable and inhalable concentrations of germanium in the aerosols were measured on Monday and Friday at the job sites using personal air samplers. Spot-urine samples were collected on the same days before and after the we ll; shift. The germanium concentrations of respirable dust correlated very well with those of inhalable dust and represented 20% of the inhalable frac tion. Workers exposed to metallic Ge dust were on average ten times less ex posed to germanium than those whose exposure involved GeO2 (3.4 versus 33.8 . mug Ge m(-3)). This difference was reflected in the urinary germanium con centrations (3.4 versus 23.4 mug Ge g(-1) creatinine). Regression analysis showed that the concentration of germanium in the inhalable fraction explai ned 42% of the post-shift urinary germanium concentration either on Monday or on Friday, whereas in a subgroup of 52 workers mainly exposed to metalli c germanium dust 57% (r=0.76) of the Monday post-shift urinary germanium wa s explained. Urinary elimination kinetics were studied in seven workers exp osed to airborne dust of either metallic Ge or GeO2. The urinary eliminatio n rate of germanium was characterised by half-times ranging from 8.2 to 18. 1 h (on average 12 h 46 min). The present study did not allow discriminatio n between the germanium species to which the workers were exposed, but it s howed fast urinary elimination kinetics for inhalation exposure to dust of metallic Ge and GeO2. It pointed out that urine samples taken at the end of the work shift call be used for biological monitoring of inorganic germani um exposure in the occupational setting.