OBJECTIVETo explore and provide the possible biological limit of urinary chromium for population occupationally exposure to soluble chromate, as to providing scientific evidences for health monitoring and risk assessment.

METHODSA cross-sectional study was conducted. The studied population contained 83 workers from different processes of the chromate plant, in addition, 10 farmers without exposure to chromate matched with exposed subjects by age, gender and smoking status were identified as a control group. The air chromium concentration for personal exposure during 8-hours shift and the urinary chromium concentration post-shift were determined and their relationship was analyzed statistically. Meanwhile, the literatures of the biological limit of urinary chromium for occupational exposure to soluble chromate were studied.

RESULTSFor the control group, the air chromium concentration had a range from 0.00 microg/m(3) to 0.08 microg/m(3) and the urinary chromium concentration from 0.40 microg/g Cre to 1.02 microg/g Cre. For the exposure group, the air chromium concentration was from 0.10 microg/m(3) to 287.00 microg/m(3) and the urinary chromium concentration was from 1.14 microg/g Cre to 79.07 microg/g Cre. The positive relationship existed in between air chromium concentration and urinary concentration. The urinary chromium concentration was increased depending on the chromate exposed level. The regress equation was that Urinary chromium concentration (microg/g Cre) = 4.16 + 236.86 x air concentration for chromate (mg/m(3)), r = 0.976. The recommendation of ACGIH (USA, 2004) was 65.1 micromol/mol Cre (30 microg/g Cre) with the same TLV-TWA of 0.05 mg/m(3) as our National standard about the air chromate concentration.

CONCLUSIONOur findings suggested that the post-shift urinary chromium concentration might be used as an exposed biomarker for chromate. Considering the recommendation of ACGIH (USA, 2004) and the feasibility of the standard performed, we suggest that the biological threshold limit of urinary chromium for occupational exposure to soluble chromate in China should be 65.1 micromol/mol Cre (30 microg/g Cre) (post-shift urine for consecutive 5 work days.).