Application of Benchmark Dose (BMD) in Estimating Biological Exposure Limit (BEL) to Cadmium

Objective: To estimate the biological exposure limit (BEL) using benchmark dose (BMD) based on two sets of data from occupational epidemiology.

Methods: Cadmium-exposed workers were selected from a cadmium smelting factory and a zinc product factory. Doctors, nurses or shop assistants living in the same area served as a control group. Urinary cadmium (UCd) was used as an exposure biomarker and urinary beta2-microgloburin (B2M), N-acetyl-13-D-glucosaminidase (NAG) and albumin (ALB) as effect biomarkers. All urine parameters were adjusted by urinary creatinine. Software of BMDS (Version 1.3.2, EPA.U.S.A) was used to calculate BMD.

Results: The cut-off point (abnormal values) was determined based on the upper limit of 95% of effect biomarkers in control group. There was a significant dose response relationship between the effect biomarkers (urinary B2M, NAG; and ALB) and exposure biomarker (UCd). BEL value was 5 microg/g creatinine for UB2M as an effect biomarker, consistent with the recommendation of WHO. BEL could be estimated by using the method of BMD. BEL value was 3 microg/g creatinine for UNAG as an effect biomarker. The more sensitive the used biomarker is, the more occupational population will be protected.

Conclusion: BMD can be used in estimating the biological exposure limit (BEL). UNAG is a sensitive biomarker for estimating BEL after cadmium exposure.