A benchmark dose analysis of the blood cadmium concentration in pregnant women using the Japan Environment and Children’s Study data

Background and aim: A safe blood cadmium (Cd) level for pregnant women, in relation to infant birth weight, has not been established; therefore, we aimed to determine a benchmark dose (BMD) for blood Cd in pregnant women using the BMD approach. Methods: We used data from 80,669 mother–child pairs in the Japan Environment and Children’s Study. Maternal blood Cd levels collected during the second/third trimester of pregnancy were used, and birth weight data were transcribed from medical records. Bayesian regression was employed to model the dose–response relationship between the Cd concentration in maternal blood and infant birth weight. A benchmark response (BMR) was set as a 100-g decrease in birth weight, which corresponded to a 5 % increase in low birth weight (LBW) infants. The BMD and its 95 % lower credible interval (BMDL) were calculated using the BMR. Results: The BMD and BMDL for the maternal blood Cd concentration associated with a 5 % increase in LBW infants were 6.25 and 4.29 µg/L, respectively. Conclusion: The BMDL of 4.29 µg/L for blood Cd can be used as a point of departure for future risk assessment of pregnant women to protect against reductions in birthweight.