Cadmium Mobilization during Pregnancy and Lactation in Highly Exposed Populations

摘要

Exposure to cadmium has been associated with adverse neurobehavioral outcomes and nephrotoxic effects in both animal and human studies. Cadmium has a biological half-life on the order of decades and is stored in the liver, kidneys and bone. Consequently, breast milk may be a source of infant exposure, particularly in mothers with high cumulative lifetime exposures. We conducted a literature review of studies measuring cadmium in breast milk and of physiologically-based pharmacokinetic (PBPK) models describing cadmium mobilization during pregnancy and lactation. Few studies reported breast milk cadmium concentrations, one in a population living near a metallurgic complex, and the remaining in populations exposed through diet and smoking. The median cadmium concentration in breast milk among these studies ranged from 0.06-0.67 μg/l, and in blood it ranged from 0.54-1.54 μg/l. In a separate study, mean urinary cadmium excretion in smelter community residents was twice that of the reference population, indicating that populations with high cumulative lifetime exposures have a comparatively higher cadmium body burden. Published cadmium PBPK models do not include pregnancy or lactation as excretion pathways for mothers, or breast milk as an exposure pathway for infants. Available PBPK models consider diet and smoking as the primary routes of exposure, and do not account for exposures via dust, soil, or ambient air. Our review of the literature showed that 1) breast milk is an understudied cadmium exposure pathway for infants whose mothers have high cadmium body burden, 2) current PBPK models do not consider pregnancy or lactation as cadmium excretion pathways, and only take into account smoking and diet exposures. Studies monitoring cadmium biomarkers during pregnancy and lactation are necessary in order to estimate prenatal and infant cadmium exposure, and to parameterize PBPK models that incorporate cadmium mobilization during pregnancy and lactation.