Kyung Hee University's Professor Kim Joo-hee's research team, Placenta's Cadmium and Methylmercury Transfer Differences Identified

A research team led by Professor Kim Joo-hye of KAIST's Nursing Science College has uncovered the differences in how cadmium and methylmercury pass from mother to baby during pregnancy. Using a physiological-based pharmacokinetic model, the team estimated the exposure of the fetus and newborn to heavy metals based on the test results of pregnant women.

This study introduces a new method for assessing cumulative exposure during pregnancy. The findings have been published in prestigious international journals, Environmental Science & Technology (IF: 12.2) and Environmental Pollution (IF: 7.2). Both studies utilized data from the Korean Infant Environmental Health Birth Cohort, involving approximately 6,400 mother-child pairs, as well as additional data from the research team's own cohort.

For the cadmium study, data from 2,778 women and 200 fetal blood samples were analyzed, while the methylmercury study used data from 3,625 women and 242 fetal samples. In the cadmium analysis, fetal blood concentrations were found to be approximately 0.35 times that of the mother's during both early and late pregnancy. The team noted that even higher maternal cadmium levels only resulted in a 3.3% increase in cumulative fetal exposure.

The metal-binding proteins in the placenta reduced the amount of cadmium reaching the fetus. Professor Kim Joo-hye cautioned that high maternal blood levels do not necessarily mean low fetal exposure. For the methylmercury study, data from 3,625 pregnant women and 242 newborns, along with an additional 242 mother-child pairs, were analyzed.

The results showed that fetal mercury levels were 1.8 times higher than the maternal average. In 98.7% of the analyzed cases, fetal levels were higher than maternal levels. Methylmercury converts into a form similar to amino acids, allowing it to enter the fetal amino acid transporter and cross the placenta. However, a portion of methylmercury is converted into inorganic mercury, which is excreted through the kidneys.

The team estimated that neonates' kidneys have a half-life of about 160 days, compared to about 32 days in adults. Blood methylmercury levels did not show a significant difference, and the team suggested that analysis should consider not only blood tests but also urine and other data. This research provides significant value for prenatal check-ups, as it can estimate individual fetal exposure pathways and body burdens using blood test results.

Professor Kim Joo-hye stated that measurements alone are not enough; understanding the actual amount retained in the body is crucial for reassessing risk assessment. The research team plans to develop a comprehensive exposure model that includes cadmium, mercury, lead, and other heavy metals.