Web Date: January 5, 2011
Pollutants' Passage From Mother To Child
An international team of researchers has for the first time quantified how effectively mothers pass 87 common environmental contaminants to their children. Their findings provide a way to correlate pollutant concentrations in a mother's blood to levels in her developing baby, which may help regulators pinpoint compounds that are hazardous to unborn and nursing babies (Environ. Sci. Technol., DOI: 10.1021/es1019614).
Researchers used to think that the placenta was fairly effective at protecting the fetus against foreign compounds, says Philippe Grandjean of Harvard University's School of Public Health. In recent years, researchers have documented that pregnant and lactating mothers transfer environmental contaminants to their children and that these exposures can impair neurological, reproductive, immunological, respiratory, and metabolic development.
As part of an ongoing study, Grandjean and his colleagues obtained samples of maternal blood and milk, cord blood and tissue, and placenta tissue from pregnant mothers in the Faroe Islands, which are located between Norway and Iceland. The inhabitants' traditional food includes pilot whale meat and blubber, which contain high levels of persistent pollutants such as methylmercury and polychlorinated biphenyls (PCBs). The research team analyzed the samples for chemicals that the U.S. Centers for Disease Control and Prevention (CDC) monitors routinely.
The team found that the contaminants in the mothers' blood correlated with the concentrations in media that reached offspring, such as breast milk and cord blood. These correlations suggest that researchers can use mother's blood or milk to assess fetal exposures, the authors concluded.
By comparing the concentrations of contaminants in the mothers' blood and milk with the amounts in cord blood and tissue, the researchers calculated the ratios of concentrations in mother and fetus. For example, they found that the concentrations of organohalogens compounds such as PCBs, polybrominated diphenyl ethers (PBDEs), and chlorinated pesticides, in maternal serum were 1.7-times higher than in cord serum and 2.8-times higher than in cord and placenta tissue.
The study identified compounds that merit more study due to their ease crossing the human placental barrier, says Linda Birnbaum, director of the National Institute of Environmental Health Sciences. These include some low-molecular-weight PCBs, which had concentrations that were as much as three-times greater in some fetal samples than in maternal serum.
Lynn Goldman, dean of George Washington University's School of Public Health and Health Services, says that policymakers should consider the study's findings when trying to limit women's exposure to compounds that could harm their offspring.
One of the study's co-authors, Larry Needham of CDC, died on Oct. 23 of kidney cancer.
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