Mothers with high blood levels of PCBs are less likely to give birth to males
Banned environmental pollutants have sex-skewing effect
A recent study by researchers at UC Davis has found that women exposed to high levels of polychlorinated biphenyls (PCBs) are significantly less likely to give birth to male children than women exposed to lower levels of the banned environmental pollutants.
The study, which appears in BioMed Central's open-access journal Environmental Health, provides the strongest evidence to date that maternal exposure to PCBs skews the ratio of male-to-female offspring in humans.
"These findings suggest that high maternal PCB concentrations may either favor fertilization by female sperm or result in greater male embryonic or fetal losses," said lead study author Irva Hertz-Picciotto, an epidemiologist and professor of public health at UC Davis. "The association could be due to contaminants, PCB metabolites or the PCBs themselves."
The study measured the levels of PCBs in blood taken from pregnant women during a San Francisco Bay Area study in the 1960s. The researchers then compared the PCB levels in the women's blood with the genders of their children. It found that, for every microgram of PCBs per liter of serum, the chances of having a male child fell by 7 percent.
— Irva Hertz-Picciotto, lead study author
"The women most exposed to PCBs were 33 percent less likely to give birth to male children than the women least exposed," Hertz-Picciotto said.
PCBs are a group of man-made organic pollutants widely used in industry as cooling and insulating fluids until they were banned in the 1970s over concerns about their toxicity and accumulation in the environment. They have been associated with adverse effects on immune, reproductive, nervous and endocrine systems in people and animals.
Hertz-Picciotto said that the study is also important because it will help assess the health risks of populations currently exposed to high levels of PCBs, like those that consume fish from contaminated lakes or that live near former manufacturing facilities.
Other chemicals with molecular structures that are similar to those of PCBs, like the flame retardants PBDEs (polybrominated diphenyl ethers), are widely used in plastic casings of televisions, computers and other electronics, and in foam products and textiles.
"PBDEs share many of the biochemical and toxicologic properties of PCBs," Hertz-Picciotto said. "As the levels of these substances rise in wildlife and human populations, studies like ours provide an indication of the potential effects of these newer compounds."
Other study authors include Todd Jusko of the Department of Epidemiology, School of Public Health and Community Medicine, University of Washington; Eric Willman, currently at Ecolab; Rebecca Baker (now deceased) of the Department of Epidemiology, School of Public Health, University of North Carolina-Chapel Hill; Jean Keller, currently at Quintiles, Inc.; Stuart Teplin of the Center for the Study of Development and Learning, Department of Pediatrics, University of North Carolina-Chapel Hill; and M. Judith Charles (now deceased) of the UC Davis Department of Environmental Toxicology.
Funding for the study was provided by grants from the National Institutes of Health (NIH), the National Institute of Environmental Health Sciences (NIEHS), the National Cancer Institute (NCI) and the National Institute of Child Health and Human Development (NICHD).
To view the paper online, go to http://www.ehjournal.net/.