Women exposed to high levels of PCBs (polychlorinated biphenyls - environmental pollutants) are less likely to give birth to male children, suggests a new study in the journal Environmental Health. The researchers found that among women from the San Francisco Bay Area, those exposed to higher levels of PCBs during the 50s and 60s were significantly more likely to give birth to female children.
PCBs are persistent organic pollutants identified found in human blood and breast milk. They were widely used in industry as cooling and insulating fluids for electrical equipment, as well as in construction and domestic products such as varnishes and caulks. PCBs were banned in the 1970s because of their general toxicity and persistence. They are associated with effects on immune, reproductive, nervous, and endocrine systems.
"The women most exposed to PCBs were 33 percent less likely to give birth to male children than the women least exposed," explained study author Irva Hertz-Picciotto. The researchers measured the levels of PCBs in blood taken from pregnant women during a Bay Area study in the 1960s. When they compared these levels to the children's sex, they found that for every one microgram of PCBs per liter of serum, the chance of having a male child fell by 7 percent.
"These findings suggest that high maternal PCB concentrations may either favor fertilization by female sperm or result in greater male embryonic or fetal losses. The association could be due to contaminants, PCB metabolites or the PCBs themselves," Hertz-Picciotto said.
The researchers also issued a warning about other chemicals with a similar structure to PCBs, such as the flame-retardants PBDEs (polybrominated diphenyl ethers), are currently widely used in plastic casings and foam products. According to Hertz-Picciotto, "PBDEs share many of the biochemical and toxicologic properties of PCBs. As levels of these substances rise in wildlife and human populations, studies like ours provide an indication of the potential effects of these newer compounds".
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Source: Environmental Health