Birth year, not your mother, main determinant of PCB exposure

Many studies have looked at the correlation between a mother’s reproductive behaviour—such as her childbearing age, her total number of children, or whether or not she breastfed—to her children’s exposure levels to harmful contaminants such as polychlorinated biphenyls, or PCBs. But according to new research out of the University of Toronto Scarborough (UTSC), the actions of our mothers may have little to do with our exposure when compared with the timing of our birth.

The study, published in the May issue of Environmental Health Perspectives, looked at the ways in which North American women have changed their reproductive habits during the same historical period during which PCBs rose to prominence, reached their peak and were eventually phased out. By controlling for these variable emissions, lead author and PhD candidate in environmental chemistry at UTSC Cristina Quinn has demonstrated that reproductive behaviour has a very small impact, and only in certain scenarios.

“The main determinant of exposure is when you were born relative to the emissions,” says Quinn. “Smaller confounding factors, such as your mother’s parity or your birth order, are minor compared with the year of your birth.”

For those born before 1979, when the US Congress banned PCBs, none of your mother’s reproductive characteristics would have had a significant impact on your exposure. For those born in 1980 or later, Quinn’s results suggest birth order may have had an impact on the exposure you received in utero and as an infant, but this impact is still small compared to the fact that you were born at a time when PCBs were no longer being pumped into the environment with abandon.

 “There is a still a lot of work going on to correlate your current body burden of contaminants to things like smoking, or the number of children you’ve had, and whether or not you breastfed,” says Quinn, whose work is supervised by professor of environmental chemistry Frank Wania. “But these studies all ignore the context of the emissions scenario. This is the first study to show the extent of impact from variable emissions, and to show that this is among the most important variables leading to the body burden of an individual at any given time.”