A recently published study from Brown University researchers Marcella Remer Thompson and Kim Boekelheide in the peer-reviewed journal Environmental Research indicates that the risk of above median levels of lead, mercury and PCBs in the bodies of women of child-bearing age increases with increasing age and that decreased risk of above median levels is found in women who have breast-fed an infant, leading to the almost inescapable conclusion that the toxic substances are commonly discharged from the mother in the breast milk.
The research found three statistically significant risk factors for above median levels of these three substances in females: age, eating of fish, and heavy alcohol consumption. Women in the study group of 3,173 American women aged 40 to 49 had a 30 times greater risk of having above median concentrations of these substances in their bodies than women aged 16 to 19. Part of this increased risk may stem from increased environmental exposure to these substances in the 1950s and 1960s than today. It is not known why heavy alcohol consumption leads to increased pollutant levels in the body. The only factor that led to a reduced risk of having above median concentrations of these three contaminants in a women’s body was a history of breastfeeding.
The study can be found at http://www.sciencedirect.com/science/article/pii/S0013935112002885 – abstract is free; fee required for full article. A good summary is published by Brown University at http://news.brown.edu/pressreleases/2012/11/toxicants