Polychlorinated biphenyls (PCB) found in flame retardant cloth, paint, adhesives and electrical transformers, have been banned since 1979, but if you live on top of a waste disposal site or you have a 40 year old couch, you could still be exposed to them.

A new study suggests that if you were a pregnant woman, you could have suffered endocrine disruption, in this case in thyroid production, and it could have harmed the baby. Endocrine disruptors are natural or man-made chemicals that interfere with endocrine glands and their hormones, There is no evidence that normal exposure to endocrine disrupting chemicals are harmful but studies find possible links and note they may cause a problem.

In this prospective birth cohort study, researchers looked at the effects of low-dose chemical exposure in 164 pregnant women. Tissue from their placentas, the uterine structure that provides oxygen and nutrients to the fetus, was analyzed for a specific enzyme, CYP1A1, which changes endocrine-disrupting chemicals into a form that can interfere directly with the body's thyroid hormone receptors. The effort was a collaboration between scientists in the biology department at UMass Amherst and a group led by Larissa Takser at the University of Sherbrooke, Québec, who collected placental tissue from a large epidemiological study. 

R. Thomas Zoeller of the University from Massachusetts Amherst says, "As endocrine-disrupting chemicals, PCBs interfere with the way the thyroid hormone functions, but they don't actually change the amount of the hormone found in the body. Although these effects are largely invisible in scientific studies that only judge thyroid activity by measuring hormone levels, they may be having a real impact on infants' brain development." 

Zoeller's UMass Amherst laboratory provided the framework for the analyses. "This led us to predict specific molecular events that might be occurring in the placenta," he notes, "and as best as we can tell right now, we were correct."

They found that in pregnancies where the placenta contained higher levels of CYP1A1, it also showed signs of thyroid disruption. Levels of two thyroid-regulated genes tended to be higher in these pregnancies, although the mother's overall thyroid hormone levels did not change.

"Whatever is happening in the placenta likely reflects what is happening in the fetus," says Zoeller. "To truly understand how endocrine-disrupting chemicals may be affecting pregnancies, the findings show we need to study not only hormone levels, but hormone activity at the cellular level."

The effects of endocrine-disrupting chemicals may be particularly insidious in people who smoke, Zoeller said. The enzyme CYP1A1 is supposed to clean the blood, and the body produces more of this enzyme when it is exposed to cigarette smoke. The researchers found pregnant women who smoked tended to have higher levels of the enzyme in the placental tissue.

Bolstered by success in getting PCBs banned, environmental activists have taken to calling everything an endocrine disruptor - every herbicide and even BPA has been lumped in as endocrine disruptors, which is technically true, along with a whole lot of foods.

There is no way to get rid of all endocrine disruptors, unless we want to ban things like cauliflower:

Credit: Purdue