Polybrominated biphenyls (PBBs) are man-made compounds used as flame retardants in consumer products such as computer monitors, textiles, and plastic foams. These compounds are released into the environment from poorly maintained waste sites and from improper incineration of plastics containing PBBs. Since PBBs can accumulate in the food chain, human exposure occurs through consumption of contaminated fish, meat, and dairy products. NIEHS studies show that prenatal exposure to PBBs has significant adverse effects on normal pubertal development. This information may be useful in predicting the health risks of similar compounds that have endocrine-disrupting properties.
Results of laboratory animal studies show that PBBs in the mother’s blood can cross the placenta and expose the developing fetus. Newborns can also be exposed to the compound via breastfeeding. Studies show that exposure to PBBs during gestation and early infancy may alter the hormonal balance necessary for proper growth and maturation.
In 1973, an accidental contamination of livestock feed with a PBB-based fire retardant caused widespread human exposure to these chemicals. In the months following the accident, thousands of Michigan residents ate animal and dairy products that had been contaminated with PBBs. Once a registry of over 4,000 exposed individuals was established, NIEHS-funded scientists at Emory University assessed the effects of PBB exposure on key indicators of growth and maturity in the daughters of women who had eaten the contaminated food. Breastfed girls exposed to high levels of PBBs in the womb had an onset of menstruation and public hair development one-half to one year earlier than breastfed girls who were exposed to lower levels of PBBs. No association was found between the girls’ PBB exposures and their self-reported height and weight.
NIEHS scientists will conduct additional studies to determine whether early exposure to these compounds may play a role in the development of breast and other cancers later in life. These findings will also provide researchers with a valuable model for assessing the health effects of other compounds, both natural and man-made, that interfere with endocrine function. These include polychlorinated biphenyls (PCBs), toxic chemicals once used as coolants in transformers and other electrical equipment, and dioxins, toxic compounds formed during the manufacturing of other chemicals and as byproducts of waste incineration.