In utero and Postnatal Exposure to Polybrominated Biphenyl Causes Early Puberty in Girls

PI: Michele Marcus
Emory University

Background: In 1973, an accidental contamination of animal feed in Michigan caused human exposure to polybrominated biphenyls (PBB). The PBB containing fire retardant Firemaster was inadvertently added to livestock feed in place of Nutrimaster, a magnesium supplement. In the months following many Michigan residents ate animal and dairy products that had been contaminated. After discovery of the contamination, a registry of exposed individuals was established in 1976.

Maternal ingestion of PBB and polychlorinated biphenyls leads to exposure of the fetus through the placenta and to infants via breastfeeding. PBB rodent studies demonstrated effects on the reproductive system of female pups from exposed mothers. These studies suggest that exposure to PBB during gestation and early infancy may alter hormonal signaling pathways necessary for proper growth and maturation. The present study evaluates the association between perinatal PBB exposure and age at menarche, breast development, and pubic hair development in daughters of women exposed to PBB.

Finding:. Breastfed girls exposed to high levels of PBB in utero (>7 parts per billion) had an onset of menses one-half to one year earlier than breastfed girls exposed to lower levels of PBB (11.6 years vs. 12.2-12.6 years respectively). Perinatal PBB exposure also caused earlier pubic hair development in breastfed girls but little association was found with breast development. A possible mechanism of action may involve the thyroid gland. The main PBB component of Firemaster is known to affect thyroid hormone concentrations. Normal pubertal development is partially dependent on thyroid hormones. Other animal studies have shown that exposure to PBB during pregnancy and lactation causes decreased thyroxine levels in neonates. Five of the daughters in this study have reported thyroid problems.

Implication: The associations reported from this research lend support to the hypothesis that in utero and lactational exposure to PBB have profound effects on normal pubertal development. The reports of thyroid dysfunction suggests the possibility of thyroid involvement as a mechanism of action and opens a new line of investigation for future epidemiologic and animal studies.

Citation: Blanck HM, Marcus M, Tolbert PE, Rubin C, Henderson AK, Hertzberg VS, Zhang RH, Cameron L. Age at Menarche and Tanner Stage in Girls Exposed In Utero and Postnatally to Polybrominated Biphenyl. Epidemiology. 2000 Nov;11(6):641-647.