PCB's in breastmilk pose fewer hazards than previously thought as determined by a group of scientists from the Harvard School of Medicine and the Harvard School of Public Health. Although polychlorinated biphenyls (PCBs) make their way into human breastmilk, the health benefits of breastfeeding children, even when breastmilk is contaminated with PCBs outweigh the risks of bottle feeding, the authors conclude. New Bedford Harbor in Massachusetts is amongst the most PCB polluted area in the US. PCBs have considerable health risks for the developing fetus -- hepatoxicity, neurotoxicity and immunotoxicity. Exposure in utero has been associated with low birth weight, prematurity, decreased gestational time, and developmental defects, including IQ.

Breastmilk samples were taken from four mothers living near the New Bedford Harbor. The PCB levels were significantly higher than the overall mean of women studied, 4 to 8 times higher. Evaluations of the breastfed infants from 3 and 18 months showed some adverse ef
fect on psychomotor Bayley Scales at 7 months but not at 18 months. And the breastfed infants did not score lower on the Bayley Scales at any age than the formula fed infants. The authors concluded that their findings did not justify advice against breastfeeding as the documented developmental toxicities have been associated with prenatal and not postnatal exposure. Thus despite the potential for large PCB exposure through breastmilk there is limited evidence of transmitted toxicity associated with the low to moderate levels passed through breastmilk.