The children's mental and physical growth have been followed since birth. Large fish in Lake Michigan, such as lake trout and salmon, are typically contaminated with PCBs, mercury, and a host of other chlorinated organic chemicals. The Jacobsons analyzed PCB levels in the blood of the babies' umbilical cords, thus providing a reliable measure of pre-natal exposure. At birth, a mother's overall fish consumption and the PCB level in her baby's blood both correlated with the baby's birth size. Eating more fish was linked to babies with reduced head size, diminished girth in the chest and shorter gestation.
Normal babies spend more time looking at the new face.
Babies with more PCBs in their blood, and babies whose mothers had eaten more Lake Michigan fish, spent less time looking at the new faces. Secondly, the remainder of the children were given a series of tests to measure memory and general mental capabilities and, again, the children whose mothers had eaten the most fish had the poorest memories. The balky, uncooperative behavior is of some interest by itself. Significantly, the offspring of those rats showed the same pattern of altered responses to stress, even though the offspring themselves were not fed contaminated fish. Helen Daly wonders whether rats and children don't develop similar overreactions to stress after being exposed to PCBs while in the womb.