Lead researcher Philippe Grandjean, adjunct professor at the Harvard School of Public Health, said children who were exposed to toxic industrial chemicals -- such as mercury, lead, PCBs, toluene and arsenic -- during fetal development often show signs of attention deficit disorder, autism, cerebral palsy and developmental delays later in life.
"The human brain is a precious and vulnerable organ," Grandjean said. "And because optimal brain function depends on the integrity of the organ, even limited damage may have serious consequences."
According to Grandjean and his research team, the group of chemicals that causes the most damage includes solvents, pesticides and metals. Grandjean identified 201 distinct chemicals with toxic effects, and described in his study how developing babies are far more susceptible to chemicals than adults.
During the nine months that infants are in the womb, their brains develop from a strip of highly sensitive cells that lack the protection of a fully formed blood-brain barrier, which does not develop until children are six months old.
Nursing babies are also at much higher risk of toxic chemicals than their mothers because certain pesticides and industrial compounds can accumulate in breast tissue. When infants nurse, the chemicals are passed to the baby in the breast milk at 100 times the level of the mother's exposure.
Grandjean's research also showed that young children living in environments where their chemical exposure is exceptionally high -- such as on farms -- display increased brain development problems, compared to children raised in urban environments.
According to the study, a majority of industrial chemicals aren't adequately tested for toxicity, and too much proof is required of researchers to demonstrate that a particular chemical is hazardous.