This means that maternal exposures to toxic substances on a particular day of pregnancy might cause devastating effects to a baby, while exposures on the very next day would cause no discernible effects whatsoever. The brain is a particularly sensitive target for early-life exposures. The blood brain barrier, which protects the developing brain from some chemical exposures, is not fully developed at birth. The human brain develops in overlapping phases, each presenting unique opportunities for chemical-induced damage, beginning in the womb within days of conception, and continuing through childhood. The right chemical at the right time has the potential to disrupt any of these processes.
Sensitivities continue through childhood.
An increasing number of studies are showing effects to the reproductive system and the brain following early-life exposures to an array of chemicals. Children one through five years of age eat three to four times more food per pound than the average adult. Just doing what children normally do can increase doses of chemicals. Environmental Health Perspectives 106, Supplement 3, June 1998. Exposure Factors Handbook.