Family medicine educators recently got an earful about the impact of some common environmental toxins on human development. Infants born to fathers routinely exposed to kerosene or diesel fuel -- even before the children were conceived -- have an increased incidence of neuroblastoma, Sandra Steingraber, Ph.D., told participants Sept. 21 at the Society of Teachers of Family Medicine Annual Conference in Atlanta. A mother's exposure to pesticides at 3 to 5 weeks' gestation -- before she realizes she's pregnant -- can lead to spontaneous abortion, Steingraber warned.
Slightly later in the fetal developmental process, "the amazing opera that we know as organogenesis" takes place, she said. During this critical window, maternal exposure to pesticides can lead to limb reduction deficits. State birth defect registries clearly show this correlation: By examining Minnesota's records of infants born with missing digits or limbs, for example, Steingraber confirmed that organogenesis occurred during the spring planting months, when pesticide use was at its highest.
Neurogenesis, a process Steingraber likened to a "quilting bee done by spiders," is also susceptible to the effects of environmental toxins. Fetal exposure to lead or mercury inhibits dendrite formation and can result in mental retardation.
Polychlorinated biphenyls, or PCBs, are some of the most well-studied environmental contaminants. PCBs were used in hundreds of industrial and commercial applications until the practice was outlawed in 1977. But they still contaminate the water supply in many areas, said Steingraber.
By binding to protein receptors in the brain, PCBs interfere with the supply of thyroid hormone essential for nervous system development. "It's like trying to flag down a thyroid taxi that already has a passenger on board," Steingraber explained.
FP Report is published by the
AAFP News Department.
Copyright © 2003 by
American Academy of Family Physicians.