WHEN DO ENVIRONMENTAL EFFECTS BEGIN?
Much of your growth occurs in your mother’s womb and, not surprisingly, at least some environmental effects occur during fetal growth. Examples include the administration of thalidomide during the 1950s to prevent nausea during pregnancy. Many children of women who took this drug were born with abnormal or missing limbs. (Interestingly, the drug has been resurrected in recent years to treat multiple myeloma, a cancer of bone marrow cells.) Exposure of pregnant women to thalidomide and serious viral infections have been shown to be associated with an increase in autism. Interestingly, it has been noted that the frequency of autism in the United States has risen sixtyfold in the past thirty years. Although some of this increase may be related to more frequent diagnosis, the high incidence (estimated currently to be as high as 1 in 45 births) and evidence that genetic factors cannot explain all cases, strongly suggests that environmental factor(s) may be involved.
Another potential source of effects during prenatal development is maternal nutrition. It has been noted in several studies that children and grandchildren born to parents who have conceived during times of food scarcity have smaller children on average. A recent example has shown that Gambian children conceived during times of less food (the rainy season) have lower birth weights relative to those conceived during times of more plentiful food. Similarly, babies born to heavier mothers have been reported to be healthier relative to thin mothers in underdeveloped regions of the world.
In addition to the prenatal period, environmental factors likely affect our health for the remainder of our lives. As noted earlier, chemical exposure, exercise, diet, stress, and pathogen exposures can all impact a person’s health regardless of age.