While recent emission controls on motor vehicles have decreased the release of toxic gases, the total number of cars and trucks on the road has increased, thereby negating the benefits of these controls. Tall stacks, used to disperse sulfur dioxide from large coal burning plants, have succeeded in reducing sulfur dioxide at ground level, but they have increased the proportion of sulfur dioxide converted into sulfuric acid in the air, so acid aerosol concentrations have diminished only slightly in recent years.
Estrogens in Pharmaceuticals and Pesticides
Studies by the NIEHS have shown the effects on children whose mothers took the potent synthetic estrogen DES during pregnancy to prevent miscarriage. The NIEHS and other research organizations have also performed many studies on pesticides, such as DDT and DDE, which contain chemicals that mimic estrogen or disrupt the body's hormones during pregnancy.
DDT, the first chlorinated hydrocarbon insecticide, was banned in the U.S. in 1972 after it was shown to cause an abnormality in calcium production, particularly in bird species whose eggs were laid with thin eggshells or without any shell at all. The Institute's scientists followed more than 700 North Carolina children exposed to DDE, the by-product produced when DDT begins to break down, in breast milk and found no related illness or lasting developmental abnormality. However, women with the highest levels of DDE in their milk breastfed their children less than 40 percent as long as women with lower levels. Another study in Mexico, where DDE levels in breast milk were often higher, showed a similar decrease in length of lactation, at least among second and later children. These decreased lactations may be related to the estrogenicity of DDE, since even very low doses of contraceptive estrogen can interfere with milk production.
Despite the research that has been done by the NIEHS and others, the prestigious National Academy of Sciences states in the recent report "Pesticides in the Diets of Infants and Children" that there remains a knowledge gap regarding the possible effects of pesticides on the development of the immune, nervous and reproductive systems from fetal, newborn and childhood exposures. The Academy recommended a significant research effort regarding these and other possible effects.
In response, the NIEHS is conducting a complex series of experiments with experts from the Environmental Protection Agency's Health Effects Research Laboratory evaluating the effects of common pesticides, including carbaryl, parathion, chlorpyrifos, atrazine and trichlorfon, in generations of rodents.
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