Air Pollution Linked to Birth Defects, Study Finds
Smog is "exacting a much greater toll than previously known" on developing fetuses, according to a new study by researchers at the University of California-Los Angeles, the Los Angeles Times reports. The study, which will be published in the Dec. 28 issue of the American Journal of Epidemiology, for the first time links air pollution with birth defects in Southern California, the Times reports. UCLA researchers examined "thousands of pregnant women" living in the Los Angeles area between 1987 and 1993 and compared pregnancy outcomes for women living in areas with "relatively dirty air" to women living in areas with "cleaner" air. Researchers determined that pregnant women who were exposed to high levels of ozone and carbon monoxide were three times more likely than other women to give birth to babies with cleft lips, cleft palates and defective heart valves. The greatest risk to fetuses occurred during the second month of pregnancy, when the fetus develops most of its major organs and much of its facial structure, the study found.
More than 12 other studies in the United States, Brazil, Europe, Mexico, South Korea and Taiwan have established links between air pollutants and low birthweight, premature birth, stillbirth and infant death, the Times reports. For instance, a team of U.S. and Swedish researchers reported earlier this year that pregnant women in several U.S. cities who were exposed to elevated carbon monoxide levels during their third trimester were 31% more likely than other women to give birth to underweight babies. Another study by UCLA researchers published last year found that pregnant women exposed to elevated levels of microscopic particles during the final six weeks of pregnancy were 20% more likely to deliver a baby prematurely than women whose pollutant exposure levels were lower. In addition, a 1998 study by Brazilian researchers found that pregnant women exposed to high levels of nitrogen and sulfur oxides were 18% more likely than other women to have their pregnancies end in stillbirth. Researchers in that study also found evidence of carbon monoxide in the umbilical cords of nonsmokers, suggesting that air pollutants can reach fetuses through the umbilical cord. Carbon monoxide can cut off oxygen to a fetus, resulting in death, the Times reports.
Dana Loomis, a University of North Carolina epidemiologist and co-author of a study on pollution and pregnancy, said, "There really is evidence that levels of air pollution encountered in large cities worldwide may be hazardous to the fetus. This is something that has not been recognized before. It was always assumed the fetus was isolated in the womb from things in the environment." Tracey Woodruff, a senior scientist at the U.S. Environmental Protection Agency and an author of one of the studies, added, "The research is suggestive, but preliminary. It's something to be concerned about, but nothing to panic about. It's something we need to pay attention to." EPA officials have said that before federal limits for ozone and microscopic particles can be strengthened to prevent harm to fetuses, additional research is necessary to determine what pollutants are harmful and at which stages of pregnancy they are most damaging to fetal development. In California, state officials are using the recent studies to back up a recommendation that the state Air Resources Board lower the statewide standard for airborne particle pollution by 33% (Polakovic, Los Angeles Times, 12/16).This is part of the California Healthline Daily Edition, a summary of health policy coverage from major news organizations. Sign up for an email subscription.