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Exposure to Air Toxics in Pregnancy Ups Preterm Birth

Inter-quartile range increase in polycyclic aromatic hydrocarbon exposure ups risk 30 percent

WEDNESDAY, Oct. 12 (HealthDay News) -- Maternal exposure to traffic-related air pollutants during pregnancy, especially polycyclic aromatic hydrocarbons (PAHs), is associated with an increased risk of preterm birth, according to a study published online Oct. 7 in Environmental Health.

Michelle Wilhelm, M.D., from the University of California in Los Angeles, and colleagues investigated the risk of preterm birth due to exposure to high levels of traffic-related air pollutants in pregnant women in Los Angeles. A total of 10,265 preterm births were identified between June 2004 and March 2006, and were matched to controls still in utero at the gestational age when the preterm cases were delivered. Average exposures during pregnancy were estimated for PAHs and source-specific fine particles with an aerodynamic diameter less than 2.5 µm (PM2.5) based on a Chemical Mass Balance Model, criteria-air pollutants from government monitoring data, and land use regression (LUR) estimates of nitric oxide, nitrogen dioxide, and nitrogen oxides.

The investigators found that for every inter-quartile range increase in entire pregnancy exposure to organic carbon, elemental carbon, benzene, diesel, biomass burning, and ammonium nitrate PM2.5, the odds of preterm birth increased 6 to 21 percent. For every inter-quartile range increase in PAH exposure during pregnancy, the odds of preterm birth increased 30 percent. These pollutants were positively associated with preterm birth, and clustered together in a factor analysis. LUR exposure metrics showed weaker odds of preterm birth (3 to 4 percent per inter-quartile range increase).

"These latest analyses provide additional evidence of traffic-related air pollution's impact on preterm birth for women living in Southern California and indicate PAHs as a pollutant of concern that should be a focus of future studies," the authors write.

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