Birth Outcomes and Prenatal Exposure to Ozone, Carbon Monoxide, and Particulate Matter: Results from the Children’s Health Study

Abstract

Exposures to ambient air pollutants have been associated with adverse birth outcomes. We investigated the effects of air pollutants on birth weight mediated by reduced fetal growth among term infants who were born in California during 1975–1987 and who participated in the Children’s Health Study. Birth certificates provided maternal reproductive history and residence location at birth. Sociodemographic factors and maternal smoking during pregnancy were collected by questionnaire. Monthly average air pollutant levels were interpolated from monitors to the ZIP code of maternal residence at childbirth. Results from linear mixed-effects regression models showed that a 12-ppb increase in 24-hr ozone averaged over the entire pregnancy was associated with 47.2 g lower birth weight [95% confidence interval (CI), 27.4–67.0 g], and this association was most robust for exposures during the second and third trimesters. A 1.4-ppm difference in first-trimester carbon monoxide exposure was associated with 21.7 g lower birth weight (95% CI, 1.1–42.3 g) and 20% increased risk of intrauterine growth retardation (95% CI, 1.0–1.4). First-trimester CO and third-trimester O3 exposures were associated with 20% increased risk of intrauterine growth retardation. A 20-μg/m3 difference in levels of particulate matter ≤ 10 μm in aerodynamic diameter (PM10) during the third trimester was associated with a 21.7-g lower birth weight (95% CI, 1.1–42.2 g), but this association was reduced and not significant after adjusting for O3. In summary, O3 exposure during the second and third trimesters and CO exposure during the first trimester were associated with reduced birth weight.

Are environmental pollutants risk factors for low birth weight?

“…Meanwhile, the study is consistent with Salam et al 12 , who point to a 40% increase in the odds of low birth weight. These authors did not identify low birth weight according to the pollutants PM 10 , NO 2 , and CO.…”

“…PM 10 was not associated with low birth weight, in agreement with the findings by Junger & Leon 9 , Salam et al 12 , and Maisonet et al 13 . Meanwhile, our findings disagree with those of Medeiros & Gouveia 8 and Bell et al 14 .…”

“…Ozone, not usually cited as associated with low birth weight, was identified as increasing the odds of low birth weight in a study in California by Salam et al 12 including some five thousand full-term newborns from 1975 to 1987.…”

“…These authors did not identify low birth weight according to the pollutants PM 10 , NO 2 , and CO. They used a single pollutant model, and in the multivariate model, ozone remained significantly associated with low birth weight 12 .…”

Pre and Post-Natal Exposure to Air Pollution is Public Health Problem

“…The maternal exposure to O 3 in the second and to CO in third month of pregnancy caused a loss in weight of babies [7][8][9][10]. Moreover, the pregnant women who inhaled NO 2 during gestational period present an increase of 25% premature delivery [11].…”