In Utero Household Air Pollution Exposure Increases Infants' Risk of Poor Lung Function

Infants whose mothers were exposed to carbon monoxide in the second and third trimester were at highest risk for reduced lung function when they were tested at 1 month of age.

Alison Lee, MD, MS

New research, conducted as part of the Ghana Randomized Air Pollution and Health Study (GRAPHS), found that children born to mothers exposed to increased carbon monoxide (CO) during pregnancy, specifically during the pseudoglandular and canalicular phases of lung development, were at increased risk for reduced lung function at 1 month of age.

Presented at the 2018 American Thoracic Society International Conference, this is the first study to investigate the association between household air pollution and lung development beginning in utero, and to identify critical windows of exposure during pregnancy.

“Our research suggests that children, especially girls, born to mothers with increased households air pollution exposures during pregnancy have impaired lung function measurable at birth,” lead author Alison Lee, MD, MS, Icahn School of Medicine, Mount Sinai, said. “Exposures during the second and third trimesters appear to have the largest impact. These findings have implications for future respiratory health.”

The GRAPHS study recruited Ghanaian women during early pregnancy and randomized them to 1 of 3 groups: 2 cookstove interventions and 1 control group.

The control group used a 3-stone fire, the traditional means of cooking in Ghana; intervention group 1 was given BioLite Stoves, improved combustion efficiency biomass stoves; and intervention group 2 was given LPG gas stoves, similar to those used in the US.

Four, 72-hour CO personal air pollution exposure measurements were performed during pregnancy and calculated to estimate weekly prenatal CO exposure.

A subset of study children (n = 400) performed infant lung function testing per ATS protocol age 1 month of age.

The primary lung function outcome was the ratio of time to peak expiratory flow to expiratory time (TPEF:TE). Tidal volume (TV, mL), respiratory rate (RR, breath/min), minute ventilation (MV, mL/min) and passive respiratory system compliance (Crs, mL/cm H2O) were also measured.

Researchers applied multivariable linear regression models to estimate the association between average prenatal CO exposure and lung function. Distributed lag models estimated the time-varying association between lung function variables and weekly CO exposures.

Models were adjusted statistically to rule out variables that may have affected results like child sex, birthweight, gestational age at birth, weight, height and age at lung function test, socioeconomic status and maternal education.

“Women are commonly the primary cooks and continue to cook while pregnant, so a child’s exposure to household air pollution begins in utero,” Lee added. “Importantly, we know that lung function development progresses rapidly over gestation and alterations in lung development secondary to toxic maternal exposures impair lung development with lasting effects. Lung function at birth has been shown to predict lung function through adulthood and increase risk for future respiratory symptoms and disease.”

The mothers mostly had no (46%) or <12 years (51%) education and were never smokers.

At lung function testing, infants were term (gestational age 39.7 weeks, IQR 39—40.7) and 30 days old (IQR 27–30.3). The median prenatal CO exposure was 1.1ppm (0.6–1.9).

A significant association was found between increased prenatal CO exposure and TPEF:TE (12—23 weeks), increased RR (13–29 weeks) and reduced Crs (18–24 weeks). Infants whose mothers were exposed to CO in the second and third trimester were at highest risk for reduced lung function when they were tested at 1 month of age.

Understanding temporal effects of household air pollution on lung development may clarify underlying mechanisms which is critical for development of preventative strategies, researchers concluded.

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