Setting a Growth Trajectory: Household Air Pollution Exposures Before and After Birth.

Poor growth in young children has lifelong implications for health, including impaired cognitive, motor, and social development, among other health and economic consequences.[1] Undernutrition and related growth deficiencies are especially a problem in low- and middle-income countries (LMICs).[2] However, optimal growth depends on more than just adequate nutrition, and a better understanding of the factors involved can help policy makers and health experts develop appropriate interventions. In a study published recently in Environmental Health Perspectives,[3] investigators explored the potential role of household air pollution (HAP) in infant growth trajectories.

HAP has been associated with decreased birth weight.[4,5] However, until now, no studies have reported an exposure–response relationship between exposure to HAP and early childhood growth trajectories.

Optimal growth depends on more than just having enough food to eat. A child’s growth trajectory begins in utero and can be affected by numerous factors. Image: © Nyani Quarmyne/Panos Pictures.

The current analysis included 1,144 children from the Ghana Randomized Air Pollution and Health Study (GRAPHS). This study enrolled more than 1,400 pregnant women from 35 Ghanaian communities to assess how cooking with two different types of household cookstoves compared with cooking over an open fire in relation to birth outcomes and infant pneumonia risk.[4,6,7,8] In addition, the authors prospectively collected anthropometric measures every 3 months to assess whether exposure to HAP was associated with infant growth trajectories. Intervention households received either a liquified petroleum gas (LPG) stove or an improved biomass stove, whereas just over one-third of the households continued using open fires to cook. Households that cooked with improved biomass stoves or open fires received an LPG stove after the infant’s first birthday.

The women underwent four 72-hour carbon monoxide (CO) exposure assessments during pregnancy, one before they received the new stove and three after; infants were also assessed for CO exposure. In a subset of mothers, fine particulate matter () was measured once before and once after delivery.

The results were striking. “Household air pollution exposure during critical windows of development, specifically the prenatal period and the first year of life, were associated with impairment of nearly every metric of infant growth,” says study coauthor Alison Lee, an assistant professor of medicine at Mount Sinai Hospital. Higher exposures to HAP during pregnancy, as indexed by mothers’ CO and measurements, were associated with shorter length in their babies. Higher infant exposures were associated with smaller head circumference, mid-upper arm circumference, and weight for length by age 12 months. Infants born to women who used LPG stoves had greater growth in head circumference and mid-upper arm circumference, compared with infants born to women who cooked with fire. Furthermore, a small increase in prenatal HAP exposure was associated with higher risk of being on a trajectory consistent with persistent stunting over the first year of life. The authors found no evidence of an association between improved biomass stoves and any measures of growth.

“Both the exposure and outcome data were carefully collected, [and] the statistical analysis was sophisticated,” says John Balmes, a professor of medicine at the University of California, San Francisco, School of Medicine, who was not involved in the study. “The major weakness was the lack of data on nutrition and enteric infections.”

Peggy Lai, an assistant professor of medicine at Massachusetts General Hospital and research associate at the Harvard T.H. Chan School of Public Health, particularly notes the finding that infant growth trajectories appear to be set at birth. This finding “highlights the importance of early interventions; here, early means in the prenatal period,” says Lai, who was not involved in the study. “Multiple anthropometric measurements were used as outcomes, and while they are all likely correlated, it would [have been] helpful to prespecify which measurements were the ones of primary interest at the outset.”

Lai says the exposure–response analyses of pre- and postnatal exposures to CO and , coupled with the finding that there may be some effect of the LPG intervention on growth trajectories, raises a question of why. “Further mechanistic work would be important to design effective interventions for childhood undernutrition,” she says.

In addition, given growing evidence that environmental exposures can affect the gut microbiome,[9] Lai says, “It is possible that air pollution exposure may affect the developing infant gut microbiome, which has causal implications for growth and undernutrition.”

The research team plans to continue their work with the children over time. “GRAPHS is extending cohort followup through 8 years of age to understand how early-life household air pollution shapes lung health,” says Lee. “We hope to extend that work to also examine cardiovascular health and neurodevelopment.”

GRAPHS is part of a collaboration between Kintampo Health Research Center in Ghana and Columbia University that began more than 15 years ago around their mutual interest in researching how household air pollution affects health. “We are committed to training more environmental health researchers in Ghana and other LMICs,” says coauthor Kwaku Poku Asante, director of the Kintampo center. “It is exciting to have a female early career researcher [first author Ellen Boamah-Kaali] participate in data collection and lead this very important publication.”

Lai commends the study group for ensuring that their work was a true partnership between in-country and U.S.-based investigators. She says, “While it may take longer for research findings to be published, as local investigators often have insufficient protected time for research, this partnership is truly commendable and should serve as a role model for this type of work.”