TOPLINE:

Personal exposure to fine particulate matter with a diameter of ≤ 2.5 μm (PM_2.5) or carbon monoxide (CO) from biomass cooking showed no association with the risk for severe pneumonia in infants.

METHODOLOGY:

• Researchers conducted an exposure-response analysis to evaluate the longitudinal association between exposure to household air pollution (primarily PM2.5 and CO) and the risk for severe pneumonia in infants across Guatemala, India, Peru, and Rwanda from May 2018 to September 2021.
• They used data from a previous trial and included 3061 pregnant women who had live births (mean gestational age at birth, 39.3 weeks; 48.2% girls) and were randomly assigned to use a liquefied petroleum gas stove with continuous fuel supply or to continue usual biomass cooking.
• The 3061 included infants contributed to 11,996 infant-quarters (3-month intervals). Personal 24-hour exposures to PM2.5 and CO were measured in pregnant women at baseline, 24-28 weeks, and 32-36 weeks of pregnancy and in infants at 3, 6, and 12 months of age.
• The primary endpoint was severe pneumonia during infancy, ascertained using active surveillance at sentinel health facilities.

TAKEAWAY:

• A total of 175 episodes of severe pneumonia were identified in 160 infants during 11,996 infant-quarters, with a mean of 5.8 episodes per 100 infant-years.
• Despite numerically higher risks at higher exposures, analyses found no significant association between exposure to PM2.5 and the risk for severe pneumonia (prenatal adjusted risk ratio [RR], 1.03; 95% CI, 0.94-1.13; postnatal adjusted RR, 0.97; 95% CI, 0.87-1.09).
• A similar trend was observed for exposure to CO and the risk for severe pneumonia during infancy.
• Subgroup analyses also revealed no effect modification by sex, winter season, socioeconomic wealth index, or pneumococcal conjugate vaccine status.

IN PRACTICE:

“Our results suggest that neither PM_2.5 nor CO exposures from biomass cooking is a strong risk factor for severe pneumonia during infancy in low- and middle-income countries, and household-level mitigation strategies to reduce these pollutants with cleaner cooking are unlikely to have a meaningful impact on severe pneumonia during infancy,” the authors wrote.

SOURCE:

This study was led by John P. McCracken, ScD, Department of Epidemiology and Biostatistics, College of Public Health, University of Georgia in Athens, Georgia, and Eric D. McCollum, MD, MPH, Division of Pediatric Respiratory Sciences, School of Medicine, Johns Hopkins University in Baltimore. It was published online on October 29, 2025, in JAMA Network Open.

LIMITATIONS:

Residual confounding may have persisted because of unmeasured, poorly measured, or mismodeled confounders. Exposure measurement error was a concern due to the limited number of repeated measures per child and the indirect estimation of exposure in infants. As the liquefied petroleum gas stove was unvented, potential toxic effects from its combustion could not be excluded.

DISCLOSURES:

The primary trial was funded by the US National Institutes of Health in collaboration with the Bill & Melinda Gates Foundation. Two authors disclosed receiving grants from multiple National Institutes of Health organizations and other sources, outside the submitted work.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.