Early Findings from HAPIN Trial Released

October 11, 2022

Early findings from the Household Air Prevention Network Trial— an international multi-center study aimed at assessing the impact of a liquefied petroleum gas (LPG) cooking stove and fuel intervention on health—were published today in The New England Journal of Medicine.

The aim of the multi-year HAPIN trial was to determine the impacts of a randomized LPG intervention on health in diverse low- and middle-income populations on four primary outcomes: birth weight, child stunting, child pneumonia, and adult systolic blood pressure. Three thousand two hundred pregnant women (9 to <20 weeks gestation)—800 from each of India, Rwanda, Guatemala, and Peru—were randomized on a 1:1 basis, either to receive a free LPG stove and fuel or to serve as controls that continued to cook on traditional stoves with biomass. The researchers measured stove use and the pregnant woman’s exposure to air pollution throughout the gestation period.

The study was led by Emory University, Johns Hopkins University, and Colorado State University and involved investigators from the Sri Ramachandra Institute of Higher Education and Research, Universidad del Valle de Guatemala, Asociación Benéfica PRISMA, Universidad Peruano Cayetano Heredia, the London School of Hygiene and Tropical Medicine, the University of Georgia, UC Berkely,  Harvard University, Washington University in St. Louis,  Berkeley Air Quality, Oxford University. It was funded by the US National Institutes of Health in collaboration with the Bill & Melinda Gates Foundation. 

This paper, led by Thomas F. Clasen, Rose Salamone Gangarosa Chair in Sanitation and Safe Water at Rollins and MPI of the study, reports on the first of those outcomes and the one for which data is currently available. Major findings include:

  • Despite the challenge of COVID shutdowns and government restrictions--and the tendency of householders to continue to use traditional stoves and fuel even when they have access to cleaner fuels—we were able to continue the trial and achieve nearly exclusive use of the LPG stoves by the intervention arm throughout the follow up period.
  • The intervention was highly effective in reducing exposure to air pollution. Personal exposure to fine particulate matter (PM5) was 66% lower in the intervention group than in the control group (23.9 vs. 70.7 μg/M3). It was below the WHO Interim Guideline value of 35 μg/M3-IT1 limit in 69% of the intervention households compared to 23% of control households.
  • Despite the reduction in exposure to air pollution, the birth weight of infants did not differ significantly between those born to women who used LPG cookstoves and those born to women who used biomass cookstoves.
  • There was suggestive evidence that intervening earlier in gestation may be protective: infants born to women who received the intervention at less than 18 weeks’ gestation were 33.8 g (95% CI, −2.6 to 70.2) heavier than those born to women who received the intervention at a later time.

It should be noted that this study tested an intervention not an exposure. A companion study undergoing peer review and available as a pre-print found that higher maternal exposure to fine particulate or black carbon resulted in lower birth weight. 

The researchers recently received a 4-year $6.8M R01 from the National Institute for Environmental Health Sciences to continue following HAPIN children for growth and neurocognitive development outcomes until their fifth birthday.