Exposure–response relationships for personal exposure to fine particulate matter (PM2·5), carbon monoxide, and black carbon and birthweight: Results from the multi-country Household Air Pollution Intervention Network (HAPIN) trial

Background Household air pollution (HAP) from solid fuel use is associated with adverse birth outcomes, but data on exposure-response relationships are limited. We examined associations between HAP exposures and birthweight in rural Guatemala, India, Peru, and Rwanda during the Household Air Pollution Intervention Network (HAPIN) trial. Methods We recruited 3200 pregnant women between 9 and <20 weeks of gestation. Women randomized to the intervention arm received a liquified petroleum gas (LPG) stove and fuel during pregnancy, while control arm women continued using biomass. We measured 24-hr personal exposures to particulate matter (PM 2·5 ), carbon monoxide (CO), and black carbon (BC) once pre-intervention (baseline), twice post-intervention, and birthweight within 24 hours of birth. We examined the relationship between the average prenatal exposure and birthweight/weight-for-gestational age z-scores using multivariate-regression models. Findings Results: showed an inter-quartile increase in average prenatal exposure to PM 2.5 (74·5 μg/m 3 ) and BC (7·3 μg/m 3 ) was associated with a 14·8 (95% confidence interval [CI]: -28·7g, - 0·8g) and 21·9g (95% CI: -37·3g, -6·1g) reduction in birthweight and reduced weight-for-gestational age z-scores of -0·03 (95% CI: -0.06, 0·00) and -0·05 (95%CI: -0·08, -0·01) standard deviations, respectively. We found no associations for birthweight or weight-for-gestational age z-scores with CO exposures. Interpretation Results: provide support for continuing efforts to reduce HAP exposure alongside other drivers of low birthweight in low- and middle-income countries. Funding The study is registered with ClinicalTrials.gov ( NCT02944682 ) and funded by the U.S. National Institutes of Health (1UM1HL134590) in collaboration with the Bill & Melinda Gates Foundation (OPP1131279).