Impact of Improved Biomass and Liquid Petroleum Gas Stoves on Birth Outcomes in Rural Nepal: Results of 2 Randomized Trials.

Joanne Katz,Scott L Zeger,Patrick Breysse,Naoko Kozuki,Steven C Leclerq,Laxman Shrestha,Subarna K Khatry,Luke C Mullany,James M Tielsch,William Checkley

doi:10.9745/ghsp-d-20-00011

Joanne Katz, Scott L Zeger + Show 8 more

Open Access

https://doi.org/10.9745/ghsp-d-20-00011

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Abstract

Few randomized trials have assessed the impact of reducing household air pollution from biomass stoves on adverse birth outcomes in low-income countries. Two sequential trials were conducted in rural low-lying Nepal. Trial 1 was a cluster-randomized step-wedge trial comparing traditional biomass stoves and improved biomass stoves vented with a chimney. Trial 2 was a parallel household-randomized trial comparing vented biomass stoves and liquid petroleum gas (LPG) stoves with a year's supply of gas. Kitchen particulate matter of 2.5 μm or less (PM2.5) and carbon monoxide (CO) were assessed before and after stove installation. Prevalent and incident pregnancies were enrolled at baseline and throughout the trials. Birth anthropometry was compared across differing exposure times in pregnancy. In trial 1, the mean 20-hour kitchen PM2.5 concentration was reduced from 1380 µg/m3 to 936 µg/m3. Among infants born before the intervention, mean birth weight and gestational age were 2627 g (SD=443) and 38.8 weeks (SD=3.1), and 39% were low birth weight (LBW), 22% preterm, and 55% small for gestational age (SGA). Adverse birth outcomes were not significantly different with increasing exposure to improved stoves during pregnancy. In trial 2, the mean 20-hour PM2.5 concentration was 885 µg/m3 in households with vented biomass and 442 µg/m3 in those with LPG stoves. Mean birth weight was 2780 g (SD=427) and 2742 g (SD=431), among households with vented and LPG stoves, respectively. Respective percentages for LBW, SGA, and preterm were 23%, 13%, and 42% in the vented stove group and not statistically different from 31%, 17%, and 42% in the LPG group. Improved biomass or LPG stoves did not reduce adverse birth outcomes. PM2.5 and CO following improved stove installation remained well above the World Health Organization indoor air standard of 25 µg/m3 or intermediate air quality guideline of 37.5 µg/m3. Trials that lower indoor air pollution further are needed.

Highlights

Low birth weight (LBW), comprising almost exclusively small for gestational age (SGA) and preterm births, is strongly associated with morbidity and mortality in infancy.[1,2] Observational studies have shown associations between reported use of biomass fuel and theseTrials of Reduced Indoor Air Pollution to Improve Birth Outcomes www.ghspjournal.org adverse birth outcomes but are subject to residual confounding even after adjustment for socioeconomic characteristics.[3–9] One study showed an adjusted 43% increased risk of preterm birth and 21% increase in SGA with use of biomass fuel, but measures of exposure were limited to reported use of solid fuels.[3]
We report here the results of 2 randomized trials to reduce indoor air pollution caused by open burning of biomass fuel sources in the home and the effects on mean birth weight and gestational age, as well as low birth weight (LBW), SGA, and preterm births
A total of 2,379 live born infants were enrolled in trial 1 and 270 and 279 in the Envirofit and liquid petroleum gas (LPG) stove groups in trial 2, respectively (Figures 1 and 2)

Summary

Introduction

Low birth weight (LBW), comprising almost exclusively small for gestational age (SGA) and preterm births, is strongly associated with morbidity and mortality in infancy.[1,2] Observational studies have shown associations between reported use of biomass fuel and theseTrials of Reduced Indoor Air Pollution to Improve Birth Outcomes www.ghspjournal.org adverse birth outcomes but are subject to residual confounding even after adjustment for socioeconomic characteristics.[3–9] One study showed an adjusted 43% increased risk of preterm birth and 21% increase in SGA with use of biomass fuel, but measures of exposure were limited to reported use of solid fuels.[3]. Multiple observational studies exist, only 2 randomized trials have examined the impact of reduced indoor air pollution on birth outcomes through the introduction of improved biomass or ethanol stoves.[10,11]. A trial in the highlands of Guatemala observed a 39% reduction in carbon monoxide (CO) levels, an increase in mean birth weight of 89 g, and a 26% lower rate of LBW among infants in households with improved biomass stoves compared with traditional ones.[10]. A more recent trial from Ibadan, Nigeria, enrolled 324 pregnancies and found an 88 g higher mean birth weight and 40% reduced prevalence of preterm birth among infants born in households provided with ethanol stoves.[11]. Few randomized trials have assessed the impact of reducing household air pollution from biomass stoves on adverse birth outcomes in low-income countries.

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