Disclosures: The HAPIN trial was funded by the NIH in collaboration with the Bill and Melinda Gates Foundation. The authors report no relevant financial disclosures.
June 22, 2022
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Gas stoves improve household air quality but may not affect gestational BP

Disclosures: The HAPIN trial was funded by the NIH in collaboration with the Bill and Melinda Gates Foundation. The authors report no relevant financial disclosures.
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Use of a gas stove, despite improving household air quality, did not improve gestational BP in pregnant participants in lower-income countries, and contrarily increased BP compared with solid fuel burning stoves, researchers reported.

Although gestational BP increased among users of both liquified petroleum gas stoves and solid biomass stoves, the elevation was greater among pregnant participants using gas stoves; however, BP response by level of exposure to particulate matter (PM2.5), black carbon and carbon monoxide (CO) was not significant, according to findings from the Household Air Pollution Intervention Network (HAPIN) trial published in Hypertension.

pregnant woman
Source: Adobe Stock

“Globally, [approximately] 3 to 4 billion people rely on solid fuels (wood, animal dung, coal and agricultural residue) for domestic cooking and heating. These fuels are often burned inside homes, using open fires or traditional stoves,” Wenlu Ye, PhD student in the Gangarosa Department of Environmental Health of Rollins School of Public Health at Emory University, and colleagues wrote. “This largely preventable exposure remains a leading risk factor for morbidity and mortality worldwide. Poor populations in low- and middle-income countries bear most of this burden.”

Although few studies have assessed the health impacts of “clean fuels,” such as biogas, ethanol, liquefied petroleum gas and natural gas, according to the 2014 WHO Guidelines for Indoor Air Quality: Household Fuel Combustion, evidence suggests these fuels, as well as electricity, are good alternatives to solid fuels in low- and middle-income countries for reaching guideline-recommended PM2.5 and CO levels.

The HAPIN trial

With the idea that liquefied petroleum gas is a clean alternative to solid fuels burned when using a biomass stove, researchers conducted the HAPIN trial, which evaluated changes in household PM2.5 and CO within 3,195 homes with a pregnant resident (mean age, 25 years; 99% no history of high BP) across Guatemala, India, Peru and Rwanda. Participants were randomly assigned to prepare food utilizing either a gas stove or biomass stove. Gas stoves were provided by the researchers to each household.

The pilot results of the HAPIN trial indicated that cooking with a gas stove was associated with a 92% reduction kitchen PM2.5 levels and a 74% reduction in exposure to PM2.5, while maternal exposure to PM2.5 was reduced to the WHO interim target of 35 g/m3, according to the study published in Environmental Pollution.

HAPIN subanalysis of gestational BP

For the present analysis, researchers measured BP and exposure to PM2.5, black carbon and CO at three time points during gestation (baseline to < 20 weeks; 24 to 28 weeks; 32 to 36 weeks) to assess whether household air pollution was associated with gestational BP.

Median 24-hour PM2.5 decreased from 84 g/m3 to 24 g/m3 within households that began using a gas stove to prepare food, with similar reduction observed in black carbon and CO.

Although systolic BP and diastolic BP increased during gestation in both gas stove and biomass stove groups, researchers reported greater increases among those assigned to use a gas stove for both systolic BP (0.69 mm Hg; 95% CI, 0.03-1.35; P = .04) and diastolic BP (0.62 mm Hg; 95% CI, 0.05-1.19; P = .03).

Researchers also noted that exposure to household air pollution in the forms of PM2.5, black carbon and CO was associated with moderately elevated systolic BP and diastolic BP, but these associations did not reach statistical significance.

“The intervention (gas stove) resulted in a considerable reduction in exposure compared with biomass stoves (controls). We observed a modest but significant increase in gestational BP in the intervention group, indicating no protective effect on gestational BP of lowering exposure,” the researchers wrote. “In contrast, we found positive but insignificant associations between HAP exposures and gestational BP in exposure-response analyses. Further studies might explore these associations in cohorts of less healthy women with higher risk of gestational BP increases.”

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