Exposure contrasts of pregnant women during the Household Air Pollution Intervention Network randomized controlled trial

Abstract

BackgroundExposure to PM2.5 arising from solid fuel combustion is estimated to result in approximately 2.3 million premature deaths and 90 million lost disability-adjusted life years annually. ‘Clean’ cooking interventions attempting to mitigate this burden have had limited success in reducing exposures to levels that may yield improved health outcomes.ObjectivesThis paper reports exposure reductions achieved by a liquified petroleum gas (LPG) stove and fuel intervention for pregnant mothers in the Household Air Pollution Intervention Network (HAPIN) randomized controlled trial.MethodsThe HAPIN trial included 3,195 households primarily using biomass for cooking in Guatemala, India, Peru, and Rwanda. 24-hour exposures to PM2.5, carbon monoxide (CO), and black carbon (BC) were measured for pregnant women once before randomization into control (n=1605) and LPG arms (n=1590) and twice thereafter (aligned with trimester). Changes in exposure were estimated by directly comparing exposures between intervention and control arms and by using linear mixed-effect models to estimate the impact of the intervention on exposure levels.ResultsMedian exposures of PM2.5, BC, and CO post-randomization in the intervention arm were lower by 66% (70.7 versus 24.0 μg/m3), 71% (9.6 versus 2.8 μg/m3), and 83% (1.2 versus ppm), respectively, compared to the control arm. Exposure reductions were similar across research locations. Post-intervention PM2.5 exposures in the intervention arm were at the lower end of what has been reported for LPG and other clean fuel interventions, with 69% of PM2.5 samples falling below the WHO Annual Interim Target 1 of 35 μg/m3.DiscussionThis study indicates that an LPG intervention with high displacement of traditional cooking can reduce exposures to levels thought to be associated with health benefits. Success in reducing exposures was likely due to strong performance of, and high adherence to the intervention.

Effects of a Liquefied Petroleum Gas Stove Intervention on Gestational Blood Pressure: Intention-to-Treat and Exposure-Response Findings From the HAPIN Trial

“…The LPG stove and fuel intervention did lead to large reductions in post-randomization personal exposures to PM 2.5 , BC, and CO, and ≈70% of the PM 2.5 exposure measurements in the intervention group were below the 2021 World Health Organization Interim Target 1 of 35 μg/m 3 . 32 Therefore, the question raised by our results of is why this intervention showed no protective effect on BP in pregnant women from this cohort, given this effect has been observed in some other studies. 23,24 Several factors may explain our largely null findings.…”

“…Detailed exposure results for these women are described elsewhere. 32 Boxplots of personal exposure to PM 2.5 , BC, and CO by intervention groups and visit are shown in Figure S2 . We observed high correlations between PM 2.5 and BC (Spearman ρ=0.86) and moderate correlation between PM 2.5 and CO (Spearman’s ρ=0.50) and BC and CO (Spearman ρ=0.48), across all visits, which were similar in the intervention and control groups.…”

“…Exposure measurement procedures have been described previously. 29 , 32 While there is no gold standard for measuring HAP, gravimetric measures—of the type we performed—are considered high quality, especially when performed with stringent QA-QC procedures. 32 Personal exposure monitoring was conducted during the 24 hours before the BP measurements.…”

“… 29 , 32 While there is no gold standard for measuring HAP, gravimetric measures—of the type we performed—are considered high quality, especially when performed with stringent QA-QC procedures. 32 Personal exposure monitoring was conducted during the 24 hours before the BP measurements. We measured personal exposures to PM 2.5 , BC, and CO at baseline and at the 2 follow-up visits.…”

“…If a gravimetric sample was considered invalid due to a missing or damaged filter or flow faults, instrument-specific nephelometric concentrations were used instead, normalized to field-based filter samples. 32 Personal exposure to BC was estimated from PM 2.5 filter samples with SootScan Model OT21 Optical Transmissometers (Magee Scientific). CO concentrations were measured using the Lascar EL-USB-300 (Lascar Electronics) at 1-minute intervals with range between 0 and 300 ppm.…”