Exposure-response relationships for personal exposure to fine particulate matter (PM2·5), carbon monoxide, and black carbon and birthweight: an observational analysis of the multicountry Household Air Pollution Intervention Network (HAPIN) trial

Associations of long-term exposure to fine particulate matter and its components with ovarian aging: Evidence from a cross-sectional study in China

This study aimed to investigate associations between long-term exposure to PM2.5, or its constituents, and ovarian aging, assessed by age at natural menopause (ANM) and early menopause (EM) prevalence. A total of 15,345 postmenopausal women were recruited from an epidemiologic survey conducted across 12 provinces in China (2023-2024). Concentrations of air pollutants [PM2.5 mass, sulfate (SO42-), nitrate (NO3-), ammonium (NH4+), organic matter (OM), and black carbon (BC)] were obtained from the Tracking Air Pollution in China database. Multivariable regression models with random effects and quantile g-computation models were used to evaluate associations. Each interquartile range increase in 5-year average concentrations of PM2.5, SO42-, NO3-, NH4+, OM, or BC were correlated with significant changes of -0.79 (95 %CI: -0.87, -0.72), -0.98 (95 %CI: -1.06, -0.90), -0.54 (95 %CI: -0.63, -0.45), -0.90 (95 %CI: -0.98, -0.81), -0.83 (95 %CI: -0.91, -0.76), and -1.02 (95 %CI: -1.09, -0.96) in ANM, respectively. Joint exposure analysis revealed that the five combined PM2.5 constituents shared a negative association with ANM in which BC provided the largest weight. These pollutants were also significantly associated with elevated EM prevalence, wherein BC provided the strongest contribution. The associations were stronger in women with a history of smoking, other hazardous environmental exposure, and lower education level.

Effect of preconception SOD2 gene variants and air pollution on gestational length: evidence from a mother-baby cohort

To explore the relationship between air pollution, preconception SOD2 gene variations, and gestational length. A study was conducted on 1,846 mother-baby pairs in Henan Province. Air pollutant was gathered from environmental monitoring stations. Peripheral blood was collected from pregnant women before pregnancy and genotyped to minimize the interference of prenatal air pollution on SOD2 gene variations. Multivariable linear regression models were used to analyze the relationship between air pollution and gestational length, with an interaction term (SNP × air pollutant) included to explore the gene-environment interactions. After adjusting for covariates, it was found that exposure to carbon monoxide (CO), sulfur dioxide (SO2), ozone (O3), fine particulate matter (PM2.5), and inhalable particulate matter (PM10) was associated with decreased gestational length, while nitrogen dioxide (NO2) exposure was associated with increased gestational length (p < 0.05). Furthermore, mothers carrying the A allele of SOD2 rs4880 had an increment of 0.17 weeks in gestational length compared to those carrying the G allele (p < 0.05). Interactions on gestational length between SOD2 gene polymorphisms (rs4880, rs5746136, and rs2758352) and exposure to CO, NO2, SO2, PM2.5, and PM10 were observed. These findings suggest that SOD2 gene variations may influence the association between prenatal air pollution and gestational length.

Quantifying the association between pregnancy exposure to biomass-attributable PM2.5 and the risk of preterm birth and stillbirth: A case-control study in Sydney, Australia for 2010-2020

Biomass combustion, including wildfires and residential wood burning, is a significant source of particulate matter (PM2.5) in Australia, with potentially distinct health effects due to its unique chemical composition. This study aimed to quantify the association between exposure to ambient biomass-attributable PM2.5 and the risk of preterm birth and stillbirth across pregnancy windows in Sydney, Australia, from 2010 to 2020. We conducted case-control studies nested within a cohort of 578,391 singleton pregnancies, including 29,954 preterm births and 2,928 stillbirths. Controls were randomly selected using risk-set sampling. Daily all-source PM2.5 estimates at a 5 km resolution were obtained from a previous study. Days exceeding the 95th percentile of all-source PM2.5 at statistical area level 4 without significant dust storm pollution were classified as biomass-affected days. For these days, biomass-attributable PM2.5 was estimated using the remainder component from a seasonal trend decomposition, with the seasonal and trend components representing nonbiomass-attributable PM2.5. Conditional logistic regressions were used to analyze associations between biomass-attributable PM2.5 exposure and outcomes, adjusting for area-level socioeconomic factors, temperature, humidity, and temporal and seasonal trends. The odds ratio for preterm birth per interquartile range increase in biomass-attributable PM2.5 was 1.002 (95% CI = 0.997, 1.007) for the entire pregnancy average exposure, with similar null results across trimesters. For stillbirth, the odds ratio was 1.002 (95% CI = 0.985, 1.019) for the entire pregnancy average exposure, with comparable null findings across trimesters. These results suggest that in Sydney, biomass-attributable PM2.5 exposure during pregnancy may not increase the risk of preterm births or stillbirths.

Associations of prenatal exposure to fine particulate matter and its constituents with small for gestational age risk: A twin study in China

This study aimed to examine the impact of PM2.5 and its constituents on small for gestational age (SGA). We collected records of 8082 twin pairs and their mothers from 21 hospitals across China. Concentrations of PM2.5 and its constituents were from the Tracking Air Pollution dataset. Generalized linear models were utilized in this observational study to explore the relationship between SGA and PM2.5. An increase in PM2.5 by one interquartile range during pregnancy was linked to a 17 % increased SGA risk (OR = 1.17, 95 % CI: 1.05-1.31), with a population attributable fraction of 18.97 % (95 %CI: 5.65 %, 30.93 %). Additionally, higher risk of SGA was associated with exposure to ammonium (OR=1.17, 95 %CI: 1.03-1.34), sulfate (OR=1.10, 95 %CI: 1.01-1.21), nitrate (OR=1.16, 95 %CI: 1.02-1.33), black carbon (OR=1.09, 95 %CI: 1.00-1.19), and organic matter (OR=1.11, 95 %CI: 1.00-1.23) during pregnancy. Similar associations were observed for SGA with PM2.5 and its constituents in late pregnancy (all P < 0.05). Furthermore, individuals conceived via assisted reproduction (OR = 1.22, 95 % CI: 1.03-1.43), with pregnancy complications (OR = 1.23, 95 % CI: 1.07-1.41), and residing in colder areas (OR = 1.20, 95 % CI: 1.02-1.40) shown more susceptible to PM2.5. Our findings provide evidence that maternal PM2.5 exposure increased SGA risk, especially during the late pregnancy.

Effects of a liquefied petroleum gas stove and fuel intervention on head circumference and length at birth: A multi-country household air pollution intervention network (HAPIN) trial

BACKGROUND

Air pollution may impair child growth and cognitive development, with potential markers including birth length and head circumference.

METHODS

The Household Air Pollution Intervention Network (HAPIN) trial was an open label multi-country-randomized controlled trial, with 3200 pregnant women aged 18-34 years (9-19 weeks of gestation) randomly assigned in a 1:1 ratio to receive liquefied petroleum gas (LPG) stove intervention compared to women continuing to cook with solid fuels for 18 months. Particulate matter ≤ 2.5 μm (PM2.5), black carbon (BC) and carbon monoxide (CO) 24-hour personal exposures were measured three times during pregnancy. Head circumference and length were measured < 24 h of birth. We conducted intention-to-treat and exposure-response analyses to determine the intervention effects and associations between household air pollution (HAP) exposure during pregnancy and head circumference, head circumference-for-gestational age Z-score, length, and length-for-gestational age Z-scores at birth.

CLINICALTRIALS

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RESULTS

Between May 2018, and Feb 2020, 3200 pregnant women were randomly assigned to intervention (n = 1593) and control groups (n = 1607) with 3060 births included in the analysis. There was a 71.9 % reduction in PM2.5 in the intervention group with similar reductions for BC and CO. Intention-to-treat analysis showed that the intervention did not affect head circumference (β = -0.01 cm, 95 %CI -0.11, 0.09), head circumference-for-gestational age Z-score (β = -0.01, 95 %CI -0.08, 0.07), or birth length (β = 0.14 cm, 95 %CI -0.01, 0.29) but did increase birth length-for-gestational age Z-score (β = 0.09, 95 %CI 0.01, 0.16). After covariate adjustment, exposure-response analysis revealed that each log-unit increase in BC was associated with a decrease in birth length-for-gestational age Z-score (β = -0.07, 95 %CI -0.13, -0.005). There was no evidence of hypothesized associations with PM2.5 or CO.

CONCLUSION

An LPG intervention reduced HAP exposure during pregnancy but had minor effects on birth length-for-gestational age Z-score. Birth length-for-gestational age was only associated with BC.

CLINICAL TRIAL REGISTRATION

The study has been registered with ClinicalTrials.gov (Identifier NCT02944682).

How Can Outdoor Air Pollutants Adversely Affect the Women's Fertility? Systematic Review

In the current century, air pollution is known as one of the most critical environmental problems and it is important to find the relations of air pollution and human health. Various air pollutants, such as volatile organic compounds (VOCs), can negatively affect women's fertility. An exhaustive electronic search was done from 2013 until July 2023 in PUBMED and The Cochrane Central Register of Controlled Trials. The following keywords were combined using Boolean hints in the databases queried: air pollution AND (fertility OR miscarriage OR embryo quality OR embryo development OR pregnancy OR implantation OR live birth). The randomized controlled trials, case-control and cohort studies analyzing the impact of air pollutants on fertility were included in the review. In this systematic review, a significant relation was found between the increase in air pollution and the reduction of fertility health, live birth rates, embryo quality, fertility, implantation rates, and miscarriage in exposed women. These results suggest low fertility health rates are associated with traffic-related air pollution. This review has concluded four components (particulate matter, nitrogen dioxide, sulfur, and carbon monoxide) of traffic pollution that can impair women's fertility. Air pollution harms women's fertility. These effects affect gamete's quality at the genetic and epigenetic level. These effects also alter fetal development. Studies have also reported an effect on fetal growth with increased miscarriages. Since air pollution is everywhere and has many sources, it seems necessary to increase the awareness of people and government officials, especially in hygiene and health, to limit air pollutants as much as possible.

Interpregnancy interval, air pollution, and the risk of low birth weight: a retrospective study in China

BACKGROUND

Both interpregnancy intervals (IPI) and environmental factors might contribute to low birth weight (LBW). However, the extent to which air pollution influences the effect of IPIs on LBW remains unclear. We aimed to investigate whether IPI and air pollution jointly affect LBW.

METHODS

A retrospective cohort study was designed in this study. The data of birth records was collected from the Jiangsu Maternal Child Information System, covering January 2020 to June 2021 in Nantong city, China. IPI was defined as the duration between the delivery date for last live birth and date of LMP for the subsequent birth. The maternal exposure to ambient air pollutants during pregnancy-including particulate matter (PM) with an aerodynamic diameter of ≤ 2.5 μm (PM2.5), PM10, ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2) and carbon monoxide (CO)-was estimated using a hybrid kriging-LUR-RF model. A novel air pollution score was proposed, assessing combined exposure to five pollutants (excluding CO) by summing their concentrations, weighted by LBW regression coefficients. Multivariate logistic regression models were used to estimate the effects of IPI, air pollution and their interactions on LBW. Relative excess risk due to interaction (RERI), attributable proportion of interaction (AP) and synergy index (S) were utilized to assess the additive interaction.

RESULTS

Among 10, 512 singleton live births, the LBW rate was 3.7%. The IPI-LBW risk curve exhibited an L-shaped pattern. The odds ratios (ORs) for LBW for each interquartile range increase in PM2.5, PM10, O3 and the air pollution score were 1.16 (95% CI: 1.01-1.32), 1.30 (1.06-1.59), 1.22 (1.06-1.41), and 1.32 (1.10-1.60) during the entire pregnancy, respectively. An additive interaction between IPI and PM2.5 was noted during the first trimester. Compared to records with normal IPI and low PM2.5 exposure, those with short IPI and high PM2.5 exposure had the highest risk of LBW (relative risk = 3.53, 95% CI: 1.85-6.49, first trimester).

CONCLUSION

The study demonstrates a synergistic effect of interpregnancy interval and air pollution on LBW, indicating that rational birth spacing and air pollution control can jointly improve LBW outcomes.

Preconception mitochondrial DNA copy number plays a crucial role in linking prenatal air pollution with the risk of preterm birth

The relationship between maternal peripheral blood mitochondrial DNA and adverse pregnancy outcomes, specifically preterm birth (PTB), remains uncertain. To investigate the effects of preconception mitochondrial DNA copy number (mtDNAcn) on the association between prenatal air pollutants exposure and PTB risk, a total of 1871 expectant mothers from six regions in Henan Province were recruited. Information regarding air pollutants was obtained from 151 environmental monitoring sites, and relative mtDNAcn was evaluated using real-time PCR analysis. After adjusting for potential confounding variables, it was determined that the risk of PTB increased with elevated levels of inhalable particulate matter (PM10), fine particulate matter (PM2.5), sulfur dioxide (SO2), carbon monoxide (CO) and ozone (O3) exposure (P < 0.05) but decreased with higher nitrogen dioxide (NO2) exposure (0.05 < P < 0.10) during the entire pregnancy. Additionally, the preconception relative mtDNAcn was lower in the PTB group (0.82 ± 0.23) compared to the term group (0.92 ± 0.29). Furthermore, for each 0.1-unit increase in preconception mtDNAcn, the risk of PTB decreased by 14.8%. Stratified analyses revealed that the risk of PTB rose with increasing O3 concentrations, regardless of the relative mtDNAcn. Moreover, the study found a significant association between PTB risk and prenatal exposure to elevated PM10, PM2.5, SO2, and CO, particularly in mothers with low mtDNAcn (≤0.88) (P < 0.05). Conversely, a decrease in the PTB risk was observed with elevated NO2 exposure in mothers with high mtDNAcn (>0.88). Interaction analysis revealed that exposure to PM10, PM2.5, SO2, NO2, and CO interacted with mtDNAcn, respectively, affecting PTB risk (P-interaction<0.05). These findings indicate a noteworthy association between PTB risk and prenatal air pollutants exposure, which is influenced by the preconception mtDNAcn.

Carbon Monoxide as a Potential Therapeutic Agent: A Molecular Analysis of Its Safety Profiles

Carbon monoxide (CO) is endogenously produced in mammals, with blood concentrations in the high micromolar range in the hemoglobin-bound form. Further, CO has shown therapeutic effects in various animal models. Despite its reputation as a poisonous gas at high concentrations, we show that CO should have a wide enough safety margin for therapeutic applications. The analysis considers a large number of factors including levels of endogenous CO, its safety margin in comparison to commonly encountered biomolecules or drugs, anticipated enhanced safety profiles when delivered via a noninhalation mode, and the large amount of safety data from human clinical trials. It should be emphasized that having a wide enough safety margin for therapeutic use does not mean that it is benign or safe to the general public, even at low doses. We defer the latter to public health experts. Importantly, this Perspective is written for drug discovery professionals and not the general public.

Cooking with liquefied petroleum gas or biomass and fetal growth outcomes: a multi-country randomised controlled trial

BACKGROUND

Household air pollution might lead to fetal growth restriction during pregnancy. We aimed to investigate whether a liquefied petroleum gas (LPG) intervention to reduce personal exposures to household air pollution during pregnancy would alter fetal growth.

METHODS

The Household Air Pollution Intervention Network (HAPIN) trial was an open-label randomised controlled trial conducted in ten resource-limited settings across Guatemala, India, Peru, and Rwanda. Pregnant women aged 18-34 years (9-19 weeks of gestation) were randomly assigned in a 1:1 ratio to receive an LPG stove, continuous fuel delivery, and behavioural messaging or to continue usual cooking with biomass for 18 months. We conducted ultrasound assessments at baseline, 24-28 weeks of gestation (the first pregnancy visit), and 32-36 weeks of gestation (the second pregnancy visit), to measure fetal size; we monitored 24 h personal exposures to household air pollutants during these visits; and we weighed children at birth. We conducted intention-to-treat analyses to estimate differences in fetal size between the intervention and control group, and exposure-response analyses to identify associations between household air pollutants and fetal size. This trial is registered with ClinicalTrials.gov (NCT02944682).

FINDINGS

Between May 7, 2018, and Feb 29, 2020, we randomly assigned 3200 pregnant women (1593 to the intervention group and 1607 to the control group). The mean gestational age was 14·5 (SD 3·0) weeks and mean maternal age was 25·6 (4·5) years. We obtained ultrasound assessments in 3147 (98·3%) women at baseline, 3052 (95·4%) women at the first pregnancy visit, and 2962 (92·6%) at the second pregnancy visit, through to Aug 25, 2020. Intervention adherence was high (the median proportion of days with biomass stove use was 0·0%, IQR 0·0-1·6) and pregnant women in the intervention group had lower mean exposures to particulate matter with a diameter less than 2·5 μm (PM2·5; 35·0 [SD 37·2] μg/m3vs 103·3 [97·9] μg/m3) than did women in the control group. We did not find differences in averaged post-randomisation Z scores for head circumference (0·30 vs 0·39; p=0·04), abdominal circumference (0·38 vs 0·39; p=0·99), femur length (0·44 vs 0·45; p=0·73), and estimated fetal weight or birthweight (-0·13 vs -0·12; p=0·70) between the intervention and control groups. Personal exposures to household air pollutants were not associated with fetal size.

INTERPRETATION

Although an LPG cooking intervention successfully reduced personal exposure to air pollution during pregnancy, it did not affect fetal size. Our findings do not support the use of unvented liquefied petroleum gas stoves as a strategy to increase fetal growth in settings were biomass fuels are used predominantly for cooking.

FUNDING

US National Institutes of Health and Bill & Melinda Gates Foundation.

TRANSLATIONS

For the Kinyarwanda, Spanish and Tamil translations of the abstract see Supplementary Materials section.

Household Air Pollution Interventions to Improve Health in Low- and Middle-Income Countries: An Official American Thoracic Society Research Statement

Background: An estimated 3 billion people, largely in low- and middle-income countries, rely on unclean fuels for cooking, heating, and lighting to meet household energy needs. The resulting exposure to household air pollution (HAP) is a leading cause of pneumonia, chronic lung disease, and other adverse health effects. In the last decade, randomized controlled trials of clean cooking interventions to reduce HAP have been conducted. We aim to provide guidance on how to interpret the findings of these trials and how they should inform policy makers and practitioners.Methods: We assembled a multidisciplinary working group of international researchers, public health practitioners, and policymakers with expertise in household air pollution from within academia, the American Thoracic Society, funders, nongovernmental organizations, and global organizations, including the World Bank and the World Health Organization. We performed a literature search, convened four sessions via web conference, and developed consensus conclusions and recommendations via the Delphi method.Results: The committee reached consensus on 14 conclusions and recommendations. Although some trials using cleaner-burning biomass stoves or cleaner-cooking fuels have reduced HAP exposure, the committee was divided (with 55% saying no and 45% saying yes) on whether the studied interventions improved measured health outcomes.Conclusions: HAP is associated with adverse health effects in observational studies. However, it remains unclear which household energy interventions reduce exposure, improve health, can be scaled, and are sustainable. Researchers should engage with policy makers and practitioners working to scale cleaner energy solutions to understand and address their information needs.

Gestational exposure to PM2.5 disrupts fetal development by suppressing placental trophoblast syncytialization via progranulin/mTOR signaling

Recent epidemiological and animal studies have indicated that ambient fine particulate matter (PM2.5) exposure during pregnancy is closely associated with intrauterine growth restriction (IUGR). However, the underlying mechanisms remain to be revealed. In this study, we found that gestational exposure to PM2.5 significantly decreased fetal weight and crown-rump length in mice, accompanied by insufficient placental trophoblast syncytialization and increased expression of progranulin (PGRN) in mice placenta. Administering PGRN neutralizing antibody to pregnant mice alleviated growth restriction and insufficient placental trophoblast syncytialization caused by PM2.5, accompanied with suppressed activation of the mTOR signaling pathway. Furthermore, in vitro experiments using human placental BeWo cells showed that 10 μg·mL-1 PM2.5 activated PGRN/mTOR signaling and suppressed forskolin-induced cell fusion, which was blocked by knockdown of PGRN. Taken together, our results demonstrated that PM2.5 exposure during pregnancy inhibited placental trophoblast syncytialization by activating PGRN/mTOR signaling, leading to abnormal placental development and IUGR. This study reveals a novel mechanism underlying the developmental toxicity of PM2.5 exposure during pregnancy.

Effects of a liquefied petroleum gas stove intervention on stillbirth, congenital anomalies and neonatal mortality: A multi-country household air pollution intervention network trial

Household air pollution (HAP) from cooking with solid fuels used during pregnancy has been associated with adverse pregnancy outcomes. The Household Air Pollution Intervention Network (HAPIN) trial was a randomized controlled trial that assessed the impact of a liquefied petroleum gas (LPG) stove and fuel intervention on health in Guatemala, India, Peru, and Rwanda. Here we investigated the effects of the LPG stove and fuel intervention on stillbirth, congenital anomalies and neonatal mortality and characterized exposure-response relationships between personal exposures to fine particulate matter (PM2.5), black carbon (BC) and carbon monoxide (CO) and these outcomes. Pregnant women (18 to <35 years of age; gestation confirmed by ultrasound at 9 to <20 weeks) were randomly assigned to intervention or control arms. We monitored these fetal and neonatal outcomes and personal exposure to PM2.5, BC and CO three times during pregnancy, we conducted intention-to-treat (ITT) and exposure-response (E-R) analyses to determine if the HAPIN intervention and corresponding HAP exposure was associated with the risk of fetal/neonatal outcomes. A total of 3200 women (mean age 25.4 ± 4.4 years, mean gestational age at randomization 15.4 ± 3.1 weeks) were included in this analysis. Relative risks for stillbirth, congenital anomaly and neonatal mortality were 0.99 (0.60, 1.66), 0.92 (95 % CI 0.52, 1.61), and 0.99 (0.54, 1.85), respectively, among women in the intervention arm compared to controls in an ITT analysis. Higher mean personal exposures to PM2.5, CO and BC during pregnancy were associated with a higher, but statistically non-significant, incidence of adverse outcomes. The LPG stove and fuel intervention did not reduce the risk of these outcomes nor did we find evidence supporting an association between personal exposures to HAP and stillbirth, congenital anomalies and neonatal mortality.

Impact of indoor environment on children's pulmonary health

INTRODUCTION

A child's living environment has a significant impact on their respiratory health, with exposure to poor indoor air quality (IAQ) contributing to potentially lifelong respiratory morbidity. These effects occur throughout childhood, from the antenatal period through to adolescence. Children are particularly susceptible to the effects of environmental insults, and children living in socioeconomic deprivation globally are more likely to breathe air both indoors and outdoors, which poses an acute and long-term risk to their health. Adult respiratory health is, at least in part, determined by exposures and respiratory system development in childhood, starting in utero.

AREAS COVERED

This narrative review will discuss, from a global perspective, what contributes to poor IAQ in the child's home and school environment and the impact that indoor air pollution exposure has on respiratory health throughout the different stages of childhood.

EXPERT OPINION

All children have the right to a living and educational environment without the threat of pollution affecting their health. Action is needed at multiple levels to address this pressing issue to improve lifelong respiratory health. Such action should incorporate a child's rights-based approach, empowering children, and their families, to have access to clean air to breathe in their living environment.

Fidelity and adherence to a liquefied petroleum gas stove and fuel intervention: The multi-country Household Air Pollution Intervention Network (HAPIN) trial

BACKGROUND

Reducing household air pollution (HAP) to levels associated with health benefits requires nearly exclusive use of clean cooking fuels and abandonment of traditional biomass fuels.

METHODS

The Household Air Pollution Intervention Network (HAPIN) trial randomized 3,195 pregnant women in Guatemala, India, Peru, and Rwanda to receive a liquefied petroleum gas (LPG) stove intervention (n = 1,590), with controls expected to continue cooking with biomass fuels (n = 1,605). We assessed fidelity to intervention implementation and participant adherence to the intervention starting in pregnancy through the infant's first birthday using fuel delivery and repair records, surveys, observations, and temperature-logging stove use monitors (SUMs).

RESULTS

Fidelity and adherence to the HAPIN intervention were high. Median time required to refill LPG cylinders was 1 day (interquartile range 0-2). Although 26% (n = 410) of intervention participants reported running out of LPG at some point, the number of times was low (median: 1 day [Q1, Q3: 1, 2]) and mostly limited to the first four months of the COVID-19 pandemic. Most repairs were completed on the same day as problems were reported. Traditional stove use was observed in only 3% of observation visits, and 89% of these observations were followed up with behavioral reinforcement. According to SUMs data, intervention households used their traditional stove a median of 0.4% of all monitored days, and 81% used the traditional stove < 1 day per month. Traditional stove use was slightly higher post-COVID-19 (detected on a median [Q1, Q3] of 0.0% [0.0%, 3.4%] of days) than pre-COVID-19 (0.0% [0.0%, 1.6%] of days). There was no significant difference in intervention adherence pre- and post-birth.

CONCLUSION

Free stoves and an unlimited supply of LPG fuel delivered to participating homes combined with timely repairs, behavioral messaging, and comprehensive stove use monitoring contributed to high intervention fidelity and near-exclusive LPG use within the HAPIN trial.