Designs of two randomized, community-based trials to assess the impact of alternative cookstove installation on respiratory illness among young children and reproductive outcomes in rural Nepal

Association of Household Utility of Cleaner Fuel With Lower Hypertension Prevalence and Blood Pressure in Chinese Adults

Objectives: To investigate whether lower hypertension prevalence or blood pressure was associated with cleaner household fuel usage for cooking and heating among Chinese adults. Methods: We enrolled 44,862 Chinese adults at the baseline of the prospective urban and rural epidemiology (PURE) study in China during 2005-2009, as a subset of the PURE-global China site. Multilevel logistic regression and generalized linear mixed models were conducted to estimate the adjusted odds ratio (AOR) and regression coefficient for hypertension and blood pressure respectively, while subgroup analysis by ambient PM2.5 concentration and location was also examined. Results: Compared with the least clean household solid fuel group, gas (AOR = 0.91, 95% CI: 0.83, 0.99) or electricity (AOR = 0.72, 95% CI: 0.60, 0.87) was associated with significantly lower levels of hypertension prevalence and blood pressure, and a similar pattern of the association was consistently observed among participants with high ambient PM2.5 exposure and those living in urban areas. Conclusion: Household utility of cleaner fuel type was associated with lower hypertension prevalence and blood pressure in Chinese adults. Our study urges the utilization of cleaner household energy to mitigate the burden of hypertension.

Assessing exposure to household air pollution in children under five: A scoping review

Understanding the differences in the approaches used to assess household air pollution (HAP) is crucial for evaluating HAP-related health effects and interpreting the effectiveness of stove-fuel interventions. Our review aims to understand how exposure to HAP from solid fuels was measured in epidemiological studies in children under five. We conducted a search of PubMed, EMBASE, Cochrane Central Register of Controlled Trials, Global Health Library, Web of Science, and CINAHL to identify English-language research articles published between January 1, 2000 and April 30, 2022. Two researchers applied the inclusion and exclusion criteria independently. Study region, type of measurement, study design, health outcomes, and other key characteristics were extracted from each article and analyzed descriptively. Our search strategy yielded 2229 records, of which 185 articles were included. A large proportion was published between 2018 and 2022 (42.1%), applied a cross-sectional study design (47.6%), and took place in low- or lower middle-income countries. Most studies (130/185, 70.3%) assessed HAP using questionnaires/interviews, most frequently posing questions on cooking fuel type, followed by household ventilation and cooking location. Cooking frequency/duration and children's location while cooking was less commonly considered. About 28.6% (53/185) used monitors, but the application of personal portable samplers was limited (particulate matter [PM]: 12/40, 30.0%; carbon monoxide [CO]: 13/34, 38.2%). Few studies used biomarkers or modeling approaches to estimate HAP exposure among children under five. More studies that report household and behavioral characteristics and children's location while cooking, apply personal exposure samplers, and perform biomarker analysis are needed to advance our understandings of HAP exposure among infants and young children, who are particularly susceptible to HAP-related health effects.

Estimating long-term average household air pollution concentrations from repeated short-term measurements in the presence of seasonal trends and crossover

Estimating long-term exposure to household air pollution is essential for quantifying health effects of chronic exposure and the benefits of intervention strategies. However, typically only a small number of short-term measurements are made. We compare different statistical models for combining these short-term measurements into predictions of a long-term average, with emphasis on the impact of temporal trends in concentrations and crossover in study design. We demonstrate that a linear mixed model that includes time adjustment provides the best predictions of long-term average, which have lower error than using household averages or mixed models without time, for a variety of different study designs and underlying temporal trends. In a case study of a cookstove intervention study in Honduras, we further demonstrate how, in the presence of strong seasonal variation, long-term average predictions from the mixed model approach based on only two or three measurements can have less error than predictions based on an average of up to six measurements. These results have important implications for the efficiency of designs and analyses in studies assessing the chronic health impacts of long-term exposure to household air pollution.

Fidelity and Adherence to a Liquefied Petroleum Gas Stove and Fuel Intervention during Gestation: The Multi-Country Household Air Pollution Intervention Network (HAPIN) Randomized Controlled Trial

BACKGROUND

Clean cookstove interventions can theoretically reduce exposure to household air pollution and benefit health, but this requires near-exclusive use of these types of stoves with the simultaneous disuse of traditional stoves. Previous cookstove trials have reported low adoption of new stoves and/or extensive continued traditional stove use.

METHODS

The Household Air Pollution Intervention Network (HAPIN) trial randomized 3195 pregnant women in Guatemala, India, Peru, and Rwanda to either a liquefied petroleum gas (LPG) stove and fuel intervention (n = 1590) or to a control (n = 1605). The intervention consisted of an LPG stove and two initial cylinders of LPG, free fuel refills delivered to the home, and regular behavioral messaging. We assessed intervention fidelity (delivery of the intervention as intended) and adherence (intervention use) through to the end of gestation, as relevant to the first primary health outcome of the trial: infant birth weight. Fidelity and adherence were evaluated using stove and fuel delivery records, questionnaires, visual observations, and temperature-logging stove use monitors (SUMs).

RESULTS

1585 women received the intervention at a median (interquartile range) of 8.0 (5.0-15.0) days post-randomization and had a gestational age of 17.9 (15.4-20.6) weeks. Over 96% reported cooking exclusively with LPG at two follow-up visits during pregnancy. Less than 4% reported ever running out of LPG. Complete abandonment of traditional stove cooking was observed in over 67% of the intervention households. Of the intervention households, 31.4% removed their traditional stoves upon receipt of the intervention; among those who retained traditional stoves, the majority did not use them: traditional stove use was detected via SUMs on a median (interquartile range) of 0.0% (0.0%, 1.6%) of follow-up days (median follow-up = 134 days).

CONCLUSIONS

The fidelity of the HAPIN intervention, as measured by stove installation, timely ongoing fuel deliveries, and behavioral reinforcement as needed, was high. Exclusive use of the intervention during pregnancy was also high.

Home environmental interventions for prevention of respiratory tract infections: a systematic review and meta-analysis

OBJECTIVES

Poor housing conditions have been associated with increased risks of respiratory infections. This review aims to determine whether modifying the physical environment of the home has benefits in reducing respiratory infections.

CONTENT

We performed a systematic review and meta-analysis of the effectiveness of home environmental interventions for preventing respiratory tract infections. Ten electronic databases were searched to identify randomized controlled trials published from inception to July 31, 2020. Random-effects meta-analyses were used to assess the study outcomes. Our search identified 14 eligible studies across 12 countries, which comprised 87,428 households in total. The type of interventions on home environment included kitchen appliance and design, water supply and sanitation, house insulation, and home heating. Meta-analysis indicated a potential benefit of home environmental interventions in preventing overall respiratory tract infections (Absolute RR=0.89, 95% CI=0.78-1.01, p=0.07; Pooled adjusted RR=0.72, 95% CI=0.63-0.84, p<0.0001). Subgroup analyses depicted that home environmental interventions had no significant impact on lower respiratory tract infections, pneumonia, and severe pneumonia. A protective effect against respiratory infections was observed in high income country setting (RR=0.82, 95% CI=0.78-0.87, p<0.00001).

SUMMARY AND OUTLOOK

Home environmental interventions have the potential to reduce morbidity of respiratory tract infections. The lack of significant impact from stand-alone housing interventions suggests that multicomponent interventions should be implemented in tandem with high-quality health systems.

The effect of clean cooking interventions on mother and child personal exposure to air pollution: results from the Ghana Randomized Air Pollution and Health Study (GRAPHS)

BACKGROUND

Clean cooking interventions to reduce air pollution exposure from burning biomass for daily cooking and heating needs have the potential to reduce a large burden of disease globally.

OBJECTIVE

The objective of this study is to evaluate the air pollution exposure impacts of a fan-assisted efficient biomass-burning cookstove and a liquefied petroleum gas (LPG) stove intervention in rural Ghana.

METHODS

We randomized 1414 households in rural Ghana with pregnant mothers into a control arm (N = 526) or one of two clean cooking intervention arms: a fan-assisted efficient biomass-burning cookstove (N = 527) or an LPG stove and cylinder refills as needed (N = 361). We monitored personal maternal carbon monoxide (CO) at baseline and six times after intervention and fine particulate matter (PM_2.5) exposure twice after intervention. Children received three CO exposure monitoring sessions.

RESULTS

We obtained 5655 48-h maternal CO exposure estimates and 1903 for children, as well as 1379 maternal PM_2.5 exposure estimates. Median baseline CO exposures in the control, improved biomass, and LPG arms were 1.17, 1.17, and 1.30 ppm, respectively. Based on a differences-in-differences approach, the LPG arm showed a 47% reduction (95% confidence interval: 34-57%) in mean 48-h CO exposure compared to the control arm. Mean maternal PM_2.5 exposure in the LPG arm was 32% lower than the control arm during the post-intervention period (52 ± 29 vs. 77 ± 44 μg/m³). The biomass stove did not meaningfully reduce CO or PM_2.5 exposure.

CONCLUSIONS

We show that LPG interventions lowered air pollution exposure significantly compared to three-stone fires. However, post-intervention exposures still exceeded health-relevant targets.

SIGNIFICANCE

In a large controlled trial of cleaner cooking interventions, an LPG stove and fuel intervention reduced air pollution exposure in a vulnerable population in a low-resource setting.

The effect of clean cooking interventions on mother and child personal exposure to air pollution: results from the Ghana Randomized Air Pollution and Health Study (GRAPHS)

BACKGROUND

Clean cooking interventions to reduce air pollution exposure from burning biomass for daily cooking and heating needs have the potential to reduce a large burden of disease globally.

OBJECTIVE

The objective of this study is to evaluate the air pollution exposure impacts of a fan-assisted efficient biomass-burning cookstove and a liquefied petroleum gas (LPG) stove intervention in rural Ghana.

METHODS

We randomized 1414 households in rural Ghana with pregnant mothers into a control arm (N = 526) or one of two clean cooking intervention arms: a fan-assisted efficient biomass-burning cookstove (N = 527) or an LPG stove and cylinder refills as needed (N = 361). We monitored personal maternal carbon monoxide (CO) at baseline and six times after intervention and fine particulate matter (PM2.5) exposure twice after intervention. Children received three CO exposure monitoring sessions.

RESULTS

We obtained 5655 48-h maternal CO exposure estimates and 1903 for children, as well as 1379 maternal PM2.5 exposure estimates. Median baseline CO exposures in the control, improved biomass, and LPG arms were 1.17, 1.17, and 1.30 ppm, respectively. Based on a differences-in-differences approach, the LPG arm showed a 47% reduction (95% confidence interval: 34-57%) in mean 48-h CO exposure compared to the control arm. Mean maternal PM2.5 exposure in the LPG arm was 32% lower than the control arm during the post-intervention period (52 ± 29 vs. 77 ± 44 μg/m3). The biomass stove did not meaningfully reduce CO or PM2.5 exposure.

CONCLUSIONS

We show that LPG interventions lowered air pollution exposure significantly compared to three-stone fires. However, post-intervention exposures still exceeded health-relevant targets.

SIGNIFICANCE

In a large controlled trial of cleaner cooking interventions, an LPG stove and fuel intervention reduced air pollution exposure in a vulnerable population in a low-resource setting.

Impact of the wood-burning Justa cookstove on fine particulate matter exposure: A stepped-wedge randomized trial in rural Honduras

TRIAL DESIGN

We evaluated the impact of a biomass stove intervention on fine particulate matter (PM2.5) concentrations using an individual-level, stepped-wedge randomized trial.

METHODS

We enrolled 230 women in rural Honduran households using traditional biomass stoves and randomly allocated them to one of two study arms. The Justa stove, the study intervention, was locally-sourced, wood-burning, and included an engineered combustion chamber and chimney. At each of 6 visits over 3 years, we measured 24-hour gravimetric personal and kitchen PM2.5 concentrations. Half of the households received the intervention after Visit 2 and half after Visit 4. We conducted intent-to-treat analyses to evaluate the intervention effect using linear mixed models with log-transformed kitchen or personal PM2.5 (separately) as the dependent variable, adjusting for time. We also compared PM2.5 concentrations to World Health Organization (WHO) guidelines.

RESULTS

Arms 1 and 2 each had 115 participants with 664 and 632 completed visits, respectively. Median 24-hour average personal PM2.5 exposures were 81 μg/m3 (25th-75th percentile: 50-141 μg/m3) for the traditional stove condition (n=622) and 43 μg/m3 (25th-75th percentile: 27-73 μg/m3) for the Justa stove condition (n=585). Median 24-hour average kitchen concentrations were 178 μg/m3 (25th-75th percentile: 69-440 μg/m3; n=629) and 53 μg/m3 (25th-75th percentile: 29-103 μg/m3; n=578) for the traditional and Justa stove conditions, respectively. The Justa intervention resulted in a 32% reduction in geometric mean personal PM2.5 (95% confidence interval [CI]: 20-43%) and a 56% reduction (95% CI: 46-65%) in geometric mean kitchen PM2.5. During rainy and dry seasons, 53% and 41% of participants with the Justa intervention had 24-hour average personal PM2.5 exposures below the WHO interim target-3 guideline (37.5 μg/m3), respectively.

CONCLUSION

The Justa stove intervention substantially lowered personal and kitchen PM2.5 and may be a provisional solution that is feasible for Latin American communities where cleaner fuels may not be available, affordable, or acceptable for some time. Clinicaltrials.gov: NCT02658383.

A hierarchical model for estimating the exposure-response curve by combining multiple studies of acute lower respiratory infections in children and household fine particulate matter air pollution

Adverse health effects of household air pollution, including acute lower respiratory infections (ALRIs), pose a major health burden around the world, particularly in settings where indoor combustion stoves are used for cooking. Individual studies have limited exposure ranges and sample sizes, while pooling studies together can improve statistical power.

Methods

We present hierarchical models for estimating long-term exposure concentrations and estimating a common exposure-response curve. The exposure concentration model combines temporally sparse, clustered longitudinal observations to estimate household-specific long-term average concentrations. The exposure-response model provides a flexible, semiparametric estimate of the exposure-response relationship while accommodating heterogeneous clustered data from multiple studies. We apply these models to three studies of fine particulate matter (PM_2.5) and ALRIs in children in Nepal: a case-control study in Bhaktapur, a stepped-wedge trial in Sarlahi, and a parallel trial in Sarlahi. For each study, we estimate household-level long-term PM_2.5 concentrations. We apply the exposure-response model separately to each study and jointly to the pooled data.

Results

The estimated long-term PM_2.5 concentrations were lower for households using electric and gas fuel sources compared with households using biomass fuel. The exposure-response curve shows an estimated ALRI odds ratio of 3.39 (95% credible interval = 1.89, 6.10) comparing PM_2.5 concentrations of 50 and 150 μg/m³ and a flattening of the curve for higher concentrations.

Conclusions

These flexible models can accommodate additional studies and be applied to other exposures and outcomes. The studies from Nepal provides evidence of a nonlinear exposure-response curve that flattens at higher concentrations.

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

BACKGROUND

Few randomized trials have assessed the impact of reducing household air pollution from biomass stoves on adverse birth outcomes in low-income countries.

METHODS

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 (PM_2.5) 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.

RESULTS

In trial 1, the mean 20-hour kitchen PM_2.5 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 PM_2.5 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.

CONCLUSIONS

Improved biomass or LPG stoves did not reduce adverse birth outcomes. PM_2.5 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.

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

Improved biomass stoves may not reduce indoor air pollution as much as is needed to have an impact on adverse birth outcomes.

Background:

Few randomized trials have assessed the impact of reducing household air pollution from biomass stoves on adverse birth outcomes in low-income countries.

Methods:

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 (PM_2.5) 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.

Results:

In trial 1, the mean 20-hour kitchen PM_2.5 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 PM_2.5 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.

Conclusions:

Improved biomass or LPG stoves did not reduce adverse birth outcomes. PM_2.5 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.

Challenges in the diagnosis of paediatric pneumonia in intervention field trials: recommendations from a pneumonia field trial working group

Pneumonia is a leading killer of children younger than 5 years despite high vaccination coverage, improved nutrition, and widespread implementation of the Integrated Management of Childhood Illnesses algorithm. Assessing the effect of interventions on childhood pneumonia is challenging because the choice of case definition and surveillance approach can affect the identification of pneumonia substantially. In anticipation of an intervention trial aimed to reduce childhood pneumonia by lowering household air pollution, we created a working group to provide recommendations regarding study design and implementation. We suggest to, first, select a standard case definition that combines acute (≤14 days) respiratory symptoms and signs and general danger signs with ancillary tests (such as chest imaging and pulse oximetry) to improve pneumonia identification; second, to prioritise active hospital-based pneumonia surveillance over passive case finding or home-based surveillance to reduce the risk of non-differential misclassification of pneumonia and, as a result, a reduced effect size in a randomised trial; and, lastly, to consider longitudinal follow-up of children younger than 1 year, as this age group has the highest incidence of severe pneumonia.

Modeling the potential health benefits of lower household air pollution after a hypothetical liquified petroleum gas (LPG) cookstove intervention

INTRODUCTION

Improved biomass and advanced fuel cookstoves can lower household air pollution (HAP), but levels of fine particulate matter (PM_2.5) often remain above the World Health Organization (WHO) recommended interim target of 35μg/m³.

METHODS

Based on existing literature, we first estimate a range of likely levels of personal PM_2.5 before and after a liquefied petroleum gas (LPG) intervention. Using simulations reflecting uncertainty in both the exposure estimates and exposure-response coefficients, we estimate corresponding expected health benefits for systolic blood pressure (SBP) in adults, birthweight, and pneumonia incidence among children <2years old. We also estimate potential avoided premature mortality among those exposed.

RESULTS

Our best estimate is that an LPG stove intervention would decrease personal PM_2.5 exposure from approximately 270μg/m³ to approximately 70μg/m³, due to likely continued use of traditional open-fire stoves. We estimate that this decrease would lead to a 5.5mmHg lower SBP among women over age 50, a 338g higher birthweight, and a 37% lower incidence of severe childhood pneumonia. We estimate that decreased SBP, if sustained, would result in a 5%-10% decrease in mortality for women over age 50. We estimate that higher birthweight would reduce infant mortality by 4 to 11 deaths per 1000 births; for comparison, the current global infant mortality rate is 32/1000 live births. Reduced exposure is estimated to prevent approximately 29 cases of severe pneumonia per year per 1000 children under 2, avoiding approximately 2-3 deaths/1000 per year. However, there are large uncertainties around all these estimates due to uncertainty in both exposure estimates and in exposure-response coefficients; all health effect estimates include the null value of no benefit.

CONCLUSIONS

An LPG stove intervention, while not likely to lower exposure to the WHO interim target level, is still likely to offer important health benefits.

Pregnancy outcomes and ethanol cook stove intervention: A randomized-controlled trial in Ibadan, Nigeria

BACKGROUND

Household air pollution (HAP) exposure has been linked to adverse pregnancy outcomes.

OBJECTIVES

A randomized controlled trial was undertaken in Ibadan, Nigeria to determine the impact of cooking with ethanol on pregnancy outcomes.

METHODS

Three-hundred-twenty-four pregnant women were randomized to either the control (continued cooking using kerosene/firewood stove, n=162) or intervention group (received ethanol stove, n=162). Primary outcome variables were birthweight, preterm delivery, intrauterine growth restriction (IUGR), and occurrence of miscarriage/stillbirth.

RESULTS

Mean birthweights for ethanol and controls were 3076 and 2988g, respectively; the difference, 88g, (95% confidence interval: -18g to 194g), was not statistically significant (p=0.10). After adjusting for covariates, the difference reached significance (p=0.020). Rates of preterm delivery were 6.7% (ethanol) and 11.0% (control), (p=0.22). Number of miscarriages was 1(ethanol) vs. 4 (control) and stillbirths was 3 (ethanol) vs. 7 (control) (both non-significant). Average gestational age at delivery was significantly (p=0.015) higher in ethanol-users (39.2weeks) compared to controls (38.2weeks). Perinatal mortality (stillbirths and neonatal deaths) was twice as high in controls compared to ethanol-users (7.9% vs. 3.9%; p=0.045, after adjustment for covariates). We did not detect significant differences in exposure levels between the two treatment arms, perhaps due to large seasonal effects and high ambient air pollution levels.

CONCLUSIONS

Transition from traditional biomass/kerosene fuel to ethanol reduced adverse pregnancy outcomes. However, the difference in birthweight was statistically significant only after covariate adjustment and the other significant differences were in tertiary endpoints. Our results are suggestive of a beneficial effect of ethanol use. Larger trials are required to validate these findings.

ERS/ATS workshop report on respiratory health effects of household air pollution

Exposure to household air pollution (HAP) from solid fuel combustion affects almost half of the world population. Adverse respiratory outcomes such as respiratory infections, impaired lung growth and chronic obstructive pulmonary disease have been linked to HAP exposure. Solid fuel smoke is a heterogeneous mixture of various gases and particulates. Cell culture and animal studies with controlled exposure conditions and genetic homogeneity provide important insights into HAP mechanisms. Impaired bacterial phagocytosis in exposed human alveolar macrophages possibly mediates several HAP-related health effects. Lung pathological findings in HAP-exposed individuals demonstrate greater small airways fibrosis and less emphysema compared with cigarette smokers. Field studies using questionnaires, air pollution monitoring and/or biomarkers are needed to better establish human risks. Some, but not all, studies suggest that improving cookstove efficiency or venting emissions may be associated with reduced respiratory symptoms, lung function decline in women and severe pneumonia in children. Current studies focus on fuel switching, stove technology replacements or upgrades and air filter devices. Several governments have initiated major programmes to accelerate the upgrade from solid fuels to clean fuels, particularly liquid petroleum gas, which provides research opportunities for the respiratory health community.

Characterizing Particulate Matter Exfiltration Estimates for Alternative Cookstoves in a Village-Like Household in Rural Nepal

Alternative stoves are an intervention option to reduce household air pollution. The amount of air pollution exiting homes when alternative stoves are utilized is not known. In this paper, particulate matter exfiltration estimates are presented for four types of alternative stoves within a village-like home, which was built to reflect the use of local materials and common size, in rural Nepal. Four alternative stoves with chimneys were examined, which included an alternative mud brick stove, original Envirofit G3355 model, manufacture altered Envirofit G3355, and locally altered Envirofit G3355. Multiple linear regression was utilized to determine estimates of PM2.5 exfiltration. Overall exfiltration fraction average (converted to a percent) for the four stoves were: alternative mud brick stove with chimney 56%, original Envirofit G3355 model with chimney 87%, manufacture altered Envirofit G3355 model with chimney 69%, and locally altered Envirofit G3355 model with chimney 69%. Alternative cookstoves resulted in higher overall average exfiltration due to direct and indirect ventilation relative to traditional, mud-based stoves. This contrast emphasizes the need for an improved understanding of the climate and health implications that are believed to come from implementing alternative stoves on a large scale and the resultant shift of exposure burden from indoors to outdoors.

Assessing Exposure to Household Air Pollution: A Systematic Review and Pooled Analysis of Carbon Monoxide as a Surrogate Measure of Particulate Matter

BACKGROUND

Household air pollution from solid fuel burning is a leading contributor to disease burden globally. Fine particulate matter (PM_2.5) is thought to be responsible for many of these health impacts. A co-pollutant, carbon monoxide (CO) has been widely used as a surrogate measure of PM_2.5 in studies of household air pollution.

OBJECTIVE

The goal was to evaluate the validity of exposure to CO as a surrogate of exposure to PM_2.5 in studies of household air pollution and the consistency of the PM_2.5-CO relationship across different study settings and conditions.

METHODS

We conducted a systematic review of studies with exposure and/or cooking area PM_2.5 and CO measurements and assembled 2,048 PM_2.5 and CO measurements from a subset of studies (18 cooking area studies and 9 personal exposure studies) retained in the systematic review. We conducted pooled multivariate analyses of PM_2.5-CO associations, evaluating fuels, urbanicity, season, study, and CO methods as covariates and effect modifiers.

RESULTS

We retained 61 of 70 studies for review, representing 27 countries. Reported PM_2.5-CO correlations (r) were lower for personal exposure (range: 0.22-0.97; median=0.57) than for cooking areas (range: 0.10-0.96; median=0.71). In the pooled analyses of personal exposure and cooking area concentrations, the variation in ln(CO) explained 13% and 48% of the variation in ln(PM_2.5), respectively.

CONCLUSIONS

Our results suggest that exposure to CO is not a consistently valid surrogate measure of exposure to PM_2.5. Studies measuring CO exposure as a surrogate measure of PM exposure should conduct local validation studies for different stove/fuel types and seasons. https://doi.org/10.1289/EHP767.

Perceptions of Improved Biomass and Liquefied Petroleum Gas Stoves in Puno, Peru: Implications for Promoting Sustained and Exclusive Adoption of Clean Cooking Technologies

Many households in low- and middle-income countries cook with inefficient biomass-burning stoves, which cause high levels of household air pollution and threaten long-term health. Although clean stoves and fuels are available, uptake and consistent use has been low. Using observations and in-depth interviews, we assessed the attitudes, preferences, and beliefs about traditional versus liquefied petroleum gas (LPG) stoves in rural Puno, Peru. A total of 31 in-depth interviews were conducted with primary cooks and their families, health workers, community leaders, and improved stove contractors. Six in-home observations of meal preparation were also conducted. Six major barriers to consistent use of clean stoves were identified: (1) perceived differences in food taste and nutrition by stove type; (2) cooking niches filled by different stoves; (3) social norms related to cooking practices; (4) safety concerns; (5) comparative costs of using different stoves; and (6) lack of awareness and concern about long-term health risks. These findings suggest that to successfully reduce household air pollution, clean cooking programs and policies must consider the many factors influencing adoption beyond health, such as cost, taste, fears, and cultural traditions. These factors could be incorporated into community-based and national efforts to scale-up sustained and exclusive adoption of clean cooking.

Study design of a cluster-randomized controlled trial to evaluate a large-scale distribution of cook stoves and water filters in Western Province, Rwanda

Background

In Rwanda, pneumonia and diarrhea are the first and second leading causes of death, respectively, among children under five. Household air pollution (HAP) resultant from cooking indoors with biomass fuels on traditional stoves is a significant risk factor for pneumonia, while consumption of contaminated drinking water is a primary cause of diarrheal disease. To date, there have been no large-scale effectiveness trials of programmatic efforts to provide either improved cookstoves or household water filters at scale in a low-income country. In this paper we describe the design of a cluster-randomized trial to evaluate the impact of a national-level program to distribute and promote the use of improved cookstoves and advanced water filters to the poorest quarter of households in Rwanda.

Methods/Design

We randomly allocated 72 sectors (administratively defined units) in Western Province to the intervention, with the remaining 24 sectors in the province serving as controls. In the intervention sectors, roughly 100,000 households received improved cookstoves and household water filters through a government-sponsored program targeting the poorest quarter of households nationally. The primary outcome measures are the incidence of acute respiratory infection (ARI) and diarrhea among children under five years of age. Over a one-year surveillance period, all cases of acute respiratory infection (ARI) and diarrhea identified by health workers in the study area will be extracted from records maintained at health facilities and by community health workers (CHW). In addition, we are conducting intensive, longitudinal data collection among a random sample of households in the study area for in-depth assessment of coverage, use, environmental exposures, and additional health measures.

Discussion

Although previous research has examined the impact of providing household water treatment and improved cookstoves on child health, there have been no studies of national-level programs to deliver these interventions at scale in a developing country. The results of this study, the first RCT of a large-scale programmatic cookstove or household water filter intervention, will inform global efforts to reduce childhood morbidity and mortality from diarrheal disease and pneumonia.

Trial registration

This trial is registered at Clinicaltrials.gov (NCT02239250).

Estimating Indoor PM2.5 and CO Concentrations in Households in Southern Nepal: The Nepal Cookstove Intervention Trials

High concentrations of household air pollution (HAP) due to biomass fuel usage with unvented, insufficient combustion devices are thought to be an important health risk factor in South Asia population. To better characterize the indoor concentrations of particulate matter (PM_2.5) and carbon monoxide (CO), and to understand their impact on health in rural southern Nepal, this study analyzed daily monitoring data collected with DataRAM pDR-1000 and LASCAR CO data logger in 2980 households using traditional biomass cookstove indoor through the Nepal Cookstove Intervention Trial–Phase I between March 2010 and October 2011. Daily average PM_2.5 and CO concentrations collected in area near stove were 1,376 (95% CI, 1,331–1,423) μg/m³ and 10.9 (10.5–11.3) parts per million (ppm) among households with traditional cookstoves. The 95^th percentile, hours above 100μg/m³ for PM_2.5 or 6ppm for CO, and hours above 1000μg/m³ for PM_2.5 or 9ppm for CO were also reported. An algorithm was developed to differentiate stove-influenced (SI) periods from non-stove-influenced (non-SI) periods in monitoring data. Average stove-influenced concentrations were 3,469 (3,350–3,588) μg/m³ for PM_2.5 and 21.8 (21.1–22.6) ppm for CO. Dry season significantly increased PM_2.5 concentration in all metrics; wood was the cleanest fuel for PM_2.5 and CO, while adding dung into the fuel increased concentrations of both pollutants. For studies in rural southern Nepal, CO concentration is not a viable surrogate for PM_2.5 concentrations based on the low correlation between these measures. In sum, this study filled a gap in knowledge on HAP in rural Nepal using traditional cookstoves and revealed very high concentrations in these households.

Stepped wedge cluster randomised trials: a review of the statistical methodology used and available

BACKGROUND

Previous reviews have focussed on the rationale for employing the stepped wedge design (SWD), the areas of research to which the design has been applied and the general characteristics of the design. However these did not focus on the statistical methods nor addressed the appropriateness of sample size methods used.This was a review of the literature of the statistical methodology used in stepped wedge cluster randomised trials.

METHODS

Literature Review. The Medline, Embase, PsycINFO, CINAHL and Cochrane databases were searched for methodological guides and RCTs which employed the stepped wedge design.

RESULTS

This review identified 102 trials which employed the stepped wedge design compared to 37 from the most recent review by Beard et al. 2015. Forty six trials were cohort designs and 45 % (n = 46) had fewer than 10 clusters. Of the 42 articles discussing the design methodology 10 covered analysis and seven covered sample size. For cohort stepped wedge designs there was only one paper considering analysis and one considering sample size methods. Most trials employed either a GEE or mixed model approach to analysis (n = 77) but only 22 trials (22 %) estimated sample size in a way which accounted for the stepped wedge design that was subsequently used.

CONCLUSIONS

Many studies which employ the stepped wedge design have few clusters but use methods of analysis which may require more clusters for unbiased and efficient intervention effect estimates. There is the need for research on the minimum number of clusters required for both types of stepped wedge design. Researchers should distinguish in the sample size calculation between cohort and cross sectional stepped wedge designs. Further research is needed on the effect of adjusting for the potential confounding of time on the study power.

Household air pollution and lung cancer risk among never-smokers in Nepal

More than half of the global population relies on biomass fuels (wood, charcoal, crop residue, dung) for cooking and/or heating purposes. Household air pollution (HAP) resulting from the use of these solid fuels is of particular concern, given the overall prevalence as well as the intensity of exposure and the range of potential adverse health outcomes. Long term exposure to HAP is a major public health concern, particularly among women and children in low and middle income countries. In this study, we investigated the association between exposure to HAP resulting from combustion of biomass and lung cancer risk among Nepalese population. Using a hospital-based case-control study (2009-2012), we recruited 606 lung cancer cases and 606 healthy controls matched on age (±5 years), gender, and geographical residence. We used unconditional logistic regression to compute odds ratios (ORs) and 95% Confidence Intervals (95% CI) for lung cancer risk associated with HAP exposures, adjusting for potential confounders (tobacco use, TB status, SES, age, gender, ethnicity, and exposure to second hand smoke. In our overall analysis, we observed increased risk of lung cancer among those who were exposed to HAPs (OR: 1.77, 95% CI: 1.00-3.14). A more detailed analysis stratified by smoking status showed considerably higher risk of lung cancer associated with increasing duration of exposure to HAP from biomass combustion, with evidence of a borderline exposure-response relationship (Ptrend=0.05) that was more pronounced among never-smokers (Ptrend=0.01). Our results suggest that chronic exposure to HAP resulting from biomass combustion is associated with increased lung cancer risk, particularly among never-smokers in Nepal.

Validation of the St. George's Respiratory Questionnaire in Nepal

The St. George's Respiratory Questionnaire (SGRQ) is a standardized questionnaire for measuring impaired health and perceived well-being in chronic airway disease, but it is not available in the Nepali language. We translated the original SGRQ into Nepali and validated its use in 150 individuals aged 40 to 80 years with and without COPD.We also examined if the SGRQ could be used as a screening tool to identify individuals at risk for COPD. We translated the SGRQ following a standard protocol. The validation study was then conducted in both community and hospital-based settings in Nepal. We enrolled 100 participants from a community setting who were not actively seeking medical care, 50 of which met criteria for chronic obstructive pulmonary disease (COPD) (post-bronchodilator forced expiratory volume in 1 second [FEV₁]/ forced vital capacity [FVC]<70%) and 50 who did not. We also enrolled 50 participants with an established diagnosis of COPD who attended outpatient pulmonary clinics. All participants completed the questionnaire. We used linear regressions to compare average SGRQ scores by disease status categories and by lung function values, adjusted for age, sex, height and body mass index (BMI).All 150 participants (mean age 59.8 years, 48% male, mean BMI 20.5 kg/m²) completed the SGRQ. In multivariable regression, the average SGRQ total score was 23.9 points higher in established cases of COPD and 18.1 points higher in community cases of COPD when compared to participants without COPD living in the community (all p<0.001). The SGRQ total score also increased by an average of 2.1 points for each 100 mL decrease in post-FEV₁ (p<0.001). The area-under-the-curve for the SGRQ total score as a predictor of COPD was 0.77 (95% confidence interval [CI] 0.68 to 0.85) and the optimal cutoff to identify COPD was 33 points.We developed a Nepali-validated version of SGRQ, which correlated well with both disease status and severity.

Indoor Particulate Matter Concentration, Water Boiling Time, and Fuel Use of Selected Alternative Cookstoves in a Home-Like Setting in Rural Nepal

Alternative cookstoves are designed to improve biomass fuel combustion efficiency to reduce the amount of fuel used and lower emission of air pollutants. The Nepal Cookstove Trial (NCT) studies effects of alternative cookstoves on family health. Our study measured indoor particulate matter concentration (PM2.5), boiling time, and fuel use of cookstoves during a water-boiling test in a house-like setting in rural Nepal. Study I was designed to select a stove to be used in the NCT; Study II evaluated stoves used in the NCT. In Study I, mean indoor PM2.5 using wood fuel was 4584 μg/m3, 1657 μg/m3, and 2414 μg/m3 for the traditional, alternative mud brick stove (AMBS-I) and Envirofit G-series, respectively. The AMBS-I reduced PM2.5 concentration but increased boiling time compared to the traditional stove (p-values < 0.001). Unlike AMBS-I, Envirofit G-series did not significantly increase overall fuel consumption. In Phase II, the manufacturer altered Envirofit stove (MAES) and Nepal Nutrition Intervention Project Sarlahi (NNIPS) altered Envirofit stove (NAES), produced lower mean PM2.5, 1573 μg/m3 and 1341 μg/m3, respectively, relative to AMBS-II 3488 μg/m3 for wood tests. The liquid propane gas stove had the lowest mean PM2.5 concentrations, with measurements indistinguishable from background levels. Results from Study I and II showed significant reduction in PM2.5 for all alternative stoves in a controlled setting. In study I, the AMBS-I stove required more fuel than the traditional stove. In contrast, in study II, the MAES and NAES stoves required statistically less fuel than the AMBS-II. Reductions and increases in fuel use should be interpreted with caution because the composition of fuels was not standardized--an issue which may have implications for generalizability of other findings as well. Boiling times for alternative stoves in Study I were significantly longer than the traditional stove--a trade-off that may have implications for acceptability of the stoves among end users. These extended cooking times may increase cumulative exposure during cooking events where emission rates are lower; these differences must be carefully considered in the evaluation of alternative stove designs.

Determining particulate matter and black carbon exfiltration estimates for traditional cookstove use in rural Nepalese village households

A majority of black carbon (BC) emitted to the atmosphere in the Indo-Gangetic Plain (IGP) region is from burning biomass fuel used in traditional, open-design cookstoves. However, BC and particulate matter (PM) household emissions are not well characterized. Household emission information is needed to develop emission profiles to validate regional climate change models and serve as a baseline for assessing the impact of adopting improved stove technology. This paper presents field-based household PM and BC exfiltration (amount exiting) estimates from village homes in rural Nepal that utilize traditional, open-design cookstoves. Use of these stoves resulted in a 26% mean PM exfiltration, ranging from 6% to 58%. This is a significant departure from an 80% estimate cited in previous reports. Furthermore, having a window/door resulted in an 11% increase in exfiltration when an opening was present, while fuel type had a marginally significant impact on emission. Air-exchange rates (AER) were determined with average (95% CI) AER of 12 (10-14) per hour, consistent with previous studies. In addition, BC to PM2.5 mass-ratio composition during cooking was ascertained, with an average (95% CI) of 31% (24-39), agreeing with previous biomass fuel emission composition literature.