Challenging unverified assumptions in causal claims: Do gas stoves increase risk of pediatric asthma?

The use of unverified models for risk estimates and policy recommendations can be highly misleading, as their predictions may not reflect real-world health impacts. For example, a recent article states that NO2 from gas stoves "likely causes ∼50,000 cases of current pediatric asthma from long-term NO2 exposure alone" annually in the United States. This explicitly causal claim, which is contrary to several methodology and review articles published in this journal, among others, reflects both (a) An unverified modeling assumption that pediatric asthma burden is approximately proportional to NO2; and (b) An unverified causal assumption that the assumed proportionality between exposure and response is causal. The article is devoid of any causal analysis showing that these assumptions are likely to be true. It does not show that reducing NO2 exposure from gas stoves would reduce pediatric asthma risk. Its key references report no significant associations - let alone causation - between NO2 and pediatric asthma. Thus, the underlying data suggests that the number of pediatric asthma cases caused by gas stoves in the United States is indistinguishable from zero. This highlights the need to rigorously validate modeling assumptions and causal claims in public health risk assessments to ensure scientifically sound foundations for policy decisions.

Parental Report of Indoor Air Pollution Is Associated with Respiratory Morbidities in Bronchopulmonary Dysplasia.

OBJECTIVE: To determine the association between indoor air pollution and respiratory morbidities in children with bronchopulmonary dysplasia (BPD) recruited from the multicenter BPD Collaborative. STUDY DESIGN: A cross-sectional study was performed among participants <3 years old in the BPD Collaborative Outpatient Registry. Indoor air pollution was defined as any reported exposure to tobacco or marijuana smoke, electronic cigarette emissions, gas stoves, and/or wood stoves. Clinical data included acute care use and chronic respiratory symptoms in the past 4 weeks. RESULTS: A total of 1011 participants born at a mean gestational age of 26.4 ± 2.2 weeks were included. Most (66.6%) had severe BPD. More than 40% of participants were exposed to ≥1 source of indoor air pollution. The odds of reporting an emergency department visit (OR, 1.7; 95% CI, 1.18-2.45), antibiotic use (OR, 1.9; 95% CI, 1.12-3.21), or a systemic steroid course (OR, 2.18; 95% CI, 1.24-3.84) were significantly higher in participants reporting exposure to secondhand smoke (SHS) compared with those without SHS exposure. Participants reporting exposure to air pollution (not including SHS) also had a significantly greater odds (OR, 1.48; 95% CI, 1.08-2.03) of antibiotic use as well. Indoor air pollution exposure (including SHS) was not associated with chronic respiratory symptoms or rescue medication use. CONCLUSIONS: Exposure to indoor air pollution, especially SHS, was associated with acute respiratory morbidities, including emergency department visits, antibiotics for respiratory illnesses, and systemic steroid use.

Factors Determining Black Carbon Exposures among Pregnant Women Enrolled in the HAPIN Trial.

Residential biomass burning is an important source of black carbon (BC) exposure among rural communities in low- and middle-income countries. We collected 7165 personal BC samples and individual/household level information from 3103 pregnant women enrolled in the Household Air Pollution Intervention Network trial. Women in the intervention arm received free liquefied petroleum gas stoves and fuel throughout pregnancy; women in the control arm continued the use of biomass stoves. Median (IQR) postintervention BC exposures were 9.6 µg/m3 (5.2-14.0) for controls and 2.8 µg/m3 (1.6-4.8) for the intervention group. Using mixed models, we characterized predictors of BC exposure and assessed how exposure contrasts differed between arms by select predictors. Primary stove type was the strongest predictor (R2 = 0.42); the models including kerosene use, kitchen location, education, occupation, or stove use hours also provided additional explanatory power from the base model adjusted only for the study site. Our full, trial-wide, model explained 48% of the variation in BC exposures. We found evidence that the BC exposure contrast between arms differed by study site, adherence to the assigned study stove, and whether the participant cooked. Our findings highlight factors that may be addressed before and during studies to implement more impactful cookstove intervention trials.

The gas stove-childhood asthma kerfuffle: A teaching opportunity.

Several recent news stories have alarmed many politicians and members of the public by reporting that indoor air pollution from gas stoves causes about 13% of childhood asthma in the United States. Research on the reproducibility and trustworthiness of epidemiological risk assessments has identified a number of common questionable research practices (QRPs) that should be avoided to draw sound causal conclusions from epidemiological data. Examples of such QRPs include claiming causation without using study designs or data analyses that allow valid causal inferences; generalizing or transporting risk estimates based on data for specific populations, time periods, and locations to different ones without accounting for differences in the study and target populations; claiming causation without discussing or quantitatively correcting for confounding, external validity bias, or other biases; and not mentioning or resolving contradictory evidence. We examine the recently estimated gas stove-childhood asthma associations from the perspective of these QRPs and conclude that it exemplifies all of them. The quantitative claim that about 13% of childhood asthma in the United States could be prevented by reducing exposure to gas stove pollution is not supported by the data collected or by the measures of association (Population Attributable Fractions) used to analyze the data. The qualitative finding that reducing exposure to gas stove pollution would reduce the burden of childhood asthma in the United States has no demonstrated validity. Systematically checking how and whether QRPs have been addressed before reporting or responding to claims that everyday exposures cause substantial harm to health might reduce social amplification of perceived risks based on QRPs and help to improve the credibility and trustworthiness of published epidemiological risk assessments.

Thermal performance of gasifier cooking stoves: A systematic literature review.

A systematic literature review was conducted to summarize the overall thermal performance of different gasified cooking stoves from the available literature. For this purpose, available studies from the last 14 years (2008 to 2022) were searched using different search strings. After screening, a total of 28 articles were selected for this literature review. Scopus, Google Scholar, and Web of Science databases were used as search strings by applying "Gasifier cooking stove" AND "producer gas cooking stove" AND "thermal performance" keywords. This review uncovers different gasified cooking stoves, cooking fuels, and fabrication materials besides overall thermal performances. The result shows that the overall thermal performance of different gasified cooking stoves was 5.88% to 91% depending on the design and burning fuels. The premixed producer gas burner with a swirl vane stove provided the highest overall thermal performance range, which was 84% to 91%, and the updraft gasified stove provided the lowest performance, which was 5.88% to 8.79%. The result also demonstrates that the wood pellets cooking fuel provided the highest thermal performance and corn straw briquette fuel provided the lowest for gasified cooking stoves. The overall thermal performance of wood pellets was 38.5% and corn straw briquette was 10.86%.

Gas and Propane Combustion from Stoves Emits Benzene and Increases Indoor Air Pollution.

Exposure pathways to the carcinogen benzene are well-established from tobacco smoke, oil and gas development, refining, gasoline pumping, and gasoline and diesel combustion. Combustion has also been linked to the formation of nitrogen dioxide, carbon monoxide, and formaldehyde indoors from gas stoves. To our knowledge, however, no research has quantified the formation of benzene indoors from gas combustion by stoves. Across 87 homes in California and Colorado, natural gas and propane combustion emitted detectable and repeatable levels of benzene that in some homes raised indoor benzene concentrations above well-established health benchmarks. Mean benzene emissions from gas and propane burners on high and ovens set to 350 °F ranged from 2.8 to 6.5 µg min-1, 10 to 25 times higher than emissions from electric coil and radiant alternatives; neither induction stoves nor the food being cooked emitted detectable benzene. Benzene produced by gas and propane stoves also migrated throughout homes, in some cases elevating bedroom benzene concentrations above chronic health benchmarks for hours after the stove was turned off. Combustion of gas and propane from stoves may be a substantial benzene exposure pathway and can reduce indoor air quality.

Resilient clean cooking: Maintaining household clean cooking in Ecuador during the COVID-19 pandemic.

Decades of government subsidies for LPG and electricity have facilitated near-universal clean cooking access and use in Ecuador, placing the nation ahead of most other peer low- and middle-income countries. The widespread socio-economic impacts of the COVID-19 pandemic has threatened the resilience of clean cooking systems globally, including by altering households' ability to purchase clean fuels and policymakers' considerations about continuing subsidy programs. As such, assessing the resilience of clean cooking in Ecuador during the pandemic can offer important lessons for the international community, especially other countries looking to ensure resilient transitions to clean cooking. We study household energy use patterns using interviews, newspaper reports, government data on household electricity and LPG consumption, and household surveys [N = 200 across two rounds]. The LPG and electricity distribution systems experienced occasional disruptions to cylinder refill delivery and meter reading processes, respectively, which were associated with pandemic-related mobility restrictions. However, for the most part, supply and distribution activities by private and public companies continued without fundamental change. Survey participants reported increases in unemployment and reductions in household income as well as increased use of polluting biomass as a secondary fuel. Ecuador's LPG and electricity distribution systems were resilient throughout the pandemic, with only minimal interruption of the widespread provision of low-cost clean cooking fuels. Our findings inform the global audience concerned about the resilience of clean household energy use on the potential for clean fuel subsidies to facilitate continued clean cooking even during the COVID-19 pandemic.

Childhood asthma and household exposures to nitrogen dioxide and fine particles: a triple-crossover randomized intervention trial.

OBJECTIVE: Triple-crossover randomized controlled intervention trial to test whether reduced exposure to household NO2 or fine particles results in reduced symptoms among children with persistent asthma. METHODS: Children (n = 126) aged 5-11 years with persistent asthma living in homes with gas stoves and levels of NO2 15 ppb or greater recruited in Connecticut and Massachusetts (2015-2019) participated in an intervention involving three air cleaners configured for: (1) NO2 reduction: sham particle filtration and real NO2 scrubbing; (2) particle filtration: HEPA filter and sham NO2 scrubbing; (3) control: sham particle filtration and sham NO2 scrubbing. Air cleaners were randomly assigned for 5-week treatment periods using a three-arm crossover design. Outcome was number of asthma symptom-days during final 14 days of treatment. Treatment effects were assessed using repeated measures, linear mixed models. RESULTS: Measured NO2 was lower (by 4 ppb, p < .0001) for NO2-reducing compared to control or particle-reducing treatments. NO2-reducing treatment did not reduce asthma morbidity compared to control. In analysis controlling for measured NO2, there were 1.8 (95% CI -0.3 to 3.9, p = .10) fewer symptom days out of 14 in the particle-reducing treatment compared to control. CONCLUSIONS: It remains unknown if using an air cleaner alone can achieve levels of NO2 reduction large enough to observe reductions in asthma symptoms. We observed that in small, urban homes with gas stoves, modest reductions in asthma symptoms occurred using air cleaners that remove fine particles. An intervention targeting exposures to both NO2 and fine particles is complicated and further research is warranted. REGISTRATION NUMBER: NCT02258893.

Monitoring results of coal-burning-borne endemic fluorosis in Yunnan Province in 2020 / 中华地方病学杂志

Objective:To learn about the current situation of prevention and control of coal-burning-borne endemic fluorosis (coal burning fluorosis for short) in Yunnan Province, and comprehensively evaluate the implementation effect of prevention and control measures.Methods:From August to November 2020, according to the requirements of the Monitoring Program of Yunnan Province for Coal-burning-borne Endemic Fluorosis (2019 edition), monitoring was carried out in all natural villages in the disease areas of 13 counties (cities and districts, hereinafter referred to as counties) of the province, and 30 households were selected from each natural village to monitor the use of stoves and the formation of related healthy living behaviors. At the same time, children aged 8 - 12 years in the natural villages in the disease areas were examined for the prevalence of dental fluorosis. The evaluation for control and elimination of disease areas was carried out in accordance with the Evaluation Approach for Control and Elimination of Priority Endemic Diseases (2019 edition).Results:A total of 392 244 households were investigated, and the rates of qualified improved stoves, the correct utilization of qualified improved stoves and correct drying of corn and pepper were 99.42% (389 982/392 244), 99.70% (388 796/389 982) and 99.07% (388 579/392 244), respectively. A total of 227 057 children aged 8 - 12 years were examined, 9 413 children of dental fluorosis were detected, the detection rate of dental fluorosis was 4.15%, the dental fluorosis index was 0.10, and the prevalence intensity was negative. Taking the county as a unit, except Fuyuan and Zhenxiong, which reached the control standard of the disease area, the remaining 11 counties reached the elimination standard.Conclusion:The prevention and control measures on coal burning fluorosis are implemented well in Yunnan Province and healthy lifestyle has gradually taken shape, with the overall condition of the disease reduced.

Nitrated and oxygenated polycyclic aromatic hydrocarbons emissions from solid fuel combustion in rural China: Database of 12 real-world scenarios for residential cooking and heating activities.

Polycyclic aromatic hydrocarbons (PAHs) derivatives such as oxygenated PAHs (oPAHs) and nitrated PAHs (nPAHs), are receiving raising concerns due to their high toxic potential. Incomplete solid fuel combustion can release large quantities of PAHs derivatives, especially in low-efficiency domestic stoves. In this study, field measurements were conducted in rural Chinese homes to determine emissions of nPAHs and oPAHs from solid fuel combustion. A total of 12 fuel-stove combinations including cooking and space heating activities were investigated. Emission factors (EFs) of total nPAHs and oPAHs were in the range of 1.0-682.1 µg/kg and 0.01-131.7 mg/kg, respectively, with arithmetic means and stand deviations of 53.5 ± 72.5 µg/kg and 13.9 ± 24.4 mg/kg, respectively. The EFs of nPAHs and oPAHs for coal combustion (including honeycomb briquette, coal chunk, and peat tested in this study) were 30.2 ± 28.1 µg/kg and 1.5 ± 2.9 mg/kg, respectively, much lower than that for biomass burning (p < 0.05). The combustion phase could significantly affect the PAHs derivative emissions with higher emissions at initial phase than that at stable phase. Fuel type was found to affect the EFs, composition profiles, and ratios of PAHs derivatives to parent PAHs. This study tries to have an insight of PAHs derivative emissions from various solid fuel combustion, which would be useful in understanding the atmospheric PAHs derivative pollutions in China.

Using the carbon balance method based on fuel-weighted average concentrations to estimate emissions from household coal-fired heating stoves.

In China, household coal burning accounts for a large proportion of primary fine particulate matter (PM2.5), black carbon (BC), organic carbon (OC), polycyclic aromatic hydrocarbons (PAHs) and carbon monoxide (CO) emissions. Previous field investigations generally measured short-term emissions from heating coal stoves, which did not provide a full characterization of the actual conditions in most cases, or resulted in large uncertainties in the calculated emission factors (EFs). In this study, we propose a sampling design using a chimney partial-capture dilution system in the field measurement of household coal-fired heating stoves emissions during selected periods within the different burn phases and then using the carbon balance method (CBM) based on fuel-weighted average concentrations (FWAC) from the different burn phases to quantify emissions. We evaluated this proposed methodology by comparing the results with a laboratory total-capture dilution-tunnel system. Statistical analysis indicated that emissions measured during the selected burn cycle periods using the dilution sampling system can generally represent emissions at different burn phases; however, different dilution ratios can affect EFs for PM2.5 and OC. EFs of air pollutants derived by CBM with FWAC are more representative of the actual emissions than simple average concentration (SAC) and time-weighted average concentrations (TWAC). In the field application, to quantify FWAC, it is suggested to determine the ratio of power in the jth burn phase (Pj) to that in the high power phase (PH) of the stove, i.e., Pj/PH values with the calorimeter. If measured Pj/PH values are not available, the recommended value in this study is also suggested.

Sub-micron particle number emission from residential heating systems: A comparison between conventional and condensing boilers fueled by natural gas and liquid petroleum gas, and pellet stoves.

Pollutant emissions from residential heating systems represent a main concern in terms of outdoor air quality. Differently from other pollutants, sub-micron particle emission from heating systems has not yet been exhaustively characterized by the scientific literature, with limited data available, in particular, for gas-fueled boilers. In the present paper, an experimental campaign to measure the sub-micron particle number concentrations and distributions at the stack of different automatically-fed small-scale heating systems (conventional and condensing boilers fueled by natural gas and liquid petroleum gas, and pellet stoves) was performed. Based on the measured concentrations, corresponding emission rates and emission factors were also estimated. The results of the experimental campaign revealed that the highest concentrations were measured for pellet stoves (median value >107 part. m-3), whereas conventional (about 1 × 106 part. m-3) and condensing boilers (<106 part. m-3) presented much lower concentrations. No effect of the fuel (natural gas, liquid petroleum gas) on the total concentration measured at the stack of boilers was recognized, whereas a smaller distribution mode (at 10 nm) was measured for gas-fired boilers. Because of the particle concentration values, the highest particle emission rates and factors were the pellet stove ones (median values of 2.1 × 1015 part. h-1 and 8.4 × 1013 part. kWh-1, respectively), whereas emission rates for conventional and condensing boilers were about 5 × 1013 part. h-1 and 2 × 1013 part. h-1, respectively. The estimated emission factors were also adopted to perform a simplified evaluation of the relative contributions of the investigated automatically-fed small-scale heating systems in terms of particle number on a national scale (Italy): we obtained that the pellet stove contribution is the main one as it accounts for 87% of total emissions of particle number for heating purpose.

Hydrogen and wood-burning stoves.

Wood-burning stoves, in Kenya and Mexico, are reviewed. With a Kenyan stove, burning charcoal, only 24% of the energy released reached the cooking pot. Initially, the proportion of CO in the leaving gases was 3%. Indoor concentrations of particulate matter (less than 2.5 µm diameter) can be abnormally high near a stove. Decarbonization, by using H2, is facilitated by a distribution system. Replacement by H2 would ultimately rest upon wind or water power, or it being a by-product in the production of heavier hydrocarbons from CH4. The averaged burning rate in the Kenyan stove was 10 kW, over 20 min, with an initial peak value of about 30 kW. A possible replacement is a hob, composed of an array of small diameter H2 jet flames. As an example, combustion of a 2 mm internal diameter H2 jet flame, with a H2 exit velocity of 27.2 m s-1, would release 0.84 kW. Bearing in mind its improved efficiency, a single compact hob with an array of about 10 jets would suffice. A difficulty is the low mass-specific energy of H2. H2 has a high acoustic velocity, and both high velocity subsonic combustion and blending with natural gas are briefly discussed. This article is part of the theme issue 'Developing resilient energy systems'.

Stable nitrogen isotope composition of NOx of biomass burning in China.

Owing to the local characteristics of stable nitrogen isotopes in nitrogen oxides (δ15N-NOx) emitted from biomass burning, the lack of data on δ15N-NOx values associated with biomass burning in China limits the use of this parameter in identifying and quantifying the sources of atmospheric nitrate (NO3-) and NOx. The results showed that the δ15N-NOx values of open burning and rural cooking stoves in China ranged from -3.7‰ to 3.1‰ and -11.9‰ to 1.5‰, respectively. The δ15N values of nine biomass fuel sources (δ15N-biomass) ranged from 0.1‰ to 4.1‰. Significant linear relationships between the δ15N-biomass values and δ15N-NOx values of open burning (δ15N-NOx = 1.1δ15N-biomass - 2.7; r2 = 0.63; p < 0.05) and rural cooking stoves (δ15N-NOx = 1.7δ15N-biomass - 9.8; r2 = 0.72; p < 0.01) suggested that the variations in δ15N-NOx values from biomass burning were mainly controlled by the biomass fuel source. The isotopic fractionation of nitrogen during the biomass burning process might have led to the higher δ15N-NOx values from open burning in comparison to rural cooking stoves. By combining the δ15N-NOx values of biomass burning with biomass burning emission inventory data, a model for calculating the δ15N-NOx values of biomass burning in different regions of China was established, and the estimated δ15N-NOx value of biomass burning at the national scale was -0.8 ± 1.2‰. But the limited δ15N-biomass values increase the uncertainty of model in national scale.

An appraisal of air quality, thermal comfort, acoustic, and health risk of household kitchens in a developing country.

Few studies have documented the air quality, noise, thermal comfort, and health risk assessment of household kitchens related to Sub-Sahara Africa. In this paper, air quality (CO and PM2.5), thermal comfort (relative humidity (RH) and temperature), noise, and health risk in urban household kitchens with kerosene-fueled stoves were presented. This study was carried out during the dry season (summer) in the Southwestern part of Nigeria. At the breathing zone, PM2.5 and CO concentrations in the assessed kitchens were measured. In addition, the noise level, RH, and air temperature in the assessed kitchens were also determined. Furthermore, an evaluation of the heat index and health risk of the exposed population to the kerosene-fueled stove kitchens was carried out. During cooking, average CO and PM2.5 concentrations were 24.77 ± 1.05 ppm and 138.10 ± 2.61 µg/m3, respectively, while the RH was 68.34 ± 0.73%, noise level was 51.14 ± 1.08 dB, and temperature was 29.86 ± 0.23 °C. The CO and noise levels were relatively slightly lower and PM2.5 was significantly higher than the thresholds recommended by World Health Organisation. In most of the kitchens, the heat index evaluation revealed the possibility of heat exhaustion, heat cramps, and sunstroke with prolonged exposure of the vulnerable group. The air quality index depicted unhealthy (CO exposure) and very unhealthy (PM2.5 exposure) while the hazard quotient (> 1) implied possible health risk concerning exposure by inhalation. Better design of kitchen with adequate ventilation and improved stoves are suggested.

Do improved biomass cookstove interventions improve indoor air quality and blood pressure? A systematic review and meta-analysis.

OBJECTIVES: This systematic review and meta-analysis evaluates the most recent evidence to examine whether use of improved biomass cookstoves in households in low-middle income countries results in reduction in mean concentrations of carbon monoxide (CO) and particulate matter of size 2.5 µm (PM2.5) in the cooking area, as well as reduction in mean systolic (SBP) and diastolic blood pressure (DBP) of adults using the cookstoves when compared to adults who use traditional three stone fire or traditional biomass cookstoves. METHODS: We searched databases of scientific and grey literature. We included studies if published between January 2012 and June 2021, reported impact of ICS interventions in non-pregnant adults in low/middle-income countries, and reported post-intervention results along with baseline of traditional cookstoves. Outcomes included 24- or 48-h averages of kitchen area PM2.5, CO, mean SBP and DBP. Meta-analyses estimated weighted mean differences between baseline and post-intervention values for all outcome measures. RESULTS: Eleven studies were included; ten contributed estimates for HAP and four for BP. Interventions lead to significant reductions in PM2.5 (-0.73 mg/m3, 95% CI: -1.33, -0.13), CO (-8.37 ppm, 95%CI: -13.20, -3.54) and SBP (-2.82 mmHg, 95% CI: -5.53, -0.11); and a non-significant reduction in DBP (-0.80 mmHg, 95%CI: -2.33, 0.73), when compared to baseline of traditional cookstoves. Except for DBP, greatest reductions in all outcomes came from standard combustion ICS with a chimney, compared to ICS without a chimney and advanced combustion ICS. CONCLUSION: Among the reviewed biomass stove types, ICS with a chimney feature resulted in greatest reductions in HAP and BP.

A critical review of pollutant emission factors from fuel combustion in home stoves.

A large population does not have access to modern household energy and relies on solid fuels such as coal and biomass fuels. Burning of these solid fuels in low-efficiency home stoves produces high amounts of multiple air pollutants, causing severe air pollution and adverse health outcomes. In evaluating impacts on human health and climate, it is critical to understand the formation and emission processes of air pollutants from these combustion sources. Air pollutant emission factors (EFs) from indoor solid fuel combustion usually highly vary among different testing protocols, fuel-stove systems, sampling and analysis instruments, and environmental conditions. In this critical review, we focus on the latest developments in pollutant emission factor studies, with emphases on the difference between lab and field studies, fugitive emission quantification, and factors that contribute to variabilities in EFs. Field studies are expected to provide more realistic EFs for emission inventories since lab studies typically do not simulate real-world burning conditions well. However, the latter has considerable advantages in evaluating formation mechanisms and variational influencing factors in observed pollutant EFs. One main challenge in field emission measurement is the suitable emission sampling system. Reasons for the field and lab differences have yet to be fully elucidated, and operator behavior can have a significant impact on such differences. Fuel properties and stove designs affect emissions, and the variations are complexly affected by several factors. Stove classification is a challenge in the comparison of EF results from different studies. Lab- and field-based methods for quantifying fugitive emissions, as an important contributor to indoor air pollution, have been developed, and priority work is to develop a database covering different fuel-stove combinations. Studies on the dynamics of the combustion process and evolution of air pollutant formation and emissions are scarce, and these factors should be an important aspect of future work.

Is there any demand for improved cooking stoves? Evidence from Bangladesh.

Despite the multifarious benefits of improved cooking stoves (ICSs) over traditional biomass stoves, the ICSs adoption rate in rural Bangladesh remains nominal. This paper provides evidence that there is a growing demand for this environmentally friendly and less-hazardous stove. Using a discrete choice experiment (DCE) technique, we surveyed 259 sample households in the south-western region of Bangladesh. The results from the mixed logit model suggest that households are willing to pay (WTP) about $7 on average for a 'realistic' (i.e., one unit or 25 %) reduction in fuel consumption and smoke emission. Moreover, we found that a one-unit (33 %) reduction of cooking time and maintenance frequency increases households' WTP by about $3 and $5 respectively. Finally, this study underscores that extensive promotion, lower installation costs and higher social awareness about health risks and environmental degradation are likely to promote ICSs adoption.

Air pollution and lung function in children.

In this narrative review, we summarize the literature and provide updates on recent studies of air pollution exposures and child lung function and lung function growth. We include exposures to outdoor air pollutants that are monitored and regulated through air quality standards, and air pollutants that are not routinely monitored or directly regulated, including wildfires, indoor biomass and coal burning, gas and wood stove use, and volatile organic compounds. Included is a more systematic review of the recent literature on long-term air pollution and child lung function because this is an indicator of future adult respiratory health and exposure assessment tools have improved dramatically in recent years. We present "summary observations" and "knowledge gaps." We end by discussing what is known about what can be done at the individual/household, local/regional, and national levels to overcome structural impediments, reduce air pollution exposures, and improve child lung function. We found a large literature on adverse air pollution effects on children's lung function level and growth; however, many questions remain. Important areas needing further research include whether early-life effects are fixed or reversible; and what are windows of increased susceptibility, long-term effects of repeated wildfire events, and effects of air quality interventions.

Mass absorption cross-section of black carbon from residential biofuel stoves and diesel trucks based on real-world measurements.

Black carbon (BC) as an important part of atmospheric aerosols imposes adverse effects on atmospheric visibility, health, and climate change. Mass absorption cross-section (MACBC) is an essential parameter in BC quantitative and model research, which is of growing concern in recent decades. In this study, we conducted real-world measurements on BC emissions from two major sources of residential biofuel stoves and diesel trucks. BC emissions and MACBC values are quantified based on the photoacoustic and thermo-optical methods. The impacts of typical factors from biofuel stoves (biofuel and stove types) and diesel trucks (vehicle types, emission standards, and driving conditions) on BC/EC, MACBC values, and the relationships between BC and EC, BC/PM2.5 and MACBC are analyzed comprehensively. We find the BC and EC emissions from these two sources present good correlations, and those emissions are almost equal from diesel trucks, while the EC emissions from biofuel burning are slightly higher than BC. The typical factors for analysis may affect the optical properties of BC, and then will affect the mass ratio of BC/EC, indirectly. We have calculated the equivalent MACBC values and compared those with previous studies. Then, we further divided the equivalent MACBC values under several typical factors, which are 5.84 and 2.71 m2/g for improved and simple biofuel stoves, and 5.91 and 4.64 m2/g for light-duty and heavy-duty diesel trucks, respectively. Furthermore, the MACBC and BC/PM2.5 under the main operational metrics generally present good correlations. Our results will help to enhance the understanding of MACBC and provide effective data support for BC quantification and atmospheric model research.